Cells: The Basis of Life

Transcription

1 Slide 1 / 192 Slide 2 / 192 ells: The asis of Life Slide 3 / 192 Slide 4 / 192 ells Unit Topics lick on the topic to go to that section Prokaryotes Eukaryotes Viruses ellular efenses Prokaryotes Return to Table of ontents Slide 5 / 192 ll ells ll cells have 4 things in common. They are surrounded by a plasma membrane (or cell membrane). They contain a semifluid substance called the cytosol/cytoplasm. They contain structures called chromosomes, which carry the cell's genes. They have ribosomes, which assemble amino acids into proteins. Slide 6 / 192 Eukaryotes vs. Prokaryotes There are 3 key differences between prokaryotic and eukaryotic cells. Eukaryotic cells are usually larger than prokaryotic cells. Eukaryotic cells have small compartments inside them call organelles. Most eukaryotes (but not all) are multi-cellular organisms.

2 Slide 7 / Which is NOT a basic feature of all cells? Slide 7 (nswer) / Which is NOT a basic feature of all cells? ll cells are surrounded by a plasma membrane. ll cells are surrounded by a plasma membrane. ll cells contain a semifluid substance called the cytoplasm. ll cells contain a semifluid substance called the cytoplasm. ll cells contain structures called chromosomes, which are contained in the nucleus. ll cells contain structures called chromosomes, which are contained in the nucleus. ll cells have ribosomes. ll cells have ribosomes. nswer Slide 8 / scientist is trying to determine if a newly discovered organic object is alive. It has a plasma membrane, organelles, and N, but no ribsomes. Is this organic material alive? Yes Slide 8 (nswer) / scientist is trying to determine if a newly discovered organic object is alive. It has a plasma membrane, organelles, and N, but no ribsomes. Is this organic material alive? Yes No No nswer No Slide 9 / 192 Prokaryotes: 2 Types Slide 10 / 192 We Rely on acteria! acteria rchaea Often we think of bacteria as being primarily harmful organisms. While there are harmful bacteria, most are beneficial; we depend on them. acteria cover all the external surfaces of our bodies. This includes our digestive tracts since that is also considered to be external. acteria live in cooperation with you; they protect you against harmful bacteria and help you digest food. Without these bacteria, which have evolved with us, as we evolved, we could not live healthy lives.

3 Slide 11 / 192 We Rely on acteria! In fact, the number of bacterial cells living on us is greater than the number of our own cells. Those bacteria have more unique genetic material than do our own genes. That bacterial genetic material allows them to create enzymes or products that are essential to us. Slide 12 / 192 We Rely on acteria! Newborn babies get innoculations of these bacteria from their mothers, so that their digestive systems can function. There are also bacteria in many food sources, like yogurt and cheese. bacteria on skin - National Geographic Magazine Slide 13 / 192 ntibiotics When we take antibiotics to fight a harmful bacteria, it's usually recommended to consume probiotics, such as yogurt, to replace any of our helpful bacteria that might be accidentally harmed. In fact, most antibiotics themselves are derived from bacteria. They are created in nature by bacteria to fight other bacteria. When then use them in the form of antibiotic pills or injections to fight harmful bacteria. Slide 14 / 192 rchaea rchaea were classified as bacteria until very recently. In 1977, they were separated from bacteria into their own domain, or grouping. rchaea Many archaea are extremophiles, organisms that live in environments where life had been considered impossible. They have be found living in areas of extreme temperature (such as hydrothermal vents), ph solutions of lower than 3 and higher than 9, and solutions with high salt, methane, or heavy metal concentrations. Slide 15 / 192 rchaea While archaea have many cell structures and metabolic pathways in common with bacteria, research has shown that their genes and factors involved in their gene expression are more like those of eukaryotes (the class of organisms that include animals, plants, and fungi). This has led scientists to believe that archaea developed after bacteria. Slide 16 / The earliest living organisms were probably: animals archaea bacteria plants LU ( Y)

4 Slide 16 (nswer) / The earliest living organisms were probably: Slide 17 / Prokaryotes can live in which of the following environments? animals archaea bacteria plants nswer the ocean acidic lakes hydrothermal vents under the rctic ice E all of the above Slide 17 (nswer) / Prokaryotes can live in which of the following environments? the ocean acidic lakes hydrothermal vents under the rctic ice E all of the above nswer E Slide 18 / 192 Order/Organization ll prokaryotes are unicellular, meaning a single cell is considered an entire organism. They can live on their own, but most form colonies, large groups (millions, billions or more) live in a tightly packed area. They have a variety of shapes and functions. Slide 19 / 192 Prokaryotic Shapes Slide 20 / 192 Structures Prokaryotes have many different structures, each having a specific job or function. These structures within the cell operate like small molecular machines. They are used for various functions that help maintain the life of the overall organism.

5 Most prokaryotes have a cell wall. The cell wall is outside the cell's plasma membrane and maintains the cell's shape, provides physical protection, and prevents the cell from bursting in a hypotonic environment. In bacteria, this cell wall is made of a strong carbohydrate fiber called peptidoglycan. In rchaea, various cell wall types exist. Slide 21 / 192 ell Surface The cell wall of some prokaryotes is covered by a capsule, a sticky layer of polysaccharide or protein. The cell wall and capsule are in addition to the plasma membrane, and are found covering it. They do not replace it. Slide 22 / 192 ell Surface Slide 23 / 192 Flagella Most motile prokaryotes propel themselves by flagella, a tail-like protein structure. This allows these prokaryotes to exhibit taxis, the ability to move toward or away from certain stimuli. hemotaxis is movement in response to chemicals in the environment. Phototaxis is movement in response to light. Slide 25 / Interesting note: Flagellum is the latin word for whip. 5 What structure allows a prokaryote to adhere to environmental surfaces? cell wall sex pili flagellum fimbriae There are two basic types of pili: Slide 24 / 192 Pili short attachment pili, also known as fimbriae, that are usually quite numerous - fimbriae allow cells to attach to other cells or to inanimate objects. long conjugation pili, also called "F" or sex pili that are few in number - sex pili allow bacteria to transfer genetic information from one cell to another Pili are thin, protein tubes originating from the prokaryotic cell membrane. fimbriae Slide 25 (nswer) / What structure allows a prokaryote to adhere to environmental surfaces? cell wall sex pili flagellum fimbriae nswer

6 Slide 26 / What structure allows a prokaryote to exhibit taxis? Slide 26 (nswer) / What structure allows a prokaryote to exhibit taxis? cell wall sex pili flagellum fimbriae cell wall sex pili flagellum fimbriae nswer Slide 27 / In bacteria, the is made of a substance called peptidoglycan. capsule pili flagellum cell wall Slide 27 (nswer) / In bacteria, the is made of a substance called peptidoglycan. capsule pili flagellum cell wall nswer Slide 28 / 192 Inside the ell The fluid which fills the cell is called the cytoplasm. Floating in the cytoplasm are the ribosomes and the bacterial chromosome, a double-stranded, circular structure containing the prokaryote's N. Prokaryotes usually only have one chromosome and the area where it is located is known as the nucleoid. Slide 29 / 192 Plasmids Many prokaryotes also have plasmids, smaller circular N molecules that are independent of the bacterial chromosome. Plasmids contain genes for adaptations like resistance against antibiotics, making a sex-pilus (F-pilus), making toxins, and guarding against heavy metal toxicity.

7 Slide 30 / 192 F Plasmids The presence of an F plasmid (or an F factor) gives the prokaryotic cell the ability to have fertility, by forming a sex pilus. This allows the prokaryote to donate N to other prokaryotes in its colony, increasing their genetic variability. Slide 31 / 192 R Plasmids R plasmids give a bacteria cell antibiotic resistance. ntibiotic resistance gives the bacterial cell immunity to certain types of antibiotics. When a bacterial population is exposed to an antibiotic, individuals with the R plasmid will survive and increase in the overall population. Note: The "F" factor is located in the bacterial chromosome. Slide 32 / Which is the shape of a bacterial chromosome? Slide 32 (nswer) / Which is the shape of a bacterial chromosome? spiral spiral rod rod spherical spherical circular circular nswer Slide 33 / How many chromosomes do most prokaryotes have? Slide 33 (nswer) / How many chromosomes do most prokaryotes have? nswer 1

8 Slide 34 / 192 Slide 34 (nswer) / The area where a bacterial chromosome is located is called: 10 The area where a bacterial chromosome is located is called: capsule capsule flagella flagella nucleoid ribosome nucleoid ribosome nswer Slide 35 / acteria that have R plasmids can cause medical problems in animals because they. Slide 35 (nswer) / acteria that have R plasmids can cause medical problems in animals because they. control conjugation in bacteria control conjugation in bacteria are used as vectors to transfer genes are used as vectors to transfer genes make bacteria resistant to antibiotics make bacteria resistant to antibiotics E code for N polymerase protect bacteria against mutations E code for N polymerase nswer protect bacteria against mutations Slide 36 / 192 Slide 36 (nswer) / ntibiotic resistance first arose as the result of ntibiotic resistance first arose as the result of... increased antibiotic use increased antibiotic use introduction of F factors into the genome introduction of F factors into the genome a genetic mutation a genetic mutation competition for resources among bacterial colonies competition for resources among bacterial colonies nswer

9 Slide 37 / 192 Slide 38 / 192 Prokaryotic Reproduction Prokaryotic cells divide and reproduce by binary fission, the splitting of one cell into two. In order for each cell to have a complete copy of the N, the bacterial chromosome must be replicated prior to cell division. bacterial chromosome capsule cell membrane ribosome nucleoid cell wall flagella fimbriae Slide 39 / 192 inary Fission Slide 40 / t the end of binary fission, there are two prokaryotic cells one has all the parent N fter the chromosome is replicated, the cell divides in half with one copy in each new cell. both have only parent N both have only daughter N both have half parent and half daughter N Slide 40 (nswer) / 192 Slide 41 / t the end of binary fission, there are two prokaryotic cells one has all the parent N both have only parent N both have only daughter N both have half parent and half daughter N nswer Eukaryotes Return to Table of ontents

10 Slide 42 / 192 Surface rea to Volume Ratio t the time when prokaryotic cells were evolving, there were most likely different sizes of cells. cell's efficiency and ability to survive depended on its surface area to volume ratio. The volume of the cell determines the amount of chemical activity it can carry out per unit time. The surface area of the cell determines the amount of substances the cell can take in from the environment and the amount of waste it can release. Slide 43 / 192 We know that cells need to be small enough so that they have an increased surface area to volume ratio, but be large enough to perform the chemical reactions of metabolism. Most Efficient Limits of ell Size Least Efficient s a cell grows in size, it's surface area to volume ratio decreases. It performs chemical reactions faster, but it has a harder time getting nutrients in and waste out. The smaller the cell, the larger its surface area and the smaller its volume. The bigger the cell, the smaller the surface area is compared to its large volume inside. Slide 44 / 192 ell Size Eukaryotic cells are, on average, much larger than prokaryotic cells. The average diameter of most prokaryotic cells is between 1 and 10µm. y contrast, most eukaryotic cells are between 5 to 100µm in diameter. nimal ell (Eukaryote) To increase efficiency in the larger cell, eukaryotes evolved many bacterium-sized parts known as organelles. Organelles subdivide the cell into specialized compartments. Slide 45 / 192 Organelles acterium (Prokaryote) They play many important roles in the cell. Some transport waste to the cell membrane. Others keep the molecules required for specific chemical reactions located within a certain compartment so they do not need to diffuse long distances to be useful. Slide 46 / 192 Organelles Slide 47 / How did eukaryotes solve the problem of diffusion? Organelles making up Eukaryotic cells include: Vacuoles Lysosomes Smooth Endoplasmic Reticulum Ribosomes Rough Endoplasmic Reticulum Peroxisome hloroplasts s Golgi pparatus Mitochondria y remaining the same size as prokaryotes. y using a nucleus. ompartmentalization. They haven't solved the problem.

11 Slide 47 (nswer) / 192 Slide 48 / How did eukaryotes solve the problem of diffusion? 15 Which is NOT an advantage of compartmentalization? y remaining the same size as prokaryotes. y using a nucleus. ompartmentalization. They haven't solved the problem. nswer It allows incompatible chemical reactions to be separated. It increases the efficiency of chemical reactions. It decreases the speed of reactions since reactants have to travel farther. Substrates required for particular reactions can be localized and maintained at high concentrations within organelles. Slide 48 (nswer) / 192 Slide 49 / Which is NOT an advantage of compartmentalization? It allows incompatible chemical reactions to be separated. It increases the efficiency of chemical reactions. It decreases the speed of reactions since reactants have to travel farther. nswer Substrates required for particular reactions can be localized and maintained at high concentrations within organelles. Multicellular Organisms Even with organelles, the size of the cell is limited to about 1000µm 3. This is why large organisms must consist of many smaller cells. Slide 50 / 192 iversity of Eukaryotes Protists: The first eukaryotic cells. Protists are single-celled eukaryotes. They range from protozoans to algae. Fungi: These organisms evolved second in time along with plants. Examples include mushrooms, molds, and mildews. Slide 51 / How did eukaryotes solve the problem of small surface area to volume ratio? by remaining the same size as prokaryotes by becoming multicellular organisms by compartmentalizing functions into organelles they haven't solved the problem Plants: Plants vary in type from the first plants called mosses to the modern flowering plants. nimals: nimals were the last eukaryotes to evolve. nimals range from ancient sponges and hydra to primates.

12 Slide 51 (nswer) / How did eukaryotes solve the problem of small surface area to volume ratio? by remaining the same size as prokaryotes by becoming multicellular organisms by compartmentalizing functions into organelles they haven't solved the problem nswer Slide 52 / Identify a single-celled eukaryote. Mushroom E. coli lgae rustacean Slide 52 (nswer) / Identify a single-celled eukaryote. Slide 53 / 192 The Mushroom E. coli lgae rustacean nswer The defining organelle in eukaryotic cell is the nucleus. The nucleus of the cell contains the N and controls the cell's activities by directing protein synthesis from N. prokaryotes: pro: before karyon: kernel/seed (nucleus) eukaryote: eu: true karyon: kernel/seed (nucleus) So prokaryote = "before a nucleus" nd eukaryote = "true nucleus" Slide 54 / 192 Inside the Slide 55 / Main Functions of the The nucleus is enclosed by a double cell membrane structure called the nuclear envelope. The nuclear envelope has many openings called nuclear pores. Nuclear pores help the nucleus "communicate" with other parts of the cell. 1. To keep and contain a safe copy of all chromosomes (N) and pass them on to daughter cells in cell division. 2. To assemble ribosomes (specifically in the nucleolus). 3. To copy N instructions into RN (via transcription). Inside the nucleus is a dense region known as the nucleolus. The nucleolus is where rrn is made and ribosomes are assembled. They then exit through the nuclear pores.

13 Slide 56 / ells that contain a "true nucleus" and other membrane bound organelles are. Slide 56 (nswer) / ells that contain a "true nucleus" and other membrane bound organelles are. archaea. archaea. bacteria. bacteria. eukaryotes. prokaryotes. eukaryotes. prokaryotes. nswer Slide 57 / 192 Slide 57 (nswer) / Where is the N of a eukaryote found? 19 Where is the N of a eukaryote found? Nucleolus Nucleolus Nucleoid region Nucleoid region Mitochondria Mitochondria nswer Slide 58 / How does the nucleus control the activities of the cell? Slide 58 (nswer) / How does the nucleus control the activities of the cell? y making N. y making N. y directing protein synthesis. y directing protein synthesis. y allowing N to leave the nucleus to make proteins. y allowing N to leave the nucleus to make proteins. y sending instructions to the mitochondria. y sending instructions to the mitochondria. nswer

14 Slide 59 / 192 Ribosomes Slide 60 / 192 Ribosomes Recall that the ribosome is made of rrn and proteins. This is where translation occurs. Ribosomes consist of two subunits, a small and a large. Each subunit consists of proteins and rrn. The two subunits come together when proteins need to be made. Small subunit Large subunit Recall ribosomes make peptide bonds between amino acids in translation. The instructions for making ribosomes are in the N. From N, rrn is made. Some of the rrn is structural and other rrn holds the code from the N to make the ribosomal proteins from mrn. transcription translation N mrn Protein Slide 61 / 192 Ribosomes Two types of ribosomes exist in eukaryotic cells: free ribosomes and bound ribosomes. ound ribosomes are attached to internal membranes in the cell's endomembrane system. Free ribosomes move freely through the cytoplasm and produce proteins and enzymes used internally by the cell. Slide 62 / 192 The Endomembrane System Several organelles, some made up mainly of membranes, form a type of assembly line in the cell. They make a protein, then process and ship it to its final destination in the cell membrane or outside the cell. Organelles included in this system include the nucleus, rough and smooth endoplasmic reticulum, golgi appartus, and lysosomes. ollectively, we refer to them as the endomembrane system. Note: The plasma membrane is also considered part of this system Slide 63 / 192 The Endomembrane System Slide 64 / 192 Endoplasmic Reticulum When RN leaves the nucleus, it enters the endoplasmic reticulum (ER). This organelle is a series of membrane-bound sacs and tubules. It is continuous with the outer membrane of the nuclear envelope (reticulum comes from the latin word for little net). There are two types of endoplasmic reticulum: rough and smooth

15 Slide 65 / 192 Rough Endoplasmic Reticulum Rough ER has ribosomes attached to its membrane (thus a rough appearance). These ribosomes synthesize proteins that will be used in the plasma membrane, secreted outside the cell or shipped to another organelle called a lysosome. s proteins are made by the ribosomes, they enter the lumen (opening) of the ER where they are folded and processed. Slide 66 / 192 Smooth Endoplasmic Reticulum This type of ER is called Smooth because it lacks ribosomes on its surface. (it looks smooth compared to rough ER) There are a variety of functions of this organelle, which include: making lipids. processing certain drugs and poisons absorbed by the cell. storing calcium ions (for example, in muscle cells). Note: The liver is an organ that detoxifies substances that are brought into the body. Therefore, liver cells have huge amounts of Smooth ER Slide 67 / Where are ribosomal subunits made in the cell? Slide 67 (nswer) / Where are ribosomal subunits made in the cell? ytoplasm ytoplasm Nucleolus Nucleolus On the Plasma membrane nswer On the Plasma membrane Slide 68 / List all the parts of the endomembrane system. rough and smooth endoplasmic reticulum, golgi appartus, lysosomes nucleus, rough and smooth endoplasmic reticulum, golgi appartus, lysosomes nucleus, rough and smooth endoplasmic reticulum, golgi appartus nucleus, rough and smooth endoplasmic reticulum, golgi appartus, lysosomes, plasma membrane Slide 68 (nswer) / List all the parts of the endomembrane system. rough and smooth endoplasmic reticulum, golgi appartus, lysosomes nucleus, rough and smooth endoplasmic reticulum, golgi appartus, lysosomes nucleus, rough and smooth endoplasmic reticulum, golgi appartus nucleus, rough and smooth endoplasmic reticulum, golgi appartus, lysosomes, plasma membrane nswer

16 Slide 69 / Where are the proteins of the K+/Na+ pump synthesized? Slide 69 (nswer) / Where are the proteins of the K+/Na+ pump synthesized? free ribsomes free ribsomes nucleus rough endoplasmic reticulum smooth endoplasmic reticulum nucleus nswer rough endoplasmic reticulum smooth endoplasmic reticulum Slide 70 / 192 Protein Transport Once the proteins are processed, short chains of sugars are sometimes linked to these proteins, which are then known as glycoproteins. These glycoproteins serve as "zip codes" that will tell the protein where it will go. When the molecule is ready to be exported out of the ER, it gets packaged into a transport vesicle. This vesicle is made of membranes from the ER itself. The transport vesicle travels to another organelle known as the Golgi apparatus. The main function of this organelle is to finish, sort, and ship cell products. It works like the postal department of the cell. Structurally, the golgi consists of stacked flattened sacs (sort of looks like a stack of pita bread). Slide 71 / 192 Golgi pparatus Slide 72 / 192 Golgi pparatus The Golgi is located near the cell membrane. The Golgi works closely with the ER of a cell. It receives and modifies substances manufactured by the ER. Once the substances are modified, they are shipped out to other areas of the cell. One key difference between the Golgi apparatus and endoplasmic reticulum is that the sacs comprising the Golgi are not interconnected. Slide 73 / 192 The Golgi pparatus & the ER The Golgi receives transport vesicles that bud off from the ER and contain proteins. It takes the substances contained in these vesicles and modifies them chemically in order to mark them and sort them into different batches depending on their destination. The finished products are then packaged into new transport vesicles which will then move to lysosomes, or will be inserted into the plasma membrane or dumped out of the cell if the protein is a secretory protein. Video on Protein Trafficking through the Golgi

17 Slide 74 / Which organelle receives and modifies substances from the endoplasmic reticulum? Slide 74 (nswer) / Which organelle receives and modifies substances from the endoplasmic reticulum? Ribosomes Lysosomes Golgi odies Ribosomes Lysosomes Golgi odies nswer Slide 75 / difference between the Golgi pparatus and the ER is that Slide 75 (nswer) / difference between the Golgi pparatus and the ER is that The ER takes the vesicles from the Golgi to transport The ER takes the vesicles from the Golgi to transport The sacs making the Golgi are not interconnected The sacs making the Golgi are not interconnected The Golgi has ribosomes, the ER does not There is no difference, they are part of the same organelle The Golgi has ribosomes, the ER does not nswer There is no difference, they are part of the same organelle Slide 76 / 192 Slide 77 / 192 Lysosomes Lysosomes Some proteins from the Golgi pparatus are transported to the lysosomes. s the name suggests, a lysosome is an organelle that breaks down other substances. (lyse: to cause destruction) They consist of hydrolytic enzymes enclosed within a membrane. Hydrolytic enzymes break polymers into monomers (hydrolysis). Lysosomes may fuse with food-containing organelles called vacuoles and then the enzymes digest the food, releasing nutrients into the cell. Protists do this. amaged or unneeded proteins may become enclosed within a membranous vesicle which then fuses with a lysosome. The organic molecules from the breakdown process are recycled and reused by the cell.

18 Slide 78 / 192 Peroxisomes peroxisome is a specific type of lysosome that forms and breaks down hydrogen peroxide (H2O2) which is toxic to cells. In all cells, hydrogen peroxide forms constantly (from the combining of hydrogen and oxygen as bi-products of metabolism) and needs to be broken down quickly. Slide 79 / Which organelle contains hydrolytic enzymes that break down other substances? Endoplasmic Reticulum Golgi odies Lysosomes Vacuoles Important note: Peroxisomes are not part of the endomembrane system. Slide 79 (nswer) / Which organelle contains hydrolytic enzymes that break down other substances? Endoplasmic Reticulum Golgi odies Lysosomes Vacuoles nswer Slide 80 / Which is not a function of lysosomes? aiding the cell in creating ribosomes fusing with vacuoles to digest food breaking polymers into monomers recycling worn out cell parts Slide 80 (nswer) / Which is not a function of lysosomes? aiding the cell in creating ribosomes Slide 81 / 192 Plasma Membrane Remember the plasma membrane is a phospholipid bilayer with proteins and other molecules interspersed throughout. fusing with vacuoles to digest food breaking polymers into monomers nswer recycling worn out cell parts Some proteins from the golgi apparatus become embedded in the membrane. Others are transported through the membrane to the external environment.

19 Slide 82 / 192 Plasma Membrane The 3 main functions of the plasma membrane: Selective permeability Protection Structural support Slide 83 / Which of the following statements about the role of phospholipids in forming membranes is correct? they are completely insoluble in water they form a single sheet in water they form a structure in which the hydrophobic portion faces outward they form a selectively permeable structure Slide 83 (nswer) / Which of the following statements about the role of phospholipids in forming membranes is correct? they are completely insoluble in water they form a single sheet in water they form a structure in which the hydrophobic portion faces outward nswer they form a selectively permeable structure Slide 84 / ctive transport moves molecules with their concentration gradients without the use of energy with their concentration gradients using energy against their concentration gradients without the use of energy against their concentration gradients using energy Slide 84 (nswer) / ctive transport moves molecules Slide 85 / Which of the following processes includes all others? with their concentration gradients without the use of energy passive transport with their concentration gradients using energy facilitated diffusion against their concentration gradients without the use of energy diffusion of a solute across a membrane against their concentration gradients using energy osmosis nswer

20 Slide 85 (nswer) / Which of the following processes includes all others? passive transport facilitated diffusion diffusion of a solute across a membrane osmosis nswer Slide 86 / 192 Large Molecules and the Plasma Membrane Many proteins created by the cell are too large to pass through the membrane, even using protein carrier or integral proteins. How do these macromolecules exit the cell? Then, the substance uses other ways of getting into or out of a cell by fusing with the cell membrane. There are several special functions of the membrane as larger substances enter and exit the cell. Slide 87 / 192 Slide 88 / 192 To excrete a macromolecule from the cell, the vesicles that enclose the proteins fuse with the plasma membrane and the vesicles then open up and spill their contents outside of the cell. Exocytosis Exocytosis Insulin - Secretory Protein Insulin is a protein hormone made by certain cells of the pancreas that enable cells to take glucose (sugar) in from the blood. Insulin is a secretory protein made in the rough ER. Specifically, it is secreted out of the pancreas cells into the blood stream. This process is known as exocytosis. The vesicle will become part of the cell membrane. This is how secretory proteins from the Golgi exit the cell. This is true for insulin in the pancreas. Slide 89 / 192 Endocytosis Slide 90 / Types of Endocytosis The opposite of exocytosis is endocytosis. In this process, the cell takes in macromolecules or other particles by forming vesicles or vacuoles from its plasma membrane. This is how many protists ingest food particles

21 Slide 91 / Types of Endocytosis Slide 92 / The process by which a cell ingests large solid particles; it is known as "cell eating". Phagocytosis is for taking in solid particles. ("phago" mean to eat) Pinocytosis is for taking in liquids. However what the cell wants is not the liquid itself, but the substances that are dissolved in the liquid. ("pino" means to drink) Receptor-mediated endocytosis requires the help of a protein coat and receptor on the membrane to get through. Pinocytosis Phagocytosis Exocytosis Osmoregulation Slide 92 (nswer) / The process by which a cell ingests large solid particles; it is known as "cell eating". Slide 93 / Protein coated vesicles move through the plasma membrane via this process: Pinocytosis Phagocytosis Phagocytosis ctive Transport Exocytosis Osmoregulation nswer Receptor-Mediated Endocytosis Pinocytosis Slide 93 (nswer) / Protein coated vesicles move through the plasma membrane via this process: Slide 94 / fter a vesicle empties its contents outside a cell, the vesicle becomes part of: Phagocytosis the Golgi ctive Transport the plasma membrane Receptor-Mediated Endocytosis Pinocytosis nswer another vesicle the extracellular fluid

22 Slide 94 (nswer) / fter a vesicle empties its contents outside a cell, the vesicle becomes part of: Slide 95 / 192 Energy-onverting Organelles the Golgi the plasma membrane hloroplasts reside in plant cells and some protists and convert solar radiation into energy stored in the cell for later use. another vesicle nswer the extracellular fluid Mitochondria reside in all eukaryotic cells and convert chemical energy from glucose into TP. Interestingly, both chloroplasts and mitochondria have their own N, separate from that found in the nucleus of the cell. They also have a double cell membrane. Slide 96 / 192 hloroplasts Slide 97 / 192 Thylakoids These organelles convert solar energy to chemical energy through photosynthesis. hloroplasts are partitioned into three major compartments by internal membranes: Thylakoids Stroma Intermembrane space eukaryotic chloroplast Remember that during photosynthesis it is on the thylakoid that the Light ependent Reactions take place. In prokaryotes, thylakoids are areas of highly folded membranes. eukaryotic chloroplast In eukaryotes, they are stacked in the chloroplasts. The fluid outside these stacks of thylakoids is called the stroma; this is where the alvin cycle takes place. Slide 98 / 192 Mitochondria Slide 99 / 192 Mitochondria and Respiration Mitochondria are sometimes referred to as the "powerhouses" of the cell. They convert chemical energy (glucose) into a more usable and regenerative form of chemical energy (TP). The mitochondrion is also partitioned like the chloroplast. They only have two compartments as opposed to three in the chloroplast. Matrix Remember cell respiration must take place near a membrane so that a proton gradient can be built in a "membrane space" that is separate from the rest of the cell. Thus, the membrane would separate the inner volume, with a deficit of protons, from the outside, with an excess. In prokaryotes, the "inter-membrane space" is between the cell membrane and the cell wall. In eukaryotes, that membrane is the inter-membrane space of the mitochondria in between the inner membrane and outer membrane. Intermembrane space

23 Slide 100 / 192 The Evolution of Eukaryotes The mitochondria and chloroplast are different from other eukaryotic organelles because they have their own N, their own ribosomes, and have a double cell membrane. In 1970, Lynn Margulis published the "Theory of Endosymbiosis" to explain these facts. The theory states that the mitochondria and chloroplast were once free-living prokaryotes that got taken up (or "eaten") by another prokaryote. The mitochondria was a bacteria that could make its own TP. The chloroplast was a bacteria that could perform photosynthesis. endo: within bio: life sym: together sis: condition endosymbiosis = living together, within Slide 101 / 192 The Mitochondrial Eve Since mitochondrial N is not in the cell nucleus, it is only passed along from mother to child; animals, including you, inherit your mitochondria from your mother only. This is because the egg from our mothers contained her organelles. (ad's sperm only contains the chromosomes, none of his organelles usually). ll of our organelles we inherited from our mothers. Mitochondrial N is a way to trace maternal heritage through a family or through a species. The "Mitochondrial Eve" is the first human female that gave rise to all humans. In theory, we can trace all humans back to her through our mitochondrial N. Slide 102 / Which organelle converts food energy into chemical energy that the cell can use? Slide 102 (nswer) / Which organelle converts food energy into chemical energy that the cell can use? hloroplast hloroplast Mitochondrion Golgi Mitochondrion Golgi nswer Slide 103 / Which organelle converts solar energy into chemical energy in plants and other photosynthetic organisms? Slide 103 (nswer) / Which organelle converts solar energy into chemical energy in plants and other photosynthetic organisms? hloroplast hloroplast Mitochondrion Golgi Mitochondrion Golgi nswer

24 Slide 104 / Which of the following is not true of mitochondria and chloroplasts? They are present in all eukaryotic cells They have their own N They have their own ribosomes They are surrounded by a double membrane Slide 104 (nswer) / Which of the following is not true of mitochondria and chloroplasts? They are present in all eukaryotic cells They have their own N They have their own ribosomes They are surrounded by a double membrane nswer Slide 105 / Which of the following does NOT provide evidence for the endosymbiotic theory? Slide 105 (nswer) / Which of the following does NOT provide evidence for the endosymbiotic theory? Mitochondria and chloroplasts both have their own N. Mitochondria and chloroplasts both have their own N. Mitochondria and chloroplasts both come from pre-existing mitochondria and chloroplasts. Mitochondria and chloroplasts both come from pre-existing mitochondria and chloroplasts. The N of mitochondria and chloroplasts resembles the N found in nuclei. The N of mitochondria and chloroplasts resembles that of bacteria. The N of mitochondria and chloroplasts resembles the N found in nuclei. The N of mitochondria and chloroplasts resembles that of bacteria. nswer Slide 106 / 192 Slide 107 / 192 Vacuoles Vacuoles are membranous sacs and they come in different shapes and sizes and have a variety of functions. entral Vacuole entral Vacuoles entral Vacuoles in plants store water. bsorbing water makes a plant cell more turgid, or having more pressure inside - leading to strength and rigidity. entral vacuoles that are full will take over most of the cytoplasm and literally push the organelles to the sides of the cell. It can also store vital chemicals, pigments and waste products. PLNT ELL PROTIST

25 Slide 108 / 192 Turgor Pressure Increased turgor pressure results from the central vacuole being full with water. It presses out on the cell membrane which then presses out on the cell wall. The plant cell will not explode or lose its shape like an animal cell would in a hypotonic environment. ontractile vacuoles can be found in certain single-celled protists. These act as a pump to expel excess water from the cell. This is especially helpful to those organisms living in a freshwater environment to keep the cell from exploding. Slide 109 / 192 ontractile Vacuoles When the turgor pressure decreases the cell is limp and droopy. This is associated with wilted, limp lettuce, as well as droopy flowers. Food Vacuoles are mainly found in protists. The protist ingests food particles. The particles then fuse with a lysosome. The lysosome contains hydrolytic enzymes that break the food down. Slide 110 / 192 Food Vacuoles Paramecium fed dyed food showing vacuoles. Slide 111 / n organelle found in plant cells that stores water as well as other important substances is called the. Lysosome ontractile Vacuole entral Vacuole Golgi bodies Slide 111 (nswer) / n organelle found in plant cells that stores water as well as other important substances is called the. Slide 112 / Food vacuoles are primarily found in which organisms? Plants Lysosome ontractile Vacuole entral Vacuole Golgi bodies nswer nimals Protists acteria

26 Slide 112 (nswer) / Food vacuoles are primarily found in which organisms? Slide 113 / 192 ytoskeleton Plants nimals Protists acteria nswer ytoskeleton is a network of fibers within the cytoplasm. Three types of fibers collectively make up the cytoskeleton: Microfilaments Intermediate filaments Microtubules These fibers provide structural support and are also involved in various types of cell movement and motility. Slide 114 / ells can be described as having a cytoskeleton of internal structures that contribute to the shape, organization, and movement of the cell. ll of the following are part of the cytoskeleton except Slide 114 (nswer) / ells can be described as having a cytoskeleton of internal structures that contribute to the shape, organization, and movement of the cell. ll of the following are part of the cytoskeleton except the nuclear envelope. the nuclear envelope. microtubules. microtubules. microfilaments. intermediate filaments. microfilaments. nswer intermediate filaments. Slide 115 / Which of the following is not a known function of the cytoskeleton? Slide 115 (nswer) / Which of the following is not a known function of the cytoskeleton? to maintain a critical limit on cell size to maintain a critical limit on cell size to provide mechanical support to the cell to maintain the characteristic shape of the cell nswer to provide mechanical support to the cell to maintain the characteristic shape of the cell to hold mitochondria and other organelles in place within the cytosol to hold mitochondria and other organelles in place within the cytosol

27 Slide 116 / 192 ell Wall The cell wall is an outer layer in addition to the plasma membrane, found in fungi, algae, and plant cells. The composition of the cell wall varies among species and even between cells in the same individual. ll cell walls have carbohydrate fibers embedded in a stiff matrix of proteins and other carbohydrates. Plant cell walls are made of the polysaccharide cellulose. Fungal cell walls are made of the polysaccharide chitin. Slide 117 / 192 Extracellular Matrix The cells of many multi-cellular animals are surround by a extracellular matrix (EM). The EM provides structural support to the cells in addition to providing various other functions such as anchorage, cellular healing, separating tissues from one another and regulating cellular communication. The EM is primarily composed of an interlocking mesh of proteins and carbohydrates. Slide 118 / 192 Plant vs. nimal ell Organelles Slide 119 / 192 Organelles in nimal and Plant ells Only Plant oth Only nimal lick here to review the similarities and difference between plant and animal cells mitochondria golgi apparatus smooth ER central vacuole cell wall rough ER ribosomes lysosomes plasma nucleus membrane chloroplasts Slide 120 / 192 Slide 121 / 192 Viruses Viruses virus is a small infectious agent that can replicate only inside the living cells of an organism. Viruses can infect all types of organisms, though they are not organisms themselves. Return to Table of ontents Viruses are particles that are considered non-living because they cannot perform all the functions of living things. However, they share the same genetic code and use the mechanism of host cells to reproduce. bacterial phage virus

28 Slide 122 / 192 Viruses In biology viruses are important because their genetic and reproductive strategies use the same molecular components but their use is unique. Scientists have learned a lot about genetics by understanding their strategies. In addition, their infectious nature makes them a threat that requires humans to understand how they work to create defensive technology. Slide 123 / 192 Viruses The general mode of operation for all viruses is to Infect a host cell with its genetic information Hijack the molecular machinery of the host cell to manufacture the parts needed to build more viruses Package the parts together to form new viruses for release from the host cell Human immunodeficiency virus (HIV) attacking a human lymphocyte cell This E. coli cell has been attacked by bacteriophage viruses and they have injected their genetic material into the bacterial cell Slide 124 / 192 Slide 125 / 192 Viral Reproductive ycles Viruses are obligate intracellular parasites, which means they can reproduce only within a host cell. Each virus has a host range; it is limited by type of host cells that it can infect. Viruses use enzymes, ribosomes, and other parts of the host cell to synthesize new viruses. Lytic ycle The lytic cycle is a viral reproduction that causes the death of the host cell. The lytic cycle produces new phages and digests the host s cell wall, thereby releasing the new viruses. These cells have been broken open by the lytic cycle of a virus Slide 126 / 192 The Lytic ycle of a Phage Slide 127 / 192 Lysogenic ycle Unlike the lytic cycle which is detrimental to the host cell, the lysogenic cycle does not cause the cell to die. In the lysogenic cycle, the viruses N is incorporated into the host's N. Then the bacteria cell continues to replicate through binary fission, copying the viruses N and its own together. step 1

29 Slide 128 / 192 Temperate Phages Many viruses are only able to utilize the lytic cycle. Some viruses, called temperate phages, can utilize both the lytic and lysogenic cycles. When a temperate phage switches from the lysogenic cycle to the lytic cycle, it separates its phage N from the host N and then proceeds through the steps of the lytic cycle as usual. Slide 129 / Viruses are not considered living things. Why? They do not have ribosomes They do not contain nucleic acids They do not metabolize They are infectious However, sometimes when the virus N separate it takes with it some of the bacteria's N. Slide 129 (nswer) / Viruses are not considered living things. Why? They do not have ribosomes They do not contain nucleic acids They do not metabolize nswer They are infectious Slide 130 / The lytic cycle. The lysogenic cycle. results in death of the host cell; increases genetic variation in a population of cells occurs only in temperate viruses; incorporates the viral N with the host N is utilized by phages; is utilized by viruses creates full viral molecules; replicates only the viruses protein coat Slide 130 (nswer) / The lytic cycle. The lysogenic cycle. results in death of the host cell; increases genetic variation in a population of cells occurs only in temperate viruses; incorporates the viral N with the host N nswer is utilized by phages; is utilized by viruses creates full viral molecules; replicates only the viruses protein coat Slide 131 / 192 N Viruses Some viruses use N as their genetic material. It does not contain N polymerase, so in order for it to reproduce it must inject its N into a cell so that it can be copied by the host cell's polymerase. The bacteriophage example we have seen is a N virus.

30 Slide 132 / 192 RN Viruses n RN virus is a virus that has RN as its genetic material. This nucleic acid is usually single-stranded RN (ssrn), but may be double-stranded RN (dsrn). Some human diseases caused by RN viruses include SRS, influenza, hepatitis, West Nile fever, polio and measles. Slide 133 / 192 SRS Severe acute respiratory syndrome (SRS) is a viral respiratory disease in humans. n outbreak of SRS in Hong Kong nearly became a pandemic, with 8,273 cases and 775 deaths worldwide. Within weeks, SRS spread from Hong Kong to infect individuals in 37 countries in early They are enveloped RN viruses that are pathogens of mammals and birds. This group of viruses cause respiratory tract infections in a variety of animals, including humans Slide 134 / 192 Retro Viruses retrovirus is an RN virus that replicates in a host cell. First it uses its own reverse transcriptase enzyme to produce N from its RN genome, reverse of the usual pattern, thus retro. Slide 135 / 192 Retro Viruses These viruses are some of the most complex and believed to be the most advanced from an evolutionary perspective. For a virus, their entry system into cells is highly complex. They have systems to bypass the usual defenses of their host cell. HIV is a retro virus. This new N is then incorporated into the host's genome by an integrase enzyme. The cell then treats the viral N as part of its own instructions, which it follows blindly, making the proteins required to assemble new copies of the virus. Slide 136 / 192 HIV Slide 137 / 192 HIV continued...

31 Slide 138 / 192 HIV What makes HIV particularly dangerous is that it attacks the human immune system and fools it into treating it is part of the system. No immune attack is offered by the infected cells. The complex replication system is flawed and many errors are made as the virus replicates its genome. Why would this make treating with medicine difficult? Slide 139 / When a virus infects an E. coli cell, what part of the virus enters the bacterial cytoplasm? the entire virus the nucleic acid the protein capsid and enclosed nucleic acid the tail fibers Each patient has many unique variations of the virus in their system. treatment that may destroy one version will not destroy the others. In addition any attack on the virus must also be an atack on the immune system. Slide 139 (nswer) / When a virus infects an E. coli cell, what part of the virus enters the bacterial cytoplasm? the entire virus the nucleic acid the protein capsid and enclosed nucleic acid the tail fibers nswer Slide 140 / RN viruses mutate more rapidly than N viruses, making them more difficult to prevent. Which of the following is a likely cause of this rapid mutation rate? N viruses contain their own polymerase enzymes, while RN viruses hijacked cellular machinery RN can be more rapidly copied than N oth single and double stranded RN molecules can be present in a RN virus N is structurally more stable than RN Slide 140 (nswer) / 192 Slide 141 / RN viruses mutate more rapidly than N viruses, making them more difficult to prevent. Which of the following is a likely cause of this rapid mutation rate? N viruses contain their own polymerase enzymes, while RN viruses hijacked cellular machinery RN can be more rapidly copied than N nswer oth single and double stranded RN molecules can be present in a RN virus 46 Which of the following correctly outlines the steps of a retroviral infection? RN insertion - reverse transcription - integration into genome - gene expression RN insertion - integration in genome - gene expression RN insertion - gene expression - integration into genome RN insertion - integration in genome - reverse transcription N is structurally more stable than RN

32 Slide 141 (nswer) / 192 Slide 142 / Which of the following correctly outlines the steps of a retroviral infection? RN insertion - reverse transcription - integration into genome - gene expression RN insertion - integration in genome - gene expression RN insertion - gene expression - integration into genome RN insertion - integration in genome - reverse transcription nswer ellular efenses Return to Table of ontents Slide 143 / 192 Slide 144 / 192 ellular efenses ll organisms have defenses designed to prevent infection by viruses, bacteria, and other pathogens. Slide 145 / 192 Restriction Enzymes Restriction enzymes are now used by scientists to locate specific genes on a N molecules. N mixed with these enzymes is called digest a because the enzymes breaks down the fragments of N into many smaller pieces. It is important to remember that we are working with molecules. We cannot simply "grab" the piece of N we want. We must separate the unique pieces of N in the digest and select the fragment we want. This tube contains many different pieces of N Gene of interest is somewhere in here Slide 146 / 192 Gel Electrophoresis Gel electrophoresis is one way to separate N fragments based on length. The digest is loaded by pipet into a gel, that resembles Jello. The gel is a network of fibers called collagen. Small pieces of N can move through the gel quicker than the longer pieces that get tangled in the collagen fibers.

33 Slide 147 / 192 Gel Electrophoresis Slide 148 / 192 Virtual Lab N has a slightly negative charge. n electrical current is passed through the gel and the N fragments move to the positive charge. Small fragments move faster, larger fragments are slowed down by the matrix. 15k 10k start Gel electrophoresis virtual lab by the University of Utah The Gel Lab The result is that the small pieces can travel farther than the larger ones. The N is separated by size in what is know as a banding pattern. 5k Insulin gene Slide 149 / 192 nimal efenses nimals have multiple defenses against invaders. These are classified into two categories: innate immunity and acquired immunity. Innate immune defenses are generalized systems, preventing invasion by all pathogens. ll animals have some degree of innate immunity. cquired immune defenses are developed during the animal's lifetime and respond only to specific invaders, those that have been encountered previously. These defenses are only found in vertebrates. Slide 150 / 192 Innate Immunity The skin is a barrier defense with unique adaptation to protect the body. Symbiotic bacteria crowds the surface of the skin making it hard for unwelcome bacteria to find room. Thick layer of dead cells in the epidermis creates a physical barrier. Sweat glands secrete waxy substances that pathogenic microbes have a hard time adhering to. It also has a ph of less than 6 which hurts pathogenic microbes. The dermis provides distance and insulation between major vessels of the blood stream and the external environment. Extracellular fluid and fats fill this area. Slide 151 / 192 Innate Immunity Slide 152 / 192 Innate Immunity Where contact with the environment is necessary for the animal, skin cannot be used to block foreign contaminants. In these cases, another barrier defense the mucus membrane are used to stop pathogenic microbes from entering systems. Mucus cells secrete products that are rich in glycoproteins and water. It is a viscous fluid containing antiseptic enzymes that will breakdown bacterial and viral components. In mammals, this mucus serves to protect: respiratory cells, gastrointestinal (digestive) cells, urogenital (vaginal) cells, visual cells, and auditory systems. major function of this mucus is to protect against infectious agents such as fungi, bacteria, and viruses. The cells in an average human body produces about a quart of mucus per day. 1 quart

34 Slide 153 / Which of the following is not an example of the skin's defense system? Slide 153 (nswer) / Which of the following is not an example of the skin's defense system? Sweat glands Symbiotic bacteria Mucus ead skin cells Sweat glands Symbiotic bacteria Mucus ead skin cells nswer Slide 154 / 192 Innate Immunity Slide 155 / 192 Innate Immunity If a foreign invader makes it past the skin and mucous membrane, the body has specialized cells that can detect and respond. onsider a laceration (cut) on a part of your body. Immediately foreign cells are entering the break in your bodies barrier. Take a moment and describe to another person what happens in the few minutes after a cut. Make a list of your bodies responses. an you relate these symptoms to fighting infection? Slide 156 / 192 Inflammation Inflammation is a response triggered by bacteria that enters the skin. metabolic pathway is initiated by the presence of bacteria under the skin. splinter enters the skin Slide 157 / 192 Inflammation Skin Skin Extracellular fluid Mast ells Extracellular fluid Mast ells Nearby capilary Nearby capilary

35 acterial cells that were on the splinter enter the interstitial fluid. Slide 158 / 192 Inflammation Mast cells detect foreign proteins produced by the bacteria and a transduction pathway is triggered. The end result is that histamine is released from the mast cell. Slide 159 / 192 Inflammation Skin Skin Extracellular fluid Mast ells Extracellular fluid Mast ells Nearby capilary Nearby capilary Slide 160 / 192 Slide 161 / 192 Histamine acts as another signal molecule that causes the cells of the capillary to separate and blood plasma, red blood cells, and phagocytes spill into the area. Inflammation Inflammation ecause of the extra volume of fluid and cells the area becomes hot and swells. This is unfavorable conditions for the bacteria and they cannot reproduce or spread to new areas. Skin Extracellular fluid Phagocyte Skin Extracellular fluid Phagocyte Nearby capilary Nearby capilary Phagocytes are cells that eat foreign cells. They remove the bacteria, mast cells stop producing histamine and the inflammation is relieved. Skin Extracellular fluid Nearby capilary Slide 162 / 192 Inflammation Phagocyte lick here for an animation of inflammation Slide 163 / Which of the following best describes the response to bacteria entering under the surface of the skin? Mast cells produce histamine, swelling occurs, red blood cells and phagocytes enter the area, phagocytes eat the foreign cells Mast cells produce histamine, red blood cells and phagocytes enter the area, swelling occurs, phagocytes eat the foreign bacteria Histamine produces mast cells, phagocytes eat the mast cells, swelling occurs, new red blood cells enter the area Swelling occurs, mast cells produce histamine, red blood cells and phagocytes enter, phagocytes eat the foreign bacteria

36 Slide 163 (nswer) / 192 Slide 164 / Which of the following best describes the response to bacteria entering under the surface of the skin? Mast cells produce histamine, swelling occurs, red blood cells and phagocytes enter the area, phagocytes eat the foreign cells nswer Mast cells produce histamine, red blood cells and phagocytes enter the area, swelling occurs, phagocytes eat the foreign bacteria Histamine produces mast cells, phagocytes eat the mast cells, swelling occurs, new red blood cells enter the area 49 Inflammation is an example of innate immunity an example of acquired immunity a response to the presence of phagocytes a buildup of fluids in the mucus membranes Swelling occurs, mast cells produce histamine, red blood cells and phagocytes enter, phagocytes eat the foreign bacteria Slide 164 (nswer) / Inflammation is an example of innate immunity an example of acquired immunity nswer a response to the presence of phagocytes a buildup of fluids in the mucus membranes Slide 165 / 192 Specific Immunity The specific immunity of vertebrates includes two types of response: Humoral: ttacking pathogens in the extracellular matrix, prior to entering a body cell ell-mediated: estroying body cells that have been infected by pathogens or have become cancerous. oth responses are derived from white blood cells known as lymphocytes. Slide 166 / 192 The Humoral Response ll pathogenic invaders have antigens, proteins that induce the release of antibodies because they are recognized as foreign to the organism being invaded. ntibodies are molecular flags that stick to the antigen and mark them for destruction by the immune system. Slide 167 / 192 The Humoral Response The lymph system is responsible for the humoral immune response. This system is a series of vessels that filter and transport lymph, interstitial fluid that has been collected through lymph capillaries, throughout the organism. This bacterial cell has many surface proteins that the mammalian immune system will recognize as non-self proteins. ny of them could act as an antigen. If an invading microbe makes it past the innate immunity defenses, it will then be in the interstitial fluid and enter the lymph system.

37 Slide 168 / 192 Slide 168 (nswer) / ntigens are introduced by pathogens produced by mammals serve as flags for the immune system to destroy another word for antibodies 50 ntigens are introduced by pathogens produced by mammals serve as flags for the immune system to destroy another word for antibodies nswer Slide 169 / Lymph nodes are the oval-shaped organs of the lymph system. Which of the following is not true regarding lymph nodes? Slide 169 (nswer) / Lymph nodes are the oval-shaped organs of the lymph system. Which of the following is not true regarding lymph nodes? They are involved in specific immunity They contain numerous lymphocytes They filter blood Swelling of the lymph nodes indicates infection They are involved in specific immunity They contain numerous lymphocytes nswer They filter blood Swelling of the lymph nodes indicates infection Slide 170 / 192 The Humoral Response Inside the lymph nodes of the lymph system many leukocytes (white blood cells) known as cells lay dormant until they are activated by a specific antigen. Slide 171 / 192 The Humoral Response ntibodies, also know as immunoglobulins, bind with the antigen to make the pathogen highly "visible" to phagocytes and restrict the movement of the pathogen. cross section of a lymph node magnified 100x. The small dots are millions of cells. Each is slightly different than the others and will only be activated in the presence of a specific antigen. phagocyte

38 Slide 172 / 192 The Humoral Response Slide 173 / 192 The Humoral Response lonal selection is the process by which the humoral response to a specific pathogen is activated. Watch the below video and see if you can identify the antigen. lick here for an animation of clonal selection Once a specific cell is activated is remains active for the life of the organism. If the same invader ever enters the organism again it will be immediately tagged and destroyed. This is know as immune memory. The second exposure will be quickly handled by the immune system because many cells and antibodies are already circulating through the body. Slide 174 / 192 ell-mediated Response Slide 175 / 192 ell-mediated Response The last line of defense in the immune system. Once the invading pathogen has infiltrated the cells of the vertebrate, the only way to get rid of the invader is to destroy the host cell. The pathogen gains access to the cell by penetrating its membrane. ell Slide 176 / 192 ell-mediated Response Slide 177 / 192 ell-mediated Response Once inside the cell the invader begins to replicate and disrupt the cells normal function. The disruption activates special molecules designed to alert the nucleus to a problem. They start a transcription pathway and a transcription factor is produced. Transcription Factor ell ell

39 Slide 178 / 192 ell-mediated Response Slide 179 / 192 ell-mediated Response The transcription factor activates a gene that produces a membrane protein that will act as a flag to alert immune system cells that it is infected This cell is now a dendritic cell or antigen presenting cell. special leukocyte known as a helper T cell attaches to the antigens of the damaged cell. Transcription Factor Transcription Factor ell Slide 180 / 192 ell-mediated Response ell Slide 181 / 192 ell-mediated Response The helper T cell activates and releases cytokines, free floating proteins that communicate with other cells of the immune system, into the surrounding fluids. The cytokines do 2 things: They alert cells to activate humoral defenses; and they bring cytotoxic T cells that inject hydrolytic enzymes into the diseased cell. Transcription Factor Transcription Factor ell Slide 182 / 192 ell-mediated Response The diseased cell and its invaders are eliminated. ell Slide 183 / The end result of the cell mediated response is that the the T cells are destroyed the pathogen is destroyed diseased cell is destroyed diseased cell and the pathogen is destroyed Transcription Factor ell

40 Slide 183 (nswer) / The end result of the cell mediated response is that the the T cells are destroyed the pathogen is destroyed diseased cell is destroyed diseased cell and the pathogen is destroyed Slide 184 / n immune memory response is created through Humoral response ell-mediated response nswer Slide 184 (nswer) / n immune memory response is created through Humoral response ell-mediated response Slide 185 / 192 Plant Immunity acteria and viruses are as much a threat to the homeostasis of plants as they are to animals. For this reason plants must also protect themselves and be able to fight foreign pathogens. nswer Plants only have generalized defenses against pathogens. They do not have specific immunity. Much like invertebrates, the evolution of plants came long before specific immunity evolution on the tree of life. Slide 186 / 192 arrier efenses s with animals, the first line of defense against pathogens is the outer covering. Plants have varying levels of external defenses that can include waxy coatings, sticky excretions, thick cuticles and others. Slide 187 / 192 Plant Immunity Since plants have slow moving circulation systems (or no circulation at all), if a pathogen gets past the external covering individual cells are on their own to defend themselves. These spongy mesophyll cells each have an internal defense system that is triggered when contacted by a pathogen.