Prokaryotes and Eukaryotes prokaryotes Eukaryotes eukaryote Eukaryotes The Biological Nucleus Organelles Biological Nucleus biological nucleus

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1 Slide 1 / 113 Slide 2 / 113 Prokaryotes and Eukaryotes Eukaryotes prokaryotes: pro: before karyon: kernel/seed (nucleus) eukaryote: eu: true karyon: kernel/seed (nucleus) So prokaryote = "before a nucleus" nd eukaryote = "true nucleus" Slide 3 / 113 Eukaryotes eukaryotic cell contains a true nucleus, as well as other membrane bound "organelles" (parts of a cell). Organelles Slide 4 / 113 The iological Nucleus The nucleus from chemistry with protons and neutrons is not the same nucleus involved with cells. iological Nucleus ut what is a nucleus? Where did these "organelles" come from? Nucleus The biological nucleus is usually, but not always, in the center of a cell and it is sometimes referred to as the "control center" of the cell. We will come back to this in a little bit when we start looking at all of these cell parts to see what they do. For now, just know that in a eukaryotic cell, most of the cell's N is found in the nucleus. Slide 5 / 113 Slide 6 / ells that contain a "true nucleus" and other membrane bound organelles are. ll ells archaea. bacteria. eukaryotes. prokaryotes. One key difference between prokaryotic and eukaryotic cells is that eukaryotic cells are partitioned into functional compartments called organelles. ll eukaryotic cells, whether they belong to animals, plants, fungi, or protists are fundamentally similar to one another and very different from prokaryotic cells. t the end of this chapter we will discuss how eukaryotes are thought to have evolved from prokaryotes!

2 Slide 7 / 113 ll ells Slide 8 / 113 Review of Prokaryotic Structure re surrounded by a plasma membrane (or cell membrane). ontain a semifluid substance called the cytosol/cytoplasm. ontain structures called chromosomes, which carry the cell's genes. Have ribosomes, which assemble amino acids into proteins. Slide 9 / 113 Eukaryotes are different because... Eukaryotic cells have their chromosomes (structures in which their N is configured) in a nucleus that is bound by a membranous nuclear envelope. Eukaryotic cells have many membrane-bound organelles. Slide 10 / Which of the following are prokaryotic cells? Plants Fungi acteria nimals Eukaryotic cells are generally much larger than prokaryotic cells. Even still, the logistics of carrying out cellular metabolism sets limits on the size of cells. Slide 11 / 113 Slide 12 / Which is NOT a basic feature of all cells? 4 Where is the N of a prokaryote found? ll cells are surrounded by a plasma membrane. l cells contain a semifluid substance called the cytoplasm. ll cells contain structures called chromosomes, which are cont the nucleus. ll cells have ribosomes. Nucleus Nucleolus Nucleoid region Mitochondria

3 Slide 13 / 113 iversity of eukaryotes Slide 14 / 113 iversity of Eukaryotes Eukaryotes range from single-celled Protists to 100-meter tall redwood trees. 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. 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. Slide 15 / 113 Surface rea to Volume Ratio Slide 16 / 113 Smaller ell = More efficient metabolism? t the time when prokaryotic cells were evolving, there were most likely different sizes of cells. The smaller cells were more efficient than larger ones. They had an increased surface area to volume ratio. This meant that the small cell had lots of cell membrane (therefore lots of surface area) to service the smaller volume inside the cell. The smaller cell could get substances it needed in faster and get waste out faster because the substances only needed to travel a short distance from anywhere inside the cell to the cell membrane and vice versa. Smaller cells are able to have a more efficient metabolism compared to the larger cells. These smaller cells out-competed the larger ones and were able to pass this small size to their offspring. So, if it is good for a cell to be small, why didn't cells evolve to be even smaller than they are? Slide 17 / 113 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 fit the parts of the cell inside. most efficient Limits of ell Size least efficient Slide 18 / 113 Eukaryotic vs. Prokaryotic ells Eukaryotic cells are, on average, much larger than prokaryotic cells. The average diameter of most prokaryotic cells is between 1 and 10µ. y contrast, most eukaryotic cells are between 5 to 100µ in diameter. nimal ell (Eukaryote) 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. acterium (Prokaryote)

4 Slide 19 / 113 Eukaryotic vs. Prokaryotic ells Slide 20 / 113 Eukaryotic vs. Prokaryotic ells What could have been a potential problem as these first cells began to grow in diameter? Hint: think of the cell's energy and nutritional requirements iffusion allows nutrients and other molecules, such as TP, to get to where they are needed in a prokaryote. Prokaryotes are small enough for diffusion to be an effective transport mechanism. In fact, the size of these cells is probably limited by the distance that molecules need to travel inside the cell. Eukaryotes are much larger. Slide 21 / 113 Eukaryotic vs. Prokaryotic ells Slide 22 / 113 Eukaryotic Problem of iffusion The problem for larger cells is that ions and small molecules (TP, amino acids, nucleotides, etc.) cannot diffuse quickly across a large volume. If they are needed to go the other side of a cell, it could take a long time to get there. This would be detrimental to the cell. Eukaryotic cells are comprised of many bacterium-sized parts known as organelles. Organelles subdivide the cell into specialized compartments. The advantage of this is the molecules required for specific chemical reactions are often located within a certain compartment and do not need to diffuse long distances to be useful. Slide 23 / 113 Main dvantage for ompartmentalization Separating incompatible chemical reactions increases their efficiency by keeping substrates and their enzymes in close proximity. Each compartment or organelle can specialize at what it does. iffusion of nutrients and substances is easier in a larger cell because substances needed to perform reactions (like reactants and enzymes) within the organelle either travel a short distance from another organelle or are stored in the organelle itself. Slide 24 / How did eukaryotes solve the problem of diffusion? y remaining the same size as prokaryotes. y using a nucleus. ompartmentalization. They haven't solved the problem. This is why compartmentalization in the eukaryote makes this type of cell very efficient, despite its larger size.

5 Slide 25 / Which is NOT an advantage of compartmentalization? It allows incomaptible 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 26 / 113 Organelles Organelles making up Eukaryotic cells include: Nucleus Lysosomes Ribosomes Peroxisomes Rough ER Vacuoles Smooth ER hloroplasts Golgi pparatus Mitochondria Slide 27 / 113 ell Fractionation Using a technique known as cell fractionation, the cell components can be separated and each organelle can be studied individually. ell Fractionation involves splitting cells open in a test tube and getting the organelles to spill out. When put in a centrifuge, the different organelles will then settle out and make layers according to their size and weight. The heaviest settle to the bottom of the test tube. Slide 28 / 113 Nucleus The nucleus contains a blueprint for all of the functions necessary for that cell's survival. The nucleus contains N, the genetic material of the cell. The "directions" are in the N's genes. Genes are configured into structures called chromosomes. The nucleus controls the cell's activities by directing protein synthesis from N. Slide 29 / 113 Inside the Nucleus Slide 30 / 113 Prokaryotic Nucleoid 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. 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. Unlike the eukaryotic cell, the prokaryotic cell has a nucleoid where the genetic material is found that is without a nuclear membrane. Recall that the prokaryote genetic material is double-stranded and circular. Eukaryotic genetic material is usually found in the form of chromatin, a tightly coiled mass of N and associated proteins.

6 Slide 31 / Main Functions of the Nucleus Slide 32 / How does the nucleus control the activities 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). y making N. y directing protein synthesis. y allowing N to leave the nucleus to make proteins. y sending instructions to the mitochondria. Slide 33 / What is the importance of nuclear pores? Slide 34 / 113 Ribosomes They allow the nucleus to communicate with other parts of the cell. They allow N to leave the nucleus in order to direct protein synthesis. They allow RN to leave the nucleus and become functional in the cytoplasm. They allow single stranded N molecules to enter the nucleus and assemble into the double helix. 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 are needed to be made. Small subunit Large subunit Slide 35 / 113 Ribosomes Slide 36 / Where are ribosomal subunits made in the cell? 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 ytoplasm Nucleus Nucleolus On the Plasma membrane

7 Slide 37 / What do ribosomes consist of? Slide 38 / 113 The Endomembrane System proteins and N proteins and rrn proteins only N only The endomembrane system is exclusive to eukaryotic cells only. Several organelles, some made up mainly of membranes, form a type of assembly line in the cell. They make a product, then process and ship it to its final destination whether that be inside or outside the cell. Organelles included in this system include the nucleus, rough and smooth ER, golgi, and lysosomes. ollectively, we refer to them as the endomembrane system. Note: The nuclear envelope and plasma membrane also are considered part of this system Slide 39 / 113 The Endomembrane System Slide 40 / Which of following are parts of the endomembrane system? (more than one answer) smooth ER rough ER nucleus lysosome Slide 41 / The endomembrane system serves to Slide 42 / 113 Endoplasmic Reticulum ship cell products to places in and out of the cell assemble N give directions to other organelles create pathways for organelles to travel The Endoplasmic reticulum is a network within the cytoplasm (reticulum comes from the latin word for little net). This organelle is a series of membrane-bound sacs and tubules. It is continuous with the outer membrane of the nuclear envelope. There are two types of Endoplasmic Reticulum: Rough and Smooth

8 Slide 43 / 113 Rough and Smooth Endoplasmic Reticulum Slide 44 / 113 Rough and Smooth Endoplasmic Reticulum Slide 45 / 113 Smooth Endoplasmic Reticulum Slide 46 / 113 Rough Endoplasmic Reticulum This type of E.R. 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 E.R. Rough E.R. 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 E.R. where they are folded and processed. Slide 47 / 113 Rough Endoplasmic Reticulum 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. Most secretory proteins have glycoproteins. When the molecule is ready to be exported out of the E.R., it gets packaged into a transport vesicle. This vesicle is made of membranes from the E.R. itself. The transport vesicle travels to another organelle known as the Golgi apparatus. Slide 48 / 113 Insulin - a product of the Rough Endoplasmic Reticulum 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 made in the rough E.R. because it is a secretory protein. Specifically, it is secreted out of the pancreas cells into the blood stream.

9 Slide 49 / Which organelle is involved in making proteins? Smooth E.R. Ribosomes N Nuclear membrane Slide 50 / What determines if we classify endoplasmic reticulum as smooth or rough? presence or absence of nuclear pores presence or absence of genetic material presence or absence of ribosomes presence of absence of N Slide 51 / Where in the cell are lipids made? Nucleus Ribosomes Rough endoplasmic reticulum Smooth endoplasmic reticulum 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 52 / 113 Golgi pparatus Slide 53 / 113 Golgi pparatus The Golgi is located near the cell membrane. The Golgi works closely with the E.R. of a cell. It receives and modifies substances manufactured by the E.R. 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 54 / 113 The Golgi pparatus & the E.R. The Golgi receives transport vesicles that bud off from the E.R. 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 click

10 Slide 55 / difference between the Golgi pparatus and the E.R. is that The ER takes the vesicles from the Golgi to transport 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 Slide 56 / Which organelle receives and modifies substances from the endoplasmic reticulum? Nucleus Ribosomes Lysosomes Golgi odies s the name suggests, 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). Slide 57 / 113 Lysosomes Slide 58 / 113 Lysosomes Lysosomes may fuse with vacuoles containing food particles and then the enzymes digest the food, releasing nutrients into the cell. Protists do this. amaged organelles 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. Slide 59 / 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 60 / Which organelle contains hydrolytic enzymes that break down other substances? Endoplasmic Reticulum Golgi odies Lysosomes Vacuoles

11 Slide 61 / 113 Peroxisomes peroxisome is a specific lysosome that forms and breaks down hydrogen peroxide (H 2 O 2 ) 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. PLNT ELL Slide 62 / 113 Vacuoles Vacuoles are also membranous sacs and they come in different shapes and sizes and have a variety of functions. entral Vacuole PROTIST Important note: Peroxisomes are not part of the endomembrane system. Slide 63 / 113 Types of Vacuoles entral Vacuole ontractile vacuoles Food Vacuoles Slide 64 / 113 entral Vacuoles entral Vacuole in plants stores 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. Slide 65 / 113 Increased 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. Slide 66 / 113 ecreased Turgor Pressure ecreased turgor pressure results when the central vacuole is not full with water. The central vacuole pulls away from the cell membrane which pulls away from the cell wall. "Turgid" cells are synonomous with fresh fruits and veggies. The plant cell will not explode or lose its shape like an animal cell would in a hypotonic environment. When this happens the cell is limp and droopy. This is associated with wilted, limp lettuce, as well as droopy flowers. However, the plant cell will not lose its shape. Only the central vacuole shrinks.

12 ontractile vacuoles can be found in certain single-celled organisms. 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 67 / 113 ontractile Vacuoles 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 68 / 113 Food Vacuoles Paramecium fed dyed food showing vacuoles. Slide 69 / 113 Slide 70 / n organelle found in plant cells that stores water as well as other important substances is called the. 21 Food vacuoles are primarily found in which organisms? Plants Lysosome ontractile Vacuole entral Vacuole nimals Protists acteria Golgi bodies Slide 71 / 113 Energy-onverting Organelles hloroplasts reside in plant cells only and convert solar radiation into energy stored in the cell for later use. Mitochondria reside in plant and animal 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. These organelles convert solar energy to chemical energy through photosynthesis. hloroplasts are partitioned into three major compartments by internal membranes. Slide 72 / 113 hloroplasts Remember that during photosynthesis it is on the thylakoid that the Light ependant Reactions take place. In prokaryotes, thylakoids are areas of highly folded membranes.in eukaryotes, they are stacked in the chloroplasts. eukaryotic chloroplast

13 Slide 73 / 113 Mitochondria 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. The mitochondrion only has two compartments as opposed to three in the chloroplast. Slide 74 / 113 Mitochondria and Respiration 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. Slide 75 / 113 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). Slide 76 / Which organelle converts solar energy into chemical energy in plants and other photosynthetic organisms? Nucleus hloroplast Mitochondrion 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. Golgi Slide 77 / Which organelle converts food energy into chemical energy that the cell can use? Nucleus hloroplast Mitochondrion Golgi ytoskeleton is a network of fibers within the cytoplasm. Three types of fibers collectively make up the cytoskeleton: Microfilaments Intermediate filaments Microtubules Slide 78 / 113 ytoskeleton These fibers provide structural support and are also involved in various types of cell movement and motility.

14 Slide 79 / 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 80 / Which of the following is not a known function of the cytoskeleton? the nuclear envelope. microtubules. microfilaments. intermediate filaments. to maintain a critical limit on cell size 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 Slide 81 / 113 Slide 82 / 113 Plasma Membrane Remember the plasma membrane is a phospholipid bilayer with proteins and other molecules interspersed throughout. 26 Which of the following statements about the role of phospholipids in forming membranes is correct? they are completely insoluble in water The 3 main functions of the plasma membrane: Selective Permeability Protection Structural support 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 / 113 Slide 84 / 113 Large Molecules and the Plasma Membrane ut what if the substance that needs to pass through the cell membrane is too big for a protein carrier or intregal protein? 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. 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. This process is known as exocytosis. The vesicle will become part of the cell membrane Exocytosis Exocytosis The proteins the cell makes are too large to diffuse through the phospholipid bilayer. This is how secretory proteins from the Golgi exit the cell. This is true for insulin in the pancreas.

15 Slide 85 / 113 Endocytosis Slide 86 / 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 Slide 87 / Types of Endocytosis Slide 88 / The process by which a cell ingests large solid particles, therefore 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 89 / Protein coated vesicles move through the plasma membrane via this process: Slide 90 / 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 another vesicle Pinocytosis the extracellular fluid

16 Passive transport is the movement of substances from an area of high concentration to an area of low concentration without the requirement an energy input. Types include diffusion, osmosis, and facilitated diffusion. Slide 91 / 113 Membrane Transport - review Passive Transport ctive Transport (REQUIRES ENERGY) Slide 92 / 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 ctive transport is the movement of substances from an area of low concentration to an area of high concentration and requires an input of energy. Slide 93 / Which of the following processes includes all others? passive transport facilitated diffusion diffusion of a solute across a membrane osmosis Slide 94 / 113 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 95 / 113 Outside the Plasma Membrane - Extracellular Matrix The extracellular matrix (EM) found surrounding cells provides structural support to eukaryotic 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 96 / 113 ell Surfaces and Junctions ell surfaces protect, support, and join cells. ells interact with their environments and each other via their surfaces. ells need to pass water, nutrients, hormones, and many, many more substances to one another. The way that cells that are adjacent to one another communicate and pass substances to one another are called ell Junctions. nimal and plant cells have different types of cell junctions. This is mainly because plants have cell walls and animal cells do not.

17 Slide 97 / 113 Junctions specific to plant cells Plant cells are supported by rigid cell walls made largely of cellulose. They connect by plasmodesmata which are channels that allow them to share water, food, and chemical messages. Slide 98 / 113 nimal ell Junctions Tight junctions dhering junctions ommunicating (Gap) junctions Slide 99 / 113 Tight Junctions Slide 100 / 113 dhering Junctions Tight junctions can bind cells together into leakproof sheets Example: the cells of the lining of the stomach or any epithelial lining where leaking of substances is not good. tight junction dhering junctions fasten cells together into strong sheets. They are somewhat leakproof. Example: actin is held together in muscle. Slide 101 / 113 ommunicating (Gap) Junctions Gap junctions allow substances to flow from cell to cell. They are totally leaky. They are the equivalent of plasmadesmata in plants. Slide 102 / 113 Organelles in nimal and Plant ells Only Plant oth Only nimal Example: important in embryonic development. Nutrients like sugars, amino acids, ions, and other molecules pass through. mitochondria golgi apparatus smooth ER central vacuole cell wall rough ER ribosomes lysosomes plasma nucleus membrane chloroplasts

18 Slide 103 / 113 Endosymbiotic Theory Slide 104 / 113 Endosymbiotic Theory The endosymbiotic theory states that eukaryotic cells arose as a result of a symbiotic relationship between different prokaryotic cells. This idea has been best explained by the "Theory of Endosymbiosis" by Lynn Margulis in She used 2 very special eukaryotic organelles to explain: the mitochondria the chloroplast Slide 105 / 113 The Evolution of Eukaryotes Remember how we said the mitochondria and chloroplast are different from other eukarytoic organelles because they have their own N, their own ribosomes, and have a double cell membrane. Using these facts, she explained 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 make its own food. Slide 106 / 113 The Evolution of Eukaryotes When they got taken up by another prokaryote, they dragged the one prokaryote's cell membrane around theirs, thus the double cell membrane. This now allowed the "new" eukaryote to make its own TP or be able to do photosynthesis and make its own food. Thus the evolution of eukaryotes. The nucleus and flagella could also have the same possible roots although they are not as heavily supported with evidence as the mitochondria and chloroplast. Slide 107 / 113 Endosymbiosis Slide 108 / 113 Evidence for Symbiosis oth mitochondria and chloroplasts can arise only from preexisting mitochondria and chloroplasts. They cannot be formed in a cell that lacks them. oth mitochondria and chloroplasts have their own N and it resembles the N of bacteria not the N found in the nucleus. oth mitochondrial and chloroplast genomes consist of a single circular molecule of N, just like in prokaryotes. oth mitochondria and chloroplasts have their own proteinsynthesizing machinery, and it more closely resembles that of bacteria than that found in the cytoplasm of eukaryotes.

19 Slide 109 / 113 Evidence for Symbiosis oth mitochondria and chloroplasts can arise only from preexisting mitochondria and chloroplasts. They cannot be formed in a cell that lacks them. oth mitochondria and chloroplasts have their own N and it resembles the N of bacteria not the N found in the nucleus. oth mitochondrial and chloroplast genomes consist of a single circular molecule of N, just like in prokaryotes. oth mitochondria and chloroplasts have their own proteinsynthesizing machinery, and it more closely resembles that of bacteria than that found in the cytoplasm of eukaryotes. Slide 110 / 113 Evidence for Symbiosis oth mitochondria and chloroplasts can arise only from preexisting mitochondria and chloroplasts. They cannot be formed in a cell that lacks them. oth mitochondria and chloroplasts have their own N and it resembles the N of bacteria not the N found in the nucleus. oth mitochondrial and chloroplast genomes consist of a single circular molecule of N, just like in prokaryotes. oth mitochondria and chloroplasts have their own proteinsynthesizing machinery, and it more closely resembles that of bacteria than that found in the cytoplasm of eukaryotes. Slide 111 / 113 Evidence for Symbiosis oth mitochondria and chloroplasts can arise only from preexisting mitochondria and chloroplasts. They cannot be formed in a cell that lacks them. oth mitochondria and chloroplasts have their own N and it resembles the N of bacteria not the N found in the nucleus. oth mitochondrial and chloroplast genomes consist of a single circular molecule of N, just like in prokaryotes. oth mitochondria and chloroplasts have their own proteinsynthesizing machinery, and it more closely resembles that of bacteria than that found in the cytoplasm of eukaryotes. Slide 112 / Which of the following does NOT provide evidence for the endosymbiotic theory? Mitochondria and chloroplasts both have their own N. 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. Slide 113 / 113 Plant and nimal ell Organelle Review