What is a cell? Cells. Stephanie Elkowitz

Transcription

1 This PowerPoint explains and reports important concepts students should learn and master in a Life Science unit. The ideas presented should be understood by upper elementary and middle school student according to most state science standards as well as Next Generation Science Standards (NGSS). The concepts covered in this PowerPoint, as well as related activities and materials, are appropriate for upper elementary and middle school science classrooms. Concepts are differentiated by a colored shape code: Slides with a green circle deal with basic key ideas and understandings meant for upper elementary (grade 3-5) students. These concepts can or should be reviewed with intermediate/middle school (grade 6-8) students. Slides with a blue square deal with intermediate key ideas and understandings meant for middle school students. These concepts may be appropriate for high-achieving upper elementary students. According to NGSS, some of the traditionally intermediate level concepts are now recognized as upper elementary concepts. Slides with a black diamond cover advanced concepts. Some of these concepts may be appropriate for your intermediate students. Sometimes it helps students better understand the how and why of intermediate concepts if they are introduced to advanced concepts. This PowerPoint is meant to help students gain a first-order learning of Life Science concepts. Students should be able to remember and understand the information presented. Additional activities available for purchase at my store will help students apply, analyze, create and synthesize knowledge important to a complete unit covering these concepts. 1

2 Cell Theory Unicellular vs. Multicellular Prokaryotes & Eukaryotes Animal Plant Bacteria Protists Cell Membrane Structure & Function Cell Receptors & Communication Cell Transport (Passive & Active) Osmosis Tonicity Endocytosis & Exocytosis 2

3 A cell is the basic structural, functional and biological unit of all living things. A cell is tiny - it cannot be seen with the naked eye. It can only be seen with a microscope. What is a cell? 3

4 were discovered by scientist Robert Hooke in He called them cells because they resembled the cells lived in by Christian monks in a monastery. 4

5 The Cell Theory is scientific theory that describes the properties of ALL cells. There are three tenets to the Cell Theory: 1. All living things are made of cells. Some living things, such as bacteria, are made of one cell. Other living things, such as plants and animals, are made of many cells. 2. The cell is the basic unit of life. A cell is the most basic unit of structure and function in all living things. 3. arise from pre-existing cells. divide to make copies of themselves. do NOT arise spontaneous or from nonliving things. 5

6 A living thing can be made of one or more cells. Unicellular organisms are organisms made of one cell. Multicellular organisms are organisms made of many cells. Bacteria and protists are unicellular organisms. Plants, animals and fungi are multicellular organisms. 6

7 Unicellular organisms perform life functions using organelles. Organelles are structures inside of a cell. Unicellular organisms use the cell membrane to take in nutrients and gases, such as oxygen and to excrete waste. Unicellular organisms digest nutrients in organelles known as food vacuole. Unicellular organisms use cytoplasm (the jelly substance inside a cell) to transport substances throughout them. Unicellular organisms can use hair-like projections on the outside of the cell (cilia) or a tail-like structure (flagellum) that extends out of one side the cell to help them move in the environment. 7

8 Multicellular organisms are more complex than unicellular organisms. Their cells work together. Cell that work together form tissues. Tissues form organs and organs form organ systems. Organ systems perform important life functions. Multicellular organisms take in and digest nutrients using the digestive system. Multicellular organisms take in oxygen using the respiratory system. Multicellular organisms use a circulatory system to transport substances throughout their bodies. Multicellular organisms use an excretory to rid their bodies of waste. Multicellular organisms use a skeletal and muscular system to help them move throughout the environment. 8

9 There are two major types of cells: 1. Prokaryotes 2. Eukaryotes Organisms made of prokaryotic cells are called prokaryotes. Organisms made of eukaryotic cells are called eukaryotes. 9

10 Prokaryotes and eukaryotes are different for two MAJOR reasons: 1. Eukaryotes have a nucleus. Prokaryotes do not. 2. Eukaryotes have membrane-bound organelles. Prokaryotes do not. 10

11 Prokaryotes (or prokaryotic cells) do NOT contain a nucleus. Prokaryotic DNA is found clumped together in the cytoplasm in a region known as the nucleoid. Prokaryotes do NOT have membrane-bound organelles. Prokaryotes DO have ribosomes (important to making proteins). Prokaryotes have a cell membrane and cytoplasm. Most prokaryotes have a cell wall. Some prokaryotes have a capsule. Prokaryotes are very tiny, unicellular organisms. Examples: Bacteria, Archaebacteria 11

12 Eukaryotes (or eukaryotic cells) contain a nucleus. Eukaryotic DNA is found inside the nucleus. Eukaryotes have membrane bound organelles, such as mitochondria. Eukaryotes have ribosomes. Eukaryotes have a cell membrane, cytoplasm & ribosomes. Some eukaryotes have a cell wall. Eukaryotes do NOT have a capsule. Eukaryotes are unicellular or multicellular organisms. Eukaryotes are larger and more complex than prokaryotes. Examples: Protists, fungi, plants, animals 12

13 Compare and contrast prokaryotes and eukaryotes. Prokaryotes Eukaryotes 13

14 Compare and contrast prokaryotes and eukaryotes. Prokaryotes No nucleus DNA in a region called nucleoid No membranebound organelles Some have a capsule Unicellular Ex: Bacteria, Archaebacteria Ribosomes Cytoplasm & cell membrane Some have a cell wall Eukaryotes Nucleus which contains DNA Membrane-bound organelles No capsule Unicellular or multicellular organisms Ex: Plants, Animals, Fungi, Protists 14

15 When scientists study cells, they often focus on 4 different types of cells: 1. Bacteria 2. Protists 3. Animal 4. Plant Note: There are other types of cells, such as fungal cells. Fungal cells make up fungi. We will not study fungal cells in this presentation. 15

16 There are four features that ALL cells have in common: 1. They are surrounded by a cell membrane. 2. They contain cytoplasm, a jelly-like substance inside the cell. 3. They contain DNA, which codes for all characteristics of the cell. Prokaryotes usually have one long strand of DNA. Eukaryotes have multiple strands of DNA called chromosomes. 4. They contain ribosomes, structures important to making proteins. 16

17 A bacterium is a unicellular organism. Bacteria are prokaryotes. Most bacteria have a cell wall (in addition to a cell membrane). Many bacteria have a flagellum (a tail-like structure that helps them move). Most bacteria have to eat food but some can make their own food. Example: Cyanobacteria or blue-green algae perform photosynthesis. 17

18 A protist is (usually) a unicellular organism. Protists are eukaryotes. Protists do not have a cell wall. Many protists have a special structure called a contractile vacuole. A contractile vacuole helps remove excess water in the organism. Many protists have cilia (hair-like projections that help them move). Protists can make their own food or eat food. 18

19 Animals are multicellular organisms. They are made of animal cells. Animal cells are eukaryotic. Animal cells do not have a cell wall. Some animal cells have cilia or a flagellum. Animals cannot make their own food. They must eat in order to provide nutrients to their cells. Human blood cells 19

20 Plants are multicellular organisms. They are made of plant cells. Plant cells are eukaryotes. Plant cells have a cell wall. Plants cells have structures known as chloroplasts. Chloroplasts are organelles that perform photosynthesis. They enable plant cells to capture energy from the sun and make food. 20

21 Like all eukaryotic cells, animal cells contain a nucleus and organelles. Organelles are structures found inside a cell. They perform various functions. Let s study important organelles found inside an animal cell. 21

22 The cell membrane is a structure that surrounds the cell. It acts like a barrier. It allows substances to pass in and out of the cell and helps a cell communicate with other cells. Cell Membrane 22

23 Cytoplasm is jelly-like material located in the cell in which the organelles are contained. It is composed of water and dissolved nutrients and salts Cytoplasm 23

24 The nucleus is often referred to as the control center of the cell. It contains DNA and controls many of the cell s functions. Within the nucleus is a structure called the nucleolus. The nucleolus produces parts of the ribosomes. Nucleolus Nucleus 24

25 Ribosomes are small organelles where protein synthesis takes place. They are found floating freely in cytoplasm or attached to endoplasmic reticulum. Ribosome 25

26 Endoplasmic reticulum (ER) is a series of interconnected membranes found outside the nucleus. There are two types of ER: Rough ER has ribosomes attached to it giving it a rough appearance. It transports materials throughout the cell and produces proteins. Smooth ER does not have ribosomes attached to it. Like Rough ER, it transports materials throughout the cell but produces lipids instead of proteins. Rough ER Smooth ER 26

27 The Golgi Bodies (also called Golgi Apparatus or Golgi complex) sort and package materials such as proteins and carbohydrates into vesicles. These vesicles are delivered to certain part of the cell or exported from the cell. Golgi Bodies 27

28 Mitochondria are round or rod-shaped organelles with a double membrane. A mitochondrion is often called a powerhouse of the cell" because it produces energy for the cell. Mitochondria convert chemical energy in sugar to usable energy for the cell. This energy is known as ATP. Mitochondria 28

29 Vacuoles are vesicles in the cell that store nutrients, waste or water. Sometimes we name vacuoles based on what they contain. For example, a food vacuole contains food. Vacuoles 29

30 Lysosomes are small, round vesicles that contain enzymes that digest cell nutrients and break down old cell parts. To digest food, they merge with food vacuoles to digest nutrients. Lysosome 30

31 Plant cells are eukaryotic like animal cells. They have the following organelles just like animal cells: Cell membrane Cytoplasm Nucleus Nucleolus Ribosomes Rough and Smooth ER Golgi Bodies Mitochondria Vacuoles Golgi Bodies Cell Membrane 31 Cytoplasm Rough ER Smooth ER Mitochondria Vacuole Nucleus & Nucleolus Ribosome

32 Plant cells also have chloroplasts. Chloroplasts perform photosynthesis. Photosynthesis is the process of making food (sugar) using energy from the sun. Chloroplast contains green pigment called chlorophyll. Chlorophyll captures energy from sun, enabling the cell to perform photosynthesis. Chloroplast 32

33 Plant cells also have a cell wall. The cell wall is located just outside the cell membrane. The cell wall is rigid and helps provide structure and protection. Cell Wall 33

34 There are three major differences between plant and animal cells: 1. Plant cells contain chloroplasts. By performing photosynthesis, plants can make their own food. Animal cells do not contain chloroplasts and so animals must consume food in order to obtain nutrients. 2. Plant cells are surrounded by a cell wall. Animal cells are not. 3. Although both plant and animal cells contain vacuoles, plant cells contain one very large central vacuole whereas animal cells contain small vacuoles. Plant cells have a large central vacuole filled with water which helps maintain the shape of the cell. Animal cells contain multiple small vacuoles, filled with food, water or waste. 34

35 There are two other minor differences between animal and plant cells: 1. Some animal cells have cilia or flagella. in the human respiratory tract have cilia. Cilia sweep debris, mucus and dirt out of the lungs. Sperm (male reproductive cells) have flagella. A flagellum helps sperm move. Plant cells never have cilia or flagella. 2. Animal cells have structures called centrioles that help animal cells divide. Plants cells do not have centrioles. 35

36 A bacterium is a simple, unicellular, prokaryotic organism. A bacterium is very tiny. In fact, a bacterium is the smallest kind of cell. The average bacterium is 10 to 100 times smaller than a plant or animal cell. The shape of bacteria varies. Bacteria can be rod, spherical or spiral shaped. Let s study important structures found in a rod-shaped bacterium. 36

37 Bacteria are surrounded by a cell wall. The cell wall protects the bacteria and helps maintain its shape. Inside the cell wall is the cell membrane. The cell membrane controls what enters and leaves the cell. Cell Wall Cell Membrane 37

38 Some bacteria have a capsule. A capsule is an extra layer that surrounds the bacteria outside the cell wall. A capsule helps protect the bacteria from being eaten and destroyed by other cells. For example, it helps protect disease-causing bacteria from being destroyed by white blood cells. Capsule 38

39 Many bacteria (but not all) have a flagellum. A flagellum is a tail-like structure that extends out of the bacterium. It whips around and propels the bacterium forward. Flagellum 39

40 Bacteria do not have a nucleus. Their DNA is located in the cytoplasm and not in an enclosed structure. Often, bacterial DNA is clumped together in a region. We call this region the nucleoid. Nucleoid (DNA) 40

41 Many bacteria have an extra small, circular piece of DNA. This accessory DNA is called a plasmid. A plasmid can be transferred from one bacterium to another. A plasmid often carries genes that increase the bacteria s survival such as antibiotic resistance. Plasmid 41

42 Bacteria have ribosomes. Ribosomes are small, circular organelles that perform protein synthesis. Cytoplasm is the jelly-like material that fills the cell of a bacterium. It is made of water and dissolved nutrients and salts. Ribsomes Cytoplasm 42

43 Protists are a diverse group of mostly unicellular, eukaryotic organisms. There are many different kinds of protists. Some are animal-like, some are plantlike and some are funguslike. In this presentation, we will study a paramecium, an animal-like protist. Paramecium live in aquatic environments. 43

44 The cell membrane is a structure that surrounds the protist. It acts like a barrier. It allows substances to pass in and out of the cell. Cell Membrane 44

45 Cilia are small, hair-like projections that are attached to the cell membrane. They help paramecium move through water. They also help it eat. Cilia 45

46 There is an indentation on one side of the paramecium called the oral groove. This indentation is like a mouth. Cilia sweep food into the oral groove. The food is trapped in the groove. The gullet is the bottom of the oral groove. Food is forced into small vacuoles (called food vacuoles) in the gullet. Gullet Oral Groove 46

47 Vacuoles are vesicles in the cell that store nutrients, waste or water. Sometimes we name vacuoles based on what they contain. For example, a food vacuole contains food. Vacuoles 47

48 Paramecium have a special, star-shaped contractile vacuole. Paramecium live in water and sometimes they take in excess water. The contractile vacuole collects the excess water and pumps it out the cell. Without this structure, the cell would swell with water and burst. Contractile Vacuole 48

49 Lysosomes are small, round vesicles that contain enzymes that digest food. Lysosomes fuse with food vacuoles to digest nutrients inside them. Lysosomes 49

50 Paramecium have two nuclei. They have a large macronucleus and a small micronucleus. The macronucleus contains most of the organism s genetic information needed for day-to-day existence. The micronucleus contains an extra copy of the organism s genetic information. Micronucleus Macronucleus 50

51 Like other eukaryotic cells, protists also have: Mitochondria Ribosomes Smooth and Rough RE Golgi Bodies Cytoplasm Note: These organelles are not shown in most diagrams of protists. However, they are found in all protists. 51

52 Some protists have chloroplasts. Protists that have chloroplasts can perform photosynthesis and make their own food. Most algae are protists. Algae are unicellular or multicellular organisms found in aquatic environments. Multicellular algae is commonly called seaweed. 52

53 All cells have a cell membrane. A cell membrane is the structure that separates the interior of a cell from the external environment. 53

54 A cell membrane has 3 important functions: 1. It protects the contents of the cell - it acts as a barrier that keeps foreign substances outside of the cell 2. It controls what enters and leaves the cell. The membrane is selectively permeable; it selects what can pass or permeate into or out of a cell 3. It is important to cell signaling or communication. Substances outside the cell can bind to receptors on the cell membrane. These substances signal the cell to perform an action such as to synthesize a substance or export a substance. 54

55 The cell membrane is made of phospholipids. A phospholipid is a molecule made of a phosphate group (the head ) and lipid (the tail ). There are two layers of phospholipids in a cell membrane. For this reason, the cell membrane is also called the phospholipids bilayer. Hydrophilic Head Hydrophobic Tail 55

56 There are 2 parts to a phospholipid: the head and tail The head is hydrophilic (water loving) and faces outwards (to the external environment) and inward (towards the inside of the cell). The tail is hydrophobic (water fearing) and makes up the inside of the cell membrane. The tails from each layer face towards each other. Phospholipid OUTSIDE CELL Hydrophilic Head Hydrophobic Tail INSIDE CELL 56

57 There are different types of molecules embedded in the phospholipid bilayer. These molecules are important to the structure and function of the cell membrane. 57

58 Transmembrane proteins span across the entire membrane. Transmembrane proteins form channels, pumps or receptors. 58

59 Peripheral proteins are found only in the outer or inner layer of the cell membrane. These proteins help with cell signaling or catalyzing reactions in a cell. 59

60 Glycoproteins are proteins with a sugar molecule attached. Glycoproteins often act as antigens. An antigen is like an identification card. It signals to other cells what that cell is and whether the cell is foreign or belongs to the organism. 60

61 Cholesterol is a type of lipid. Cholesterol is dispersed throughout the phospholipid bilayer and help the membrane stay fluid, or flexible. Cholesterol also helps stabilize the phospholipid bilayer. 61

62 Transmembrane proteins are the most important to cell communication. They allow a cell to respond to external environmental changes and factors. Transmembrane proteins that are important to cell communication are called membrane receptors. 62

63 Membrane receptors bind signaling molecules called ligands. A ligand can be a hormone, neurotransmitter or protein. Ligands cause the function of a cell to change. Example: When the square ligand binds the receptor, substances enter the cell through the channel protein. 63

64 Ligands have a specific shape and can only fit into membrane receptors that complement their shape. Likewise, a membrane receptor has a specific shape. It has a specific shape and can bind only one signaling molecule or ligand. 64

65 A ligand binds to the cell membrane receptor on the extracellular side of the cell membrane. When it binds, it causes a change on the intracellular side of the membrane receptor protein. This change could: Open channels in the cell membrane. When the channels open, ions or other substances can enter and exit the cell. Activate enzymes. These enzymes catalyze reactions in the cell. Cause muscle contractions, nerve impulses or cell growth. 65

66 Membrane receptors are also found on the surface of organelles in a cell. When a ligand binds to the receptor on an organelle, it causes a change in the organelle. Example: Receptors found on the nucleus are called nuclear receptors. When a ligand binds to a nuclear receptor, it can cause genes to turn on or off. 66

67 Substances move across the membrane. The movement of substances in and out of is called cell transport. There are two kinds of cell transport: 1. Passive transport 2. Active transport 67

68 Passive transport is the movement of a substance down a concentration gradient. In other words, a substance moves from high concentration to low concentration. Passive transport occurs spontaneously. It does NOT require energy. Passive transport stops once the concentration of the substance evens out between the inside and outside of cell. High concentration Low concentration Even concentration 68

69 There are two kinds of passive transport: Diffusion Facilitated Diffusion 69

70 With diffusion, substances pass directly across the phospholipid bilayer. Only small substances can diffuse in and out of the cell. This is how oxygen and carbon dioxide enter and exit cells. 70

71 With facilitated diffusion, substances use a channel or carrier protein to diffuse across a membrane. Both proteins create channels across the membrane. A channel protein often allows ions (charged particles) to enter and exit a cell. A carrier protein is more selective than a channel protein. It often helps larger substances, such as simple sugars, diffuse across a membrane. Channel protein Carrier protein 71

72 Active transport is the movement of a substance against a concentration gradient. It is the movement from low concentration to high concentration. Active transport does not occur spontaneously. It requires energy (ATP). Low concentration High concentration 72

73 Active transport occurs with the help of transmembrane proteins. The proteins act as pumps. The pumps use ATP to transport substance from low concentration to high concentration. They break ATP down into ADP, releasing energy which is used to move the substance across the membrane. 73

74 Active transport is important to all forms of life. For example: Plants have pumps in the cells of their roots that help extract salts and minerals for the soil. Salts and minerals exist in very dilute solutions in the soil. Without active transport pumps, plants would not be able to obtain these vital nutrients. Human cells have active transport pumps that maintain fluid balance and volume of cells. They also rely on active transport to help conduct nerve signals. 74

75 Osmosis is a special type of passive transport. It is the diffusion of water. Specifically, it is facilitated diffusion of water with a channel protein. Osmosis is the movement of water from a high concentration of water to low concentration of water. Water High water concentration Low water concentration 75

76 We don t refer to the concentration of water in a solution. We refer to the concentration of the solute in a solution. High water concentration Low solute concentration Low water concentration High solute concentration 76

77 Osmosis occurs across cell membranes when the solute concentration is different inside and outside a cell. When the concentration of solute is lower outside a cell, the concentration of water is higher. Therefore, water moves from outside the cell to inside the cell. 77

78 When the concentration of solute is higher outside a cell, the concentration of water is lower. Therefore, water moves from inside the cell to outside the cell. 78

79 If the solute concentration is the same inside the cell and outside the cell, water does not diffuse across the membrane. 79

80 Tonicity is a measure to compare the concentration of water in two different solutions. It compares concentration in terms of the solute, not the solvent (water). There are three classifications of tonicity that one solution can have relative to another: 1. Isotonic 2. Hypertonic 3. Hypotonic 80

81 A solution that contains the same concentration as another solution is called isotonic. In other words, an isotonic solution has the same concentration as another solution. A solution that contains more solute than another solution is called hypertonic. In other words, a hypertonic solution is more concentrated compared to another solution. A solution that contains less solute than another solution is called hypotonic. In other words, a hypotonic solution is less concentrated compared to another solution. 81

82 Animal cells and plant cells change shape and size due to osmosis. There are three scenarios where osmosis could change the shape and size of the cells: 1. The cell is placed in a hypertonic solution. 2. The cell is placed in a hypotonic solution. 3. The cell is placed in an isotonic solution 82

83 When a cell is placed in an isotonic solution, the container has the same solute concentration compared to inside the cell. Therefore, water does not enter or leave the cell. The cells remain their normal size and shape. Animal cell Plant cell 83

84 When a cell is placed in a hypertonic solution, there is a higher solute concentration in the container compared to inside the cell. Therefore, water leaves the cell. Animal cells shrink and shrivel. With plant cells, the cell wall remains rigid but the cell membrane pulls away and the inside of the cell shrinks. Water leaves the cell Animal cell Plant cell Water leaves the cell 84

85 When a cell is placed in a hypotonic solution, there is a lower solute concentration in the container compared to inside the cell, so water enters the cell. Animal cells swell and burst. The cell wall in plant cells prevents the cell from bursting. The pressure inside the cell increases due to some water entering the cell. This pressure is called turgor pressure. Water enters the cell Animal cell Plant cell Water enters the cell 85

86 The images below are actual pictures of red blood cells in a hypertonic, hypotonic and isotonic solution. Which image shows an example of red blood cells in a hypertonic solution? What about a hypotonic and isotonic solution? 86

87 Hypertonic solution Red blood cells shrink Isotonic solution Hypotonic solution Red blood cells swell 87

88 IV or intravenous therapy is the direct infusion of medication or liquid substances into a person s bloodstream. When a person receives IV therapy, it s imperative that the solute concentration of the infused liquid is isotonic to the concentration of blood. If not, blood cells can shrivel or swell. This can be deadly to a patient. 88

89 Some cells perform a special type of active transport called endocytosis and exocytosis. In endocytosis, cells engulf substances. In exocytosis, cells expel substances. 89

90 In endocytosis, cells consume or absorb substances by engulfing them. Endocytosis allows cells to absorb large molecules that cannot pass across the cell membrane or through channels in the membrane. There are three major types of endocytosis: 1. Phagocytosis 2. Pinocytosis 3. Receptor-Mediated Endocytosis 90

91 Phagocytosis is the process by which a cell engulfs a solid particle. In phagocytosis, the cell membrane extends around the particle. Phagocytosis is used by bacteria and protists to eat. For this reason, phagocytosis is also called cell eating. Phagocytosis is also used by white blood cells in the human body to engulf pathogens and cell debris. 91

92 Pinocytosis is a non-specific process by which a cell brings particles into the cell. The cell membrane invaginates or pinches around the particle. This process is often used to take in extracellular fluid. For this reason, pinocytosis is also called cell drinking. 92

93 Receptor-mediated endocytosis is a specific form of endocytosis. In receptor-mediated endocytosis, substances bind to receptors on the membrane. This causes the membrane to invaginate. The cell internalizes the substances bound to the receptors. This form of endocytosis is often used for cell communication. These receptors often bind hormones. When the hormones enter the cell, they signal a reaction in the cell. 93

94 Exocytosis is a process that expels substances out of a cell. Exocytosis is important to expelling wastes from a cell. It is also important to releasing proteins made by the cell. This is the most common way cells release hormones or enzymes. 94

95 Exocytosis occurs in three steps: 1. Golgi bodies package substances to be expelled from the cell into vesicles. 2. The vesicles travel to the cell membrane. 3. The vesicles fuse with the cell membrane and the contents inside the vesicle are expelled out of the cell. Step 2 Step 1 Step 3 95

96 Images obtained from commons.wikimedia.org courtesy: Roger Moreno, NIAID, NEON_ja, Fleliaer, Calleamanecer, Zephyris, harmid Other images obtained from the Public Domain Clipart by Stephanie Elkowitz 96