7.1 Life is Cellular. Mrs. Baldessari Biology

Transcription

1 7.1 Life is Cellular Mrs. Baldessari Biology The key to every biological problem must finally be sought in the cell, for every living organism is, or at some time has been, a cell. E.B. Wilson,

2 Cells are Us 2

3 Cells are Us Cilia on a protozoan Sperm meets egg 3

4 Lesson Overview Life Is Cellular THINK ABOUT IT What s the smallest part of any living thing that still counts as being alive? Can we just keep dividing living things into smaller and smaller parts, or is there a point at which what s left is no longer alive? As you will see, there is such a limit. The smallest living unit of any organism is the cell. 4

5 Cells are Us A person contains about 100 trillion cells. That s 100,000,000,000,000 or 1 x cells. There are about 200 different cell types in mammals (one of us). Red and white blood cells above vesselforming cells. nerve cell 5

6 CELL SIZE Smallest cell in the human body is the sperm cell Largest cell in the human body is the egg cell 6

7 Most cells are small 1. Surface to volume ratio: cell has to be small enough to get Waste out Nutrients in 2. The nucleus can only control a certain size cell 7

8 Lesson Overview Life Is Cellular The Discovery of the Cell What is the cell theory? The cell theory states: - All living things are made up of cells. - Cells are the basic units of structure and function in living things. - New cells are produced from existing cells. 8

9 Early Microscopes Prototypes were developed in the late 1500 s by European eyeglass makers It was not until the mid-1600s that scientists began to use microscopes to observe living things. Early compound microscope 17 th century 9

10 In 1665, Robert Hooke used an early compound microscope to look at cork Observed that cork was made up of thousands of hollow chambers Dubbed them cells since they looked like the monatsery s tiny rooms called cellula. Today we know that living cells are not empty chambers, but contain a huge array of working parts, each with its own function. 10

11 Anton von Leewenhoek FIRST person to OBSERVE and DESCRIBE MICROSCOPIC ORGANISMS and LIVING CELLS Late 1600 s- Dutch textile salesman Created different types of microscopes Discovered over 5,000 types of microscopic life Lenses were able to magnify up to 300X. 11

12 Lesson Overview Life Is Cellular Early Microscopes Anton van Leeuwenhoek examined pond water and other things, including a sample taken from a human mouth. He drew the organisms he saw in the mouth which today we call bacteria. 12

13 The Cell Theory In 1838, German botanist Matthias Schleiden concluded: plants are made of cells The next year, German biologist Theodor Schwann stated that all: Animals are made of cells Schleiden Schwann 13

14 Cell Theory In 1855, German physician Rudolf Virchow concluded that new cells could be produced only from the division of existing cells. 1. All living things are made of cells. 2. Cells are the basic unit of structure and function 3. New cells come from preexisting cells. *cells are different shapes and sizes based on their function 14

15 Lesson Overview Life Is Cellular Exploring the Cell How do microscopes work? Most microscopes use lenses to magnify the image of an object by focusing light or electrons. 15

16 A Sense of Scale and Abundance Bacteria on the Head of a Pin 16

17 Exploring the Cell- 3 major types of microscopes 1. There are 1) Light Microscope Allows light to pass through a specimen and uses two lenses to form an image. The first set of lenses, located just above the specimen, produces an enlarged image of the specimen. The second set of lenses magnifies this image still further. Because light waves are diffracted, or scattered, as they pass through matter, light microscopes can produce clear images of objects only to a magnification from 40 1,000 times depending on objective being used 17

18 Lesson Overview Life Is Cellular 1) Light Microscopes magnification from 40 1,000 Eyepiece magnifies 10X Total magnification calculation: multiply the eyepiece by the objective being used. Example- eyepiece (10X) times low power objective (4X) = 40X Used to magnify objects that light can pass through. Uses slides 18

19 Dissecting Microscope Magnifies 10 to 30 times Eyepiece magnifies 10X Objectives: 1X and 2X (3X) Used to magnify objects that light cannot pass through Used mostly by research scientists and jewelers Advantage: objects are 3-D Disadvantage: can t view small objects 19

20 Lesson Overview Life Is Cellular Light Microscopes and Cell Stains A problem with light microscopy is that most living cells are nearly transparent, making it difficult to see the structures within them. Using chemical stains or dyes can usually solve this problem. Some of these stains are so specific that they reveal only compounds or structures within the cell. 20

21 Lesson Overview Life Is Cellular Light Microscopes and Cell Stains Some dyes give off light of a particular color when viewed under specific wavelengths of light, a property called fluorescence. Fluorescent dyes can be attached to specific molecules and can then be made visible using a special fluorescence microscope. Fluorescence microscopy makes it possible to see and identify the locations of these molecules, and even to watch them move about in a living cell. 21

22 Lesson Overview Life Is Cellular 2) Electron Microscopes Light microscopes can be used to see cells and cell structures as small as 1 millionth of a meter. To study something smaller than that, scientists need to use electron microscopes. Electron microscopes use beams of electrons, not light, that are focused by magnetic fields. Electron microscopes offer much higher resolution than light microscopes. There are two major types of electron microscopes: transmission and scanning. 22

23 Electron Microscope -Two types: Transmission and Scanning Uses electrons to illuminate objects Can magnify from 30,000 to 9 million times Mostly large institutions have them Costly to own and maintain Can only be used to look at dead specimens Used for cytology, forensics, and virology 23

24 Lesson Overview Life Is Cellular Transmission Electron Microscopes Transmission electron microscopes make it possible to explore cell structures and large protein molecules. Because beams of electrons can only pass through thin samples, cells and tissues must be cut first into ultra thin slices before they can be examined under a transmission electron microscope. Transmission electron microscopes produce flat, twodimensional images. 24

25 Transmission Electron Microscope TEM- thin slices need to be made to have clear images, images are 2-D Useful for studying internal structures 25

26 Lesson Overview Life Is Cellular Scanning Electron Microscopes In scanning electron microscopes, a pencil-like beam of electrons is scanned over the surface of a specimen. Because the image is of the surface, specimens viewed under a scanning electron microscope do not have to be cut into thin slices to be seen. Scanning electron microscopes produce threedimensional images of the specimen s surface. 26

27 SEM- samples do not need to be cut, are in 3-D Useful for studying external structure 27

28 Lesson Overview Life Is Cellular Electron Microscopes Because electrons are easily scattered by molecules in the air, samples examined in both types of electron microscopes must be placed in a vacuum in order to be studied. Researchers chemically preserve their samples first and then carefully remove all of the water before placing them in the microscope. This means that electron microscopy can be used to examine only nonliving cells and tissues. 28

29 General info about cells Cells come in a variety of shapes Range in size from microscopic bacteria to giant amoeba Mycoplasma pneumoniae Chaos carolinensis Giant amoeba, approximately 1mm in length 29

30 General info about cells c. All contain DNA d. All have a cell membrane- an outer, flexible barrier Cell membrane Nucleuscontaining DNA 30

31 Two Main Categories of Cells a. Eukaryotes- have cells that enclose their DNA in a nucleus b. Prokaryotes- cells that do not enclose their DNA in a nucleus 31

32 Lesson Overview Life Is Cellular Prokaryotes and Eukaryotes How are prokaryotic and eukaryotic cells different? Prokaryotic cells do not separate their genetic material within a nucleus. In eukaryotic cells, the nucleus separates the genetic material from the rest of the cell. 32

33 Prokaryotes and Eukaryotes Organisms whose cell contain a nucleus and other membrane bound organelles are called EUKARYOTES Organisms whose cells never contain (or lack) a nucleus and other membrane bound organelles are called PROKARYOTES 33

34 A rat liver cell (with color enhancement to show organelles) 34

35 It s Crowded In There An artist s conception of the cytoplasm - the region of a cell that s not in the nucleus or within an organelle. 35

36 It s Crowded In There A micrograph showing cytoskeleton (red), ribosomes (green), and membrane (blue) 36

37 Two Fundamentally Different Types of Cells 37

38 Lesson Overview Life Is Cellular Prokaryotes and Eukaryotes Cells fall into two broad categories, depending on whether they contain a nucleus. The nucleus is a large membrane-enclosed structure that contains the cell s genetic material in the form of DNA. The nucleus controls many of the cell s activities. 38

39 Lesson Overview Life Is Cellular Prokaryotes and Eukaryotes Eukaryotes are cells that enclose their DNA in nuclei. Prokaryotes are cells that do not enclose DNA in nuclei. 39

40 Prokaryotes Are generally smaller than eukaryotic cells Have no nucleus Carry out all of life s processes Ex: bacteria Bacillus anthracis 40

41 Eukaryotes a. Are generally larger and more complex than prokaryotes b. Contain dozens of membrane bound structures that are specialized c. Nucleus separates DNA from rest of cell 41

42 Eukaryotes Come in a variety of shapes and size Ex: protists, fungi, plant, and animal cells 42

43 Lesson Overview Life Is Cellular Eukaryotes Eukaryotic cells are generally larger and more complex than prokaryotic cells. Most eukaryotic cells contain dozens of structures and internal membranes. Many eukaryotes are highly specialized. There are many types of eukaryotes: plants, animals, fungi, and organisms commonly called protists. 43

44 Us vs. Them - Eukaryotes and Prokaryotes 44

45 7.2 Cell Structure Cell organization Organelles- tiny organs ; the specialized structures within the cell that perform a function 45

46 Animal vs Plant cells 46

47 Animal and Plant Cells Have More Similarities Than Differences 47

48 The cell as a factory The different organelles of a cell can be compared to a living version of a modern factory Cells, like factories follow instructions to produce products 48

49 Cytoplasm Cytoplasm- the portion of the cell outside of the nucleus; the fluid that fills the entire cell Makes up about 70% of the cells volume. Most of the cells chemical reactions occur here 49

50 The Nucleus Control center of the cell Surrounded by a nuclear envelope with pores DNA is in the form of chromatin which condenses down into chromosomes Prokaryotic cells lack a nucleus, but they do have DNA 50

51 Lesson Overview Life Is Cellular The Nucleus Most nuclei also contain a small, dense region known as the nucleolus. The nucleolus is where the assembly of ribosomes begins. 51

52 Organelles that Store, Clean-up, and Support 1. Vacuoles- large sac-like, membrane enclosed structures - store water, salts, proteins, carbohydrates 2. Lysosomes- the clean-up crew ; small organelles filled with enzymes 3. Cytoskeleton-The framework of the cell ; a network of protein filaments; made up of microfilaments and microtubules; some parts help in transport of materials a. Centrioles - Are located near the nucleus; help organize cell division; not found in plant cells 52

53 Vacuoles large sac-like, membrane enclosed structures Function- store water, salts, proteins, carbohydrates Larger in plant cells Found in some unicellular organisms and animal cells Ex: Paramecium Contractile vacuole in paramecium cell 53

54 Vacuoles Typically called vesicles in animal cells- store and move materials between cell organelles and to the cell surface 54

55 Lesson Overview Life Is Cellular Vacuoles and Vesicles saclike, membrane-enclosed structures that store materials such as water, salts, proteins, and carbohydrates Larger in plant cells 55

56 Lysosomes- the clean-up crew ; small organelles filled with enzymes Break down many types of materials Lipids Carbohydrates Proteins Cellular debri Found mostly in animal cells 56

57 The Lysosome Functions: Digesting food or cellular invaders Recycling cellular components 57

58 Lesson Overview Life Is Cellular Lysosomes Lysosomes are small organelles filled with enzymes that function as the cell s cleanup crew. Lysosomes perform the vital function of removing junk that might otherwise accumulate and clutter up the cell. Found mostly in white blood cells Have been linked to diseases, such as Tay Sach s Tay Sach s is a disorder that is caused by a genetic defect that prevents the formation of an essential enzyme that breaks down lipids These lipids build up in the body and can cause nerve damage; prognosis is not good 58

59 The Lysosome This bacterium about to be eaten by an immune system cell will spend the last minutes of its existence within a lysosome. 59

60 Many Diseases are Caused by Lysosome Malfunction 60

61 Cytoskeleton The framework of the cell ; a network of protein filaments Some parts help in transport of materials Aids the cell in movement Made up of microfilaments and microtubules 61

62 The Cytoskeleton The name is misleading. The cytoskeleton is the skeleton of the cell, but it s also like the muscular system, able to change the shape of cells in a flash. Maintains the shape of the cell Aids in movement An animal cell cytoskeleton 62

63 A Cytoskeleton Gallery 63

64 The Cytoskeleton in Action Cilia on a protozoan Beating sperm tail at fertilization Smoker s cough is due to destruction of cilia linking the airways. 64

65 Cytoskeleton Microfilaments- threadlike structures made up of a protein called actin Help cell maintain shape and allow it to move Assembly and dissasembly are responsible for amoeboid movement 65

66 Cytoskeleton Microtubules- are hollow structures made up of proteins known as tubulins Important for cells in maintaining shape, as well as for cell division Help build projections from the cell surface 66

67 Centrioles Are located near the nucleus Function- help organize cell division Not found in plant cells 67

68 Organelles That Build Proteins 1. Ribosomes- are small pieces of RNA and protein; the worktable for making proteins 2. Endoplasmic Reticulum- Protein synthesis (about half the cell s proteins are made here); Protein movement (transport) 3. Golgi Apparatus-Proteins produced in the rough ER move here for packaging 68

69 Organelles That Build Proteins Ribosomes- are small pieces of RNA and protein Function- the worktable for making proteins Build proteins based on DNA s coded instructions Located throughout the cell 69

70 Ribosomes and the Endoplasmic Reticulum 70

71 Ribosome Ribosomes Are Not Surrounded by a membrane. They are the site of PROTEIN SYNTHESIS (Production or Construction) in a cell. 71

72 Cystic Fibrosis Click here to see the article. 72

73 Endoplasmic reticulum- ER Found in eukaryotic cells only Internal membrane system responsible for assembling lipids for the cell membrane Also assembles proteins for and other materials that are exported from the cell Two types- rough and smooth 73

74 The Rough Endoplasmic Reticulum Studded with ribosomes Protein synthesis (about half the cell s proteins are made here). Protein movement (transport) 74

75 The Rough Endoplasmic Reticulum Rough ER- builds proteins; contains ribosomes on its surface Rough ER chemically modifies the proteins made by the ribosomes Produces proteins that will eventually be secreted out of the cell 75

76 Smooth ER IS NOT Covered with RIBOSOMES and processes LIPIDS and CARBOHYDRATES. The Smooth ER is involved in the synthesis of steroids in gland cells, the regulation of calcium levels in muscle cells, and the breakdown of toxic substances by liver cells. 76

77 Smooth ER- known as smooth because there are no ribosomes on its surface Contains enzymes that allow it to synthesize membrane and detoxify drugs Highly concentrated in liver cells Right: rough er; Left: smooth er Human liver cell 77

78 Golgi Apparatus Found in eukaryotic cells Proteins produced in the rough ER move here Appears as a stack of flat discs Function- modifies, sorts, and packages proteins and other materials from the ER for storage in the cell or release outside the cell 78

79 Golgi Apparatus Processing, Packaging and Secreting Organelle of the Cell that is made of flattened SAC 79

80 Animal vs. Plant Cells Chloroplasts Are a Big Part of the Difference 80

81 Cells In a Leaf 81

82 Two Other Unique Features of Plant Cells The central vacuole may occupy 90% of a plant cell. 82

83 Organelles that Capture and Release Energy 1. Chloroplasts - Found in plant cells, algae, and some bacteria; Capture light energy and convert it into food that contains chemical energy ; Where photosynthesis occurs 2. Mitochondria-Found in all eukaryotic cell; powerplant of the cell; Converts the chemical energy stored in food into compounds that are more convenient for the cell to use (ATP) 83

84 Chloroplasts Found in plant cells, algae, and some bacteria Capture light energy and convert it into food that contains chemical energy Where photosynthesis occurs 84

85 The Chloroplast Think of the chloroplast as the solar panel of the plant cell. Only plants have chloroplasts; they perform photosynthesis 85

86 Chloroplast Structure 2 membranes surround the organelle Stacks of membranes called grana are where chlorophyll occurs Chlorophyll- green pigment 86

87 Mitochondria Found in all eukaryotic cells Function- powerplant of the cell Converts the chemical energy stored in food into compounds that are more convenient for the cell to use (ATP) 87

88 The Mitochondrion Think of the mitochondrion as the powerhouse of the cell. Both plant and animal cells contain many mitochondria. 88

89 Mitochondrial Diseases 89

90 Mitochondria and Health 90

91 Lesson Overview Life Is Cellular Cellular Boundaries Cells are surrounded by a barrier known as the cell membrane. Many cells, including most prokaryotes, also produce a strong supporting layer around the membrane known as a cell wall. 91

92 Lesson Overview Life Is Cellular Cell Membranes All cells contain a cell membrane that regulates what enters and leaves the cell and also protects and supports the cell. 92

93 Cell membrane The Cell Membrane is a complex barrier separating the cell from it's external environment. The "Selectively Permeable" Membrane regulates what passes into and out of the cell. 93

94 Lesson Overview Life Is Cellular Cell Membranes The composition of nearly all cell membranes is a double-layered sheet called a lipid bilayer, which gives cell membranes a flexible structure and forms a strong barrier between the cell and its surroundings. 94

95 Cell membrane- outermost boundary of the cell Is made up of a flexible double layer called a lipid bilayer Gives cell shape and holds cytoplasm in Receptor Proteins Hydrophilic Head Hydrophobic Tails 95 Lipid Bilayer

96 Cell membrane- Selective Permeability- some substances can cross over the cell membrane, some cannot Gets in: Oxygen, water, and Carbon Dioxide Does Not Get in: Sodium, Potassium, Calcium, Chlorine, proteins (need active support), most large molecules 96

97 You will not be tested on the material presented on the next 7 slides covering lipids and fluid mosaic model these slides do not appear in you powerpoint this material is covered in Honors Bio ad AP bio I am presenting it for those who like to understand how things work. 97

98 Lesson Overview Life Is Cellular The Properties of Lipids that control how a cell membrane works Many lipids have oily fatty acid chains attached to chemical groups that interact strongly with water. The fatty acid portions of such a lipid are hydrophobic, or water-hating, while the opposite end of the molecule is hydrophilic, or water-loving. 98

99 Lesson Overview Life Is Cellular The Properties of Lipids When such lipids are mixed with water, their hydrophobic fatty acid tails cluster together while their hydrophilic heads are attracted to water. A lipid bilayer is the result. 99

100 Lesson Overview Life Is Cellular The Properties of Lipids The head groups of lipids in a bilayer are exposed to water, while the fatty acid tails form an oily layer inside the membrane from which water is excluded. 100

101 Lesson Overview Life Is Cellular The Fluid Mosaic Model Most cell membranes contain protein molecules that are embedded in the lipid bilayer. Carbohydrate molecules are attached to many of these proteins. 101

102 Lesson Overview Life Is Cellular The Fluid Mosaic Model Because the proteins embedded in the lipid bilayer can move around and float among the lipids, and because so many different kinds of molecules make up the cell membrane, scientists describe the cell membrane as a fluid mosaic. 102

103 Lesson Overview Life Is Cellular The Fluid Mosaic Model Some of the proteins form channels and pumps that help to move material across the cell membrane. Many of the carbohydrate molecules act like chemical identification cards, allowing individual cells to identify one another. 103

104 Lesson Overview Life Is Cellular The Fluid Mosaic Model Although many substances can cross biological membranes, some are too large or too strongly charged to cross the lipid bilayer. If a substance is able to cross a membrane, the membrane is said to be permeable to it. A membrane is impermeable to substances that cannot pass across it. Most biological membranes are selectively permeable, meaning that some substances can pass across them and others cannot. Selectively permeable membranes are also called semipermeable membranes. 104

105 Cell Wall Plant cells have a cell wall. A Cell Wall DOES NOT REPLACE the Cell Membrane Cells with WALLS also have a CELL MEMBRANE. Plant Cells are covered by a Rigid Cell Wall that lies Outside the Cell Membrane. 105

106 Cellular Walls Cell Wall- a strong, supporting layer around the cell membrane Found in prokaryotes, plants, and fungi Not found in animal cells 106

107 Cellular Walls Function- supports, shapes, and protects the cell Porous enough to allow water, O2, and CO2 to pass through In plants, it s made up of cellulose Right: products made from cellulose 107

108 The Central Vacuole Controls Turgor Pressure Flaccid no water Turgid full of water 108

109 Cellular Anatomy 109

110 Plants vs Animals Chloroplasts Cell Wall Centrioles Both Nucleus Cytoskeleton Nucleolus Vacuoles Mitochondria Ribosomes Golgi Apparatus Lysosomes ER Cytoplasm 110

111 Cell Structure Review You must know the similarities and differences between plant and animal cells You must be able to locate the various organelles in a cell diagram You must know the function of each organelle 111

112 The Nucleus - review The largest membranebound organelle in the eukaryotic cell Enclosed by the nuclear envelope contains pores Contains a dark spot - the nucleolus builds ribosomes Contains chromatin (DNA and proteins) when coiled forms chromosomes

113 Plasma Membrane - review Composed of a phospholipid bilayer with embedded proteins Provides a barrier that controls what enters and leaves the cell. All cells, both prokaryotic and eukaryotic, contain plasma membranes. 113

114 Cell Wall - review Both prokaryotic and eukaryotic cells can have a cell wall. Composed of cellulose in plant cells. A rigid, protective covering that provides structural support

115 Cell fluid which surrounds the organelles and contains many dissolved solutes. Site of many cellular chemical reactions. Cytoplasm - review 115

116 Bag-like storage structure Can take up to 90% of the volume of a plant cell Stores food, water, wastes, or other substances Animal cell vacuoles are much smaller Vacuole - review 116

117 The site of cellular respiration. Mitochondria - review Provides energy for the cell by producing a molecule called ATP. Has a highly folded inner membrane that provides increased surface area for chemical reactions

118 Site of photosynthesis. Chloroplast - review Contains the green pigment chlorophyll. Has a highly folded inner membrane that provides increased surface area for chemical reactions

119 Ribosomes - review Composed of RNA and protein Made up of two subunits Responsible for protein synthesis Found in both prokaryotic and eukaryotic cells 119

120 Other Organelles - review Other organelles help to carry out cell functions. ER makes lipids and helps build new membrane. Golgi receives and modifies proteins and then ships them to new locations in the cell. Lysosomes digest worn out cell parts and food. Golgi Apparatus Endoplasmic Reticulum Lysosome Transport Vesicle 120