Biology: An Illustrated Guide to Science PDF

SCIENCE VISUAL RESOURCES BIOLOGY An Illustrated Guide to Science The Diagram Group *Biology Prelims (1–7).qxd 6/19/07 5:18 PM Page 2 Biology: An Illustrated Guide to Science Copyrig...

SCIENCE VISUAL RESOURCES BIOLOGY An Illustrated Guide to Science The Diagram Group *Biology Prelims (1–7).qxd 6/19/07 5:18 PM Page 2 Biology: An Illustrated Guide to Science Copyright © 2006 The Diagram Group Author: Gareth Price Editorial: Jamie Stokes Consultant: Helen Fortin Design: Anthony Atherton, Richard Hummerstone, Tim Noel-Johnson, Lee Lawrence, Phil Richardson Illustration: Peter Wilkinson Picture research: Neil McKenna Indexer: Martin Hargreaves All rights reserved. No part of this book may be reproduced or utilized in any form or by any means, electronic or mechanical, including photocopying, recording, or by any information storage or retrieval systems, without permission in writing from the publisher. For information contact: Chelsea House An imprint of Infobase Publishing 132 West 31st Street New York NY 10001 For Library of Congress Cataloging-in-Publication data, please contact the publisher. ISBN-10: 0-8160-6162-9 ISBN-13: 978-0-8160-6162-4 Chelsea House books are available at special discounts when purchased in bulk quantities for businesses, associations, institutions, or sales promotions. Please call our Special Sales Department in New York at 212/967-8800 or 800/322-8755. You can find Chelsea House on the World Wide Web at http://www.chelseahouse.com Printed in China CP Diagram 10 9 8 7 6 5 4 3 2 This book is printed on acid-free paper. Introduction Biology is one of eight volumes of The Science Visual Resources Set. It contains six principle sections, a comprehensive glossary, a web site guide, and an index. Biology is a learning tool for students and teachers. Full-color diagrams, graphs, charts, and maps on every page illustrate the essential elements of the subject, while bulleted text provides key definitions and step-by-step explanations. Unity looks at the basic chemistry of all biological systems such as carbohydrates, fats, and proteins and describes the essential instruments and techniques of biology. The section also illustrates the most vital life processes, from photosynthesis to respiration. Continuity considers the ways in which biological systems reproduce. The section covers the basics of all forms of biological reproduction, from those of unicellular organisms to flowering plants and mammals. It also details the genetic mechanisms of inheritance. Diversity provides an overview of the vast range of living organisms that inhabit Earth. It describes the major categories that biologists use to classify these organisms and provides examples of each. Maintenance examines the ways in which various living organisms carry out everyday life processes such as breathing, eating, movement, and excretion. Human biology takes a closer look at the essential biological structures and functions of the human body. It describes how the raw materials required are taken in, digested, and transported to where they are needed; how waste products are removed; and how the body is able to sense and interact with its environment. Ecology provides a brief look at how living organisms influence and are influenced by the planet on which they live. It traces the broadest of all biological processes: the complex webs of survival that link the simplest bacteria to the most sophisticated carnivores. Finally, the section outlines the elemental relations by which chemical and geological processes form the conditions for life.  Contents 1 UNITY 8 Simple carbohydrates 29 Lysosomes 9 Complex carbohydrates 30 Summary of 10 Important polysaccharides photosynthesis 11 Amino acids 31 Chloroplast: structure 12 Protein structure 32 Chemistry of 13 Classification of proteins photosynthesis 14 Enzymes: mechanism 33 Summary of aerobic 15 Enzymes and coenzymes respiration 16 Enzymes and inhibitors 34 Mitochondrion: structure 17 Fatty acids and glycerol 35 ATP structure 18 Light microscope 36 Electron transfer chain 19 Cells: light microscope 37 Anaerobic respiration 20 Electron microscope 38 Chromosome structure 21 Animal cell: electron 39 Summary of protein microscope synthesis 22 Plant cell: electron 40 Base pairing microscope 41 DNA structure 23 Cell substructure 42 DNA replication 24 Plasma membrane: 43 DNA transcription structure 44 Rough endoplasmic 25 Plasma membrane: reticulum: structure osmosis 45 Transfer RNA 26 Plasma membrane: active 46 Messenger RNA transport translation 27 Plasma membrane: 47 Gene control endocytosis 48 Transformation 28 Plasma membrane: 49 Genetic engineering exocytosis 2 CONTINUITY 50 Mitosis in an animal cell 57 Mature stamen 51 Asexual reproduction: 58 Pollen formation fission 59 Pollination 52 Asexual reproduction: 60 Plant fertilization vegetative propagation 61 Seed development 53 Meiosis: first division 62 Human reproductive 54 Meiosis: second division system: male 55 Crossing over and genetic 63 Human reproductive variation system: female 56 Flower structure 64 Spermatogenesis: testis  65 Spermatogenesis: 82 Human sex linkage: sperm hemophilia 66 Oogenesis: meiotic 83 Amniocentesis division 84 Inheritance of blood 67 Oogenesis: ovarian cycle groups 68 Sexual intercourse 85 Chromosome mutation: 69 Human fertilization types 70 Contraception 86 Chromosome mutation: 71 Twins syndromes 72 Fetal development 87 Gene mutation: types 73 Placenta 88 Gene mutation: sickle- 74 Birth cell shape 75 Variation 89 Gene mutation: sickle- 76 Monohybrid cross: peas cell anemia 77 Dihybrid cross: guinea 90 Evidence for evolution: pigs primitive and advanced 78 Codominance 91 Evidence for evolution: 79 Karyotype preparation adaptive radiation 80 Human chromosomes 92 Evidence for evolution: 81 Human sex inheritance continental drift 3 DIVERSITY 93 Classification of living 104 Kingdom Plantae: organisms Angiospermae: life cycle 94 Kingdom Monera: 105 Kingdom Animalia: Bacteria classification 95 Kingdom Protista: 106 Kingdom Animalia: Amoeba Porifera 96 Kingdom Protista: 107 Kingdom Animalia: Paramecium Cnidaria 97 Kingdom Protista: 108 Kingdom Animalia: Spirogyra Platyhelminthes 98 Kingdom Fungi: 109 Kingdom Animalia: Rhizopus Platyhelminthes: 99 Kingdom Plantae: tapeworm classification 110 Kingdom Animalia: 100 Kingdom Plantae: Platyhelminthes: liver Bryophyta fluke 101 Kingdom Plantae: 111 Kingdom Animalia: Pteridophyta Nematoda 102 Kingdom Plantae: 112 Kingdom Animalia: Gymnospermae Nematoda: life cycle 103 Kingdom Plantae: 113 Kingdom Animalia: Angiospermae Annelida  114 Kingdom Animalia: 120 Kingdom Animalia: Mollusca Echinodermata 115 Kingdom Animalia: 121 Kingdom Animalia: Mollusca: Gastropoda Chondrichthyes 116 Kingdom Animalia: 122 Kingdom Animalia: Insecta Osteichthyes 117 Kingdom Animalia: 123 Kingdom Animalia: Crustacea Amphibia 118 Kingdom Animalia: 124 Kingdom Animalia: Chilopoda and Reptilia Diplopoda 125 Kingdom Animalia: Aves 119 Kingdom Animalia: 126 Kingdom Animalia: Arachnida Mammalia 4 MAINTENANCE 127 Nutrition: types 142 Coordination: nervous 128 Nutrition: Protista systems 129 Nutrition: leaf structure 143 Excretion and 130 Nutrition: stomata osmoregulation: Protista 131 Transport: stem structure 144 Locomotion: earthworm 132 Transport: woody stem 145 Locomotion: 133 Transport: root structure grasshopper 134 Transport: water and 146 Reproduction: viruses minerals in plants 147 Reproduction: butterfly 135 Transport: food in plants 148 Reproduction: frog 136 Transport: frog 149 Growth and 137 Respiration: plants development: plants: 138 Respiration: gas monocotyledons exchange across body 150 Growth and surfaces development: plants: 139 Respiration: respiratory dicotyledons surfaces in animals 151 Growth and 140 Respiration: fish development: plants: 141 Respiration: frog tropisms 5 HUMAN BIOLOGY 152 Nutrition: digestive 155 Nutrition: small intestine system 156 Nutrition: digestion and 153 Nutrition: teeth absorption 154 Nutrition: liver, stomach, 157 Transport: circulatory and pancreas system map 158 Transport: circulatory 175 Coordination: nervous system scheme system 159 Transport: heart 176 Coordination: nerve structure impulse 160 Transport: heartbeat 177 Coordination: synapse 161 Transport: regulation of 178 Coordination: autonomic heartbeat nervous system 162 Transport: blood vessels 179 Coordination: brain 163 Transport: capillaries and structure tissues 180 Coordination: brain 164 Transport: lymphatic function system 181 Coordination: taste 165 Transport: blood 182 Coordination: smell composition 183 Coordination: ear 166 Transport: blood types structure 167 Respiration: respiratory 184 Coordination: hearing system and balance 168 Respiration: lungs 185 Coordination: eye 169 Respiration: breathing structure 170 Excretion: excretory 186 Coordination: light systems sensitivity 171 Excretion: urinary system 187 Coordination: endocrine 172 Excretion: kidney system structure 188 Coordination: pituitary 173 Excretion: kidney gland function 189 Locomotion: skeleton 174 Excretion: skin structure 190 Locomotion: joints 6 ECOLOGY 191 Terrestrial biomes 195 Energy flow 192 Carbon cycle 196 Pyramid of biomass 193 Nitrogen cycle 197 Food web 194 Water cycle APPENDIXES 198 Key words 205 Internet resources 207 Index  8 UNITY Simple carbohydrates Key words Types of carbohydrate carbohydrates condensation reaction glycosidic bond starch sugar sugars Types of carbohydrate Carbohydrates are chemical compounds that contain carbon and the elements of water: hydrogen and oxygen. A few also contain nitrogen or monosaccharides disaccharides sulfur. (CH2O)n * There are two main groups of carbohydrates: sugars and starches. Sugars are small, water soluble molecules that taste sweet. Starches are very large, insoluble molecules. Carbohydrates may be monosaccharides, disaccharides, or polysaccharides. polysaccharides Monosaccharides Simple sugars all have the same general formula Cn(H2O)n. The simplest common sugar found in animals is glucose (C6H12O6). Glucose has two molecular forms: a straight single monosaccharide unit chain and a ring. About 98 percent of (* n = usually 3 to 6) the sugar molecules in a solution are in ring form. Disaccharides Molecular structure of glucose Disaccharides (see page 9) are sugars made by linking together two hydrogen monosaccharide rings by a condensation reaction. An OH group oxygen from each monosaccharide unit reacts together to make water (H2O) and form an oxygen bridge between the sugar rings. Maltose (C12H22O11) is a disaccharide that is a product of starch digestion and is also found in some germinating seeds. It is formed by two glucose carbon molecules joined together by a glycosidic (C-O-C) bond. OH groups at the end of a disaccharide © Diagram Visual Information Ltd. molecule can link with more rings to make longer chains. However, most sugars have three rings or fewer.  9 Complex carbohydrates UNITY Key words Complex carbohydrates cellulose sugar glycogen Two glucose molecules polysaccharide respiration H H starch H C OH H C OH Polysaccharides Carbohydrates with large numbers of C O C O rings in their molecules are called H H H H polysaccharides. Polysaccharides are used in living H + H things for energy storage and to build C C C C structures (see page 10). OH H OH H OH OH Energy storage C C C C Starches are large polysaccharides formed (synthesized) by joining long chains of monosaccharide units (such H OH H OH as glucose) together. Since starches are insoluble, they form granules within a cell and do not upset the OH OH water balance of the cell in the way that the same amount of soluble sugar would. When energy is needed, a reaction, called hydrolysis breaks the starch condensation reaction hydrolysis down into its sugar molecules. These (synthesis) (breakdown) sugar molecules can then be used to provide energy by respiration. Animals use the polysaccharide H2O H2O glycogen as a carbohydrate energy storage molecule. Building structures Cell walls in plants are made of a polysaccharide called cellulose. A Disaccharide: Maltose cellulose molecule may contain H H thousands of monosaccharide units bonded together. The links between the H C OH H C OH monosaccharide units in cellulose are arranged to produce a flat molecule C O C O that is stronger than a steel fiber. H H H H These molecules run through the cell walls of plants like the steel rods in reinforced concrete. C C C C OH H OH H © Diagram Visual Information Ltd. OH OH C C O C C glycosidic bond H OH H OH  10 UNITY Important Key words cellulose polysaccharide polysaccharides exoskeleton glucose glycogen Uses of polysaccharides polysaccharides gut α glucose structural polysaccharides β glucose Polysaccharides in animals In animals polysaccharides are mainly acetylglucosamine cellulose used for energy storage. In humans up (plant cell walls) to 10 percent of the weight of the liver can be glycogen—an instant store of energy that is easier to mobilize than fat, which is used for long-term energy storage. A typical glycogen molecule may chitin (arthropod contain 300 to 400 glucose units in a exoskeletons branching molecule. and fungi) Glycogen also occurs in yeasts and bacteria. Chitin is made of acetylglucosamine, glucose units with an amino group attached. It is common in shellfish (the edible crab can be 70 percent chitin) where it is an important part of the shell. Chitin is also found in the exoskeleton of insects. Chitin is a structural polysaccharide storage and is not used as an energy store. polysaccharides Polysaccharides in plants Plants store starch as granules inside starch glycogen (plant cells) (liver and their cells. Roots such as potatoes and muscles) carrots are often rich in starch, which provides the energy needed for the next generation to develop before it can produce its own food by photosynthesis. Cellulose is a structural polysaccharide and gives the cell wall its strength. Animals cannot digest cellulose, and so it passes through the gut largely untouched as roughage. © Diagram Visual Information Ltd.  11 Amino acids UNITY Key words Generalized amino variable group (R) amino acid acid structure H R O peptide bond polypeptide N C C ( amino group (basic) H H non-variable part OH carboxyl group (acidic) ( Chemical structure Amino acid molecules are made of Natural amino acids four groups bonded with a single carbon atom. Three of these groups Glycine (Gly) Alanine (Ala) Valine (Val) Serine (Ser) Threonine (Thr) Aspartic acid (Asp) are non-variable. H CH3 CH3 CH3 OH CH3 O OH The amino group NH2 is a basic group, which means it behaves as an alkali in CH CH2 H C OH C solution. At the other end of the molecule is a CH2 carboxyl group (COOH), which acts as an organic acid. The third group is a hydrogen atom. The fourth group is variable. It is often Asparagine (Asn) Cysteine (Cys) Leucine (Leu) Isoleucine (Ile) Methionine (Met) shown in diagrams by the letter R. O NH2 SH CH3 CH3 CH3 CH3 Different amino acids have different R groups. C CH2 CH CH2 S Natural amino acids CH2 CH2 CH CH3 CH2 There are about 20 naturally occurring amino acids. CH2 The simplest amino acid is glycine. The R group here is a single hydrogen atom. More complicated amino acids, such Glutamic acid (Glu) Glutamine (Gln) Phenylalanine (Phe) Tyrosine (Tyr) Arginine (Arg) as proline, have R groups containing O OH O NH2 OH NH2 many atoms, complex rings, and sometimes elements such as sulfur or C C C NH phosphorus. CH2 CH2 CH2 NH Joining amino acids Amino acids can join to make chains CH2 CH2 CH2 CH2 called polypeptides when the acid group from one amino acid reacts with CH2 the carboxyl group of another. The reaction releases water and produces a CH2 link called a peptide bond. Lysine (Lys) Tryptophan (Trp) Histidine (His) Proline (Pro) More amino acids can be added at each end of the new molecule (see CH2 NH2 HC N CH2 CH2 page 12). CH2 CH CH2 CH C OH © Diagram Visual Information Ltd. CH2 NH C NH NH O CH2 C CH CH2 CH2 non-variable part of amino acid molecule  12 UNITY Protein structure Key words Example of protein structure amino acid hemoglobin Insulin insulin (produced in pancreas) peptide bond B-polypeptide A-polypeptide protein chain chain Phe Gly Small molecules All proteins are made of small amino acid molecules linked by peptide Val Ile bonds in long chains resembling a string of beads. Asn Val The number and order of amino acids in the chain decides how the protein will behave. Gln Glu Some proteins have more than one chain of amino acids and some have His Gln Ser Leu extra groups of atoms added. For disulfide example, hemoglobin, which bridge transports oxygen from the lungs to Leu Cys S S Cys Tyr cells throughout the body, is a protein disulfide with four amino acid chains wrapped bridge Cys S S Cys Val Gln around a central group containing iron. Gly Ala Ser Leu Protein size Insulin (right) is a small protein molecule with only 51 amino acids on Ser Glu two chains tethered together by 3 disulfide bridges. His Asn Some of the large immunity proteins have thousands of amino acids and are bigger than some simple living Leu Tyr Leu Val Tyr organisms! disulfide bridge Val Leu Cys S S Cys Twisting and turning The amino acid chain twists as it grows. The twisted chain then forms a Glu Ala Gly Asn spiral. The spiral shape is held together by links along its length. Glu peptide Arg bond Thr Tyr Phe Phe Gly Pro © Diagram Visual Information Ltd. Lys Ala  13 Classification of proteins UNITY Key words Types of protein proteins collagen enzyme hemoglobin hormone peptide bond fibrous Types of protein There are two main groups of proteins: fibrous and globular. Both groups have the same basic structure—they are long chains of amino acids joined by peptide bonds. The difference between the two groups depends on the way the structural contractile (e.g., collagen) (e.g., myosin) protein chains are arranged. Fibrous proteins Fibrous proteins have chains twisted into spiral shapes held together by strong bonds to make the molecule look like a spring. Fibrous proteins can be divided into structural and contractile proteins. globular Structural proteins form the structure of an organism. For example, they can be found in skin and hair. Collagen fibers in the skin give it elasticity and keep it smooth. Contractile proteins such as myosin help muscles contract. Globular proteins Globular proteins have chains that wind in and out of each other, twisting into complex shapes that look like a ball of wood. Their chains are held together with a mixture of strong and weak bonds. Globular proteins often have more than one chain and can contain extra non-protein groups. For example, hemoglobin contain iron ions. Globular proteins are often delicate and easily damaged by heat or chemicals. If their molecular shape is changed by heat they cannot work properly. There are various types of globular © Diagram Visual Information Ltd. proteins. Some transport smaller molecules. Some act as enzymes, controlling the rate of chemical reactions. Some have a protective function. Still others are hormones, enzymes transport protective hormones (e.g., hemoglobin) (e.g., antibodies) (e.g., insulin) the chemical messengers of the body.  14 UNITY Enzymes: mechanism Key words Lock-and-key hypothesis active site enzyme Enzyme + substrate substrate enzyme active site Enzymes and reactions Enzymes are proteins that control the substrate molecules rate of reactions in living things. Sugar reacts easily with oxygen to give active site carbon dioxide and water—but outside organisms it needs to be unchanged heated to well above 300°F (150°C) enzyme to start the reaction. Inside living used again organisms, enzymes make the same reaction work at temperatures as low Enzyme + product as the freezing point. Each reaction has its own enzyme—if the enzyme is missing the reaction does not take place. An enzyme for one reaction will not work on another reaction. Most reactions in living things are product broken down into many steps—and molecule each step needs its own enzyme. There are two hypotheses of enzyme action: lock and key and induced fit. Enzyme-substrate Lock-and-key hypothesis complex In this hypothesis, when the chemicals involved in a reaction (the substrates) get near an enzyme molecule, they “fit” into a part of the molecule called the active site, like a key in a lock. The enzyme is shaped so that the important parts of each chemical are close enough to each other to react Induced-fit hypothesis together. When the reaction has occurred, the new chemicals (the products) do not fit in the lock and are released. This leaves the enzyme free to catalyze another reaction. Induced-fit hypothesis This hypothesis suggests that the substrate helps the enzyme to form © Diagram Visual Information Ltd. the correct shape to receive it.  15 Enzymes and coenzymes UNITY Key words The coenzyme mechanism active site substrate coenzyme enzyme Enzyme enzyme- + coenzyme coenzyme complex Coenzymes coenzyme Coenzymes are usually small enzyme molecules that are needed in some enzyme reactions to help the reaction active site work properly. As with enzymes, many coenzymes only work with particular enzyme reactions. If the coenzyme is missing, the reaction will not work properly. Enzyme The coenzyme from another reaction + coenzyme + substrate substrate will not do the job. molecules molecules Vitamins and minerals are often involved in reactions as coenzymes. The coenzyme mechanism Most enzymes will not react with any chemical other than their substrate. Unchanged This is known as specificity—the enzyme + coenzyme enzyme is specific for a particular are used again. substrate. Some enzymes can only react in the presence of a coenzyme. The Enzyme- coenzyme binds to the enzyme and substrate changes its shape. The active site is complex now ready to receive its normal substrate. The substrate bonds to the enzyme and reacts to produce the required product. Reusing the coenzyme When the enzyme-catalyzed reaction has occurred, the product is released from the enzyme-coenzyme complex. The coenzyme is also released and becomes available for another product molecule reaction. Respiration in cells is a good example Enzyme of a complex enzyme pathway that + coenzyme + product depends on a collection of coenzymes. © Diagram Visual Information Ltd.  16 UNITY Enzymes and inhibitors Key words Inhibitors A noncompetitive inhibitor binds to another active site enzyme part of the enzyme and blocks the active site. inhibitor noncompetitive substrate inhibitor Inhibitors A competitive inhibitor binds Inhibitors reduce or destroy the to the active site and blocks it. activity of an enzyme—sometimes to enzyme dangerous levels. There are two types of inhibitors: active competitive inhibitors and non- site competitive competitive inhibitors. inhibitor Competitive inhibitors enzyme Competitive inhibitors bind with the active site of an enzyme. In effect, they “compete” with the normal substrate for this site and block it. Many competitive inhibitors are released from the active site so the enzyme can be regenerated. The substrate higher the concentration of the molecules “normal” substrate compared with the inhibitor, the less effect the inhibitor has. The inhibitor is not displaced by Non-competitive inhibitors excess substrate A non-competitive inhibitor does not substrate molecules. bind to the active site. It binds with a molecules different part of the enzyme molecule. This distorts the shape of the enzyme so it cannot function properly. Non-competitive inhibitors are not released from the enzyme molecule so the enzyme cannot be regenerated. Even a low concentration of a non- The inhibitor competitive inhibitor can be very is displaced by excess dangerous. substrate Cyanide is a non-competitive inhibitor molecules. that completely blocks an essential enzyme in the respiration pathway. It is therefore a very powerful poison. © Diagram Visual Information Ltd.  17 Fatty acids and glycerol UNITY Key words Glycerol: molecular Stearic acid (saturated): model fatty acid structure single bond glycerol O H C H C OH HO Glycerol H C OH Glycerol is a small molecule with three OH groups emerging from a short H C OH Oleic acid (unsaturated): model carbon chain. It is important in the formation of lipids, substances H O double bond insoluble in water that include fats and oils. C Fatty acids HO Fatty acids are long chains of carbon atoms (sometimes up to 30 or 40) with a COOH group at one end. The Glycerol molecule COOH group means that they behave H2O O as acids in solution. H Fatty acids may be saturated (having Three fatty acid molecules only a single carbon-to- H C OH HO C carbon bond [see stearic acid], or unsaturated (one or stearic more double or triple H2O O acid carbon-to-carbon bonds [see oleic acid]). The number and location of double bonds H C OH HO C varies. Fatty acids are the building stearic H2O O acid blocks of fat. Fatty acids react with glycerol to bond their long chains to H C OH HO C the OH group in glycerol. When three fatty acids join stearic H acid on all three of the OH groups in glycerol, a triglyceride (fat) is formed. Tristearin (triglyceride) Some triglycerides are simple and have only one type of fatty acid joined to H O the glycerol molecule. Other triglycerides are mixed: they have H C O C three different fatty acids joined onto one glycerol molecule. O Triglycerides H C O C The fat on meats such as bacon © Diagram Visual Information Ltd. consists of a variety of mixed O triglycerides. Different fats have different mixtures of these triglycerides. H C O C H  18 UNITY Light microscope Key words Light microscope objective lens ocular lens eyepiece containing ocular lens Two lenses A light microscope uses two coarse adjustment knob sets of lenses, objective and ocular lenses, to create body tube fine magnifications of up to 1000X. adjustment knob revolving The lens near the specimen is nose piece low power called the objective lens. This objective lens cannot produce an image by high power itself. objective The lens in the eyepiece at lens the end of the viewing tube is arm called the ocular lens. This helps to focus the beams of eye light to produce the image. To calculate the magnification stage of the microscope, you have eyepiece (ocular lens) to multiply the magnification diaphram of the objective lens by the magnification of the ocular lens. mirror Two focusing devices Lenses in microscopes are very delicate. To prevent them base from being damaged by scratching them against the sample, the light microscope uses two-stage focusing. The coarse adjustment knob moves the low power objective lens through a large Image formation distance. When the area you objective wish to observe is in the lens center of the field of view and in sharp focus, you may click the high power objective lens into place. The image should already be nearly in focus. If specimen any adjustment is needed, use diaphram only the fine adjustment knob. © Diagram Visual Information Ltd. A clear light The diaphragm regulates the mirror amount of light reaching the lamp object.  19 Cells: light microscope UNITY Key words Generalized animal cell cellulose plasma chloroplast membrane cytoplasm vacuole nucleus photosynthesis nucleus nuclear envelope Cell size nucleoplasm Typical cells are anything between nucleolus.005 and.025 mm (.0002 and.001 in). This is about ten times smaller than the diameter of a human hair. Light microscopes can only see relatively large structures in a cell plasma membrane because they can only magnify up to cytoplasm 1,000X. food granules Animal cells The cell contains a large nucleus, which helps to control the cell. The nucleus is separated from the secretory granules cytoplasm by the nuclear envelope (membrane). Inside the nucleus, the nucleoplasm, the liquid matrix of the nucleus, surrounds the nucleolus, where proteins are synthesized. The area outside the nucleus but within the outer membrane is called Generalized plant cell cell wall of the cytoplasm. It often contains a neighboring cell collection of smaller bodies such as food or secretory granules, and cell wall sometimes small vacuoles (small sacs enveloped in a membrane). These are plasma envelope often very difficult to see with a light microscope. Plant cells Plant cells are surrounded by a thick cell wall made of cellulose. Immediately inside the cell wall is the vacuole plasma membrane of the plant cell. This is identical to the plasma chloroplast membrane of animal cells. Plant cells have a large central vacuole that occupies much of the cell volume. cytoplasm It stores salts, water, water soluble nucleus pigments, and potentially toxic nucleolus molecules in the form of crystals. © Diagram Visual Information Ltd. The cytoplasm contains many of the nucleoplasm inclusions (globules, granules, etc.) nuclear found in animal cells and a large envelope vacuole. Sometimes large green disc- shaped bodies called chloroplasts are present: these carry out photosynthesis.  20 UNITY Electron microscope Key words specimen Electron microscope Simplified section through a simple transmission electron microscope illuminating HT cable system Electrons not light insulator An electron microscope (EM) uses electrons rather than shield and filament beams of light. Magnetic and electric fields are used to anode focus the electrons instead of glass lenses. The use of electrons allows condenser lens Image formation magnifications up to 10,000X and beyond. electron gun Function specimen door Electron microscopes function just like light microscopes condenser specimen lens except that they use a beam airlock of electrons instead of light to stage image the specimen. Through a series of magnetic lenses objective and apertures, the lens microscope focuses a beam of specimen electrons on a specimen. The beam interacts with the sample, and the microscope intermediate lens objective records the results of the lens interaction as an image. objective lens Types of information aperture projector lens Electron microscopes can examine the tomography eyepiece intermediate lens (surface features) of an object, the morphology (size and shape of the particles) of an projection object, the composition of the chamber object, and the arrangement of the atoms in the object. window projector lens Disadvantages Specimens need very fluorescent complicated preparation screen before they can be used in the EM. This treatment can © Diagram Visual Information Ltd. sometimes produce artefacts, camera objects that have nothing to door do with the sample. imaging system plate camera to vacuum pump fluorescent screen  21 Animal cell: UNITY electron microscope Key words centriole mitochondrion endopasmic plasma reticulum membrane Animal cell Golgi body ribosome pinocytotic plasma membrane smooth lysosome vesicle endoplasmic reticulum Smaller sizes The electron microscope can see much smaller objects than the light cytoplasm microscope is able to see. Membrane structures The cell uses a double-layered membrane to build many structures: the plasma membrane, Golgi body, rough lysosomes, and the endoplasmic endoplasmic reticulum. reticulum The plasma membrane covers the ribosome whole of the outside of the cell. The endoplasmic reticulum is a meshwork of the same membrane that Golgi runs throughout the cell. It is used for body intracellular transport. Ribosomes, usually found on the rough endoplasmic reticulum, synthesize centrioles protein. The Gogli body is involved with the creation of the endoplasmic reticulum and in the secretion of some substances from the cell. It is the packaging center of the cell. Lysosomes contain digestive enzymes. nucleus Other structures nuclear The nucleus controls the cell. It is envelope separated from the cytoplasm by the nuclear envelope. The nucleus nuclear contains the nucleolus, which contains pore the DNA templates for ribosomal RNA, nucleolus and chromatin, the substances from which chromosomes are made. chromatin Openings in the cell's nuclear envelope, called nuclear pores, allow lysosome the exchange of materials between the nucleus and the cytoplasm. mitochondrion Mitochondria are the site of aerobic respiration, which gives the cell © Diagram Visual Information Ltd. energy. The mitrochondrion is sometimes referred to as the “powerhouse” of the cell. Pinocytotic vesicles contain soluble molecules from outside the cell. Centrioles, found only in animal cells, help the cell to divide.  22 UNITY Plant cell: Key words chloroplast lysosome electron microscope endoplasmic mitochondrion reticulum plasma Plant cell Golgi body membrane granum ribosome cell wall Plant and animal cells Many of the structures found in animal cells are also present in plant cells. plasma membrane However, plant cells do not contain centrioles. cytoplasm Membrane structures The plant cell uses a double- layered membrane to build many structures: the plasma nucleus membrane, Golgi body, lysosomes, nuclear envelope and endoplasmic reticulum. These membrane-based structures carry out nuclear pore exactly the same functions in plants nucleolus and animals (see page 23). The plasma membrane in plants has mitochondrion the same double-layered structure as it chromatin has in animals but is further supported by a cell wall. The cell wall is a tough smooth endoplasmic cellulose-rich structure that surrounds reticulum the plant cell. The plasma membrane is not attached to the cell wall, but ribosome when a plant cell is fully filled with water, the membrane is pressed rough tight against the cell wall. endoplasmic reticulum Other structures Plant cells have a large central vacuole enclosed by the vacuole tonoplast. The nucleus controls the cell. Mitochondria are the site of aerobic respiration, which gives the cell energy by granum breaking down glucose. Ribosomes, usually tonoplast found on the rough (vacuole membrane) endoplasmic reticulum, make protein. Chloroplasts © Diagram Visual Information Ltd. Chloroplasts are only found in green plants. They are green-colored bodies Golgi body that carry out photosynthesis to make sugar for the plant. cell wall of neighboring cell The grana in the chloroplasts contain the phot