Unit 1 Cells and Multicellular Organisms

UNIT 1

QCE BIOLOGY Unit 1 Cells and Multicellular Organisms

Kerri Humphreys © Science Press 2019 First published 2019

Science Press All rights reserved. No part of this publication Unit 7, 23-31 Bowden Street may be reproduced, stored in a retrieval system, Alexandria NSW 2015 Australia or transmitted in any form or by any means, Tel: +61 2 9020 1840 Fax: +61 2 9020 1842 electronic, mechanical, photocopying, recording [email protected] or otherwise, without the prior permission of www.sciencepress.com.au Science Press. ABN 98 000 073 861 Contents

Introduction v 35 Developing the Cell Theory 52 Words to Watch vi 36 Experiment – The Light Microscope 54 37 Experiment – Using a Light Microscope 55 Topic 1 Cells As the Basis Of Life 38 Experiment – Making a Wet Mount 56 39 Experiment – Drawing Biological Diagrams 57 1 Assumed Knowledge Topic 1 4 40 Measurement 58 2 Development Of the Model Of the Cell Membrane 5 41 Drawing Scaled Diagrams 60 3 The Current Cell Membrane Model 7 42 Writing a Practical Report 61 4 Membrane Proteins and Cholesterol 9 43 Experiment – Plant Cells 63 5 Passive Transport 10 44 Experiment – Animal Cells 64 6 Diffusion and Osmosis 11 45 The Light Microscope and Cell Organelles 65 7 Experiment – Membranes, Diffusion and Osmosis 13 46 The Electron Microscope and Cell Organelles 67 8 Experiment – Plasmolysis 14 47 Mitochondria 68 9 Energy and Active Transport 15 48 Chloroplasts 69 10 Active Transport 16 49 Golgi Bodies 70 11 Exocytosis 17 50 Cell Organelles Summary 71 12 Endocytosis 19 51 Comparing Prokaryotes and Eukaryotes 72 13 Experiment – Surface Area To Volume Ratio 20 52 Enzymes and Membranes 73 14 Experiment – Material Exchange and 22 53 Enzymes and Reactions 75 Concentration Gradient 54 Experiment – Enzyme Activity and pH 76 15 Material Exchange and the Nature Of 23 55 Experiment – Enzyme Activity and Temperature 77 the Material 56 Experiment – Enzyme Activity and Substrate 78 16 Experiment – Surface Area and Rate 24 Concentration Of Reaction 57 Enzymes and Inhibitors 79 17 Characteristics Of Living Things 25 58 Allosteric Activation and Inhibition 80 18 Cell Input and Output 26 59 Enzyme Deficiencies 81 19 Matter 28 20 Water 30 60 Coenzymes 82 21 Chemicals In Cells 32 61 Metabolism 84 22 Experiment – Substances In Tissues 34 62 Autotrophs and Heterotrophs 85 23 Carbohydrates 35 63 Photosynthesis 86 24 Lipids 36 64 Play – Inside Photosynthesis 87 25 Protein Structure 38 65 Light, Chlorophyll and Photosynthesis 91 26 Amino Acids and Proteins 40 66 Experiment – Chlorophyll and Photosynthesis 93 27 Polar and Non-Polar Amino Acids 41 67 Experiment – Light and Photosynthesis 94 28 Nucleic Acids 42 68 Reactions In Photosynthesis 95 29 Prokaryotes 43 69 Photosynthesis and Productivity 97 30 Eukaryotes 45 70 Aerobic Respiration 98 31 The Modern Light Microscope 46 71 Anaerobic Respiration 99 32 The Electron Microscope 48 72 Reactions In Respiration 100 33 The Stereo Microscope 49 73 Experiment – Carbon Dioxide, Respiration 102 34 Technology and the Development Of the 50 and pH Cell Theory Topic 1 Test 103

Science Press Surfing QCE Biology Unit 1 Cells and Multicellular Organisms iii 98 Elimination 146 Topic 2 Multicellular Organisms 99 Specialised Digestive Systems 147 100 Play – Amino and Lipidet, a Most 149 74 Assumed Knowledge Topic 2 108 Lamentable Tragedy 75 Stem Cells 109 101 Removal Of Wastes 154 76 Stem Cell Research 111 102 Wastes and Respiratory and Excretory 155 77 Cells, Tissues, Organs and Systems 113 Systems 78 Differentiation and Specialised Cells 114 103 Excretory Organs 156 79 Human Organ Systems 116 104 The Kidney 157 80 Plant Tissues and Cells 117 105 Renal Hormones 159 81 Plant Organs 119 106 Renal Dialysis 160 82 Animal Ethics 121 107 Stomates 161 83 Organ and Tissue Transplantation 122 108 Experiment – Leaf Stomates 163 84 Bioartificial Organs 123 109 Experiment – Transpiration 164 85 Respiratory Systems 124 110 Leaves 166 86 Alveoli 127 111 Transport Systems In Plants 168 87 Gas Exchange, Breathing and Ventilation 128 112 Experiment – Movement In Xylem 171 88 Gas Concentrations Around the Body 129 113 Radioisotopes Track the Movement Of 172 89 Chemical Monitoring 131 Substances In Organisms 90 The Digestive System 132 114 Root Structure 174 91 Microscopic Digestive Surfaces 134 115 Adaptations In Plants 175 92 Experiment – Rat Dissection 135 Topic 2 Test 177 93 Teeth 137 94 Mechanical Digestion 139 Answers 181 95 Chemical Digestion 140 Syllabus Cross-Reference 225 96 Accessory Digestive Organs 142 Index 229 97 Absorption 144

Science Press iviv Unit 1 Cells and Multicellular Organisms Surfing QCE Biology Introduction

This book covers the Biology content specified in the Queensland Certificate of Education Biology Syllabus. Sample data has been included for suggested experiments to give you practice to reinforce practical work in class. Each book in the Surfing series contains a summary, with occasional more detailed sections, of all the mandatory parts of the syllabus, along with questions and answers. All types of questions – multiple choice, short response, structured response and free response – are provided. Questions are written in exam style so that you will become familiar with the concepts of the topic and answering questions in the required way. Answers to all questions are included. A topic test at the end of each topic contains an extensive set of summary questions. These cover every aspect of the topic, and are useful for revision and exam practice.

Science Press Surfing QCE Biology Unit 1 Cells and Multicellular Organisms v Words To Watch

account, account for State reasons for, report on, give explain Make something clear or easy to understand. an account of, narrate a series of events or transactions. extract Choose relevant and/or appropriate details. analyse Interpret data to reach conclusions. extrapolate Infer from what is known. annotate Add brief notes to a diagram or graph. hypothesise Suggest an explanation for a group of facts apply Put to use in a particular situation. or phenomena. assess Make a judgement about the value of something. identify Recognise and name. calculate Find a numerical answer. interpret Draw meaning from. clarify Make clear or plain. investigate Plan, inquire into and draw conclusions classify Arrange into classes, groups or categories. about. comment Give a judgement based on a given statement justify Support an argument or conclusion. or result of a calculation. label Add labels to a diagram. compare Estimate, measure or note how things are list Give a sequence of names or other brief answers. similar or different. measure Find a value for a quantity. construct Represent or develop in graphical form. outline Give a brief account or summary. contrast Show how things are different or opposite. plan Use strategies to develop a series of steps or create Originate or bring into existence. processes. deduce Reach a conclusion from given information. predict Give an expected result. define Give the precise meaning of a word, phrase or propose Put forward a plan or suggestion for physical quantity. consideration or action. demonstrate Show by example. recall Present remembered ideas, facts or experiences. derive Manipulate a mathematical relationship(s) to give relate Tell or report about happenings, events or a new equation or relationship. circumstances. describe Give a detailed account. represent Use words, images or symbols to convey design Produce a plan, simulation or model. meaning. determine Find the only possible answer. select Choose in preference to another or others. discuss Talk or write about a topic, taking into account sequence Arrange in order. different issues or ideas. show Give the steps in a calculation or derivation. distinguish Give differences between two or more different items. sketch Make a quick, rough drawing of something. draw Represent by means of pencil lines. solve Work out the answer to a problem. estimate Find an approximate value for an unknown state Give a specific name, value or other brief answer. quantity. suggest Put forward an idea for consideration. evaluate Assess the implications and limitations. summarise Give a brief statement of the main points. examine Inquire into. synthesise Combine various elements to make a whole.

Science Press vivi Unit 1 Cells and Multicellular Organisms Surfing QCE Biology UNIT QCE BIOLOGY 1

UNIT 1

Cells and Multicellular Organisms

Science Press Surfing QCE Biology Unit 1 Cells and Multicellular Organisms 1 Notes

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Science Press 2 Unit 1 Cells and Multicellular Organisms Surfing QCE Biology UNIT QCE BIOLOGY 1

TOPIC 1

Cells As the Basis Of Life

Science Press Surfing QCE Biology Unit 1 Cells and Multicellular Organisms 3 1 Assumed Knowledge Topic 1

QUESTIONS 16. Why is photosynthesis an important process in ecosystems? 1. Identify seven properties of living organisms. 17. Name the four basic groups of organic compounds. 2. The cell is the basic unit of life. What structural 18. What are inorganic compounds? features of cells are possessed by all living things? 19. Define respiration. 3. Draw a fully labelled diagram of a plant cell as seen 20. Distinguish between an autotroph and a heterotroph. under a light microscope. 21. Define diffusion. 4. Draw a fully labelled diagram of an animal cell as 22. Define osmosis. seen under a light microscope. 23. The diagram shows an experiment where a bag made 5. Identify the following parts of a light microscope of dialysis tubing which acts as a selectively permeable and use by a person. membrane was filled with molecules and placed in a A beaker containing the same type of molecules.

B X

Molecule Selectively permeable membrane

C Y D E Figure 1.3 Experiment set-up.

F After a few hours it was noted that there were more molecules in area X. Explain what had happened. Figure 1.1 Light microscope. 24. The diagram shows an Amoeba, which is a eukaryotic single celled organism that can change its 6. Describe one safety precaution you should follow shape and is found in freshwater streams and ponds while using a light microscope. usually in decaying bottom vegetation. 7. What is the function of the nucleus of a cell? Bacterium 8. What is the function of the cell membrane? Nucleus 9. What is cytoplasm? Amoeba 10. Define protoplasm. 11. Describe a chloroplast. 12. Define photosynthesis. Figure 1.4 Amoeba. 13. The diagram shows a photosynthesis experiment using pond weed in a tank. What process is being shown in this diagram? 25. What are the two main energy sources for cells? Gas collecting 26. Define an enzyme. 27. What is meant by pH? Gas bubble 28. The graph shows the action of an enzyme at different pH. Pond weed Rennin activity over pH range

Water tank

Figure 1.2 Photosynthesis experiment.

(a) What gas is collecting in the test tube? Reaction rate (b) Describe a distinguishing test to identify this gas. 0 1 2 3 4 5 6 7 14. Which group of organisms can photosynthesise? Figure 1.5 Enzyme action and pH. 15. Identify the materials required by multicellular organisms for photosynthesis. What is the optimal pH for this enzyme from this graph?

Science Press 4 Unit 1 Cells and Multicellular Organisms Surfing QCE Biology 2 Development Of the Model Of This was the first indication that the membrane had molecular dimensions. Although his measurements were the Cell Membrane accurate his assumption that the cell membrane was a single molecular layer meant he misinterpreted the data. In the 19th century scientists realised that there had to be some form of semipermeable barrier around cells that separated Evert Gorter and F Grendel the internal contents of the cell from its environment. Several observations and experiments had provided some information In 1925 Gorter and Grendel removed the lipids from a about this barrier. The cell membrane is not usually visible known number of red blood cells and calculated the total under normal light microscopes which means that detail of cell area. They found that the total lipids compressed into its structure was not easily seen before the invention of the a monolayer that was twice the total cell area. From this electron microscope in the 20th century. they suggested the bilayer concept of the cell membrane. It was obvious that animal cells needed to have some kind of boundary and experiments with plant cells also showed JF Danielli that there was a barrier around the cytoplasm beside the In 1940 Danielli theorised that the cell membrane cell wall. The plant cell wall is easily seen under the light consisted of inner and outer layers of protein with two microscope and 19th century scientists found that the layers of lipid between them. He calculated the total cytoplasm of a plant cell placed in strong solutions, e.g. salt width of the membrane to be 8.0 nm. solution, pulled away from the cell wall showing the cytoplasm was surrounded by some kind of membrane. Outer protein layer Mucus Moritz Traube Moritz Traube (1826-1894) realised that cell membranes were molecular sieves and produced artificial semipermeable Lipid layers membranes to explain the physical-chemical theory of plant cell growth. Traube created artificial cells by putting droplets of glue in tannic acid. He suggested that the barrier Inner around cells was formed by an interfacial reaction of the cell protein layer Pore protoplasm with the extracellular fluid. Figure 2.1 Danielli model of the cell membrane.

Quincke J David Robertson In 1888 Quincke suggested the existence of a thin lipid layer at the boundary of the protoplasm. In his studies he Robertson took electron micrographs of cell membranes showed how a cell forms a spherical shape in water and if that showed the cell membrane consisted of two electron a cell is broken into two it will form two smaller spherical dense layers separated by a wider lighter area. The shapes in water. This behaviour is similar to the behaviour measured total thickness of the membrane was 7.5 nm. of oil in water and led to his suggestion that the cell He suggested the unit membrane which is a lipoprotein membrane was a fluid layer of fat less than 100 nm thick. sandwich with lipids arranged between two layers of protein. The two dark electron dense areas were the head groups and associated proteins and the two lipid Ernest Overton monolayers were lying in opposite orientation. Overton found that the ability of a substance to pass through the membrane was related to its chemical nature. Mueller and Rudin Non-polar substances could quickly pass through the membrane and the speed with which a substance penetrated Mueller and Rudin suggested the BLM which can stand depended on the fat solubility of the substance. for either the ‘black lipid membrane’ or the bimolecular lipid membrane’. They ‘painted’ a solution of lipid in organic solvent across an aperture to create an artificial Hugo Fricke bilayer. They then determined different properties of the In 1923 Fricke conducted experiments to measure the membrane which showed correlation with natural cell capacitance of the red blood cell membrane. He assumed membranes, e.g. lateral fluidity, high electrical resistance, the membrane to be an oil film and calculated that the cell and self-healing after puncture. membrane was 3.3 nm thick.

Science Press Surfing QCE Biology Unit 1 Cells and Multicellular Organisms 5 Frye and Edidin A study of different membranes has shown that all membranes are not identical with membrane thickness In 1970 Frye and Edidin used fluorescent dye labelling varying from 5 to 10 nm depending on the location of the techniques to conclusively demonstrate the notion of fluidity membrane. Different membranes have different proteins of the cell membrane. In their experiments they fused human and carbohydrates or similar proteins and carbohydrates and mouse cells in culture to produce human-mouse cell but in different proportions, e.g. the cell membrane hybrids and used antibodies labelled with fluorescent dyes to has more cholesterol than other membranes and the identify the proteins of mouse or human origin. They found mitochondrial membrane has more proteins than other that immediately after fusion the human and mouse proteins membranes. were to be found in separate halves of the hybrid cells. Then after a short time and incubation at 37°C the human and mouse proteins were intermixed over the cell surface. They QUESTIONS thus showed that the proteins in the cell membrane could move from place to place on the cell membrane. 1. Explain why 19th century scientists knew that the cell membrane existed but did not clearly describe

Human its structure. cell 2. Explain why 19th century scientists knew that plant 40 minutes cells had a barrier around the cell contents besides + the cell wall. 3. Construct a table to summarise the work of Traube, Mouse Mouse and Cells Quincke, Overton, Fricke, Gorter and Grendel, cell human fused protein mix Danielli, Robertson, Mueller and Rudin, Frye and Proteins tagged with Edidin and Singer and Nicolson. fluorescent antibodies 4. In the Singer and Nicolson proposal, what is Figure 2.2 Frye and Edidin experiment. the difference between peripheral and integral membrane proteins? 5. Jonathan Singer and Garth Nicolson What is the glycocalyx? 6. The diagram shows a model of the cell membrane In 1972 Singer and Nicolson proposed the fluid that was proposed in 1935. mosaic model of the cell membrane. This model kept the lipid bilayer and suggested that the proteins were Phospholipid Polar pore macromolecules embedded in the bilayer going partway or completely across the membrane. They distinguished between peripheral proteins which dissociate from the membrane when the membrane is treated with polar reagents, e.g. extreme pH or high salt and integral membrane proteins which are inserted in the membrane and can only be dissociated with reagents that are detergents which displace the membrane lipids.

Protein molecule More recent research e Figur 2.3 Model of cell membrane proposed in 1935. More recent research has shown the presence of a carbohydrate layer on the outer surface of the cell Who proposed this model? membrane known as the glycocalyx. The glycocalyx (A) Taube. consists of specific carbohydrates that form complexes (B) Danielli. with membrane proteins (glycoproteins) and membrane (C) Mueller and Rudin. lipids (glycolipids). The glycocalyx is involved in the (D) Singer and Nicolson. protection of the cell surface and different complexes 7. What is the name of the current model of the cell act as markers for cell-cell interactions, e.g. interactions membrane? between leucocytes (white blood cells) with endothelial (A) Lipid monolayer model. cells of blood vessels which can lead to the inflammatory (B) Glycocalyx model. response if the endothelial cells are injured. There is also (C) Unit membrane model. ongoing research into the structure of channel proteins in (D) Fluid mosaic model. the membrane. There is also research into the structure of other membranes relating structure to function.

Science Press 6 Unit 1 Cells and Multicellular Organisms Surfing QCE Biology 3 The Current Cell Membrane Most of the phospholipids and some of the proteins can ‘drift’ and move their position and hence their location Model is ‘fluid’. The model also explains why the membrane is semipermeable and how different molecules pass through The cell membrane forms a barrier around the outside of the the membrane. cell, containing the cell contents. It is semipermeable, i.e. compounds such as water may easily enter and leave the cell Movement of phospholipids but larger molecules such as polysaccharides cannot. Phospholipids move laterally within the membrane. The movement is very fast which means a particular Fluid mosaic model phospholipid can move about 2 μm in one second. In 1972 Jonathan Singer and Garth Nicolson proposed the fluid mosaic model to represent the structure of the Lateral movement cell membrane. Phospholipids form a bilayer with the can be very rapid, hydrophobic (water hating) end of the lipid facing the e.g. adjacent phosholipids middle of the membrane and the hydrophilic (water swap positions 107 loving) end facing towards the watery contents of the cell. times per second

Phospholipid Figure 3.3 Lipid bilayer. Tail bilayer Unsaturated hydrocarbon tails of phospholipids often have ‘kinks’ that reduce tight packing of the molecules Head Water and increase membrane fluidity. Many organisms regulate the amount of unsaturated fatty acids in their membranes Figure 3.1 Lipid bilayer. to compensate for temperature changes. Lipids become There is a range of protein molecules throughout the a solid at low temperatures (like cooking grease) and phospholipid bilayer. Different proteins serve different at low temperatures membranes with high amounts of functions and are found on specific types of cell unsaturated hydrocarbons have a greater capacity to stay membranes. Carbohydrates are present on the surface fluid and not crystallise. of the cell membrane and are important in cell-cell recognition. This is important in the immune response and Unsaturated tails of phospholipids increase the rejection of foreign cells, e.g. transplanted tissues and fluidity of the cell organs. Some carbohydrates bond to the lipids forming membrane as the glycolipids. Most carbohydrates bond with the proteins kinks keep the molecules separated forming glycoproteins.

Outside cell Carbohydrate Figure 3.4 Unsaturated tails of phospholipids increase fluidity chain of the cell membrane.

Glycolipid Membrane proteins Embedded in the phospholipid bilayer there are large protein molecules. Integral membrane proteins (IMPs) are permanently attached to the membrane. Some IMPs extend from one side of the membrane to the other side and are called transmembrane proteins. Some proteins extend only partway across the bilipid layer or the protein Peripheral can be attached to the surface and part of the integral protein Phospholipid Integral bilayer (transmembrane) protein (peripheral protein). The proteins have different glycoprotein Integral membrane Cholesterol compositions and different functions. Inside cell protein • Transport proteins – assist the movement of ions, small Figure 3.2 Fluid mosaic model. molecules or macromolecules in or out of the cell.

Science Press Surfing QCE Biology Unit 1 Cells and Multicellular Organisms 7 • Membrane receptor proteins – communicate with the environment, e.g. they can receive a signal from a hormone, neurotransmitter, cytokine or growth factor which triggers the cell to carry out a specific internal response, e.g. signals the nucleus to begin gene expression to start the synthesis of a particular protein. • Membrane enzymes – some enzymes that modify

molecules needed near the cell surface are found on ATP either side of the cell membrane. Diffusion Facilitated through diffusion lipid bilayer Signal transduction Signal transduction occurs when an extracellular molecule Passive transport Active transport activates an IMP receptor in the cell membrane. The receptor Figure 3.6 Transport across the cell membrane. sends the message into the cell. The message may signal the activation of a particular gene to start gene expression to make a particular protein or the message may alter specific QUESTIONS chemical reactions in the cell and alter cell metabolism. 1. What is meant by semipermeable? 2. External signal Who proposed the fluid mosaic model of the cell membrane? The receptor integral 3. Describe the structure of the cell membrane. membrane protein 4. What is the function of carbohydrates on the surface picks up the signal from the external environment of the cell membrane? and transmits a signal 5. Why is the model called the ‘fluid’ model? across the membrane 6. What is the importance of the ‘kinks in the which triggers a change in cellular activity unsaturated hydrocarbon tails of phospholipids? Internal response 7. Outline what happens to lipids at low and high temperatures. 8. Outline the benefits of lipids having high amounts of unsaturated hydrocarbons. Figure 3.5 Fluid mosaic model. 9. What are integral membrane proteins? 10. Construct a table to summarise the action of three Diffusion across the cell membrane types of proteins associated with the cell membrane. 11. Describe how water crosses the cell membrane. Molecules soluble in lipids, e.g. oxygen and carbon 12. Describe how water soluble amino acids cross the dioxide, dissolve in the phospholipid bilayer and diffuse cell membrane. across the membrane. Molecules not soluble in lipids, 13. When is active transport involved in the movement of e.g. water, also diffuse across the cell membrane through substances across the cell membrane? small transitory openings made by the movement of the 14. fluid lipids. Aquaporins are integral membrane proteins Explain why some substances cannot cross the cell that form pores in the membrane that act as water channels membrane. allowing the fast movement of water in or out of the cell. 15. What is the name of the current model of the cell membrane? (A) Fluid mosaic. Facilitated diffusion across the cell (B) Biprotein layer. membrane (C) Trilipid layer. Many compounds need to combine with a particular (D) Drifting protein. ‘carrier’ molecule to cross the membrane. As the carrier 16. How does most water cross the cell membrane? molecule moves across the membrane, it transports the (A) Active transport. molecule with it, e.g. large water soluble molecules such (B) Attached to a large carrier protein. as amino acids and simple sugars combine with transport (C) Dissolving in the phospholipid layer. integral proteins. If energy is used to move a chemical (D) Diffusion through aquaporins. against a concentration gradient, it becomes active transport across the membrane.

Science Press 8 Unit 1 Cells and Multicellular Organisms Surfing QCE Biology 4 Membrane Proteins and The naming of the fluidmosaic model refers to mosaics of different proteins embedded in the lipid bilayer. Cholesterol Cholesterol There are two types of membrane proteins – integral membrane proteins (IMP) that protrude and are Cholesterol is a steroid lipid that is mainly hydrophobic permanently attached to the membrane and peripheral with a hydroxyl group [OH] on one end and it is only proteins that are attached only to one side of the slightly soluble in water. Cholesterol embedded in the membrane and do not penetrate the membrane. cell membrane makes the membrane less fluid giving the membrane a degree of stability and firmness. The rigid Extracellular fluid Glycoprotein planar part of the cholesterol blocks movement of the first Oligosaccharide Peripheral protein part of the fatty acid chain. Integral proteins Glycolipid HO

Integral Cholesterol protein CH Peripheral 3 Cytosol protein H H CH H H H Figure 4.1 Cholesterol and membrane proteins in cell membrane. 3 CC C C C CH3 H H H CH3 CH3 Functions of membrane proteins Figure 4.2 Cholesterol. There are many kinds of proteins in cell membranes with each having a specific function. In a cell membrane cholesterol can align with the phospholipids on either side of the bilayer and prevents Table 4.1 Functions of membrane protein. the tight packing of phospholipids. The ringed part of cholesterol is rigid and flat and aligns next to the first Role Diagram Description of function part of hydrocarbon tails of the phospholipids in animal Channel Channel proteins have a hydrophilic cell membranes as the hydroxyl group is attracted to the proteins channel that allows certain molecules polar head and lower oxygen atoms of the phospholipid. for passive and ions to cross, e.g. aquaporins for transport Channel protein water movement. The flexible linear tail of cholesterol aligns near the lower part of the fatty acid chain of the lipid bilayer making the Carrier Carrier proteins change shape taking proteins a substance across the membrane. centre of the bilayer the most fluid. At high concentrations for active If moving a substance against a cholesterol helps separate the phospholipids so that the transport Carrier protein concentration gradient energy, fatty acid chains do not come together and crystallise. e.g. ATP is needed, e.g. sodium- potassium pump in animal cells. It helps prevent extremes, e.g. too fluid or too firm. The cholesterol also reduces permeability to some solutes. Membrane Enzymes Enzymes in a series or system can bound be embedded in the membrane enzymes with the active sites exposed to QUESTIONS the aqueous solution. This allows Substrate Active sites a reaction series in a metabolic pathway to occur, e.g. enzyme ATP 1. Identify the two main types of membrane proteins. synthase for aerobic respiration. 2. Outline how membrane proteins can be involved Attachment Integral proteins can bind to in passive transport and active transport across the to adjacent proteins from adjacent cells, membrane. cells e.g. forming tight junctions or gap junctions. 3. How are membrane proteins involved in reaction

Tight junction pathways such as aerobic respiration? 4. How are some glycoproteins involved in cell-cell Cell Some glycoproteins are detected recognition? Identification by recognition sites on proteins of other cells and act as identification 5. What is cholesterol? indicators. 6. Draw a diagram to show how cholesterol aligns with

Glycoprotein phospholipids. 7. Discuss how cholesterol affects the properties of a Hormone Hormone Some integral proteins have a binding membrane. binding sites site for a specific hormone, e.g. for signal transduction The hormone triggers a response in the cell.

Science Press Surfing QCE Biology Unit 1 Cells and Multicellular Organisms 9 5 Passive Transport Semipermeable Semipermeable membrane membrane

Passive transport is the movement of particles that does not require an input of energy. Diffusion is the movement of particles from an area of high concentration of particles to an area of low concentration of particles. This leads to the random spreading out of particles. Osmosis is a type of diffusion. In biology, osmosis refers to the movement of water, Weak Strong Medium across a semipermeable membrane, from an area of high (water) (sugar solution) water concentration to an area of low water concentration. Figure 5.3 Osmosis.

• = Particle When comparing two solutions, hypertonic is used to •• • describe the more concentrated solution and hypotonic •••• Area of high concentration describes the less concentrated solution. If the two solutions ••••• ••• have the same concentration they are called isotonic. • • Particles move out • Area of low concentration QUESTIONS

Figure 5.1 Diffusion. 1. Define diffusion. 2. Define osmosis. The rate of diffusion depends on the concentration 3. How does the concentration gradient influence the difference – the greater the difference, the faster the rate rate of diffusion? of diffusion. The difference in the number of particles 4. How is active transport related to the concentration compared to the number of particles in another area is gradient? called the concentration gradient. Substances will move 5. What is the difference between hypertonic, down a concentration gradient by passive transport. hypotonic and isotonic solutions? Substances can move against a concentration gradient, 6. In what ways are the processes of diffusion and however, energy is needed to force the particles to move osmosis similar and different? to a place of higher concentration of those particles and 7. If a human red blood cell was placed in distilled water, this movement is called active transport. explain what would happen to the cell. 8. If a strong sucrose solution is placed one side of When a semipermeable membrane separates two a semipermeable membrane and a weak sucrose solutions, only the small molecules can pass through the solution is placed the other side of the membrane, membrane, e.g. water moves across by osmosis. what would you expect to happen? Semipermeable membrane (A) The sucrose will move from the weak sucrose (very highly magnified) solution to the strong sucrose solution. Sugar solution Water (B) The sucrose will move from the strong sucrose solution to the weak sucrose solution. (C) The water will move from the weak sucrose Sugar molecule Water molecule solution to the strong sucrose solution. (D) The water will move from the strong sucrose solution to the weak sucrose solution. 9. Figure 5.4 shows the movement of particles.

Most water molecules move in this direction

Figure 5.2 Semipermeable membrane.

If water and a sucrose solution are separated by a semipermeable membrane, the water molecules can move across the membrane, but the sucrose molecules cannot. e Figur 5.4 Movement of particles. The osmotic pressure wants to equal out the concentrations, What is the best name for this movement? so the water will move into the sugar solution, trying to (A) Osmosis (B) Diffusion. equalise the concentrations, causing the volumes to change. (C) Dissolving (D) Active transport.

Science Press 10 Unit 1 Cells and Multicellular Organisms Surfing QCE Biology 6 Diffusion and Osmosis Factors affecting the rate of diffusion The rate of diffusion depends on the following. Diffusion is the movement of particles from an area • Concentration gradient – the difference in the number of high concentration of particles to an area of low of particles in one area to the number of particles in concentration of particles. Diffusion is due to the random another area forms a concentration gradient between movement of particles. The particles will spread out until the two areas. The higher the concentration gradient the they evenly fill the available space. faster the rate of diffusion. In diffusion particles move Net diffusion stops when equilibrium is reached. At down a concentration gradient. equilibrium the molecules continue to move but there is • Size of the molecule – the size of a particle and its no net change in concentration. mass is inversely proportional to the rate of diffusion. The smaller the particle the faster the rate of diffusion. Molecules before moving about Molecules after moving about • Temperature – particles at high temperatures have more energy than particles at low temperatures. The particles at high temperatures move faster than particles at low temperatures. The rate of diffusion is directly proportional to temperature. The higher the temperature, the faster the rate of diffusion.

Figure 6.1 Diffusion. • Diffusion distance – the distance the particle has to travel will affect the time it takes for particles to Diffusion is passive transport as energy does not need spread to another area. The further the distance, the to be provided for the movement to occur unlike active slower the rate of diffusion. transport which requires an input of energy. In diffusion • Permeability of the particle – permeability is the ability the particles move down a concentration gradient from an of the particle to pass through. Solubility refers to the area of high concentration to an area of low concentration amount of a substance that can be dissolved in a given while in active transport the particles move against the amount of solvent. Substances that dissolve in lipids concentration gradient from an area of low concentration can more easily pass through a cell membrane than to an area of high concentration. substances that dissolve in water. The rate of diffusion across a membrane is related to the permeability of the particle. Substances that can move across a membrane High by simple diffusion include carbon dioxide, oxygen and ethanol. The membrane is not permeable to ions. Rate of diffusion • Surface area of the membrane over which the

Low molecule moves – if diffusion occurs across a Low High membrane then the greater the surface area of the Concentration gradient membrane, the faster the rate of diffusion. High temperature High concentration − faster diffusion gradient − faster diffusion Extracellular space Hydrophobic Small uncharged Large uncharged molecule polar molecules polar molecule Ions + + + Small particles Rate of Long distance − H2O Na , K , H O2, CO2, N2 Glucose diffuse faster diffusion slower diffusion Glycerol Ca2+ Steroids Sucrose Urea Cl– Ethanol

Slow Fast Permeability of particles

Cytoplasmic space Large suface area of membrane − faster diffusion Figure 6.3 Permeability across a membrane.

Figure 6.2 Factors affecting the rate of diffusion.

Science Press Surfing QCE Biology Unit 1 Cells and Multicellular Organisms 11 Osmosis 17. Glucose has the formula C6H12O6 while sucrose has the formula C H O . Explain why when carrying out Osmosis is a type of diffusion. It is the movement 12 22 11 experiments using dialysis tubing to show that some of water from an area of high concentration of water substances can cross a membrane while other substances to an area of low concentration of water across a cannot cross the membrane you need to use an aqueous semipermeable membrane. (Note: In chemistry osmosis sucrose solution and not an aqueous glucose solution. refers to the net movement of any solvent, not just water.) 18. The diagram shows an animal cell in a container The process of osmosis is highly important in filled with distilled water osmoregulation. Osmoregulation is the active regulation of the osmotic pressure of body fluids so they do not Water molecule become too dilute or concentrated in particular areas. Animal cell Osmotic pressure is the pressure needed to stop the Nucleus flow of water across a semipermeable membrane. The water potential is the physical property that predicts the direction in which water will flow and is determined by the solute concentration and the applied pressure. Figure 6.5 Animal cell in a container of water.

(a) What would you expect to happen to the animal cell? Explain your answer. (b) If it was a plant cell in the container, would the result be the same? Explain your answer. 19. The kidney can change the permeability of the collecting duct. How does this assist excretion for the body? Water molecules move 20. In plants sugar (sucrose) is loaded into the phloem Sugar molecules against a concentration gradient. Explain why water Water molecules follows the sugar into the phloem. Figure 6.4 Osmosis. 21. Which of the following does not cross the cell membrane by simple diffusion? QUESTIONS (A) Carbon dioxide. (B) Glucose. (C) Ethanol. (D) Oxygen. 1. Define diffusion. 22. The diagram shows the results of an experiment 2. Why does diffusion occur? using dialysis tubing. 3. What is meant by a concentration gradient? 4. During diffusion, how do the particles move with respect to the concentration gradient? 5. How does the size of the particle affect the rate of diffusion? 6. How does temperature affect the rate of diffusion? 7. What is the relationship between the rate of diffusion and how far the particle has to travel? 8. Define permeability. Beaker X Beaker Y 9. Define solubility. 10. If two molecules, one water soluble and one lipid Figure 6.6 Experiment using dialysis tubing. soluble had equal size, which one would more easily Pure distilled water and sucrose solution were used pass through a cell membrane? in setting up the equipment. Which of the following 11. For two lipid soluble molecules, would a small molecule best accounts for the results of this experiment? or a large molecule have the fastest rate of diffusion? (A) Sucrose solution was in bag Y with distilled water 12. Identify two substances that enter the human body outside and water moved out of the bag by osmosis. by diffusion. (B) Sucrose solution was in bag X with distilled water 13. Define osmoregulation. outside and water moved out of the bag by osmosis. 14. What is meant by the water potential? (C) Water was in bag Y with sucrose solution outside 15. Define osmotic pressure. and water moved into the bag by osmosis. 16. In an aqueous solution of glucose, what is the (D) Water was in bag X with sucrose solution outside solvent and what is the solute? and water moved out of the bag by osmosis.

Science Press 12 Unit 1 Cells and Multicellular Organisms Surfing QCE Biology 7 Experiment – Membranes, QUESTIONS Diffusion and Osmosis 1. What is meant by a semipermeable membrane? 2. In this experiment what was acting as a Some senior biology students wished to perform a semipermeable membrane? first-hand investigation to show how a semipermeable 3. What happened to the iodine molecules? membrane allows osmosis and diffusion of some 4. Compare and explain the results of gas jar 1 and gas substances to occur but prevents the movement of other jar 2. substances. 5. Explain the results in gas jar 4. They collected four gas jars, four 20 cm lengths of dialysis 6. Identify the substances that were able to pass tubing, string, a measuring cylinder, sucrose solution, through the dialysis tubing. distilled water, starch solution, iodine solution, glucose 7. Identify the substances that were not able to pass solution and parafilm. They set up the following apparatus. through the dialysis tubing. 8. When the overall size of molecules has been Gas jar 1 Gas jar 2 Gas jar 3 Gas jar 4 measured, it is found that starch molecules are Parafilm very large as they are a polysaccharide made of or plastic many glucose units; sucrose is not as large as it is a wrap disaccharide made of two monosaccharides joined together; glucose is a monosaccharide and smaller; and water and iodine molecules are very small. Thread Propose a hypothesis to relate the size of molecules to the results of this experiment. Tes-tape 9. In this experiment, dialysis tubing was used to represent a cell membrane. Explain why, or why not, this was a suitable substitute to show the nature of a Thread selectively permeable membrane.

In bag 20 mL water 20 mL sucrose 20 mL starch 20 mL glucose 10. Outline how this experiment showed the difference 100 mL 100 mL 100 mL water 100 mL between diffusion and osmosis. In cylinder concentrated water containing water sucrose dilute iodine 11. The diagram below shows what happened when two solution (yellow colour) identical animal cells were each placed in different solutions. Figure 7.1 Set-up for experiment. Cell X Cell Y H O H O Once the equipment was set up and each jar was suitably 2 2 labelled, the students noticed that the Tes-tape in jar 4 began to turn green before the end of the lesson. They recorded the ‘fullness’ of each bag and then left the equipment overnight in the laboratory. The next day they recorded any changes in the ‘fullness’ of each bag and any colour changes. Their results are in the following Shrivelled table. Lysed Table 7.1 Student results. e Figur 7.2 Animal cells placed in solutions. Initial appearance Final appearance

Gas jar 1 Bag nearly full. Bag more empty with What type of solutions would have caused these shrivelled appearance. results?

Gas jar 2 Bag nearly full. Bag extended and very Solution for cell X Solution for cell Y full. (A) Sucrose Distilled water Gas jar 3 Bag nearly full, water Bag full and blue-black outside a pale yellow colour and water outside (B) Distilled water Sucrose colour. colourless. (C) Distilled water Glucose Gas jar 4 Bag nearly full, during Bag nearly full, Tes-tape lesson Tes-tape turned reverted to yellow. (D) Sucrose Glucose green.

Science Press Surfing QCE Biology Unit 1 Cells and Multicellular Organisms 13 UNIT QCEBIOLOGY TOPIC 1 Cells As the Basis Of Life 1 Topic 1 Test

Section A – Multiple Choice (20 marks) 4. A thin section of an unknown tissue was stained with several different dyes to determine if the tissue 1. The diagram shows the structure of the cell membrane. came from a plant or from an animal. Which of the following is least likely to show that the tissue is from a plant? (A) Iodine showed starch granules. (B) Sudan IV stained lipid droplets. (C) Toluidine blue showed lignified cell walls. (D) Phloroglucin stained lignin in xylem vessels. 5. While investigating the difference between plant and Q animal cells, students needed to make wet mount slides of different tissues. Which of the following methods is Figure TT1.1 Cell membrane. the preferable method to use when placing a cover slip on a prepared specimen on a microscope slide? What does structure Q represent? (A) Carbohydrate. (B) Cholesterol. A C (C) Glycocalyx. (D) Phospholipid. 2. Which organisms do not have cells with membrane bound organelles? (A) Fungi. (B) Protists. Cover slip Cover slip (C) Eukaryotes. (D) Prokaryotes. 3. The diagram shows a plant cell and an animal cell. A B D Probe Cover slip Probe Cover slip B

C Structure Figure TT1.3 Experimental method. X 6. D What energy source is needed by an autotroph? (A) Light only. (B) Organic chemicals only. Plant cell Animal cell (C) Inorganic chemicals only. (D) Light or inorganic chemicals. Figure TT1.2 Plant cell and animal cell. 7. What are the main products of photosynthesis? Which structure in the plant cell performs the same (A) Oxygen and water. function as structure X in the animal cell? (B) Oxygen and glucose. (A) Structure A (B) Structure B. (C) Carbon dioxide and water. (C) Structure C (D) Structure D. (D) Carbon dioxide and glucose.

Science Press Surfing QCE Biology Unit 1 Cells and Multicellular Organisms 103 Answers

20. An autotroph can make its own organic molecules from inorganic Topic 1 Cells As the Basis Of Life substances whereas a heterotroph obtains organic food molecules by eating other organisms. 1 Assumed Knowledge Topic 1 21. Diffusion is the movement of particles from an area of high 1. Living organisms can – 1. Respire. 2. Assimilate food and concentration of particles to an area of low concentration of synthesise organic molecules. 3. Grow. 4. Reproduce. 5. Respond particles. to stimuli from their environment. 6. Excrete. 7. Locomotion 22. Osmosis is the movement of water, across a semipermeable 2. The cells of living things have a cell membrane, cytoplasm and DNA. membrane, from an area of high water to an area of low water. 3. Plant cell. 23. The experiment has shown diffusion with the movement of Nucleus Cell wall Cell membrane Vacuole molecules through the selectively permeable membrane from area Y where there was a high concentration of molecules to area X where there was a low concentration of molecules. 24. The diagram shows Amoeba feeding by the process of phagocytosis with the unicell engulfing large particulate matter (a bacterium in this instance). 25. Two main energy sources for cells are light and chemicals. 26. An enzyme is a biological catalyst that speeds up a reaction and is not consumed in the reaction. 27. pH is equal to the negative log of the hydrogen ion concentration and is a measure of the acidity or alkalinity of a solution. Chloroplast Cytoplasm 28. According to the graph the optimal pH is 2.8 which is an acidic 4. Animal cell. environment. Cell membrane 2 Development Of the Model Of the Cell Membrane 1. Nineteenth century scientists knew that there had to be a barrier around cells that separated the internal contents of the cell from the surrounding environment. Light microscopes do not clearly show the structure of the cell membrane. And thus it was not until the 20th century and the invention of the electron microscope that the structure of the cell membrane became more visible. 2. When 19th century scientists placed plant cells in strong solutions, e.g. salt solutions they noticed that the cytoplasm pulled away Nucleus Cytoplasm from the cell wall. This showed that there was some kind of membrane around the cell contents. 5. A = eye of person using the light microscope, B = ocular lens, 3. C = objective lens, D = specimen, E = condenser lens, Scientist Contribution F = light source. Traube Realised cell membranes were molecular sieves and 6. When using a light microscope, you should always wear shoes produced artificial semipermeable membranes. He with covered toes, as the microscope is heavy and if you drop it suggested the barrier was formed by an interfacial you could damage exposed skin on your feet. reaction of the cell protoplasm with the extracellular fluid. 7. The nucleus stores information needed to control all cell activities. 8. The cell membrane surrounds the cell contents from the external Quincke Suggested the existence of a thin lipid layer at the environment and controls the substances that can leave or enter the cell. boundary of the protoplasm and calculated that the 9. Cytoplasm is a general term for the contents of a cell outside the fluid layer of fat was less than 100 nm thick. nucleus and within the cell membrane. Overton Found that the ability of a substance to pass 10. Protoplasm is the semi-fluid transparent substance that makes up through the membrane was related to its chemical the living matter of plant and animal cells including the nucleus nature. Non-polar, fat soluble substances passed most easily through the layer. and cytoplasm. 11. A chloroplast is a green organelle found in green tissues of plants Fricke Calculated that the membrane was 3.3 nm thick and that captures sunlight in photosynthesis to manufacture sugars assumed that it was a single molecular layer. from carbon dioxide and water. Gorter and Grendel Suggested the bilayer concept of the cell membrane 12. Photosynthesis is a process where the energy of sunlight is used to by measuring lipids from red blood cells and using convert carbon dioxide and water into sugars and oxygen. the total cell area of the red blood cell. 13. (a) The gas being released and collected is oxygen. Danielli Suggested that the cell membrane had outer layers (b) The distinguishing test for oxygen gas is showing the gas will of protein with two layers of lipids between them. relight a glowing stick. He calculated the total width of the membrane to 14. Groups of organisms that can photosynthesise include plants, algae be 8.0 nm. and photosynthetic bacteria. Robertson Took electron micrographs of cell membranes and 15. Carbon dioxide and water are needed for photosynthesis using showed the total thickness was 7.5 nm. Suggested light energy and in the presence of chlorophyll. the unit membrane. 16. Photosynthesis is important in ecosystems as it converts light Mueller and Rudin Suggested the BLM and determined different energy into chemical energy to begin most food chains on Earth properties of the cell membrane. and also provides oxygen which is needed for respiration. Frye and Edidin Showed the fluidity of cell membrane using mouse 17. The four basic groups of organic compounds are proteins, and human cell hybrids carbohydrates, lipids and nucleic acids. 18. Inorganic compounds are molecules that do not contain carbon Singer and Nicolson Proposed the fluid mosaic model of the cell membrane with lipid bilayer and peripheral and (excluding some carbonates and simple oxides of carbon). integral proteins. 19. Respiration is the chemical reactions in which cells obtain energy from food.

Science Press Surfing QCE Biology Unit 1 Cells and Multicellular Organisms 181