Dot-Point-VCE-Biology-Units-3-4-Sample

VCE BIOLOGY UNITS 3 AND 4 • Kerri Humphreys • © Science Press 2017 First published 2017 Science Press Private Bag 7023 Marrickville NSW 1475 Australia Tel: +61 2 9516 1122 Fax: +61 2 9550 1915 sales@sciencepress.com.au www.sciencepress.com.au All rights reserved. No part of this publication may be reproduced, stored in a retrieval system, or transmitted in any form or by any means, electronic, mechanical, photocopying, recording or otherwise, without the prior permission of Science Press. ABN 98 000 073 861 Contents Words to Watch iv Introduction v Dot Points Unit 3 How Do Cells Maintain Life? vi Unit 4 How Does Life Change and Respond to Challenges Over Time? vii Questions Unit 3 How Do Cells Maintain Life? 1 Unit 4 How Does Life Change and Respond to Challenges Over Time? 149 Answers Unit 3 How Do Cells Maintain Life? 252 Unit 4 How Does Life Change and Respond to Challenges Over Time? 304 Appendix Index339 Science Press Dot Point VCE Biology Units 3 and 4 iii Contents Words to Watch account, account for State reasons for, report on, give an account of, narrate a series of events or transactions. examine Inquire into. 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 or phenomena. explain Make something clear or easy to understand. extract Choose relevant and/or appropriate details. apply Put to use in a particular situation. assess Make a judgement about the value of something. identify Recognise and name. calculate Find a numerical answer. clarify Make clear or plain. investigate Plan, inquire into and draw conclusions about. classify Arrange into classes, groups or categories. justify Support an argument or conclusion. comment Give a judgement based on a given statement or result of a calculation. label Add labels to a diagram. compare Estimate, measure or note how things are similar or different. measure Find a value for a quantity. construct Represent or develop in graphical form. plan Use strategies to develop a series of steps or processes. interpret Draw meaning from. list Give a sequence of names or other brief answers. outline Give a brief account or summary. contrast Show how things are different or opposite. predict Give an expected result. create Originate or bring into existence. propose Put forward a plan or suggestion for consideration or action. deduce Reach a conclusion from given information. define Give the precise meaning of a word, phrase or physical quantity. recall Present remembered ideas, facts or experiences. demonstrate Show by example. relate Tell or report about happenings, events or circumstances. derive Manipulate a mathematical relationship(s) to give a new equation or relationship. describe Give a detailed account. represent Use words, images or symbols to convey meaning. design Produce a plan, simulation or model. select Choose in preference to another or others. determine Find the only possible answer. sequence Arrange in order. discuss Talk or write about a topic, taking into account different issues or ideas. show Give the steps in a calculation or derivation. distinguish Give differences between two or more different items. solve Work out the answer to a problem. draw Represent by means of pencil lines. suggest Put forward an idea for consideration. estimate Find an approximate value for an unknown quantity. summarise Give a brief statement of the main points. sketch Make a quick, rough drawing of something. state Give a specific name, value or other brief answer. synthesise Combine various elements to make a whole. evaluate Assess the implications and limitations. Science Press Words to Watch iv Dot Point VCE Biology Units 3 and 4 Introduction What the book includes This book provides questions and answers for each dot point in the Victorian Certificate of Education Study Design for each core topic in the Year 12 Biology syllabus: Unit 3 How Do Cells Maintain Life? • Area of Study 1 How Do Cellular Processes Work? • Area of Study 2 How Do Cells Communicate? Unit 4 How Does Life Change and Respond to Challenges Over Time? • Area of Study 1 How Are Species Related? • Area of Study 2 How Do Humans Impact On Biological Processes? •Area of Study 3 P ractical Investigation – There are activities and practical investigations placed within Area of Study 1 and Area of Study 2 that can be used to develop the student investigation. Format of the book The book has been formatted in the following way: 1.1 Subtopic from syllabus. 1.1.1 Assessment statement from syllabus. 1.1.1.1 First question for this assessment statement. 1.1.1.2 Second question for this assessment statement. The number of lines provided for each answer gives an indication of how many marks the question might be worth in an examination. As a rough rule, every two lines of answer might be worth 1 mark. How to use the book Completing all questions will provide you with a summary of all the work you need to know from the syllabus. You may have done work in addition to this with your teacher as extension work. Obviously this is not covered, but you may need to know this additional work for your school exams. When working through the questions, write the answers you have to look up in a different colour to those you know without having to research the work. This will provide you with a quick reference for work needing further revision. Science Press Dot Point VCE Biology Units 3 and 4 v Introduction Unit 3 How Do Cells Maintain Life? Dot Point Page Dot Point Area of Study 1 How Do Cellular Processes Work? Page 1.6 Cellular respiration 80 1.6.1 The purpose of cellular respiration. 80 1.6.2 Glycolysis. 81 1.1 Plasma membranes 5 1.6.3 Mitochondria. 82 1.1.1 The fluid mosaic model. 5 1.6.4 84 1.1.2 Cellular organelles. 11 The Krebs cycle and electron transport chain. 1.1.3 Endocytosis. 13 1.6.5 Anaerobic cellular respiration. 88 1.6.6 Factors that affect cellular respiration. 91 1.2 Nucleic acids and proteins 15 1.2.1 Nucleic acids code for proteins. 15 1.2.2 Protein diversity and the proteome. 16 1.2.3 Four levels of protein structure. 20 1.2.4 Polypeptide synthesis and condensation polymerisation. 26 1.2.5 The structure of DNA. 28 1.2.6 Gene expression, transcription and translation. 35 1.3 Gene structure and regulation 43 1.3.1 Area of Study 2 How Do Cells Communicate? 2.1 Cellular signals. 95 2.1.1 Animal hormones, neurotransmitters, cytokines and pheromones. 95 2.1.2 Signal transduction. 103 2.1.3 The difference in hydrophilic and hydrophobic signals and receptors. 105 2.1.4 Apoptosis. 106 Structural genes and regulatory genes. 43 2.1.5 Malfunctions in apoptosis. 108 1.3.2 Stop/start instructions, promoter regions, exons and introns. 44 2.2 Responding to antigens 109 1.3.3 The lac operon in prokaryotes. 48 2.2.1 Non-self antigens, self antigens and allergens. 109 1.4 Structure and regulation of biochemical pathways 51 2.2.2 Pathogens and barriers. 110 1.4.1 Enzymes as protein catalysts. 51 2.2.3 The innate immune response. 122 1.4.2 Enzyme action, inhibition and control factors. 52 2.2.4 The lymphatic system. 126 2.2.5 The adaptive immune response. 128 1.4.3 Cycling of coenzymes. 65 2.3 Immunity 134 1.5 Photosynthesis 67 2.3.1 Natural and artificial immunity. 134 1.5.1 The purpose of photosynthesis. 67 2.3.2 Vaccination programs. 135 1.5.2 Chloroplasts. 68 2.3.3 Malfunctions of the immune system. 139 1.5.3 Light dependent and light independent reactions. 71 2.3.4 Monoclonal antibodies and cancer. 146 1.5.4 Factors that affect the rate of photosynthesis. 74 Answers to How Do Cells Maintain Life? 252 Science Press Dot Points vi Dot Point VCE Biology Units 3 and 4 Unit 4 How Does Life Change and Respond to Challenges Over Time? Dot Point Page Dot Point Area of Study 1 How Are Species Related? Page Area of Study 2 How Do Humans Impact On Biological Processes? 1.1 Changes in the genetic make-up of a population 153 1.1.1 Allele frequencies in gene pool and mutations. 153 1.1.2 Processes of evolution. 168 1.1.3 Manipulation of gene pools and selective breeding. 172 1.2 Changes in biodiversity over time 174 1.2.1 Life forms in Earth’s geological history. 174 1.2.2 Evidence of change. 181 1.2.3 Divergent and convergent evolution, 191 extinctions. 1.3 Determining relatedness between 200 species 1.3.1 Molecular homology. 200 1.3.2 Phylogenetic trees. 205 1.3.3 Evolution of novel phenotypes, beak formation. 211 1.4 Human change over time 213 1.4.1 Primates, hominoids, hominins. 213 1.4.2 Hominin evolution from Australopithecus to Homo. 219 1.4.3 The human fossil record. 226 2.1 DNA manipulation 231 2.1.1 The use of enzymes. 231 2.1.2 Amplification of DNA using PCR. 234 2.1.3 Gel electrophoresis. 236 2.1.4 Recombinant plasmids. 238 2.2 Biological knowledge and society 239 2.2.1 Gene cloning, genetic screening, DNA profiling. 239 2.2.2 Genetically modified and transgenic organisms. 243 2.2.3 Strategies for new diseases. 245 2.2.4 Rational drug design. 247 2.2.5 Antibiotics and antiviral drugs. 249 Answers to How Does Life Change And Respond to Challenges Over Time? 304 Science Press Dot Point VCE Biology Units 3 and 4 vii Dot Points DOT POINT Unit 3 How Do Cells Maintain Life? Science Press Dot Point VCE Biology Units 3 and 4 1 Unit 3 How Do Cells Maintain Life? DOT POINT AREA OF STUDY 1 How Do Cellular Processes Work? Science Press Dot Point VCE Biology Units 3 and 4 3 Unit 3 How Do Cells Maintain Life? 1.1 Plasma membranes. 1.1.1 The fluid mosaic model of the structure of the plasma membrane and the movement of hydrophilic and hydrophobic substances across it based on their size and polarity. 1.1.1.1 What is the name of the current model of a plasma membrane and when was it first proposed? �� 1.1.1.2 Draw a labelled diagram of a plasma membrane. 1.1.1.3 Outline the roles of the plasma membrane. �� 1.1.1.4 Distinguish between hydrophilic and hydrophobic and relate this to the structure of a phospholipid. �� Science Press Dot Point VCE Biology Units 3 and 4 5 Unit 3 How Do Cells Maintain Life? 1.1.1.5 What is an amphipathic molecule? �� 1.1.1.6 Draw a phospholipid and describe its basic structure in membranes. Phospholipid �� 1.1.1.7 Explain why phospholipids form bilayers in water. �� 1.1.1.8 Explain how the hydrophobic and hydrophilic regions of phospholipids affect the transport of materials across the plasma membrane. �� 1.1.1.9 Distinguish between integral proteins, peripheral proteins and glycoproteins. �� Science Press Unit 3 How Do Cells Maintain Life? 6 Dot Point VCE Biology Units 3 and 4 1.1.1.10 Explain why a phospholipid bilayer is stable, yet fluid and identify the factors that affect fluidity. �� 1.1.1.11 Complete the table to summarise the permeability of the plasma membrane. Type of molecule Permeability Examples Hydrophobic Small polar Large polar Ions and charged particles 1.1.1.12 Use your understanding of the structure of the plasma membrane to explain why it is important to place tissues or organs to be used in medical procedures in a solution with the same osmolarity as the cytoplasm. �� Science Press Dot Point VCE Biology Units 3 and 4 7 Unit 3 How Do Cells Maintain Life? 1.1.1.13 Complete the table to summarise some of the roles of membrane proteins. Role Channel proteins for passive transport Diagram Description of function Channel protein Carrier protein for facilitated diffusion Carrier protein Carrier proteins for active transport Carrier protein Enzymes Membrane bound enzymes Active sites Attachment to adjacent cells Tight junction Recognition site Cell identification Glycoprotein Hormone Hormone binding sites Science Press Unit 3 How Do Cells Maintain Life? 8 Dot Point VCE Biology Units 3 and 4 1.1.1.14 Discuss how the presence of cholesterol in the plasma membrane affects the properties of the plasma membrane. �� 1.1.1.15 Distinguish between simple diffusion and facilitated diffusion across a membrane. �� 1.1.1.16 Use an example to explain simple diffusion across a membrane. �� 1.1.1.17 Use an example to explain facilitated diffusion across a membrane. �� 1.1.1.18 The diagram shows a sodium ion channel. Outline what is happening in these two diagrams. �� Na+ Na+ Na+ Na+ Na+ Na+ Na+ Na+ Na+ Na+ + + + + + + + − − − − − − − − − − − − − − + + + + + + + �� Na+ �� Sodium ion channel state A Na+ Sodium ion channel state B Science Press Dot Point VCE Biology Units 3 and 4 9 Unit 3 How Do Cells Maintain Life? high ow igh w 1.1.1.19 Define active transport. �� 1.1.1.20 Use an example of explain active transport across a membrane. �� 1.1.1.21 Complete the table to explain the functioning of the sodium-potassium pump. Diagram Outside cell What is happening [Na+] high [K+] low Na+ Na+ Inside cell Outside cell P ADP Na+ + ATP [Na+] high [K+] low P Na+ K+ OutsideNa cell + P ADP Na+ + ATP Inside cell P P K+Na+ P Outside cell P K+ K+ Na + Na + Na+ Outside cell K+ K+ P P ADP P + ADP [Na ] high [K+] low P PP P Na+ K + + + KNa P ADP K++ + ATP Inside Na cell K+ P P [Na+] high [K+] low P Outside cell P P Na+ K+ Outside cell Na+ K Na+ + ATP + K + Inside cell P ADP P P P P K+ Outside cell K+ K+ P P P Science Press Unit 3 How Do Cells Maintain Life? 10 Dot Point VCE Biology Units 3 and 4 1.1.2 The role of different organelles including ribosomes, endoplasmic reticulum, Golgi apparatus and associated vesicles in the export of a protein product from the cell through exocytosis. 1.1.2.1 Define cytosis. �� 1.1.2.2 Define vesicle. �� 1.1.2.3 Define exocytosis. �� 1.1.2.4 Glands are involved in exocytosis. Distinguish between endocrine glands and exocrine glands. �� 1.1.2.5 Ribosomes are involved in exocytosis. Distinguish between free ribosomes and attached ribosomes. �� 1.1.2.6 Endoplasmic reticulum is involved in exocytosis. Distinguish between rough and smooth endoplasmic reticulum and their products. �� Science Press Dot Point VCE Biology Units 3 and 4 11 Unit 3 How Do Cells Maintain Life? 1.1.2.7 Complete the table and label the diagram to show the sequence of events in the production of a protein product to its secretion and export from the cell. Diagram What happens at: Ribosomes A B Endoplasmic reticulum C D E F Golgi apparatus G Plasma membrane H I Science Press Unit 3 How Do Cells Maintain Life? 12 Dot Point VCE Biology Units 3 and 4 1.1.3 Cellular engulfment of material by endocytosis. 1.1.3.1 Define endocytosis. �� 1.1.3.2 Discuss why endocytosis is needed for some substances to cross the plasma membrane. �� 1.1.3.3 Distinguish between pinocytosis and phagocytosis. �� 1.1.3.4 Annotate the diagram to show the difference between pinocytosis and phagocytosis and how each process can occur. Phagocytosis Pinocytosis Liquid or finely divided solid Solid material Science Press Dot Point VCE Biology Units 3 and 4 13 Unit 3 How Do Cells Maintain Life? 1.1.3.5 Describe receptor mediated endocytosis and give an example. �� 1.1.3.6 Draw a flow chart to show the steps involved in the invagination of the plasma membrane. �� 1.1.3.7 Complete the table to compare endocytosis and exocytosis. Feature Endocytosis Exocytosis Cell Diagram Cell Substance Substance Definition How it affects the plasma membrane Science Press Unit 3 How Do Cells Maintain Life? 14 Dot Point VCE Biology Units 3 and 4 DOT POINT Answers Science Press Dot Point VCE Biology Units 3 and 4 251 Answers Unit 3 How Do Cells Maintain Life? 1.1.1.1 1.1.1.2 Current model of the plasma membrane is the fluid mosaic model first proposed by Jonathon Singer and Garth Nicolson in 1972. Structure of plasma membrane Glycoprotein Integral protein Hydrophilic head Phospholipid Hydrophobic bilayer tail Cholesterol Peripheral protein 1.1.1.3 The plasma membrane: 1. Separates a cell from its external environment. 2. Acts as a selective barrier around the cell. 3. Creates and maintains concentration gradients between its internal and its external environment. 4. Maintains pH and charge differences. 5. Is important in cell-cell recognition. 6. Has receptor molecules for cell signalling. The surface area of the plasma membrane is important as it determines the rates of chemical exchange into and out of the cell. 1.1.1.4 Hydrophilic means attracted to water, e.g. the polar end of a phospholipid whereas hydrophobic means repels water, e.g. the lipid chains of the phospholipid. 1.1.1.5 An amphipathic molecule has both a hydrophobic region and a hydrophilic region. 1.1.1.6 Phospholipids form the structural basis of plasma membranes. The polar end consists of choline and phosphate and the non-polar end consists of two chains of fatty acids. The different ends allows the membrane to control the movement of substances across its structure. Phospholipid Polar end is hydrophilic Two chains of fatty acids are non-polar and hydrophobic 1.1.1.7 When a phospholipid is placed in water it will naturally form a bilayer with the heads facing outwards due to the polarity of this region attracting water. The tails with no charge will face inwards. 1.1.1.8 The hydrophobic core of the fatty acid hydrocarbon tail prevents the movement of ions and polar molecules and stops the cell dissolving in water. While the hydrophilic ends of the phospholipids have a negatively charged phosphate group which is in contact with aqueous solutions on either side of the membrane and can interact with their environment, e.g. polarity attracts water. 1.1.1.9 Integral proteins contact the hydrophobic core of the phospholipid bilayer – some are transmembrane and span the entire membrane. Integral proteins have sections that are hydrophobic and the ends contacting the aqueous solution outside/inside the membrane are hydrophilic. While peripheral proteins are loosely connected to the surface of the membrane – some contact integral proteins. While glycoproteins are proteins that have a carbohydrate covalently bonded on the external side of the membrane. 1.1.1.10 The bilayer is very stable due to the bonds with the water and the bonds between each phospholipid. It is fluid as the phospholipids can move along the structure as the hydrophobic properties of the fatty acid chains and the hydrophilic properties of the head means the phospholipids cannot flip vertically. The loose packing of the phospholipids also allows movement along the horizontal plan. The fluidity of the membrane depends on the types of lipids present in the membrane. The presence of saturated fatty acids (with all C–C single bonds) makes the membrane less fluid, e.g. will become solid at room temperature. While the presence of unsaturated fatty acid (with some double bonds C=C) makes the membrane more fluid. The double bonds cause the fatty acid chains to take on a ‘bent’ appearance that prevent tight packing of the phospholipids, e.g. will be liquid at room temperature. The presence of cholesterol also increases stability and reduces fluidity allowing movement in the centre of the bilipid layer. 1.1.1.11 1.1.1.12 Type of molecule Permeability Examples Hydrophobic Freely permeable Nitrogen, oxygen, hydrocarbons Small polar Freely permeable Water, carbon dioxide, urea, glycerol Large polar Not permeable Glucose and other uncharged monosaccharides, disaccharides Ions and charged particles Not permeable Amino acids, ions of hydrogen, sodium, potassium, calcium, chlorine, magnesium and hydrogen carbonate ion The plasma membrane controls substances that enter or leave cells. Water crosses the plasma membrane by osmosis moving down a concentration gradient going through aquaporins that are transport proteins in the plasma membrane. The water potential is the tendency of the water molecules to enter or leave the cell and is determined by the solute potential and pressure potential. If tissues or organs to be used in medical procedures are placed in an isoosmotic solution there is no net movement of water between the cells and their environment. However, if there is a difference in osmolarity (the solute concentration expressed as a molarity) water will move by osmosis from the hypoosmotic solution to the hyperosmotic solution which will damage the cells and reduce their viability. Thus, isotonic solutions need to be used in medical procedures, e.g. as intravenously infused fluids, in saline eye drops, to pack donor organs, during skin grafts. Science Press Answers 252 Dot Point VCE Biology Units 3 and 4 1.1.1.13 Role Diagram Description of function Channel proteins have a hydrophilic channel that allows certain molecules and ions, e.g. aquaporins assist water movement in osmosis. Movement is by facilitated diffusion as the material moves down a concentration gradient. Channel proteins for passive transport Channel protein Carrier proteins change their shape during the process of passing a solute across the plasma membrane. The movement of the solute can occur in either direction. Carrier proteins are usually very specific, e.g. glucose transporter. Movement is by facilitated diffusion as the material moves down a concentration gradient. Carrier protein for facilitated diffusion Carrier protein Carrier proteins change shape to take the substance across the membrane. Energy (e.g. ATP) is needed and the substance is moved against a concentration gradient, e.g. sodium-potassium pump in animal cells. Carrier proteins for active transport Carrier protein Membrane bound enzymes Enzymes Proteins that are enzymes can be embedded in the membrane in a series or system with the active sites exposed to the aqueous solution. A sequence of reactions in a metabolic pathway can occur, e.g. ATP synthase in aerobic respiration. Active sites Integral proteins can bind to proteins from adjacent cells, e.g. forming tight junctions. Attachment to adjacent cells Tight junction Cell identification Recognition site Some glycoproteins in plasma membranes are detected by recognition sites on proteins of other cells. The glycoproteins act as identification indicators. Glycoprotein Hormone binding sites Hormone Integral proteins have a binding site for a specific hormone. The hormone triggers a response in the cell. 1.1.1.14 Cholesterol is a steroid lipid that is mainly hydrophobic with a hydroxyl group [OH]. It is only slightly soluble in water. The cholesterol aligns with the phospholipid on both sides of the bilayer – the ringed portion which is rigid and flat lie next to the first part of hydrocarbon tails of the phospholipids in the cell membrane of animals and the cholesterol’s linear tail embeds in the lower part of the fatty acid chain. The hydroxyl group is attracted to the polar head and lower oxygens of the phospholipid. Embedded cholesterol in the cell membrane makes the membrane less fluid. It gives stability and firmness with the rigid planar part of the cholesterol blocking movement of the first part of the fatty acid chain. The flexible tail of the cholesterol which lies near the centre of the bilayer makes the middle part of the bilayer the most fluid. At high concentrations cholesterol helps separate the phospholipids so that the fatty acid chains do not come together and crystallise. It helps prevent extremes, e.g. too fluid or too firm. The cholesterol also reduces permeability to some solutes. 1.1.1.15 Simple diffusion refers to the movement of particles down a concentration gradient due to the random movement of particles. Whereas facilitated diffusion is also the passive movement of particles, does not require an input of energy (ATP), but involves the assistance of other molecules, e.g. transport proteins. 1.1.1.16 If oxygen molecules are more concentrated on the outside of a cell, the oxygen will diffuse across the plasma membrane into the cell, e.g. for aerobic cellular respiration. Substances that move across the cell membrane by simple diffusion are usually small and non-charged or lipid molecules. 1.1.1.17 Channel proteins that have a hydrophilic channel allow water molecules to move into/out of the cell. Water is a small molecule and can cross the membrane by simple diffusion, however the movement through the channel proteins (aquaporins) is faster than simple diffusion and assists osmoregulation. Facilitated diffusion is considered passive transport because the substance moves down a concentration gradient. Science Press Dot Point VCE Biology Units 3 and 4 253 Answers + 1.1.1.18 Sodium ion channel state A shows the closed gate conformation of the transport protein. It is maintaining the resting potential with the sodium unable to enter. Sodium ion channel state B shows the open gate conformation allowing the sodium ions to move into the cell by facilitated diffusion down the concentration gradient. The diagram shows the gating of the sodium ion channel. 1.1.1.19 Active transport is the movement of substance across a membrane against a concentration gradient or electrochemical gradient using energy (ATP). It can involve carrier proteins. 1.1.1.20 Many animal cells have a sodium-potassium pump where sodium ion (Na+) are exchanged for potassium ions (K+). The sodiumpotassium pump is involved with maintaining the electrochemical gradient, e.g. in nerve cells. When the sodium-potassium pump pumps sodium out of the cell and potassium into the cell the interior of the cell becomes negative and the exterior becomes positive, e.g. to return a nerve cell to the resting state. Protein pumps only transport a particular substance in a specific direction across the membrane. 1.1.1.21 Diagram Outside cell [Na+] high [K+] low What is happening Cells maintain a high Na+ outside and low Na+ concentration inside a cell and a high K+ concentration inside + cell. In the cell membrane carrier proteins have two states. From inside the cell a cell and low K+ outside theNa Na+ ions from the cytoplasm can fit into the carrier protein and binds to the sodium-potassium pump. Na+ Inside cell Outside cell P ADP Na+ + ATP [Na+] high [K+] low P + + NaNa binding with the carrier proteins stimulates the chemical reaction phosphorylation using ATP and a phosphate group is attached to the protein. ADP is released. + K Outside cell Na+ P ADP Na+ + ATP Inside cell [Na+] high [K+] low [Na+] high [K+] low + Outside cell Na+ Na+ Na+ K+ Outside cell K+ P ADP [Na+] high P [K+] low P ADP P K P + ] high P[Na [K+] low Na+ K+ P P Outside cell + P ADP Outside cell Inside cell Na+ P A K+ ion from outside the cell binds to the carrier protein. K+ Na+ + ATP K+ K+ P P P K+ Na+ Inside cell P Phosphorylation makes the protein change shape causing the Na+ to be released outside the cell. This is K+ active transport of Na+ across the cell membrane from the cytoplasm to the extracellular fluid. PP cell ell P P K+Na P + ATP + ATP K+ The carrier protein now has a form that fits K+ rather than Na+. Facilitated diffusion occurs as no energy is Na+ in the transport across the plasma membrane. used K+ Na+ + ATP P ADP P P P P The phosphate group is released from the carrier protein causing the carrier protein to release K+ into the K+ cytoplasm and the protein reverts back to its other state. Outside cell K+ K+ P P P 1.1.2.1 Cytosis is the passage of large ‘packages’ of material across the membrane. 1.1.2.2 A vesicle is a sac made of membrane that contain various substances. 1.1.2.3 Exocytosis is the process when vesicles inside the cell fuse with the cell membrane and the contents of the vesicle are secreted from the cell. 1.1.2.4 Endocrine glands are ductless glands that secrete hormones, e.g. thyroid gland secretes thyroxine and the adrenal glands secrete adrenaline whereas exocrine glands secrete into ducts that lead to an epithelial surface, e.g. sweat glands secrete sweat onto the skin and mammary glands secrete milk. 1.1.2.5 Free ribosomes are found unattached in the cytosol and produce proteins that function within the cytosol. While bound ribosomes are attached to the nuclear membrane or to endoplasmic reticulum and produce proteins that will become part of the plasma membrane or will be bound within another organelle, e.g. lysosome or will be packaged for secretion. Science Press Answers 254 Dot Point VCE Biology Units 3 and 4 1.1.2.6 1.1.2.7 Endoplasmic reticulum (ER) is a large network of membranes throughout the cell. Rough ER has ribosomes on its outer surface membrane and is involved in protein secretion whereas smooth ER does not have ribosomes on its outer surface membrane and is involved in the synthesis and secretion of lipids including steroid hormones. Diagram What happens at: Nucleus Ribosomes carry out protein synthesis in gene expression. They produce polypeptide chains on rough endoplasmic reticulum (rER). Rough endoplasmic reticulum Free ribosome Transport vesicle Vesicle fuses with membrane Cis Golgi Vesicle released Endoplasmic reticulum forms a large network of membranes throughout the cell. Rough endoplasmic reticulum is continuous with the outer membrane of the nuclear envelope. The new protein formed at the ribosome enters the lumen of the rER and is sectioned off to form a vesicle. Glycoproteins that have carbohydrates attached to the protein are formed here. The transport vesicle separates and travels though the cytoplasm to a Golgi apparatus. Smooth endoplasmic reticulum produces lipids, e.g. oils, phospholipids and steroids. Golgi apparatus is a stack of flattened sacs. The transport vesicle from the rER joins with the cis face which is the convex side of the Golgi apparatus and its contents are added to the lumen. As the product travels from the cis to the trans sides of the Golgi apparatus it is modified, e.g. Golgi enzymes modify the carbohydrates of the glycoproteins. Small vesicles bud off from the ends of the stacks. Plasma membrane – the transport vesicles from the Golgi apparatus travel to and fuse with the plasma membrane. The product is secreted in exocytosis. Plasma membrane Vesicle releases contents 1.1.3.1 Endocytosis is the process where a cell takes in macromolecules by forming vesicles from the plasma membrane. Endocytosis requires an energy input and is a form of active transport. 1.1.3.2 Endocytosis is needed as the materials are large and cannot move across the plasma membrane by diffusion or with the assistance of carrier or channel proteins. 1.1.3.3 Pinocytosis and phagocytosis are two types of endocytosis. Pinocytosis is a type of endocytosis in which the cell takes in extracellular fluid and its dissolved solutes and can occur by invagination of the plasma membrane or by the formation of vesicles at the base of a pinocytic channel. Whereas phagocytosis is a type of endocytosis where large, particulate substances are taken into a cell and can occur by invagination of the plasma membrane or by the formation of pseudopods. 1.1.3.4 Phagocytosis Solid enclosed by pseudopodia, e.g. Amoeba feeding Pinocytosis Invagination of plasma membrane, e.g. liver cells Invagination of plasma membrane, e.g. white blood cell Liquid or finely divided solid Vesicles form at base of pinocytic channel Solid material 1.1.3.5 Receptor mediated endocytosis involves the receptor proteins on the cell surface membrane. The particle to be taken in binds to a receptor site in a ‘lock and key’ manner. After binding the area forms an invagination that will become a vesicle that moves further inside the cell. Cholesterol travels in the blood as low density lipoproteins (LDLs) and specific LDL receptor sites on cell membranes allow cholesterol to be taken into a cell by receptor mediated endocytosis. Science Press Dot Point VCE Biology Units 3 and 4 255 Answers 1.1.3.6 Small section of the plasma membrane forms a pocket → pocket sinks deeper into the cell → membrane pinches in to form a vesicle → vesicle is separated from the plasma membrane. 1.1.3.7 Feature Endocytosis Diagram Exocytosis Cell Cell Substance Substance Definition Cell takes up substances by surrounding it with membrane. Substances are released from the cell when vesicles fuse with the membrane. How it affects the plasma membrane During endocytosis the membrane changes shape, infolds and encloses substance to be taken into the cell, e.g. substance is highly polar or too large to enter by other means. During exocytosis the membrane fuses with the vesicle, changes shape and expels the substance. Vesicles are created by rER and then modified by Golgi apparatus. The fluidity of the membrane allows the phospholipids from the vesicle to combine with the plasma membrane to form the new membrane that includes the phospholipids from the vesicle. 1.2.1.1 A nucleic acid is a polymer composed of many nucleotide monomers that encode instructions for the synthesis of proteins in cells and through the actions of proteins for all cellular activities. 1.2.1.2 Nucleic acids are very important as they not only make up the genetic material of all living things as well as of viruses and transmit hereditary information but by determining protein synthesis they determine the structure, function and activities of cells. 1.2.1.3 Nucleic acids include DNA and RNA. 1.2.1.4 A nucleotide is a three-part molecule consisting of a pentose sugar covalently bonded to a nitrogenous base and a phosphate group. Nucleotide 1.2.1.5 Sugar Nitrogenous bases Phosphate O − Ribose HOCH2 O Deoxyribose OH HOCH2 O Purine OH N HC HO OH HO N C N Adenine (A) C C Pyrimidine N CH N H N HC H C N O P OH O − CH CH Guanine (G) Cytosine (C) Thymine (T) Uracil (U) 1.2.2.1 A proteome is a full protein set that is encoded in a genome that can be expressed by a cell, tissue or organism. 1.2.2.2 Proteomics is the study of proteomes and their functions in large scale investigations of the biochemistry and genetics of gene products. 1.2.2.3 As each person has a unique DNA sequence, the proteins produced by that sequence will form a unique set of products – a unique proteome. Different types of cells will make different proteins and have different proteomes. A study of proteomes shows significant similarities in the proteomes of different species. 1.2.2.4 Proteins are long complex polymers built from linear sequences of amino acids joined together by peptide bonds in polypeptide chains. 1.2.2.5 20 kinds of amino acids are commonly found in polypeptides. 1.2.2.6 Since amino acids can react with each other by condensation with the amino group of one amino acid reacting with the carboxyl group of another to form a peptide bond, there are many possible sequences of amino acids that will form a huge range of polypeptides. The polypeptide will have a repeating sequence that forms the backbone of the molecule and the different side chains of each amino acid give each polypeptide its particular structure and functionality. 1.2.2.7 Polypeptides are synthesised in cells on ribosomes. 1.2.2.8 Basic components of an amino acid. NH2 X CH COOH Science Press Answers 256 Dot Point VCE Biology Units 3 and 4

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