How to Pass Higher Human Biology for CfE PDF

Hodder Gibson Copyright statement 1. This is an Accessible Digital Copy of a printed book. The original digital file from which this Accessible Copy was made was kindly provided by Hachette UK Limited. All rights to the Accessible digital copy are retained by the rightsholders of the printed books. 2. This Accessible Digital Copy is for the personal use of an “Authorised Person” who is defined as “a pupil who is visually impaired or otherwise disabled and by reason of such visual impairment or disability is unable to read or access the original printed book”. 3. An Authorised Person is regarded as “visually impaired” in accordance with s.31F (9) of the Copyright, Designs and Patents Act 1988, or, as appropriate, as a “disabled person” in accordance with s.1 of the Disability Discrimination Act 1995. 4. No other pupils can use this book. 5. This Accessible Copy may be stored on the students’ personal computer or other electronic device, or on a secure password-protected intranet limiting access to the student(s) only. 6. The user of this Accessible Digital Copy must have legal access to a print copy of the book, bought either for personal use or as part of a class set. 7. If the pupil cannot access the Accessible Digital Copy, it may be converted into another Alternative Format. The book may not be altered except as required for conversion to the Alternative Format, and conversion must retain the integrity of the text. 8. The student may print pages of the book for personal use only. 9. The Accessible Copy may not be further copied, nor may it be supplied to any other person, without permission. It may not be made available on the world wide web or copied or transferred to any third party. 10. The Accessible Digital Copy should be deleted once the pupil has completed the course for which it was supplied. 11. Do not supply this Accessible Copy to other pupils. If you require another Accessible Copy of this book for more pupils, download another copy from the Books for All Scotland Database. 12. Please note that that usage of Accessible Digital Copies outwith these terms and conditions may result in legal action against you and/or your educational establishment. for CfE Biology Human Higher How to Pass HIGHER Human Biology for CfE Billy Dickson and Graham Moffat i 847417_FM_HTPH_Bio_CfE_i-xii.indd 1 24/09/15 8:51 am The Publishers would like to thank the following for permission to reproduce copyright material: Photo credits p.85 © Isabelle Limbach/iStockphoto/Thinkstock; p.144 © Ely William Hill in 1915, published in Puck, an American humour magazine, on 6 November 1915 Every eﬀort has been made to trace all copyright holders, but if any have been inadvertently overlooked the Publishers will be pleased to make the necessary arrangements at the first opportunity. Although every eﬀort has been made to ensure that website addresses are correct at time of going to press, Hodder Gibson cannot be held responsible for the content of any website mentioned in this book. It is sometimes possible to find a relocated web page by typing in the address of the home page for a website in the URL window of your browser. Orders: please contact Bookpoint Ltd, 130 Park Drive, Milton Park, Abingdon, Oxon OX14 4SE. Telephone: (44) 01235 827720. Fax: (44) 01235 400454. Lines are open 9.00–5.00, Monday to Saturday, with a 24-hour message answering service. Visit our website at www.hoddereducation.co.uk. Hodder Gibson can be contacted direct on: Tel: 0141 848 1609; Fax: 0141 889 6315; email: [email protected] © Billy Dickson, Graham Moﬀat 2015 First published in 2015 by Hodder Gibson, an imprint of Hodder Education, An Hachette UK Company, 2a Christie Street Paisley PA1 1NB Impression number 5 4 3 2 1 Year 2019 2018 2017 2016 2015 All rights reserved. Apart from any use permitted under UK copyright law, no part of this publication may be reproduced or transmitted in any form or by any means, electronic or mechanical, including photocopying and recording, or held within any information storage and retrieval system, without permission in writing from the publisher or under licence from the Copyright Licensing Agency Limited. Further details of such licences (for reprographic reproduction) may be obtained from the Copyright Licensing Agency Limited, Saﬀron House, 6–10 Kirby Street, London EC1N 8TS. Cover photo © vectorus–Fotolia Illustrations by Aptara, Inc. Typeset in CronosPro light, 13/15 Pts by Aptara, Inc. Printed in Spain A catalogue record for this title is available from the British Library ISBN: 978 1 4718 4741 7 847417_FM_HTPH_Bio_CfE_i-xii.indd 2 21/09/15 7:50 pm Contents Introduction v Unit 1 Human cells Key Area 1.1 Division and diﬀerentiation of human cells 1 Key Area 1.2 Structure and replication of DNA 10 Key Area 1.3 Gene expression 16 Key Area 1.4 Genes and proteins in health and disease 23 Key Area 1.5 Human genomics 29 Key Area 1.6 Metabolic pathways 35 Key Area 1.7 Cellular respiration 42 Key Area 1.8 Energy systems in muscle cells 48 Practice Course Assessment 56 Unit 2 Physiology and health Key Area 2.1 The structure and function of reproductive organs and gametes 64 Key Area 2.2 Hormonal control of reproduction 68 Key Area 2.3 The biology of controlling fertility 74 Key Area 2.4 Ante- and postnatal screening 83 Key Area 2.5 The structure and function of arteries, capillaries and veins 91 Key Area 2.6 The structure and function of the heart 97 Key Area 2.7 Pathology of cardiovascular disease (CVD) 106 Key Area 2.8 Blood glucose levels and obesity 112 Practice Course Assessment 127 847417_FM_HTPH_Bio_CfE_i-xii.indd 3 21/09/15 7:50 pm Unit 3 Neurobiology and communication Key Area 3.1 Divisions of the nervous system and parts of the brain 135 Key Area 3.2 Perception and memory 140 Key Area 3.3 The cells of the nervous system and neurotransmitters at synapses 149 Key Area 3.4 Communication and social behaviour 158 Practice Course Assessment 167 Unit 4 Immunology and public health Key Area 4.1 Non-specific defences 171 Key Area 4.2 Specific cellular defences 175 Key Area 4.3 The transmission and control of infectious disease 181 Key Area 4.4 Active immunisation and vaccination, and the evasion of specific immune responses by pathogens 184 Practice Course Assessment 193 Skills of scientific inquiry 197 Your assignment 214 Your exam 219 Glossary 223 847417_FM_HTPH_Bio_CfE_i-xii.indd 4 21/09/15 7:50 pm Introduction General introduction Welcome to How to Pass Higher Human Biology! The fact that you have opened this book and are reading it shows that you want to pass your SQA Higher Human Biology course. This is excellent because passing and passing well needs that type of attitude. It also shows you are getting down to the revision that is essential to pass and get the best grade possible. The idea behind the book is to help you to pass, and if you are already on track to pass, it can help improve your grade. It can help boost a C into a B or a B into an A. It cannot do the work for you, but it can guide you in how best to use your limited time. In producing this book we have assumed that you have followed an SQA Higher Human Biology course at school or college this year and that you have probably, but not necessarily, already studied National 5 Biology. We recommend that you download and print a copy of the Higher Human Biology Course Assessment Notes (pages 7–56) from the SQA website at www.sqa.org.uk. You should note that in your exam only the material included in the Mandatory Course Key Areas can be examined. Skills of scientific inquiry, described on pages 59–62 of the Notes, are also examined. You should get copies of any specimen or past papers that are available on the SQA website. We have tried to keep the language simple and easy to understand and we have used the language of SQA Higher support materials. This is the language used in the setting of the exam papers. Although we have covered the entire Higher course within these materials, we have tried to emphasise those areas that cause most diﬃculty for students. We have concentrated on support for the examination element of the course assessment, which is worth about 83% of your final grade. The other 17% is covered in your assignment and you will have support for this from school or college, although we have provided some material in the short chapter on pages 214–218. We suggest that you use this book throughout your course. Use it at the end of each Key Area covered in class, at the end of each Unit in preparation for Unit assessment, before your preliminary examination and, finally, to revise the whole course in the lead up to your final examination. There is a grid on page x that you can use to record and evaluate your progress as you finish each Unit. v 847417_FM_HTPH_Bio_CfE_i-xii.indd 5 21/09/15 7:50 pm Introduction Course assessment outline The Higher Human Biology course is assessed in three parts: the National Units, an assignment and a course examination. It is necessary to pass all assessments to achieve a course award. The grading of the course award (A, B, C or D) comes from the assignment and course exam marks. National Units Each of the four National Units is assessed at your school or college on a pass or fail basis. There are diﬀerent methods of Unit assessment. Each school or college will have its own approach but all students have to pass a knowledge test in each Unit and write up an experiment they have carried out. Your school or college will assess the Units and you will probably have a chance to try Unit assessments again if you need to. You must pass all four Units. Assignment (20 marks) The assignment is an open-book task that is based on some research that you have carried out in class time. The investigation will be supervised by teachers, and you will have to write up the work in the form of a report during a controlled assessment. During the write-up you will have access to your research material and notes. The assignment has several stages: 1 Selecting a topic 2 Planning the investigation 3 Identifying resources 4 Carrying out the investigation 5 Selecting and gathering relevant information 6 Writing up an investigation report in a controlled assessment The write-up is marked out of 20 marks, with some of the marks being for scientific inquiry skills and some for the application of knowledge. Marks available Skills 15 Knowledge and understanding 5 Total 20 The marks are allocated as follows: Skills, knowledge and understanding Mark allocation Aim 1 Applying knowledge and understanding of biology 5 Selecting information 2 Processing and presenting data/information 4 Analysing data/information 2 Conclusion(s) 1 Evaluation 3 Presentation 2 vi 847417_FM_HTPH_Bio_CfE_i-xii.indd 6 21/09/15 7:50 pm Introduction The assignment is marked by the SQA and contributes 17% of the overall grade for the course. We have provided an assignment evidence checklist on page xi–xii that will allow you to check that you are prepared for the controlled assessment. Course examination (100 marks) The Higher examination is a single paper consisting of a booklet of questions in two sections: Section 1 contains 20 multiple-choice questions for 1 mark each. Section 2 contains a mixture of restricted- and extended-response questions for a total of 80 marks. The questions range from 1 to around 10 marks and the higher-mark allocation questions oﬀer a choice. The majority of the marks test knowledge, with an emphasis on the application of knowledge. The remainder test the application of scientific inquiry, analysis and problem-solving skills. There will usually be an opportunity to comment on, or suggest modifications to, an experimental situation. The course examination is marked by SQA and contributes 83% to the overall grade for the course. The various components of the Higher assessment system are as follows: Higher Human Biology Assessment Who does the assessing? Units (pass or fail) Unit 1 tests School staﬀ Unit 2 tests School staﬀ Unit 3 tests School staﬀ Unit 4 tests School staﬀ Course (graded A–D) Assignment (worth 17% of grade) Marked by SQA out of 20 marks Examination (worth 83% of grade) Marked by SQA out of 100 marks 20 multiple-choice marks and 80 restricted- and extended-response marks About this book Course content The course content section is split into four units, which cover the four Units of Higher Human Biology. Each unit is divided into Key Areas. Each Key Area has the following features: Key points ! These list and expand the content statements from the SQA specification using words and phrases needed to answer examination questions. Where a key term appears for the first time it is in bold and you will find it listed in the key words section at the end of each chapter and in the Glossary on pages 223–240. It is essential to read the definitions when working with vii 847417_FM_HTPH_Bio_CfE_i-xii.indd 7 21/09/15 7:50 pm Introduction the key points. After having worked on a Key Area, the key points should Hints & tips ★ be easy to understand. You might want to use the boxes to show progress. Where we offer a tip to We suggest marking like this – if you are having difficulty, like this + if help learning it is boxed you have done further work and are more comfortable and this * if you are like this. These tips can be confident you have learned a particular idea. Alternatively you could traffic very general or can be light them using coloured dots: red for ‘not understood’, orange for ‘more specific to the content of the work needed’ and green for ‘fully understood’. Key Area. Many tips alert you to topics that are linked to other areas in the Summary notes course and where you can These give a summary of the knowledge required in each Key Area. You read more. The tips are must read these carefully. You could use a highlighter pen to emphasise suggestions – don’t feel certain words or phrases and you might want to add your own notes in you need to use them all. the margin in pencil. In these summary notes we have tried to give examples of the biology from life situations. There are diagrams to illustrate many of the key learning ideas. Some areas contain separate boxes, providing relevant examples relating human biology to modern life. Key words These are the terms introduced in the chapter that also appear in the glossary. They could be used to produce flash cards for each Key Area at a time – maybe better than doing the whole glossary at once! Questions ? These are designed to help you assess your knowledge and understanding of the key points and should be attempted on separate paper. Mark your own work using the answers provided towards the end of each Unit. Good performance in these tests is a sign of learning and progress in the course. The questions are in two parts: Restricted response This part has a set of restricted-response questions. Those worth 1 mark are usually straightforward and start with name, state or give. They can usually be answered quickly with a word or two. Those worth 2 marks are often more complex and require a description or explanation. They usually require two- or three-part answers. Extended response This includes two extended-response questions worth between 4 and 10 marks. These questions require detailed answers. In your exam the higher-mark questions will usually offer a choice. viii 847417_FM_HTPH_Bio_CfE_i-xii.indd 8 21/09/15 7:50 pm Introduction Practice course assessment Schools can have widely diﬀering ways of assessing Units. Although the practice assessment is designed to test Units, it can also give you an idea of your overall progress in the course. We have designed the assessments to be like mini course exams, with multiple-choice, restricted-response and extended-response questions. We have included a practice assessment linked to each Unit. The questions are intended to replicate the types to expect in the course exam. They allow you to judge how you are doing overall. Most questions test knowledge and its application and some test scientific inquiry skills. The questions are provided in roughly the same proportion as in your final exam. Give yourself a maximum of 60 minutes to complete the tests for Units 1 and 2 and about 30 minutes for Units 3 and 4, but don’t worry if you go over this suggested time. Your timing will improve with further revision and practice. Mark your own work using the answers provided at the end of each Unit. Although Units are not graded, you could grade your work as you go along to give you an idea of how well you are doing in the course. The table below shows a suggested grading system. Mark out of 50 (Units 1 and 2) Mark out of 25 (Units 3 and 4) Grade 20–24 marks 10–12 marks D 25–30 marks 13–15 marks C 31–35 marks 16–18 marks B 36+ marks 19+ marks A Skills of scientific inquiry: three approaches This science skills section oﬀers three diﬀerent approaches to revising and improving your skills of scientific inquiry. In the first, we oﬀer some tips and hints for tackling exam questions, grouped under each skill area. The second approach involves four practice questions in which all the individual skills have been identified for you so that you can work to your strengths and improve weaker areas. The third approach focuses on one investigation and provides questions about the thinking that should go into experimental design. Most students should use all three sections. Your assignment We give an introduction to the assignment, some suggestions for suitable topics and some information, with hints, to help you complete the task. On page xi–xii is a grid that summarises assignment criteria on which you can record evidence for your controlled assessment. There are some hints and tips there too. Your exam We give some hints on approaches to your final exams in general as well as more specific tips for your Higher Human Biology exam. ix 847417_FM_HTPH_Bio_CfE_i-xii.indd 9 21/09/15 7:50 pm Introduction Glossary We have given the meanings of the special terms that occur in the Assessment Specification for Higher Human Biology in the context of the Key Areas where they first appear in the book. You could use the glossary to make flash cards. A flash card has the term on one side and the definition on the other. Get together with a friend and use these cards to test each other. Answers Short answers are provided for all of the questions in this book. These are intended to replicate SQA standard answers but we have tried to keep the answers short, and any instructions simple, to make them easier to use – there will often be other acceptable answers. Record of progress and self-evaluation Use the grid below to record and evaluate your progress as you finish each of the four Units. Feature As an indicator of progress, I have… Unit 1 Unit 2 Unit 3 Unit 4 Key points used the minus (–), plus (+), star (*) system to identify areas of strength and areas requiring further attention for each of the key points sections Summary notes read and thought about the summary notes for each Key Area and used highlighters to pick out the main points Hints & tips read and thought about the hints and tips and exam technique advice for each Unit Key words used the key words to make a set of flash cards for each Key Area Questions answered, marked and corrected the restricted-response questions at the end of each Key Area of each Unit answered, marked and corrected the extended-response questions at the end of each Key Area of each Unit Practice course answered and marked Section 1 of the practice assessment assessment (5 or 10 multiple-choice marks for each Unit) answered and marked Section 2 of the practice assessment (20 or 40 restricted- and extended-response marks for each Unit) Skills of scientific read and thought about the tips given for each of the skills for inquiry each Unit answered, marked and corrected the skills questions in each Unit gone through and thought about the skills areas points in context and looked at the answers to these Glossary used the glossary terms and definitions to create a set of flash cards for each Unit x 847417_FM_HTPH_Bio_CfE_i-xii.indd 10 21/09/15 7:50 pm Introduction Assignment evidence checklist Hints & tips ★ Your preparation for the communication stage of your assignment Remember RALF! should allow you to produce a report that has evidence of the following R – Referencing in full assessment points. A – Accurate calculations and plotting Assessment Evidence Check L – Labels, headings and point/out of units Topic My topic is related to a Key Area of Higher Human F – Formats appropriate Biology Aim/1 My aim(s) have been clearly stated and I have described what is to be investigated Applying knowledge I have clearly explained the topic I have researched, and understanding using correct biological terms and key ideas; I have Hints & tips ★ of human biology/5 made at least five correct statements from the Key If using commercial Area spreadsheet software like Selecting My information has been selected from a variety of Microsoft Excel, major information/2 sources and minor gridlines must This information includes some of the following: be included. raw data from an experiment/practical activity, extracted tables, graphs, diagrams and text The information I have selected is relevant, reliable and could give similar or diﬀerent perspectives; it is suﬃcient to make a conclusion to fulfil my aim Hints & tips ★ When commenting on Processing and My information is processed and presented in a reliability, a reason for the presenting variety of forms, using calculations and units where information/4 appropriate comment must be given such as large sample size This processing includes performing calculations accurately, plotting graphs from tables, populating used, repeated trials a table from other sources and/or summarising undertaken or sourced data referenced text has been peer-reviewed. I have made it clear where my raw or extracted data/information came from My presentation of processed data/information includes appropriate formats from the following: summary, graph, table, chart or diagram (including Hints & tips ★ When commenting on at least one graph, table, chart or diagram) validity, a reason for the I have used suitable scales, units, headings and labels comment must be given Analysing data/ My analysis includes the interpretation of data/ such as only the information/2 information used in the report in order to identify independent variable was relationships and trends changed or stating that all Concluding/1 My conclusion(s) are clearly stated and relate to the other variables were the aim(s); they are supported by the data I have included controlled. xi 847417_FM_HTPH_Bio_CfE_i-xii.indd 11 21/09/15 7:50 pm Introduction Evaluating/3 I have included an evaluation of my individual sources and an evaluation of the investigation as a whole Hints & tips ★ References may be My judgements of the investigation are based on unbiased if sourced from a criteria, which may include the following: scientific journal, whereas Reliability of data/information it is possible that some Validity of sources commercial companies may Evaluation of experimental procedures be biased by the need to sell products. Presentation/2 My report has an appropriate structure, with an informative title and headings I have given full, traceable references to at least two sources used in the report in suﬃcient detail to allow someone else to find them again Hints & tips ★ Citing other sources to back up data can improve its robustness. xii 847417_FM_HTPH_Bio_CfE_i-xii.indd 12 21/09/15 7:50 pm Unit 1 Human cells Key Area 1.1 Division and diﬀerentiation of human cells Key points ! 1 Cellular differentiation is the process by which a cell develops more specialised functions by expressing the genes characteristic of that type of cell. 2 Stem cells are unspecialised somatic cells that can divide to make copies of themselves (self-renew) and to make cells that differentiate into specialised cells of one or more types. 3 The cells of the early embryo are pluripotent and can make almost all of the differentiated cell types of the body. 4 The cells of the early embryo can be cultured in the laboratory to give a supply of embryonic stem cells. 5 Tissue (adult) stem cells are multipotent as they can make almost all of the cell types found in a particular tissue type. 6 Tissue (adult) stem cells are involved in the growth, repair and renewal of the cells found in that tissue. 7 Tissue (adult) stem cells in bone marrow differentiate into red blood cells, platelets and the various forms of phagocytes and lymphocytes. 8 Somatic cells are diploid cells and contain two sets of homologous chromosomes. 9 Diploid cells in humans have 23 pairs of homologous chromosomes. 10 During cell division the nucleus of a somatic cell divides by mitosis to maintain the diploid chromosome number. 11 Somatic cells divide by mitosis to form more somatic cells, which differentiate to form different body tissue types such as epithelial, connective, muscle and nervous tissues. 12 Mutations in somatic cells are not passed to offspring. 13 Germline cells divide by mitosis to produce more germline cells or by meiosis to produce haploid gametes. 14 Mutations in germline cells can be passed to offspring. 15 Research and therapeutic uses of stem cells focus on areas such as the repair of damaged or diseased organs or tissues, for example corneal transplants and skin grafts for burns. 16 Stem cells can also be used as model cells to study how diseases develop or for drug testing. 1 847417_1.1_HTPH_Bio_CfE_001-009.indd 1 22/09/15 6:10 pm Key Area 1.1 17 There are ethical issues related to stem cell use and its regulation. 18 Cancer cells divide excessively to produce a mass of abnormal cells called a tumour. 19 Cancer cells do not respond to regulatory signals and may fail to attach to each other. 20 If cancer cells fail to attach to each other they can spread through the body to form secondary tumours. Summary notes The human life cycle and cell division The human life cycle is shown in Figure 1.1. The gametes (sperm and egg cells) are haploid, which means that they each contain one complete set of human chromosomes. The zygote is diploid – it contains two complete sets of chromosomes. The zygote grows and develops by the processes of mitosis and diﬀerentiation to produce the adult body made up of many diploid cells. Some of these are germline cells, which can also undergo meiosis to produce haploid gametes. The main body tissue types are epithelial, connective, muscle and nerve tissue. The body organs are formed from a variety of these tissues. diploid somatic cells in embryo repeatedly divide by mitosis and differentiate to produce adult tissues and organs diploid germline cells divide by meiosis to produce haploid gametes each with diploid somatic cells one complete set of chromosomes repeatedly divide by mitosis and differentiate to produce the embryo haploid gametes diploid zygote cell with two complete sets of chromosomes fertilisation Figure 1.1 Human life cycle Mitosis and cell division Humans, like most living organisms, grow by producing new cells. Both somatic and germline cells can undergo mitosis. New cells are produced when the nuclei of diploid parent cells divide by mitosis and their cytoplasm is split into two. 2 847417_1.1_HTPH_Bio_CfE_001-009.indd 2 22/09/15 6:10 pm Division and differentiation of human cells Before mitosis, the DNA that makes up the chromosomes of a parent cell is copied exactly in a process called replication. Following replication, each chromosome appears as a double structure made up of two chromatids – each chromatid is a replicated chromosome. During mitosis, the chromatids are pulled apart and two new diploid daughter cells are produced. Figure 1.2 shows a cell with a diploid number of four undergoing mitosis and cytoplasm splitting. Each daughter cell is diploid and identical to the parent cell because it has an exact copy of the parent cell’s genetic information. Germline cells and meiosis Hints & tips ★ There is more about replication of DNA in Key Area 1.2 on pages 13–14. diploid somatic chromosomes chromatids two new diploid or germline cell with their DNA split and somatic or germline with four replicated move apart cells produced chromosomes Figure 1.2 Stages of mitosis in a cell with a diploid number of four Germline cells are found in the ovaries of females and the testes of males. Hints & tips ★ They can divide by mitosis to form more germline cells. They can also Try using eight pieces of divide by another process called meiosis, which results in the formation of drinking straw or wool haploid gametes – eggs (ova) in ovaries and sperm in the testes. and some sticky tape to The stages of meiosis are shown in Figure 1.3. Note that the cell is make four model illustrated with a diploid number of four for clarity – diploid cells in chromosomes – use them humans have 46 chromosomes. The haploid gametes produced by to practise the meiosis are genetically diﬀerent from each other, which leads to the chromosome movements variation we see in the human population. in mitosis and meiosis. diploid germline chromosomes with chromatids four daughter cells cell with four their DNA replicated split and haploid differentiate chromosomes form homologous move apart daughter into four pairs and are cells form haploid pulled apart gametes Figure 1.3 Stages of meiosis in a male germline cell with a diploid number of four Cellular differentiation The cell is the basic unit of human body structure. Diﬀerent cells become specialised to carry out diﬀerent functions through the process of diﬀerentiation. This process depends on the control of gene expression. Specialised cells express the genes characteristic of that cell type. 3 847417_1.1_HTPH_Bio_CfE_001-009.indd 3 22/09/15 6:10 pm Key Area 1.1 A human muscle cell expresses or switches on human muscle cell genes and therefore human muscle cells produce human muscle cell proteins. This idea is shown in Figure 1.4. unspecialised cells unspecialised cells divide and start differentiation specialised muscle cells specialised blood cells specialised nerve cells with correct genes with correct genes with correct genes switched on and other switched on and other switched on and other genes switched off genes switched off genes switched off muscle cells produce blood cells produce nerve cells produce muscle proteins blood proteins such as nerve proteins such as such as actin haemoglobin acetylcholine Figure 1.4 Flow chart to show diﬀerentiation in human cells The result of diﬀerentiation is a variety of cells specialised for diﬀerent functions, as shown by the examples in Figure 1.5. Hints & tips ★ There is more about muscle cells in Key Area 1.8 on pages 48–50 blood cells in Key smooth muscle cells – have long spindle shapes red blood blood cells – havee a large laarge ge surface surface ace area ar a ea nerve cells – ne n have ha long fibres, which Area 4.2 on pages with actin and myosin, which for exchange xchange of oxygen carry the electrical messages ca 176–179 contract during involuntary and have haemoglobin to of nerve impulses, and they movement such as peristalsis carry oxygen release neurotransmitters nerve cells in Key Figure 1.5 Specialisation in human cells Area 3.3 on pages 150–154. Specialisation of cells leads to the formation of a variety of tissues and organs. Tissues A living tissue is made from a group of cells with a similar structure and function, which all work together to do a particular job. There are four basic types of human tissue: epithelial, connective, muscle and nervous tissue, as shown in Figure 1.6. epithelial tissue connective tissue muscle tissue nervous tissue Figure 1.6 Variety of human tissues 4 847417_1.1_HTPH_Bio_CfE_001-009.indd 4 22/09/15 6:10 pm Division and differentiation of human cells The following table shows the location and specialised functions of the diﬀerent tissues. Human Location Specialised function tissue Epithelial Lines tubes, cavities and surfaces of Secretion, protection, structures throughout the human body; absorption, sensitivity many glands contain epithelial cells Connective Found throughout the body, including Support, connection and in the central nervous system; located in separation of diﬀerent types between other tissues; examples include of tissue and organs of the fatty tissue, blood and bone body; specialised functions include storage and defence Muscle Makes up muscles of the body including Contract and relax to bring skeletal muscle, the heart, and the about various movements smooth muscle in the digestive system including locomotion, heartbeat and peristalsis Nerve Makes up the nervous system – the Allows rapid electrical brain and spinal cord in the central processing and nervous system and the branching communication to control peripheral nerves other body functions Organs An organ is made up of a group of diﬀerent tissues working together to perform a particular function. Diﬀerent organs carry out diﬀerent functions. Examples of organs in humans include the heart and brain. Organ systems An organ system is made up of a group of diﬀerent organs that work together to do a particular job. Examples of organ systems in humans include the circulatory system and nervous system, as shown in Figure 1.7. circulatory system, nervous system, which consists of which consists of heart and brain, spinal cord blood vessels and nerves Figure 1.7 Examples of human systems 5 847417_1.1_HTPH_Bio_CfE_001-009.indd 5 22/09/15 6:10 pm Key Area 1.1 Stem cells and their therapeutic use Human stem cells are relatively unspecialised somatic cells. They can divide to produce cells that can diﬀerentiate into various cell types and more stem cells. In early embryos, embryonic stem cells are pluripotent, which means they can diﬀerentiate into all cell types that make up the adult organism, as shown in Figure 1.8. The inner cell mass of an early embryo at the blastocyst stage contains the pluripotent stem cells. These cells can self-renew, under the right conditions in the laboratory, to produce a supply of embryonic stem cells. stem cells within early embryo inner cell mass blastocyst fertilised egg pluripotent stem cells liver blood muscle nerve more stem cells Various differentiated cells can be produced following the division of stem cells. Figure 1.8 Embryonic stem cells In adults, stem cells within tissues are multipotent, which means they can diﬀerentiate to replace damaged cells of the type found in that particular tissue, as shown in Figure 1.9. brain nerve cells heart heart muscle cells bone marrow blood cells Figure 1.9 Tissue (adult) stem cells 6 847417_1.1_HTPH_Bio_CfE_001-009.indd 6 22/09/15 6:10 pm Division and differentiation of human cells Tissue (adult) stem cells in bone marrow diﬀerentiate into blood cells. There are several diﬀerent types, including red blood cells, platelets and the various forms of phagocyte and lymphocyte, as shown in Figure 1.10. undifferentiated stem cell in bone marrow red re ed blood cells – platelets – phagocytes – lymphocytes – ccarry arry oxygen h help e in blood clotting el defence defence ★ Figure 1.10 Diﬀerentiated blood cells Hints & tips Stem cell research There is more about Stem cell research provides information on how cell processes such as phagocytes and growth, diﬀerentiation and gene regulation work. Stem cells can be used lymphocytes in Key therapeutically to repair damaged or diseased organs and tissue. Current Areas 4.1 and 4.2 on uses include corneal and skin grafts. They can also be used as model cells pages 173 and 176–179 to study how diseases develop or for drug testing. platelets in Key There are various ethical issues raised by stem cell research. The following Area 2.7 on page 108. table summarises some of these issues. Ethical question Notes Is the prevention of Embryonic stem cell research gives us a moral dilemma. suﬀering more important It forces us to choose between two moral principles than the duty to preserve important to humans: the duty to prevent or ease human life? suﬀering and the duty to respect the value of human life. Is there a possibility of Embryonic stem cells might be used to change the stem cells being used body characteristics of already healthy and well eugenically? individuals. Could stem cells become It is possible that stem cells might be bought and sold part of a commercial trade commercially, and treatment could become subject to in biological material? the ability of an individual to pay. Embryonic stem cell research could lead to new medical treatments, Hints & tips ★ which could save human lives and relieve human suffering. On the Ethical issues are difficult. other hand, to obtain embryonic stem cells, an early-stage embryo Make sure that you are has to be destroyed, meaning the loss of a potential human life. Stem aware of why the issues cell research is strictly regulated. For example, researchers must be exist – you could be asked granted a licence to use stem cells, embr yos cannot be used beyond to give an example of an 14 days of development and human embryos cannot be implanted issue in your exam. into another species. 7 847417_1.1_HTPH_Bio_CfE_001-009.indd 7 22/09/15 6:10 pm Key Area 1.1 Cancer cells Cancer cells are abnormal cells that do not respond to regulatory signals in the body and so avoid being destroyed by the immune system. They Hints & tips ★ can divide rapidly and excessively to produce a mass of abnormal cells There is more about called a tumour. Normal cells are attached to each other and their inherited mutation and surroundings in the body, but sometimes cancer cells fail to attach to disease in Key Area 1.4 on each other and spread round the body in the bloodstream to form pages 24–27. secondary tumours, as shown in Figure 1.11. normal epithelial abnormal epithelial some cancer cells cancer cells travel a secondary tumour cells lining a small cells divide rapidly fail to attach to each in bloodstream to forms where each breathing tube to form a tumour other and invade a other places in cancer cell settles within the small tube nearby blood vessel the body Figure 1.11 Stages of tumour and secondary tumour formation Mutation Mutations are changes in genetic information. Mutations in somatic cells Hints & tips ★ Although a mutation are passed to cells that are produced when the somatic cell divides. These carried in a gamete can be mutations are not passed onto oﬀspring and so only aﬀect the individual involved. An example could be a skin cancer that arises in a somatic skin passed to offspring if that cell, which divides many times to produce a tumour. gamete is fertilised, the mutation could have arisen Mutations can arise in germline cells or be present in the germline cells of at a much earlier stage, individuals with a specific mutation already present. Mutations present and have been passed in germline cells can be passed onto gametes and so could be inherited repeatedly down several by oﬀspring. Genetic diseases such as sickle cell disease and haemophilia are inherited in families because copies of the mutated gene involved are generations of a family. found in gametes. Key words Cancer cell – grows and divides in an unregulated way to produce a tumour Connective tissue – tissue that supports, connects or separates other body tissues Diﬀerentiation – changes to cells that allow them to specialise for diﬀerent functions Diploid – refers to a cell having two sets of chromosomes Embryonic stem cells – stem cells from embryos that can divide and become any type of cell Epithelial tissue – tissue that lines tubes and surfaces within the body Ethical issue – issue aﬀecting human attitudes and decisions regarding various choices Germline cell – cell that can give rise to gametes Haploid – describes a cell having one set of chromosomes (e.g. gametes) Lymphocyte – type of white blood cell involved in a specific immune response Meiosis – type of cell division resulting in four haploid gametes Mitosis – division of the nucleus of somatic or germline cells, giving two diploid daughter cells Multipotent stem cell – stem cell that has the potential to make almost all cell types found within a particular tissue Muscle tissue – tissue making up skeletal, smooth and cardiac muscle Mutation – random change to a DNA sequence 8 847417_1.1_HTPH_Bio_CfE_001-009.indd 8 22/09/15 6:10 pm Division and differentiation of human cells Nervous tissue – tissue making up the nervous system Phagocyte – defence white blood cell that can engulf and destroy foreign material Platelets – blood cell fragments important in blood clotting Pluripotent stem cell – stem cell that has the potential to make almost all diﬀerentiated cell types of the body Red blood cell – blood cell containing haemoglobin, which can carry oxygen in the bloodstream Regulatory signal – molecular signal that can be received by a cell to modify its activity Secondary tumour – cancer formed from a cell transported from a primary tumour Somatic cell – body cell that divides by mitosis to form more body cells Stem cell – unspecialised cell that can divide and then diﬀerentiate Therapeutic – used as part of a medical therapy Tissue (adult) stem cells – stem cells from tissue that divide and diﬀerentiate to become cells of that tissue Tumour – collection of cancer cells produced by excessive, uncontrolled cell division Questions ? Restricted response (structured in 1- or 2-mark parts) 1 Describe what is meant by the term diﬀerentiation as applied to cells. (2) 2 Name the four main types of body tissue that form when somatic cells diﬀerentiate in human embryos. (2) 3 Identify the types of cell that may carry mutations that: a) cannot be passed to oﬀspring (1) b) can be passed to oﬀspring. (1) 4 Give two characteristics of human cancer cells. (2) 5 Describe how secondary cancer tumours form in the body. (2) 6 Describe one ethical dilemma related to the use of embryonic stem cells. (2) Extended response (4–9 marks each) 7 Give an account of stem cells under the following headings: a) Embryonic and adult stem cells (5) b) Stem cell research and the therapeutic use of stem cells (3) 8 Compare the processes of mitosis and meiosis. (6) 9 Give an account of cells under the following headings: a) Somatic cells (3) b) Germline cells (2) Answers are on page 51. 9 847417_1.1_HTPH_Bio_CfE_001-009.indd 9 22/09/15 6:10 pm Key Area 1.2 Structure and replication of DNA Key points ! 1 Genetic information is inherited. 2 DNA is a substance that encodes genetic information of heredity in a chemical language. 3 DNA is a very long double-stranded molecule in the shape of a double helix. 4 Each strand is made up from chemical units called nucleotides. 5 A nucleotide is made up of three parts: a deoxyribose sugar, a phosphate and a base. 6 Deoxyribose molecules have five carbon atoms, which are numbered 1 to 5. 7 The phosphate of one nucleotide is joined to its carbon 5 (5' ) and linked to the carbon 3 (3' ) of the next nucleotide in the strand to form a 3' –5' sugar–phosphate backbone. 8 There are four different DNA bases called adenine (A), guanine (G), thymine (T) and cytosine (C). 9 Genetic information is encoded in the sequence of bases along the length of one of the strands of a DNA molecule. 10 The nucleotides of one strand of DNA are linked to the nucleotides on the second strand through their bases – the bases form pairs joining the strands. 11 Bases pair in a complementary way: adenine always pairs with thymine and guanine always pairs with cytosine. 12 Base pairs are held together by hydrogen bonds. 13 Each strand has a sugar–phosphate backbone with a 3' end that starts with a deoxyribose molecule and a 5' end that finishes with a phosphate. 14 The two strands of a DNA molecule run in opposite directions and are said to be antiparallel to each other. 15 Chromosomes consist of tightly coiled DNA, which is packaged with associated proteins. 16 DNA molecules replicate prior to cell division. 17 Replication is the process by which DNA molecules can direct the synthesis of identical copies of themselves. 18 DNA unwinds and unzips to form two template strands. 19 Replication starts at several places along the DNA molecule at the same time. 20 The enzyme DNA polymerase adds complementary DNA nucleotides to the 3' end of a DNA strand. 21 DNA polymerase requires primers to start replication. 22 Primers are short, complementary sequences of nucleotides that allow binding of DNA polymerase. 23 The 3' –5' lead strand is replicated continuously in the direction from its 3' end towards its 5' end. 24 Nucleotides are added as fragments on the lagging strand. 25 The replicated fragments on the lagging strand are joined together by a ligase enzyme. 10 847417_1.2_HTPH_Bio_CfE_010-015.indd 10 22/09/15 6:05 pm Structure and replication of DNA Summary notes Deoxyribonucleic acid Function of DNA Genetic information is coded into the chemical language of DNA (deoxyribonucleic acid). This genetic information gives cells the ability to synthesise specific proteins, which determine the cell’s structure and allow it to control metabolism. Copies of a cell’s genetic information are inherited by daughter cells when it divides. Structure of DNA Each DNA molecule is very long and has two strands coiled into the shape of a double helix. Each strand of the double helix is made up from nucleotides. Figure 1.12 shows a single DNA nucleotide made up of a deoxyribose sugar to which a phosphate group and a nitrogenous base are attached. The carbon atoms of the deoxyribose sugar are numbered from 1 to 5, as shown in the diagram. phosphate group 5 O oxygen 4 1 nitrogenous base 3 2 deoxyribose sugar Figure 1.12 One nucleotide of DNA with the carbon atoms of the deoxyribose sugar numbered Nucleotides are linked by their deoxyribose sugars and phosphates to form a strand with a sugar–phosphate backbone, as shown in Figure 1.13. phosphate 5’ base deoxyribose sugar 3’ 5’ base 3’ 5’ base 3’ Figure 1.13 Short strand of DNA, showing three nucleotides linked by a 3'–5' sugar–phosphate backbone Two strands are connected by hydrogen bonding between complementary pairs of bases. The base adenine (A) always pairs with 11 847417_1.2_HTPH_Bio_CfE_010-015.indd 11 22/09/15 6:05 pm Key Area 1.2 thymine (T) and guanine (G) always pairs with cytosine (C), making the two strands complementary to each other, as shown in Figure 1.14. Note that the strands run in opposite directions (antiparallel) depending Hints & tips ★ The DNA strands are a on the bonding through the carbon atoms of the sugar–phosphate bit like lanes of traffic on a backbone. One strand has deoxyribose (3' ) at one end of the molecule, road – they are essentially but its complementary strand has a phosphate group (5' ) at the same the same but run in end of the molecule. opposite directions. This is 5’ what is meant by the term P S 3’ antiparallel. S T A P P S G C S P P S A T S P P S C G S 3’ P P = Phosphate 5’ S = Deoxyribose sugar BASES A = Adenine T = Thymine G = Guanine C = Cytosine Figure 1.14 Short double strand of DNA, showing complementary base pairing and its antiparallel structure Figure 1.15 summarises the structural features of a DNA molecule. complementary base pair held together by hydrogen bonds P P C P P G A P 5’ G T C sugar–phosphate P backbone P C P G P 3’ Figure 1.15 DNA, showing the double helix, sugar–phosphate backbones, complementary base pairing and the antiparallel strands Organisation of DNA in chromosomes In the nuclei of cells, chromosomes consist of tightly coiled DNA, which is packaged with associated proteins that help to keep the DNA strands untangled, as shown in Figure 1.16. 12 847417_1.2_HTPH_Bio_CfE_010-015.indd 12 22/09/15 6:05 pm Structure and replication of DNA associated protein molecule tightly-coiled DNA molecule packed into linear chromosomes Figure 1.16 Organisation of DNA in chromosomes Hints & tips ★ There are a number of features of DNA molecules Replication of DNA that you should note for DNA is the hereditary material of cells. DNA can make precise copies of your exam: itself by a process called replication. DNA replicates before cell division double helix shape and copies are passed to daughter cells. sugar–phosphate Stages in replication of DNA backbones The double helix of DNA is unwound by an enzyme, and the hydrogen antiparallel strands bonds that connect the two strands are unzipped. The unwinding and hydrogen bonds linking unzipping forms a replication fork. Primers are short complementary strands sequences of nucleotides that allow DNA polymerase to bind. A primer complementary base joins the end of the 3'–5' leading template strand and DNA polymerase pairing rules applied to adds free DNA nucleotides to synthesise a complementary strand nucleotides. continuously. On the lagging strand, primers are added one by one into the replication fork as it widens. DNA nucleotides are added to form fragments. These fragments are then joined by DNA ligase to form a complete complementary strand. The process requires energy, which is supplied by ATP produced by the cell’s respiration. The replication process is summarised in Figure 1.17. lead strand 3’ DNA polymerase 5’ primer replication fork Hints & tips ★ 5’ In your exam you may be 3’ asked to state the fragment requirements for DNA enzyme unwinds the replication. These are: DNA 3’ double helix templates, free DNA 5’ nucleotides, primers, DNA lagging strand polymerase, DNA ligase and Figure 1.17 Replication of DNA a source of energy (ATP). 13 847417_1.2_HTPH_Bio_CfE_010-015.indd 13 22/09/15 6:05 pm Key Area 1.2 Importance of DNA replication When the DNA in a chromosome is being replicated many replication forks are formed at the same time. As a result, the DNA of whole chromosomes is replicated quickly and precisely, as shown in Figure 1.18. DNA molecule within a chromosome and positions of three replication forks DNA molecule being replicated from each replication fork new DNA molecule almost complete new DNA molecule fully replicated Figure 1.18 Multi-replication forks This is important because it ensures that precise copies of the genetic material are available for cells undergoing mitosis and meiosis, and are passed on from cell to cell and from generation to generation. Figure 1.1 on page 2 shows the importance of DNA replication in the life cycle. Key words 3'–5' – strand of nucleic acid running from a sugar to a phosphate Adenine (A) – DNA base that pairs with thymine Antiparallel – parallel strands in DNA that run in opposite directions in terms of chemical polarity Base – nitrogenous substance that is a component of DNA nucleotides Cytosine (C) – DNA base that pairs with guanine Deoxyribose – pentose sugar that is a component of DNA nucleotides DNA – deoxyribonucleic acid; molecule that holds the genetic code in living organisms DNA polymerase – enzyme that unwinds and unzips DNA; adds free nucleotides during DNA replication Double helix – the three-dimensional shape of a DNA molecule Guanine (G) – DNA base that pairs with cytosine Hydrogen bond – weak chemical link joining complementary base pairs in DNA Lagging strand – DNA strand that is replicated in fragments Lead strand – DNA strand that is replicated continuously Ligase – enzyme that joins DNA fragments Nucleotide – component of DNA consisting of a deoxyribose sugar, a phosphate group and a base Phosphate – component of DNA nucleotide Primer – short complementary strand of DNA Replication – formation of copies of DNA molecules Sugar–phosphate backbone – strongly bonded strand of DNA Template strand – DNA strand on which a complementary copy is made Thymine (T) – DNA base that pairs with adenine 14 847417_1.2_HTPH_Bio_CfE_010-015.indd 14 22/09/15 6:05 pm Structure and replication of DNA Questions ? Restricted response (structured in 1- or 2-mark parts) 1 DNA is a complex double-stranded molecule made up from nucleotide units. a) Describe the shape of a DNA molecule. (1) b) Describe how the two strands of DNA are held together. (2) c) Name the three components that make up a nucleotide. (2) d) Explain what is meant by the following terms, as applied to DNA structure: (i) complementary base pairing (1) (ii) antiparallel. (1) 2 Describe how DNA is organised in chromosomes. (2) Extended response (4–9 marks each) 3 Give an account of the replication of a molecule of DNA. (7) Answers are on page 51–52. 15 847417_1.2_HTPH_Bio_CfE_010-015.indd 15 22/09/15 6:05 pm Key Area 1.3 Gene expression Key points ! 1 Genes are encoded into DNA and the genetic code is found in all forms of life. 2 Human genes have introns (non-coding regions) and exons (coding regions). 3 Genes are transcribed and translated during gene expression. 4 Only a fraction of the genes in a cell are expressed. 5 Gene expression is controlled by the regulation of transcription and translation. 6 Gene expression can be influenced by intracellular and extracellular environmental factors. 7 Genes are expressed to produce proteins. 8 Gene expression results in the phenotype of an individual human. 9 Proteins have a variety of structures and molecular shapes, which allows a wide range of functions. 10 Proteins are formed from polypeptides, which are chains of amino acids held together by peptide bonds and folded in various ways. 11 Gene expression involves three types of RNA, which is similar to DNA. 12 RNA is single stranded, its nucleotides contain ribose instead of deoxyribose and the base uracil (U) replaces the thymine found in DNA. 13 DNA in the nucleus is transcribed to produce messenger RNA (mRNA), which carries a copy of the genetic code. 14 In transcription, RNA polymerase moves along DNA, unwinding the double helix and aligning RNA nucleotides by complementary base pairing to form a primary transcript. 15 Introns are removed from the primary transcript and the exons spliced to form a mature mRNA transcript. 16 Alternative RNA splicing allows different mRNAs to be formed from the same primary transcript depending on which RNA segments are treated as exons and introns. 17 Triplets of bases on mRNA are called codons. 18 Translation of mRNA results in the production of a polypeptide. 19 Most codons code for specific amino acids, but there are also start and stop codons, which start and stop translation. 20 Ribosomes are made from ribosomal RNA (rRNA) and proteins. 21 mRNA carries a copy of the DNA code from the nucleus to the ribosomes, where it is translated. 22 Transfer RNA (tRNA) folds because of base pairing and forms a triplet anticodon site and an attachment site for a specific amino acid. 23 Amino acids are carried by specific tRNA molecules. 24 tRNA anticodons align to their complementary codons on mRNA. 25 tRNA molecules deliver amino acids in sequence; these are then joined together by peptide bonds to form polypeptides. 16 847417_1.3_HTPH_Bio_CfE_016-022.indd 16 21/09/15 6:29 pm Gene expression 26 Following polypeptide formation, tRNA exits the ribosome to collect further amino acids. 27 Post-translational modification allows different proteins to be created by cutting and combining polypeptide chains or by adding phosphate or carbohydrate groups to the protein. 28 As a result of alternative RNA splicing and post-translational modification, one gene can express many proteins. Summary notes Hints & tips ★ There is more about the The genetic code idea of evolutionary The base sequence of DNA forms the genetic code. This code is found in relationships in Key all forms of life, suggesting that all life evolved from a common ancestor. Area 1.5 on page 30. Genes are the units of genetic code that make up the genotype of an organism, and are expressed to produce proteins, which form the structure and control the functions of the organism. The phenotype of an individual is the result of the proteins produced by the expression of its genes. Only a fraction of the genes in any cell are expressed. Figure 1.19 summarises how the genetic code results in the phenotype of an individual. DNA base sequences in the genes make up proteins produced by proteins determine the genotype gene expression the phenotype Figure 1.19 Flow chart showing how the genetic code produces the phenotype Stages of gene expression Genes are expressed in two main stages – transcription and translation. In transcription a copy of the gene, in the form of a molecule called mRNA, is created. In translation, a specific sequence of amino acids is built up using the mRNA codes, as shown in Figure 1.20. In human cells, post- translational modifications produce the final structure of the protein. messenger RNA DNA containing the carries the genetic proteins give the genetic information transcription information to translation cell its structure is transcribed to ribosomes, where and help control messenger RNA it is translated to its function produce proteins Figure 1.20 Relationships between the substances involved in gene expression Ribonucleic acid (RNA) Gene expression relies on various forms of RNA. RNA is very similar to DNA, but has diﬀerences mainly in the nucleotides that make it up. DNA nucleotides have deoxyribose sugar while RNA nucleotides have ribose. DNA nucleotide bases are adenine, thymine, guanine and cytosine. In RNA the base uracil (U) replaces thymine. Uracil also pairs with adenine 17 847417_1.3_HTPH_Bio_CfE_016-022.indd 17 21/09/15 6:29 pm Key Area 1.3 in complementary base pairing. RNA is single stranded, although there A can be some base pairing of nucleotides. RNA nucleotides are shown in ribose Figure 1.21. sugar There are three types of RNA. Messenger RNA (mRNA) carries a G complementary copy of the genetic code from the DNA in the nucleus to the ribosomes in the cytoplasm. Transfer RNA (tRNA) carries specific U amino acids to ribosomes, where they can be assembled to form

How to Pass Higher Human Biology for CfE PDF

Document Details

Tags

Related

Summary

Full Transcript

Upgrade to continue