Year 12 Biology Textbook PDF

BIOLOGY FOR ALL Year 12 TEXT BOOK Ministry of Education Curriculum Development Unit The Ministry of Education owns the copyright to this Year 12 Biology Textbook. Schools may reproduce this in part or in full for classroom purposes onl...

BIOLOGY FOR ALL Year 12 TEXT BOOK Ministry of Education Curriculum Development Unit The Ministry of Education owns the copyright to this Year 12 Biology Textbook. Schools may reproduce this in part or in full for classroom purposes only. Acknowledgement of the CAS Section of the Ministry of Education copyright must be included on any reproductions. Any other use of these Textbook must be referred to the Permanent Secretary for Education through the Director Curriculum Advisory Services. Issued free to schools by the Ministry of Education. First Edition 2015 © Ministry of Education, Fiji, 2015 Published by Curriculum Advisory Services Ministry of Education Waisomo House Private Mail bag Suva Fiji Tel: (679) 3313050 Website: www.education.gov.fj PREFACE The development of this Textbook was entirely based on the Year 12 Syllabus. It has three strands: (1) Structure and Life Processes; (2) Living Together and (3) Biodiversity, Change and Sustainability. The contents of this book have been simplified so that it can be used by all students of different capabilities. It contains very useful materials to help students and teachers to prepare for the Fiji Year 12 Certificate Examination. It is confidently believed that it will furnish Year 12 students with the necessary number and variety of exercises essential to successful instructions in biology. All examples that have been introduced can even be attempted by an average pupil without assistance. They have been carefully graded to suit the slow learners as well while there are some problems that are provided for advance learners. Teachers and students are also advised to use other resources for enhancing of teaching and learning. This textbook is just a guide to accomplish the learning outcomes. ACKNOWLEDGEMENT Throughout the process in writing this textbook, a number of people have sacrificed their valuable time to assist the Ministry of Education. They must be acknowledged for their active participation and without their insights, guidance and continued support; this book may not have been possible. The Ministry of Education, therefore, hereby acknowledges the following people for their valuable contributions to this book: Mr. Emosi Lutunaika Principal Education Officer - Curriculum, CAS Mr. Mohammed Masud Principal Education Officer - Assessment, CAS Mrs. Elena Seninawanawa Former Senior Education Officer- Biology, CAS Dr. Sainimili Mateyawa Acting Senior Education Officer- Biology, CAS Mrs. Maneesha Rao Research Officer - Biology, CAS Mrs. Shreiya Kumar Research Officer - Biology, CAS Mrs. Shalini Singh Nabua Secondary School Mrs. Parmeshwari Narayan Ratu Sir Lala Sukuna Memorial School Ms. Olivia Vukikomoala Adi Cakobau High School Ms. Alena Sovaki Nasinu Secondary School Ms. Deepa Mohan Yat Sen Secondary School Mr. Mika Mudreilagi Basden College Mr. Wilden Ramanu St. Joseph Secondary School Mr. Kitione Tuiqilai Assemblies of God High School Mr. Om Prakash Suva Sangam College Mr. Lekima Nasau Marist Brothers High School Mr. Ronesh Ram Vunimono High School Christine Porter Form 6 Biology  TABLE OF CONTENT STRANDS PAGE NUMBER 1. STRUCTURE AND LIFE PROCESSES SUB-STRAND 1.1: CELL STRUCTURE AND FUNCTION 1-14 SUB-STRAND 1.2: METABOLIC CELL PROCESSES 15-42 SUB-STRAND 1.3: GENETIC CONTINUITY AND EVOLUTION 43-68 SUB-STRAND 1.4: COMPARATIVE FORM AND FUNCTION IN PLANTS 69-162 AND ANIMALS 2. LIVING TOGETHER SUB-STRAND 2.1: ORGANISM AND THE ENVIRONMENT 163-180 3. BIODIVERSITY, CHANGE AND SUSTAINABILITY SUB-STRAND 3.1: DIVERSITY OF LIVING THINGS 181-184 SUB-STRAND 3.2: ENVIRONMENTAL ISSUES AND ECOSYSTEMS 185-193 STRAND 1 YEAR 12 SUB-STRAND 1.1 CELLULAR ORGANISATION © MINISTRY OF EDUCATION, FIJI, 2015  SUB-STRAND 1.1: CELLULAR ORGANISATION ACHIEVEMENT INDICATORS At the end of this sub-strand, students should be able to:  Use the recommended procedures to correctly prepare a wet mount.  Estimate and calculate the size and the number of cells observed at different powers of magnification.  Define and describe the features of prokaryotes and eukaryotes.  Identify, name and describe the stages of development from zygote to embryo. STRAND 1: STRUCTURE AND LIFE PROCESSES BI 12.1.1.1 MICROSCOPES Microscope (Greek: micro=small; scope=look/see) is one of the powerful tools used in Biology. It enables us to see specimen that are too small to be seen with the naked eye. Specimen – is the object/ material observed under the microscope. Power of Microscopes 1. Magnify- make tiny specimen appear big. 2. Resolve- ability to differentiate between two or more things that normally appear as one when seen with the naked eye. STRAND 1: STRUCTURE AND LIFE PROCESSES The timeline provided below shows how microscope got invented and advanced. History 14th century – The art of grinding lenses is developed in Italy and spectacles are made to improve eyesight. 1590 – Dutch lens grinders Hans and Zacharias Janssen make the first microscope by placing two lenses in a tube. 1667 – Robert Hooke studies various object with his microscope and publishes his results in Micrographia. Among his work were a description of cork and its ability to float in water. 1675 – Anton van Leeuwenhoek uses a simple microscope with only one lens to look at blood, insects and many other objects. He was first to describe cells and bacteria, seen through his very small microscopes with, for his time, extremely good lenses. 18th century – Several technical innovations make microscopes better and easier to handle, which leads to microscopy becoming more and more popular among scientists. An important discovery is that lenses combining two types of glass could reduce the chromatic effect, with its disturbing halos resulting from differences in refraction of light. 1830 – Joseph Jackson Lister reduces the problem with spherical aberration by showing that several weak lenses used together at certain distances gave good magnification without blurring the image. 1878 – Ernst Abbe formulates a mathematical theory correlating resolution to the wavelength of light. Abbe’s formula makes calculations of maximum resolution in microscopes possible. 1903 – Richard Zsigmondy develops the ultramicroscope and is able to study objects below the wavelength of light. The Nobel Prize in Chemistry 1925 1932 – Frits Zernike invents the phase-contrast microscope that allows the study of colourless and transparent biological materials. The Nobel Prize in Physics 1953 1938 – Ernst Ruska develops the electron microscope. The ability to use electrons in microscopy greatly improves the resolution and greatly expands the borders of exploration. The Nobel Prize in Physics 1986 1981 – Gerd Binnig and Heinrich Rohrer invent the scanning tunnelling microscope that gives three-dimensional images of objects down to the atomic level. The Nobel Prize in Physics 1986 » Source: http://www.history-of-the-microscope.org/history-of-the-microscope-who-invented-the-microscope.php 1|Page BIOLOGY FOR ALL YEAR 12  Types of Microscopes 1. Optical Microscope (uses light) – Normal microscopes (i) Simple Microscope (one lens) (ii) Compound Microscope (many lenses) (iii) Dissection/Stereo Microscope (3D image) NOTE: The commonly used microscopes in schools and universities are optical microscopes: (1) Compound and (2) Dissecting 1. Compound Microscope 2. Dissecting Microscope STRAND 1: STRUCTURE AND LIFE PROCESSES Source: www.deanza.edu Source: www. bmercl.uh.edu 2. Electron Microscope (uses electrons) – Advanced microscopes (i) Transmission Electron Microscope (TEM)  First type of electron microscopy.  High voltage electron beam emitted by a cathode and formed by magnetic lenses.  Ultra-thin specimen required to allow the electrons to pass through.  Image produced is 2D black and white image. Source: www. barrett-group.mcgill.ca Source: www.news-medical.net 2|Page BIOLOGY FOR ALL YEAR 12  (ii) Scanning Electron Microscope (SEM)  In TEM, the electrons in the primary beam are transmitted through the specimen but in the Scanning Electron Microscope (SEM) images are produced from the secondary electrons which are emitted from the surface due to excitation by the primary electron beam.  The electron beam is scanned across the surface of the sample in a raster pattern, with detectors building up an image by mapping the detected signals with beam position. STRAND 1: STRUCTURE AND LIFE PROCESSES Source: www. www.purdue.edu Source: www. www. gallery.asiaforest.org (iii) Scanning Transmission Electron Microscope (STEM)  STEM combines the capabilities of both an SEM and a TEM.  The electron beam is transmitted across the sample to create an image (TEM) while it also scans a small region on the sample (SEM). (iv) Reflection Electron Microscope (REM)  Uses scattered high-energy electrons falling on a surface at glancing angles to generate an image of the surface.  This type of microscope usually has two magnification characteristics: magnification in the electron beam incidence plane and magnification in the plane perpendicular to the incidence plane YEAR 12 BIOLOGY FOR ALL 3|Page  Parts of a Compound Microscope and the Respective Functions Ocular Lens (Eyepiece)  Ocular Lens (Eyepiece) - Lens through which specimen is viewed.  Objective Lens - Lens close to the specimen; magnifies the specimen together with ocular lens.  Arm- Connects the body tube to the base of the Objective Lens microscope; for holding microscope.  Stage- platform where specimen is placed. Nosepiece  Stage Control- moves the stage sideways, right and Arm left. Stage  Coarse Adjustment- brings the specimen into focus Stage Control by moving the tube or stage up/down bigger Coarse distance. Condenser Adjustment  Fine Adjustment- Fine tunes the focus and increases the detail of the specimen.  Light Switch- switches the light on/off. STRAND 1: STRUCTURE AND LIFE PROCESSES Light Source Brightness  Base- The base supports the microscope and it’s Control Fine where the light is located. Adjustment  Brightness Control-allows the user to control the amount of light produced by the Light Source. Light Switch  Light Source- provides light.  Condenser- Gathers and focuses light from the Base illuminator onto the specimen being viewed.  Nosepiece - Rotates to allow the viewer to select Source: www.microscopemaster.com different objective lenses. View of Specimens When Seen with a Microscope Approximate Diameter of the FOV Field of View (Eyepiece Lens: 10X) (FOV) Objective Total Diameter Lens Magnification (mm) 4X 40X 4.5 10X 100X 1.8 Diameter of 40X 400X 0.45 Field of View 100X 1000X 0.18 Note: These are approximate values; the microscopes can be calibrated to check the actual diameter of field of view. A specimen Steps for Preparing Wet Mounts 1. On a clean slide place a drop of water or the required stain. 2. In that drop, place the specimen. (Place a thin slice of the specimen if it is too big) 3. Lower a cover-slip at an angle of 45º to avoid trapping of air bubbles. Note: If there is excess water in the wet mount, place a piece of tissue paper near the edge of the cover-slip for it to draw and absorb water. If there is too little water; using a dropper add some more water near the edge of the cover-slip. 4. Observe the wet mount under the microscope. 45° 4|Page BIOLOGY FOR ALL YEAR 12  Focussing the Wet Mount under the Microscope for Observation 1. Place the microscope on the bench-top. (If the microscope has its own light source, then switch on the light; if it doesn’t then place the microscope near a well illuminated area) 2. Rotate the nosepiece so that the lowest objective lens is in position. (Usually the lowest objective power is 4X) 3. Place the wet mount on the stage and secure it with the stage clips. 4. Move the wet mount using the stage control knobs so that the specimen appears to be right below the objective lens. 5. Looking from the side, turn the coarse adjustment knob to move the objective lens to as close as possible to the stage or specimen. 6. Now looking through the eyepiece, bring the specimen into focus using the coarse STRAND 1: STRUCTURE AND LIFE PROCESSES adjustment knob and perfect the focus with the fine adjustment knob. 7. Once the specimen is in focus and further magnification is required, turn the objective lens to the next higher power and fine focus. This can be done for 10X and 40X objectives. Note: Specimens to be observed under 100X objective lens requires oil of immersion (Cannot be done for wet mounts) Calculating Total Magnification 𝐓𝐨𝐭𝐚𝐥 𝐌𝐚𝐠𝐧𝐢𝐟𝐢𝐜𝐚𝐭𝐢𝐨𝐧: 𝐄𝐲𝐞𝐩𝐢𝐞𝐜𝐞 𝐋𝐞𝐧𝐬 × 𝐎𝐛𝐣𝐞𝐜𝐭𝐢𝐯𝐞 𝐋𝐞𝐧𝐬 Example: The total magnification when eyepiece lens is 10X and the objective lens is 40X is equal to Total Magnification (TM): 10 × 40 = 400X Calculating Diameter of Field of View (FOV) If the diameter of the FOV is not known: 1. Put the objective on low power. 2. Place a clear plastic ruler (mm) across the FOV. 3. Bring the ruler into focus. 4. Record the number of ruler divisions seen across the diameter at low power. 5. Using that diameter calculate the diameter of higher power. Formula: TM at Low Power Diameter FOV at High Power = TM at High Power Diameter FOV at Low Power Rearranging the Formula: TM at High Power Diameter of FOV at Low Power = × Diameter FOV at High Power TM at Low Power OR TM at Low Power Diameter of FOV at High Power = × Diameter FOV at Low Power TM at High Power YEAR 12 BIOLOGY FOR ALL 5|Page  Example on Calculating Diameter of Field of View (FOV) If the diameter of FOV at 4X Objective and 10X eyepiece is 4 mm then the diameter (mm) of FOV at 40X Objective will be: TM at Low Power Diameter of FOV at High Power = × Diameter FOV at Low Power TM at High Power 40X Diameter of FOV at High Power = × 4 mm 400X Diameter of FOV at High Power = 𝟎. 𝟒 𝐦𝐦 STRAND 1: STRUCTURE AND LIFE PROCESSES Estimating Cell Size 𝐃𝐢𝐚𝐦𝐞𝐭𝐞𝐫 𝐨𝐟 𝐅𝐎𝐕 (𝐦𝐦) 𝐂𝐞𝐥𝐥 𝐒𝐢𝐳𝐞 (𝐦𝐦) = 𝐄𝐬𝐭𝐢𝐦𝐚𝐭𝐞𝐝 # 𝐨𝐟 𝐭𝐢𝐦𝐞𝐬 𝐭𝐡𝐞 𝐬𝐩𝐞𝐜𝐢𝐦𝐞𝐧 𝐟𝐢𝐭𝐬 𝐚𝐜𝐫𝐨𝐬𝐬 Example: The estimated cell size in micrometres (µm) viewed at High Power (40X Objective and 10X Eyepiece) if the diameter of FOV at Low Power (4X Objective and 10X Eyepiece) is 4 mm, would be: Step 1: Calculate the Diameter of FOV at High Power TM at Low Power Diameter of FOV at High Power = × Diameter FOV at Low Power TM at High Power 40X Diameter of FOV at High Power: × 4 mm = 𝟎. 𝟒 𝐦𝐦 400X Step 2: Estimate the cell size using the formula Diameter of FOV (mm) Cell Size (mm) = Estimated # of times the specimen fits across 0.4 mm Cell Size (mm) = = 𝟎. 𝟏 𝐦𝐦 4 6|Page BIOLOGY FOR ALL YEAR 12  Estimating Cell Size Continued Step 3: Convert millimetres (mm) to micrometres (µm) X 1000 Millimetres Microns (mm) (µm) ÷ 1000 STRAND 1: STRUCTURE AND LIFE PROCESSES Size of the specimen in (µm) = 0.1 mm × 1000 = 100 µm Immersion Oil  Immersion oil (also known as: oil of immersion) is used when focussing the specimen at 100X objective lens.  Why? Immersion oil reduces the refraction effect between the lens and the slide thus providing a crisp image.  Which Specimen? 100X objective lens is used to magnify and resolve very tiny specimen. Example: bacteria and fungi spores.  How? To observe under 100X objective, wet mounts are not prepared; instead stained dry slides of the specimen is prepared and observed without a cover-slip. The slide is focussed at the lowest power objective (usually 4X), followed by fine focus on the next higher powers (10X and 40X), and finally at 100X objective lens. Just before turning onto 100X, a drop of immersion oil is placed on the slide. 7|Page BIOLOGY FOR ALL YEAR 12  Caring for a Microscope Microscopes are expensive tools used by biologist frequently. Therefore its proper handling; care and storage are a must. Handling Microscopes 1. When carrying a microscope from one place to another, always use one hand of yours to hold the microscope at its arm and place your second hand at the base of the microscope to provide support. 2. Never place a microscope near the very edge of the table where the chances of it falling down accidently are high. Always place the microscope on a well-supported surface away from the edge. 3. If your microscope has wires for light source, place the wires securely on the table; STRAND 1: STRUCTURE AND LIFE PROCESSES never let it hanging, to avoid tripping and falling over. 4. Never wipe the lenses of the microscope with any ordinary tissue. This will spoil the lenses. There are specific tissues available to wipe the lenses. 5. Never look through the eyepiece while using coarse adjustment to focus. It can cause the stage to crash the objective lens. Storing Microscopes 1. After you have finished making your observation with the microscope; always bring the stage down and remove the slide. (Do Not Store the Microscope with the Slide) 2. Wipe the lenses with the special lens tissue and put the lowest power objective in place. 3. Turn off the light sources and wind up the wires securely. 4. Safely carry it back to the cupboard used for storing. SELF TEST 1. Calculate the total magnification if the eyepiece lens is 5X and the lowest power objective lens is 4X. 2. Estimate the size of the cell (mm) observed at a total magnification of 400X. Use the diameter of FOV from the table provided above. 4 3 Cell 8|Page BIOLOGY FOR ALL YEAR 12  3. Convert the cell size calculated in Question (2) from millimetres to microns. 4. Calculate the diameter of FOV at 1000X magnification if the diameter of FOV at 40X magnification is 5 mm. 5. Suppose 8 cells fit across the diameter of FOV calculated in Question (4). What would the size of each cell be? STRAND 1: STRUCTURE AND LIFE PROCESSES YEAR 12 BIOLOGY FOR ALL 9|Page  BI 12.1.1.2 CELL ORGANIZATION AND EMBRYONIC DEVELOPMENT CELL ORGANIZATION  Based on the Cell Nucleus, there are two types of cells: the Prokaryote Cells and Eukaryote Cells. Prokaryotes  The word Prokaryotes is derived from the ancient Greek where ‘pro’= ‘before’ and ‘karyon’= ‘nut or kernel’. STRAND 1: STRUCTURE AND LIFE PROCESSES  These organisms lack an organised cell nucleus or any other membrane-bound cell organelles. Most are unicellular, but some prokaryotes are multicellular.  Example: Archaea (microorganisms living in cold deserts, hot springs, sulphuric marsh etc), Bacteria (microorganisms living in normal conditions) and Cyanobacteria (previously known as blue green algae). Eukaryotes  The word Eukaryotes is also derived from the ancient Greek where ‘eu’= ‘good/true’ and ‘karyon’= ‘nut or kernel’ referring to nucleus.  These organisms have membrane bound nucleus and organelles.  Example: Plants, Animals, Fungi and Protists. The major differences between both are: Prokaryotes Eukaryotes  Cell wall made of muramic acid  Cell wall made of cellulose  Chlorophyll contained in the  Chlorophyll contained in the chromatophores. chloroplast.  No nucleus  Have membrane-bound nucleus  DNA lies in the cytoplasm  DNA found in nucleus  Single circular chromosome +  Many linear chromosomes plasmid  Endoplasmic reticulum present  Endoplasmic reticulum absent  Mitochondria present  Mitochondria absent  Golgi Apparatus present  Golgi Apparatus absent  DNA replication in nucleus  DNA replication in cytoplasm  DNA replication bidirectional  DNA replication unidirectional  Transcription and translation occur in a  Transcription and translation occur sequence. simultaneously. 10 | P a g e BIOLOGY FOR ALL YEAR 12  Biological Cells (Structural and functional units of living things) Prokaryotes (primitive) Eukaryotes (modern) (no nucleus or membrane bound (have nucleus and membrane bound organelles) organelles)  Kingdom Protista (Paramecium, Amoeba &  Kingdom Monera (blue-green Euglena) algae and bacteria)  Kingdom Fungi (mushrooms and yeast)  Kingdom Archaea  Kingdom Plantae [algae, bryophytes (moss), STRAND 1: STRUCTURE AND LIFE PROCESSES pteridophytes (ferns), gymnosperms (e.g. conifers) and angiosperms (flowering plants)]  Kingdom Animalia (snails, fish, bird, man) Plantae Animalia Fungi Protista  has cell wall &  no cell wall &  Unlike animal  Both animal- chloroplast no chloroplast (no mobility at like (mobile)  autotrophs  heterotrophs any stage in life) and plant-like (producers) (consumers) and unlike plant features (no chloroplast) (chloroplast) EMBRYONIC DEVELOPMENT  Embryonic Development is the series of changes an embryo undergoes as it becomes a foetus.  Development of an embryo is known as embryogenesis.  Zygote is the first stage of life and starts after the fusion of egg and sperm (male and female gamete).  When the first division in the fused cell (zygote) occurs, it no longer remains the zygote, it becomes an embryo. This is when embryogenesis occurs.  In humans, at the later stage of pregnancy (after 8 weeks), the embryo stage ends and the foetus stage begins. The organs form in embryonic stage whiles the skeleton system in foetal stage.  For this Year, we will only concentrate on the processes involved in embryogenesis. Embryogenesis: cell division Fertilization of gametes and and cellular differentiation of Foetus single-celled zygote formation the embryo. YEAR 12 BIOLOGY FOR ALL 11 | P a g e  Process in Embryogenesis 1. Cleavage 2. Blastulation 3. Gastrulation Cleavage  Mitotic cell division of the zygote.  Embryonic stage consisting of a solid, compact mass of 16 or more cells is known as morula. Gametes Zygote Morula STRAND 1: STRUCTURE AND LIFE PROCESSES Fertilization Cleavage Source: www. epigenie.com Blastulation  Blastulation is the process via which the morula changes into blastula.  Blastula is a hollow sphere of cells (also referred to as blastomeres) surrounding an inner fluid- filled cavity called the blastocoel. Blastulation Source: www.web-books.com Gastrulation  Stage in which cell movements result in a massive reorganization of the blastula into three layered structure known as the gastrula.  The differentiation of the gastrula into the three germ layers results in ectoderm, mesoderm, and endoderm.  Gastrulation involves changes in cell motility, cell shape, and cell adhesion.  Gastrulation creates a blastopore which is the opening to the archenteron.  Archenteron is the invagination (turned inside out or folded back) of mesoderm and endoderm cells that will later become the digestive tract. 12 | P a g e BIOLOGY FOR ALL YEAR 12  The mesoderm forms via differentiation of the endodermal cells that cover the dorsal region of the archenteron.  At neurula stage in embryogenesis, the ectoderm differentiates into neural tissues (nervous tissues). Blastocoel Cross- section of blastula Blastocoel STRAND 1: STRUCTURE AND LIFE PROCESSES Archenteron Endoderm Ectoderm Blastopore Source: www.bio.miami.edu Structures Formed from Ectoderm, Mesoderm and Endoderm Source: https://en.wikipedia.org Difference between Cleavage and Mitosis  Cleavage divides the hollow ball into many cells; there is no cell growth. In mitosis, cell division is accompanied with cell growth. YEAR 12 BIOLOGY FOR ALL 13 | P a g e  SELF TEST 1. One of the most visible differences between prokaryotic and eukaryotic cells is the A. presence of a cell wall in prokaryotes B. presence of a nucleus in eukaryotes C. lack of chlorophyll in eukaryotes D. larger size of prokaryotes 2. Which type of cell appeared first on the earth? A. Eukaryote B. Prokaryote 3. DNA replication in prokaryotic cells occur in the cytoplasm because A. it is unicellular. B. it is a very primitive cell. STRAND 1: STRUCTURE AND LIFE PROCESSES C. it has no endoplasmic reticulum. D. it does not have a membrane bound nucleus. 4. What are the four initial stages of embryonic development? 5. What is cell division during the first stage of embryonic development called? How can this stage be described? 6. After the morula stage, what is the next stage? What is the morphological feature that defines this stage? 7. What are the archenteron and the blastopore? During what stage of embryonic development are these structures formed? What happens to the archenteron? 8. What is the difference between cleavage and gastrulation? Which occurs first? 9. From which germ layer is the epidermis and the nervous system produced? What other organs and tissues are made from that germ layer? 10. From which germ layer are blood cells produced? What other organs and tissues are made from that germ layer? 11. From which germ layer is the liver and the pancreas produced? What other organs and tissues are made from that germ layer? 12. What is the major distinguishing factor that separates the embryonic stage from the foetal stage? A) All major organ systems form during the embryonic stage; the foetal stage consists mainly of rapid growth. B) The brain forms late in the foetal stage; all other organ systems form earlier. C) The skeletal system is laid down during the foetal stage, otherwise organ systems form during the embryonic stage. D) The major event of the embryonic stage is implantation in the uterus; all development occurs during the foetal stage 13. In which process do the cells become progressively smaller? A) Differentiation B) Cleavage C) Growth D) Morphogenesis 14. Identify three types of changes the cells experience in gastrulation. 14 | P a g e BIOLOGY FOR ALL YEAR 12 STRAND 1 YEAR 12 SUB-STRAND 1.2 METABOLIC CELL PROCESSES © MINISTRY OF EDUCATION, FIJI, 2015  SUB-STRAND 1.2: METABOLIC CELL PROCESSES ACHIEVEMENT INDICATORS At the end of this sub-strand, students should be able to:  Explain the types of energy transformation involved in the process of photosynthesis and respiration.  Describe the roles of the essential components of photosynthesis and respiration.  Describe the detailed structure of the chloroplast and relate features to adaptations for photosynthesis.  Differentiate and summarize the processes involved between the light phase and dark phase STRAND 1: STRUCTURE AND LIFE PROCESSES of photosynthesis.  Conduct experiments to investigate the factors affecting the rate of photosynthesis.  Analyse the experimental results by drawing graphs to explain how factors control rate of photosynthesis.  Describe the detailed structure of mitochondria and relate features to adaptations for respiration.  Differentiate and summarize the stages involved in respiration.  Assess the experimental results by drawing graphs to explain how factors control rate of respiration.  Describe the relationship between photosynthesis and respiration.  Name and describe the elements and components that constitute the bio-chemicals of life.  Describe the roles of the four bio-chemicals.  Study the chemical reactions to formation of monomers and polymers.  Analyse carbohydrates for their energy content (or food storage).  Study the process of DNA replication and how the process results in the transmission and conservation of the genetic code.  Explain the process of protein synthesis. BI 12.1.2.1 PHOTOSYNTHESIS Photosynthesis is the process that transforms light energy from the sun into chemical energy that is later used by organisms as an energy source to fuel their activities. The equation that best describes this transformation process is: Light Energy 6CO2 + 6H2O 6C6H12O6 + 6O2 Chlorophyll 6 Carbon dioxide + 6 Water 6 Glucose + 6 Oxygen STRAND 1: STRUCTURE AND LIFE PROCESSES Key Ingredients for Photosynthesis  Carbon dioxide – diffuses through the leaf stomata. The air spaces in the leaf allows CO2 to diffuse to the palisade (cells containing chloroplast) cells quickly.  Water – water is absorbed into the roots by osmosis and then transported to the rest of the plant.  Sunlight - pigments (coloured proteins) found in the chloroplast traps sun’s energy. The common pigments found in plants are:  Chlorophyll a and b: green pigment produced in chloroplast. These are photosynthetic pigments which absorbs energy from the entire light spectrum except for green light.  Phaeophytin: yellow-grey pigment.  Xanthophyll: yellow-brown pigment.  Anthocyanin: red-pink pigment which mainly absorbs blue-green wavelengths.  Carotene: yellow-orange pigment. This pigment mainly absorbs the blue wavelength. YEAR 12 BIOLOGY FOR ALL 15 | P a g e  Site of Photosynthesis The cell organelle responsible for carrying out photosynthesis is chloroplast. Structure of the chloroplast provided below will help you to better understand how the process of photosynthesis occurs. Chloroplast Function of the Structures Inter membrane Inner membrane  Chloroplast has 2 membranes: inner and space outer membrane. Outer membrane  Inner membrane surrounds the stroma and the grana. STRAND 1: STRUCTURE AND LIFE PROCESSES  Grana are stacks of thylakoid.  Single stack of thylakoid= granum.  Chlorophyll sits on top of each thylakoid. Stroma Thylakoid (aqueous fluid)  Grana are connected by lamellae. Granum Lamellae Lumen (stacks of (inside of  Stroma is the empty space in the thylakoid) thylakoid) chloroplast just like the cytoplasm in cell. Source: http://www.biology.tutorvista.com Stages of Photosynthesis There are two stages of photosynthesis: 1. Light reaction (thylakoid membrane) 2. Dark reaction: Krebs cycle (stroma and cell cytoplasm) Stage 1: Light Reaction: (light-dependent reaction) Step 1: Photolysis - the light energy trapped by the pigments is used to split the water molecules. Oxygen is the by-product of this reaction. It diffuses out of the chloroplasts. Light 2H2O 4H+ + O2 (waste) + Electrons Energy Step 2: Exciting the electrons- sunlight energises electrons released from water. Step 3: Electron transport chain- high energy electrons released from splitting of water, moves back and forth across the thylakoid membrane to release their energy to into ATP. ATP is a high-energy molecule that is responsible for intracellular (inside the cell) energy transfer. 16 | P a g e BIOLOGY FOR ALL YEAR 12  After the energy has been extracted from excited electrons, hydrogen ions (H+) and electrons (e-) are carried by NADPH and energy by ATP to the cell cytoplasm for the dark reaction. NADPH is like an ‘electron taxi’ responsible for carrying electrons to the dark reaction. NADPH is produced last in the light reaction. High energy e- low energy e- + ATP Source: www.clipartlord.com  Photophosphorylation is a process that uses light energy to add phosphate to ADP in order to produce ATP.  Prokaryotes (e.g. cyanobacteria previously known as blue-green algae and some other bacteria) have simple systems in which photosynthesis is used just for the production of STRAND 1: STRUCTURE AND LIFE PROCESSES energy. Therefore, cyclic photophosphorylation occurs to accomplish the conversion of ADP to ATP process for immediate energy for the cells.  In eukaryotes (plants) non-cyclic photophosphorylation occurs. This is accomplished by splitting the water molecule, converting ADP to ATP, and the provision of the reduced coenzyme NADPH to power the synthesis of energy storage molecules. Stage 2: Dark Reaction: (light-independent reaction)  H+ and ATP from light reaction and CO2 from the air react to produce glucose.  Begins in stroma and finishes in the cell cytoplasm.  Glucose is produced via complex cycle known as Calvin cycle. CO2 + H2 (from NADPH) + energy (from ATP) C6H12O6 Summary of the Photosynthesis Reaction YEAR 12 BIOLOGY FOR ALL 17 | P a g e  Factors Affecting the Rate of Photosynthesis Factors which influence the rate of photosynthesis are: 1) Light Intensity – is the strength or brightness of light. As light intensity increases the rate of photosynthesis increases provided sufficient water and carbon dioxide is present. However, this increase will be seen only till a certain increase in the light intensity. Beyond that increase, chlorophyll can get damaged. 2) Carbon dioxide (CO2) Concentration – Increase in the carbon dioxide concentration will also increase photosynthesis since carbon gets incorporated as carbohydrate (C6H12O6). STRAND 1: STRUCTURE AND LIFE PROCESSES 3) Temperature – it is not the light reaction that is affected by the change in temperature but rather the dark reaction. Temperature affects the enzymes which catalyses the reactions. All enzymes have optimal temperatures at which they work best and anything below or beyond affect their ability to catalyse reactions. 4) Water Availability – when all other factors are present in sufficient amount, the amount of water available to the plants can also affect the rate of photosynthesis. There is no problem when enough water is present but the problem arises when there is water shortage. During water shortage, the stomata will remain closed to prevent transpiration hence the plant will be deprived of CO2 since CO2 enters the leaf through stomata. 5) Mineral & Nutrient Availability - Among nutrients, low supply of nitrogen adversely affects the rate of photosynthesis since it forms the basic constituent of chlorophyll. Other essential elements which participate in photosynthesis (e.g. Mg, Fe, Cu, Mn, Cl, S and K) also affect the rate of photosynthesis. 18 | P a g e BIOLOGY FOR ALL YEAR 12 BI 12.1.2.2 RESPIRATION Respiration is the process that converts biochemical energy from food into ATP. Unlike photosynthesis which only occurs in plants and plant-like prokaryotes, respiration occurs in both the plants and animals. Plants photosynthesize during the day and respire at night. Types of Respiration 1) Aerobic Respiration: breaks down glucose using oxygen. It extracts more ATP from food than anaerobic respiration. 2) Anaerobic Respiration: breaks down glucose without oxygen. It extracts less ATP than STRAND 1: STRUCTURE AND LIFE PROCESSES aerobic respiration.  Since aerobic respiration is more efficient, most organisms use anaerobic respiration only when no oxygen is available. Aerobic Respiration The equation that best describes the aerobic respiration is: 6C6H12O6 + 6O2 6CO2 + 6H2O + Energy Glucose + Oxygen Carbon dioxide + Water + ATP Key Ingredients for Aerobic Respiration  Carbohydrate – organisms obtain carbohydrates from plants which produce carbohydrate/ glucose via photosynthesis.  Oxygen – is also produced by the photosynthesising organisms. It is a by-product of the light cycle in photosynthesis. YEAR 12 BIOLOGY FOR ALL 19 | P a g e  Site of Aerobic Respiration The cell organelle responsible for carrying out cellular respiration is mitochondria. Structure of the mitochondria given below will help you to better understand how the process of respiration occurs. Mitochondria Function of the Structures  Mitochondrion (singular noun) has 2 Inner membrane membranes: inner and outer membrane. Outer  Outer membrane covers the organelle. membrane  Inner membrane folds many times creating a STRAND 1: STRUCTURE AND LIFE PROCESSES layered structure called cristae. The folding of the inner membrane increases the surface area to volume ratio inside the organelle.  Matrix is the fluid contained in the Cristae mitochondria.  Mitochondria have its own ribosomes and Matrix DNA floating in the matrix (To be studied later). Source: http://www.micro.magnet.fsu.edu.com Stages of Aerobic Respiration Aerobic respiration occurs in three stages: 1. Glycolysis (cell cytoplasm) 2. Krebs Cycle (mitochondria matrix) 3. Respiratory Electron Transport Chain (cristae) Stage 1: Glycolysis  Occurs in cell cytoplasm  Splits glucose molecule into two pyruvate molecules  Few molecules of ATP also produced  No oxygen required C6H12O6 2 Pyruvate + Little Energy (ATP) Stage 2: Krebs Cycle  Occurs in matrix.  Breaks down pyruvate to produce more energy. 20 | P a g e BIOLOGY FOR ALL YEAR 12   Three products formed by breaking the pyruvate are: 1. CO2 (waste product) 2. energy (carried by ATP) 3. hydrogen ions (H+) and electrons (e-) (carried by NADPH)  ATP produced is used by organism as a source of energy and CO2 is excreted from the body. The hydrogen ions and electrons are carried to the last stage of the respiration- Electron Transport Chain. STRAND 1: STRUCTURE AND LIFE PROCESSES Stage 3: Respiratory Electron Transport Chain (ETC)  Similar to the ETC in photosynthesis.  Majority of the energy contained in the glucose molecule is released.  High energy electrons from Krebs cycle move back and forth across the cristae until all its energy has been released into the ATP molecules.  After all the energy is released from the electrons and hydrogen ions, oxygen is used to neutralise it by combining it to form water. 4 H+ & 4 high energy e- + O2 2H2O + Energy (carried by NADPH) (carried by ATP) Anaerobic Respiration  Small amounts of energy released from glucose.  Oxygen not used.  Disadvantages of anaerobic respiration is: 1. Maximum amount of energy cannot be extracted from the glucose 2. The by-product (lactic acid) can be poisonous to the cells if produced in large quantities.  Advantage- some energy can be released in absence of oxygen. YEAR 12 BIOLOGY FOR ALL 21 | P a g e  The equation that best describes the anaerobic respiration is: Lactic acid (bacteria and animals) Glucose ATP + Pyruvate Ethanol and CO2 (plants and fungi) Stages of Anaerobic Respiration  The only stage in the anaerobic respiration is: Glycolysis. STRAND 1: STRUCTURE AND LIFE PROCESSES  In absence of oxygen, only glycolysis can occur to breakdown glucose into pyruvate and small amount of ATP. Uses of Anaerobic Respiration  Backup Energy supply for muscles- when carrying out vigorous exercise, our heart and lungs are not be able to supply sufficient oxygen to our muscles and in such cases muscles begin to carry out anaerobic respiration until more oxygen is available.  Fermentation- fermentation by yeast is used in baking and brewing. Fermentation by bacteria is used in yogurt and cheese making processes. Factors Affecting Respiration Factors influencing the rate of respiration are: 1) Glucose Availability – glucose is the source of energy in respiration and in presence of sufficient glucose, cellular respiration will proceed effectively. 2) Oxygen Concentration – greatly influences the breakdown of glucose and the amount of energy in the form of ATP released. Aerobic respiration is only able to occur in presence of oxygen. 3) Temperature – activity of enzymes affected if the temperature is not in the optimal range. 4) Cell Activity – the rate of respiration is highly dependent on the cell activity. During vigorous activities such as exercising, the respiration rate increases and it decreases while the body the resting or sleeping. 22 | P a g e BIOLOGY FOR ALL YEAR 12 Comparison between Photosynthesis and Respiration Photosynthesis Respiration Occurs in plants and some prokaryotes (not in Occurs in plants, animals and prokaryotes animals) Energy from light is required Energy acquired from chemical reaction Producers Producers and Consumers Organism which photosynthesize are self- Organisms highly rely on the producers to sustaining survive Reactants are CO2 and water Products are CO2 and water Products are glucose and O2 Reactants are glucose and O2 By-product produced: O2 By-product produced: CO2 Occurs in chloroplast Occurs in mitochondria STRAND 1: STRUCTURE AND LIFE PROCESSES Electron transport chain Electron transport chain SELF TEST 1. Which organisms contain chloroplasts? 2. Where does the plant get energy to make its food? 3. What is the process conducted by the producers? 4. What are the raw materials (reactants) used for photosynthesis? 5. Which simple sugar is produced in photosynthesis? 6. Which gas is used and which is released in photosynthesis? 7. Which part of the plant contains most of the photosynthetic cells? 8. Where in the chloroplast (organelle) is chlorophyll (pigment) found? 9. What is the role of stomata in photosynthesis? 10. How many membranes are found in chloroplast and mitochondria? What is the empty space (space similar to cytoplasm) known as in the chloroplast and in the mitochondria? 11. What are stacks of thylakoid known as and how are these stacks connected? 12. What happens in photophosphorylation? YEAR 12 BIOLOGY FOR ALL 23 | P a g e  13. In photosynthesis process where (light reaction or dark reaction) is CO2 used? 14. What happens in photolysis? 15. What are ATP and NADPH? 16. What are some factors limiting the rate of photosynthesis? 17. What is the difference between respiration and gas exchange? 18. What is the difference between aerobic and anaerobic respiration? 19. What is the primary purpose of cellular respiration? STRAND 1: STRUCTURE AND LIFE PROCESSES 20. What is needed for cellular respiration to occur? 21. What are waste products in aerobic cellular respiration? 22. What are the waste products in anaerobic respiration in plants and animals? 23. How is the numerous folding of the inner membrane (cristae) of mitochondria advantageous? 24. What are some uses of anaerobic respiration? 25. Muscle cells require more energy than do most other cells. Which organelles would you expect to find in greater abundance in muscle cells than in most other cells? 26. How are photosynthesis and respiration opposite processes? 27. How are the by-products of respiration released from the body? 28. What are factors which limit cellular respiration? 29. Identify the similarities between the chloroplast and mitochondria. 24 | P a g e BIOLOGY FOR ALL YEAR 12 BI 12.1.2.3 CHEMICALS OF LIFE The four organic (carbon containing) molecules that make up the living things are: 1. Carbohydrates 2. Lipids 3. Proteins 4. Nucleic Acids 1. CARBOHYDRATES STRAND 1: STRUCTURE AND LIFE PROCESSES Source: www.wholebodyhealthohio.com Structure  Simple sugar molecules made of carbon, hydrogen and oxygen atoms.  It can be linked into long chains to form complex carbohydrates.  Simplest sugar ring is known as monosaccharide (mono - one; saccharide - sugar).  Some carbohydrates can be made from joining two (disaccharide) or more (polysaccharide) sugar rings. Functions  Is used for structure and energy storage; quick source of energy.  Making up the cell structure. Examples of Carbohydrates 1. Monosaccharides- single sugar molecule. Example: Glucose, Fructose and Galactose. Glucose Source: www.suppreviewers.com YEAR 12 BIOLOGY FOR ALL 25 | P a g e  2. Disaccharides- two sugar molecules joined together. Example: Lactose (milk), Sucrose (table sugar) and Maltose (molasses). 3. Polysaccharides- many simple sugar molecules joined together. Example: i. Glycogen- made of many glucose molecules. Glycogen is the form in which animal/ human body stores glucose. ii. Starch- large number of glucose joined together. It is produced by many green plants as a source of energy. iii. Cellulose- made up of hundreds and even thousands of glucose units. It is an important component of the cell wall. STRAND 1: STRUCTURE AND LIFE PROCESSES iv. Chitin- a polysaccharide found in the cell wall of fungi, exoskeleton of the arthropods and radula of the molluscs. 2. LIPIDS Source: www.livestrong.com Structure Phospholipid Bilayer  Made of carbon and hydrogen molecules.  Do not dissolve in water.  Fats and oils fall in this category. For example, ghee butter, oils, margarine, wax.  Basic structure: Long fatty acid tail attached to glycerol molecule.  Contains twice the amount of energy Hydrophilic Head Hydrophobic Tail as the carbohydrates. Source: bio1151.nicerweb.com Functions  Development of cell membrane - Phospholipid bilayer.  Long-term energy storage.  Insulation to keep the body warm.  Provides padding and protection to the internal organs.  Aids in the absorption of vitamins A, D, E and K.  Component of the steroid hormones. 26 | P a g e BIOLOGY FOR ALL YEAR 12  Type of Fats Saturated Fat Unsaturated Fat  No double bonds  Double bonds between between carbons carbons  Solid at room  Liquid at room temperature temperature  Mostly animal fats  Mostly vegetable fats  Excess consumption  Not unhealthy in contributes to NCDs moderate consumption  Examples: butter  Example: soya bean oil STRAND 1: STRUCTURE AND LIFE PROCESSES 3. PROTEINS Source: www.rivertea.com Structure  Large molecules made of chains of amino acids.  Contains carbon, oxygen, hydrogen and nitrogen atoms.  There are only 20 amino acids but these twenty can be combined in several ways to produce approximately a million different proteins.  Plays an important role in an organisms functioning.  Some examples of proteins are: skin, hair, bones, cartilages, hormones, enzymes and muscle tissues.  Four levels of protein structure are: Primary, Secondary, Tertiary and Quaternary structures. (only primary structure will be studied in Year 12). Basic amino acid structure  Carbon centre  COOH- carboxylic acid group  NH2- amino group  R- varying attachment group YEAR 12 BIOLOGY FOR ALL 27 | P a g e  Protein Formation  Nitrogen of one amino acid attached to the carbon of the carboxylic acid group of another.  The two amino acids are joined by the peptide bond.  More than two amino acids joined by peptide bond are known as polypeptide chain. Amino Acid 1 Amino Acid 2 STRAND 1: STRUCTURE AND LIFE PROCESSES Peptide Bond Water Source: http:// www.study.com Functions  Antibodies- proteins form antibodies, a component of the immune system that helps prevent infections and illnesses.  Energy- protein is the major source of energy.  Enzymes- enzymes are proteins which speed up chemical reactions in the body.  Hormones- protein is involved in production of hormones such as insulin, secretin etc.  Transportation and storage of molecules- major transportation element in the body. For example haemoglobin (protein) transports oxygen in the body. Ferritin is a protein that combines with iron and stores it in the liver.  Repair and maintenance- protein is vital in development, maintenance and repair of the body tissues. Denaturation  Denaturation is the process whereby the shape of the protein is changed due to excess heat, corrosive chemicals, change in pH, change in the salinity levels and the concentration of heavy metals.  The basic amino acid structure remains the same; only the shape of the protein is altered.  Without the proper shape, proteins cannot function properly.  Some proteins have the ability to ‘un-denature’ (go back to original shape) if placed back in the ideal conditions. 28 | P a g e BIOLOGY FOR ALL YEAR 12 Body Building Proteins  Proteins are broken into amino acids in our body.  Proteins not required immediately by the body is deaminated (breaking of amino acid) by the liver.  The amino group is converted to urea and filtered out of the blood in the kidneys which is then excreted.  The remainder of the molecule is broken down for energy. 4. NUCLEIC ACIDS STRAND 1: STRUCTURE AND LIFE PROCESSES Source: www.godandscience.org  While carbohydrates, lipids and proteins are energy sources (building materials), nucleic acids are the ‘instructors’ which tells the cells how to: (1) Assemble the building materials together; and (2) Store and release energy in cells. Types of Nucleic Acids and Nucleotides  2 types of nucleic acids which serve as ‘instructors’ are: - DNA (Deoxyribonucleic acid) - RNA (ribonucleic acid)  Nucleotides which have roles in energy transformation and transport: - ATP (energy carrier in photosynthesis and respiration reactions) Double helix structure - NAD+ and NADP+ (hydrogen and electron carriers) Structure  Nucleotides are subunits which build the nucleic acids.  Each nucleotide has 3 Phosphate Base parts: Group 1. Phosphate group 5- 2. 5-carbon sugar carbon 3. Organic base Sugar Source: www.bio.miami.edu YEAR 12 BIOLOGY FOR ALL 29 | P a g e  Structure and Function of DNA  DNA has a central role in regulating cell activity. It contains genetic information on which protein is to be made and how it should be made.  DNA is double stranded (2 nucleic acids) twisted in a spiral-helix shape.  DNA contains four different nitrogen bases: - Adenine (A) - Thymine (T) - Cytosine (C) - Guanine (G)  Nitrogen base of one strand is joined to the nitrogen base of the other.  Adenine pairs with thymine (A-T) and cytosine with guanine (C-G). STRAND 1: STRUCTURE AND LIFE PROCESSES Source: http://wallpor.com Structure and Function of RNA  RNA is responsible for transcribing and translating the genetic information.  When the cell needs to produce a certain protein, it activates the protein’s gene (the portion of DNA that codes for that protein) and produces multiple copies of that piece of DNA in the form of messenger RNA (mRNA).  The multiple copies of mRNA are then used to translate the genetic code into protein through the action of the cell’s protein manufacturing machinery, the ribosomes.  Instead of the nitrogen base Thymine (T), RNA’s have the base ‘Uracil’ (U).  There are three types of RNA: 3 Types of RNA (1) Messenger RNA (mRNA) (2) Transfer RNA (tRNA) (3) Ribosomal RNA (rRNA) Source: www.biology101.org 30 | P a g e BIOLOGY FOR ALL YEAR 12   RNA can also act as enzymes (called ribozymes) to speed chemical reactions.  In some viruses, RNA, rather than DNA, carries the viral genetic information.  It plays an important role in regulating cellular processes–from cell division, differentiation and growth to cell aging and death. The major differences between DNA and RNA are: DNA RNA  Double stranded  Single stranded  Has deoxyribose sugar  Has ribose sugar  Thymine (nitrogenous base)  Uracil instead of Thymine STRAND 1: STRUCTURE AND LIFE PROCESSES Summary Table of the Four Biochemicals Carbohydrates Lipids Proteins Nucleic Acids Building block monosaccharides fatty acids + amino acids nucleotides glycerol Elements CHO CHO CHON CHONP Functions - structure - structure - structure - contain - quick energy - long-term energy - hormones genetic source - storage - enzymes information - padding - many other - carry energy, - insulation functions electrons and H+ Associated - mono: one - saturated - peptide - DNA helix words - di: two - unsaturated - peptide bond - A, T, C, G - poly: more - denaturation and U bases than two Examples - sugar - phospholipids - muscle fibres - DNA - starch - butter - insulin - RNA - glycogen - corn oil - egg white - ATP - chitin - NADP+ YEAR 12 BIOLOGY FOR ALL 31 | P a g e  SELF TEST 1. What should Manasa load-up in order to have abundant and quick energy for a rugby match? A. Beef B. Apples C. Dalo D. Vegetable soup 2. Apart from the thick fur, polar bears have a thick layer of fat (approximately 4.5 inches). Identify the reason for such a thick layer of fat? STRAND 1: STRUCTURE AND LIFE PROCESSES A. Quick energy source B. Make the fur grow thick and long C. Provide heat insulation D. No reason; they have the fat because they like to eat a lot. 3. If Sera wants to grow healthy and thick hair, which macromolecule should she increase in her diet? A. Lipids B. Proteins C. Nucleic acids D. Carbohydrates 4. If Frank converts a polymer into a monomer in his lab, how would the resulting product be? A. No idea. B. Larger than the starting material. C. Same size as the starting material. D. Smaller than the starting material. 5. A storage form of sugar found only in plants is A. Chitin B. Starch C. Lactose D. Glycogen 6. Keratin is a (Hint: mostly found in shampoos, conditioners, hair-gels etc.) A. Lipid B. Protein C. Nucleic acid D. Carbohydrate 7. Candle wax is insoluble in water. Therefore it must be a A. Lipid B. Protein C. Nucleic acid D. Carbohydrate 32 | P a g e BIOLOGY FOR ALL YEAR 12  8. Carbohydrates have many functions in the cell. Which of the following is an incorrect match of the carbohydrate with its function? A. Sugar transport in plants: disaccharides B. Energy storage in plants: starches C. Energy storage in plants: lactose D. Sugar transport in humans: glucose 9. Identify the complementary DNA and mRNA base orders for the following single DNA strands given below? A. TACTCGGCTA B. GCTAGCTAA C. AACTGCACAT D. TACGGCATC STRAND 1: STRUCTURE AND LIFE PROCESSES 10. Proteins serve many functions in the human body. Identify the function of the proteins given below? FUNCTION PROTEIN (hormone; enzymes; energy; transport; storage; structure; defence; etc.) A. Pepsin in stomach B. Collagen and Elastin C. Testosterone D. Haemoglobin E. Antibodies F. Actin and myosin G. Amylase YEAR 12 BIOLOGY FOR ALL 33 | P a g e  BI 12.1.2.4 ENZYMES  A catalyst is any chemical that speeds up the rate of a reaction.  Enzymes are organic (contains carbon atoms) catalysts.  They are proteins that increase the rate of metabolic reactions.  The names commonly end with ‘ase’. Example: amylase, synthase, sucrose. However, the enzymes that were discovered very long time ago end with ‘in’. Example: pepsin, trypsin  For example, if you leave a spoonful of sugar undisturbed for thirty years, it will not change at all. However, if you eat the sugar, it will oxidise (broken down) in less than thirty minutes. This incredible difference in reaction rate is due to an enzyme. Enzyme Reactions STRAND 1: STRUCTURE AND LIFE PROCESSES 1. Enzymes work by lowering a reaction’s activation energy.  Activation energy is the energy required to start up a reaction. For any reaction to occur the molecules involved must collide in the right way at high speed (this requires energy).  Enzymes reduce the activation energy by binding to a substrate (grabbing) the molecules and holding them together in the right way until they react with each other. Once the reaction has finished, the enzyme breaks free. 2. Enzymes are not changed by the reaction they catalyse.  A cell uses the same enzyme molecule over and over again. Chemical reactions do not affect the enzymes that catalyses them, that is, enzymes do not get used up by the reactants. 3. Each metabolic reaction has its own enzyme to catalyse it  The chemicals that an enzyme acts on its called the substrate.  Each enzyme acts on specific substrate.  The substrate and its enzyme fit together like a lock and key. 4. Many factors affect the rate of enzyme action.  Factors such as temperature, pH, substrate concentration, enzyme concentration and substrate surface area affects enzyme action.  Every enzyme has temperature and pH conditions in which it works best. For example, stomach enzyme function best in acids. Most of your body enzymes work best at 37⁰C.  Most chemical reactions which are enzyme catalysed generally proceed more quickly as temperature increases. However, this is true only up to a certain temperature because enzymes are proteins and proteins get denature if overheated.  As substrate concentrations, enzyme concentrations and substrate surface areas increase, so does the reaction rate (as long as both substrate surface area and enzyme are available). 34 | P a g e BIOLOGY FOR ALL YEAR 12 5. Inhibitors can prevent enzymes from acting on substrates  Inhibitors are chemicals which prevents the enzyme from working until the organism need it. Every enzyme has an inhibitor made by the cell.  By using inhibitors, a cell can control the effects of its enzymes.  For example, when liver converts glycogen into glucose using enzyme (glycogen phosphorylase), then it does not want the enzyme which converts glucose into glycogen (glycogen synthase) to be working against it and therefore it produces an inhibitor to stop the enzyme (glycogen synthase) from converting glucose to glycogen. 6. Many enzymes require co-factors to function. STRAND 1: STRUCTURE AND LIFE PROCESSES  Any substance that helps an enzyme to function is called a co-factor.  Co-factors are usually vitamins or minerals.  For example, vitamin B helps the enzymes that catalyses respiration. If a person does not get vitamin B in her diet, she will become paralysed. Eventually she will die because her cells cannot get energy out of food. Enzyme Action Enzyme Cofactors Source: www. en.wikibooks.org Source: www.studyblue.com SELF TEST 1. Enzymes have the ability to catalyse reactions. How do