EDEXCEL SCIENCE B2 Name Set
Spec ref B2.1.1,2&3 Describe the function of the components of bacterial cell, plant & animal cells B2.1.4&5 Describe how cells can bee studies with a microscope & state how have improved B2.1.6&7 Recall what a gene is & describe the structure of DNA including naming base pairs Student Checklist R A G B2.1.8&9 Describe how to extract DNA from cells & explain how the structure of DNA was discovered HT ONLY B2.1.10 Describe and explain the implications of the human Genome Project B2.1.11&12 Describe the process & discuss the pros & cons of genetic engineering B2.1.13&14 Describe the process of mitosis & state where this occurs Personalised Learning Checklist Edexcel Additional Science /Biology B2 Topic 1 The building blocks of cells B2.1.15&16 Recall what occurs at fertilisation & describe the process of meiosis in forming gametes B2.1.17 Recall what cloning is and that asexual reproduction is a form of cloning HT ONLY B2.1.18 Describe the stages in the production of cloned mammals B2.1.19 Explain the advantages, disadvantages & risks of cloning mammals B2.1.20 Recall the differences in embryo & adults stem cells ability to differentiate B2.1.21 Describe the advantages, disadvantages & risks arising from stem cell research B2.1.22 Describe how the order of bases in a DNA codes for the amino acids in a protein HT ONLY B2.1.23 Describe the stages of protein synthesis, including transcription & translation B2.1.24 Describe how the sequence of amino acids in a determines the proteins shape & function B2.1.25 Explain how gene mutations change the DNA sequence & state the effects B2.1.26 Describe & explain the function of enzymes as biological catalysts B2.1.28&32 Describe & investigate how temp, concentration & ph affect enzyme action B2.1.29,30&31 Explain the lock & key hypothesis & describe how enzymes can be denatured B2.2.1 Recall the respiration equation & describe why respiration is needed B2.2.2&3 Explain how the human circulatory system facilitates respiration & Define diffusion B2.2.4 Define and explain anaerobic respiration B2.5&6 Explain why heart rate and breathing rate increase with exercise B2.2.7 Calculate heart rate, stroke volume and cardiac output, using the equation Topic 2 Organisms and energy B2.2.8 Explain why, during vigorous exercise muscles respire anaerobically B2.2.9 &10 Recall the word equation for anaerobic respiration & describe the relative amount of energy released B2.2.11 Describe how a build up of lactic acid requires extra oxygen to break it down (EPOC) B2.2.12 Explain why heart rate and breathing rate remain high after exercise B2.2.13 Describe how the structure of a leaf is adapted for photosynthesis, including B2.2.14 Recall the word equation for photosynthesis & use it to explain the process B2.2.15&16 Describe and explain the limiting factors that affect the rate of photosynthesis B2.2.17&18 Explain how water, glucose and mineral salts are transported through a plant, B2.2.19 Describe how root hair cells are adapted to take up water by osmosis B2.2.20&21 Define & investigate osmosis
B2.2.22&23 Describe how to investigate organisms using fieldwork techniques B2.3.1&2 Evaluate the evidence for evolution based on the fossil record & explain the gaps HT ONLY B2.3.3 Explain how the anatomy of the pentadactyl limb provides evidence for evolution B2.3.4&5 Describe growth & interpret growth data B2.3.6 Explain growth & development of plants & animals B2.3.8 Recall the structure & function of the components of blood Topic 3 Common systems B2.3.9 Describe the grouping and organisation of cells into organ systems B2.3.10 Recall the structure of the heart & explain how it is related to its function B2.3.11 Describe the role of the blood vessels in the circulatory system B2.3.12 Describe the structure & functions of the parts of the digestive system HT ONLY B2.3.12 Describe the function of the gall bladder in the digestive system B2.3.13 Explain the role of the muscular wall of the alimentary canal in peristalsis B2.3.14 Explain the roles of carbohydrases, amylase, proteases, pepsin & lipases HT ONLY B2.3.15 Explain the role of bile in digestion HT ONLY B2.3.16 Explain how the structure of villi allows absorption of the products of digestion B2.3.17 Investigate & describe the effect of different concentrations of digestive enzymes B2.3.18 Evaluate the evidence for the claimed benefits of the use of functional foods
B2 Knowledge Test 1. Label these diagrams of cells: 2. Complete this table to give the function of the following organelles: Organelle Cell Membrane Cell Wall Chloroplast Mitochondria Vacuole Function 3. Which type of microscope has the largest magnification? 4. State 2 differences between a bacterial cell and an animal cell. 5. Define the term gene. 6. Describe the structure of a DNA molecule. 7. State the complementary base pairs found in DNA. 8. How is complementary base pairing different if DNA is pairing with mrna? 9. What chemical substances would you need if you were trying to extract DNA from Kiwis? 10. Which scientists cracked the DNA code? 11. How did they use the work of other scientists to help them? 12. What was the purpose of the Human Genome Project? 13. State 2 potential benefits of the HGP. 14. What is a plasmid? 15. What do we mean by genetic engineering? 16. What are used to cut the DNA and stick it into the genome of the new organism? 17. Complete the table below to give one advantage and one disadvantage of Genetic Engineering for each example: Beta carotene in Golden Rice Producing insulin Production of herbicide resistant crops Advantage Disadvantage
18. Complete this table to compare mitosis and meiosis Number of daughter cells formed Are the daughter cells identical to the parent cell? Do the daughter cells have haploid or diploid nuclei? Used for Mitosis Meiosis 19. Define fertilisation. 20. Define cloning. 21. Write out the stages of cloning a mammal in 5 bullet points. 22. What is the main source of stem cells in research? What ethical issue is associated with this source? 23. Complete the table below to give one advantage and one disadvantage of each method: Cloning Embryonic stem cell research Advantage Disadvantage 24. What provides the code for the structure of a protein? 25. Write out the stages in protein synthesis in 5 bullet points. 26. What is a mutation? 27. What are the units that make up proteins? 28. Proteins are specific. What does this mean? 29. What is an enzyme? 30. How does temperature affect enzyme activity? 31. How does ph affect enzyme activity? 32. Where in the enzyme does the reaction take place? 33. If an enzyme is denatured, what does this mean? 34. Describe one use of enzymes outside of the body? 35. State 2 processes inside the body that use enzymes. 36. Define respiration and write the equation for aerobic respiration. For each substance in the equation, state where it diffuses from and to. 37. Define diffusion 38. Explain the effect exercise has on breathing rate and heart rate? 39. An athlete has a stroke volume of 76cm 3 and a heart rate of 60 bpm. Calculate their cardiac output. 40. When and why may cells start to respire anaerobically? 41. Write a word equation for anaerobic respiration. 42. What does EPOC stand for and what happens during it? 43. Describe three adaptations of a leaf for photosynthesis. 44. Write the word equation for photosynthesis. 45. State the three limiting factors for photosynthesis. 46. Describe what happens to the rate of photosynthesis as the concentration of Carbon Dioxide increases. 47. Define transpiration. 48. Describe how mineral ions are absorbed into the root. 49. Describe how water enters the root and then moves through the plant. 50. What is the function of the phloem? 51. Define Osmosis. 52. How are root hair cells adapted to their function?
53. State three reasons why there are gaps in the fossil record. 54. Describe how the pentadactyl limb provides evidence for evolution. 55. What three things must a cell do for an organism to grow? 56. Complete this table to describe the function of the different parts of the blood: Component Red Blood Cell White Blood Cell Plasma Platelets Function 57. Complete the table by putting each of these parts of the heart under the appropriate heading Pulmonary artery, pulmonary vein, aorta, vena cava, left ventricle, left atrium, right ventricle, right atrium, Carries oxygenated blood Carries deoxygenated blood 58. How is backflow of blood prevented in the heart? 59. How is the structure of the left ventricle different from the right ventricle? 60. Describe the function of the following vessels artery, vein, capillary. 61. Describe the function of each of the following parts of the digestive system: Organ Mouth Oesophagus Stomach Small intestine Large intestine Pancreas Liver Gall bladder Function 62. How does the muscular wall in the alimentary canal aid movement of food? Name the process. 63. Complete this table about digestive enzymes: Enzyme Group Example Function Amylase Breaks protein into amino acids Lipase 64. State the two functions of bile. 65. How and why is the villi adapted?
B2 Knowledge Test - Answers 1. Label these diagrams of cells: Cell membrane Chloroplast Nucleus Nucleus Cell membrane Vacuole Cell wall Cytoplasm Cytoplasm 2. Complete this table to give the function of the following organelles: Organelle Cell Membrane Cell Wall Chloroplast Mitochondria Vacuole Function Controls movement of substances in and out of the cell. Supports the cell. Absorbs LIGHT. Where photosynthesis takes place Where respiration occurs. Helps support the plant by keeping the cell rigid 3. Electron Microscope 4. Bacterial cell has plasmids, animal cell does not, bacterial cell has a flagellum, animal cell does not, bacterial cell has a cell wall, animal cell does not, bacterial cell has a circular loop of DNA, animal cell has DNA in chromosomes, animal cell has a nucleus, bacterial cell does not. 5. A section of DNA which codes for a specific protein. 6. Double helix two strands held together by hydrogen bonds between complementary bases 7. A=T, G=C 8. A pairs with U instead of T. T is replaced by U in the mrna. 9. Salt, water, washing up liquid, (protease) 10. Watson and Crick 11. Took Rosalind Franklins x ray photograph 12. To sequence all of the bases in the human genome. 13. Improved genetic testing for disorders; New ways of finding new genes that may increase risk of certain diseases; New treatments and cures for diseases; New ways of looking at changes in the genome over time; Personalised medicines that work with a particular genotype. 14. A circular loop of DNA. 15. Altering the DNA of an organism by inserting DNA from another organism into its genome. 16. Enzymes 17. Complete the table below to give one advantage and one disadvantage of Genetic Engineering for each example: Beta carotene in Golden Rice ntage Used to make vitamin A Vitamin A will reduce death and blindness. dvantage Could cross breed with wild rice and contaminate wild rice DNA
Producing insulin Production of herbicide resistant crops Can be used by vegans Supply not affected by animal diseases Supply not affected by demand for meat Can be made in vast quantities Cheaper Reduces amount of crop spraying Levels of beta carotene in Golden Rice might not be high enough to make a difference Can be expensive to buy Produces sterile seeds so farmers have to buy them every year Bacteria produce insulin slightly differently so may not work for some people Herbicide resistant weeds can develop Cross pollination with wild plants Potential loss of biodiversity 18. Complete this table to compare mitosis and meiosis Mitosis Meiosis Number of daughter cells 2 4 formed Are the daughter cells identical yes No to the parent cell? Do the daughter cells have diploid Haploid haploid or diploid nuclei? Used for Growth and repair Making gametes 19. Haploid gametes join to form a diploid zygote 20. The production of a genetically identical individual. An example of asexual reproduction. 21. Remove a diploid nucleus from a body cell; Enucleate an egg cell; Insert diploid nucleus into enucleated egg cell; Stimulate the diploid nucleus to divide by mitosis; Implant into surrogate mother. 22. Discarded embryos from fertility treatment. Embryo destroyed in the process 23.. Cloning Embryonic stem cell research Advantage Can make a genetically identical copy of an animal with desirable characteristics. Can be used to make copies of GM animals to guarantee all offspring have the trait. Embryonic stem cells can develop into almost every type of human cell. Bone marrow stem cells can be used to treat leukaemia. Adult stem cells may be used in future instead of embryonic stem cells. Disadvantage Cloned animals often die young. Cloned animals often age more quickly. Complicated process. Embryonic stem cells can come from leftover embryos from fertility treatments. Risk of rejection if not from a patients own stem cells. Could lead to tumours forming.
24. The sequence of bases on the DNA 25. DNA double helix unzips; The complementary mrna strand is made in the nucleus and passes out through a pore; mrna attaches to the ribosome; A triplet of bases on the mrna (codon) code for a specific amino acid; trna transfers amino acids to the ribosome. 26. A change in the sequence of bases in the DNA 27. Amino Acids 28. They have a specific shape, they have a specific sequence of Amino Acids 29. A biological catalyst 30. It speeds up its activity up to 40 o C after which it denatures and stops working. 31. Enzymes only work at a specific ph. Either side of the optimum, it will not work as well. 32. Active site 33. The shape of the active site has changed 34. Digestion Many enzymes break larger molecules down into smaller ones in digestion. This happens outside of the body. Stain digesting enzymes in washing powders break down stain in clothes. Microorganisms excrete enzymes onto food to break them down outside the body and then absorb the products. 35. DNA replication, protein synthesis 36. A process where all living organisms release energy from their food. Glucose + oxygen Carbon Dioxide and Water. Oxygen diffuses from air into blood and blood into cells. Glucose diffuses from gut into blood and blood into cells. Carbon dioxide diffuses from cells to blood and blood to air, water diffuses from cell to blood. 37. The movement of a substance from high to low concentration/down a concentration gradient. It is a passive process. 38. It increases it because the body has a greater demand for oxygen and glucose, and produces more waste carbon dioxide to be removed. The blood circulates these substances to and from the cells. 39. 4560cm 3 40. When there is not enough oxygen available for aerobic respiration. After a period of rapid exercise. After death. 41. Glucose Lactic Acid 42. Excess post-exercise oxygen consumption. Required more oxygen to be paid back after a period of anaerobic respiration. 43. Large surface area, contains chlorophyll to absorb light, stomata for gas exchange. 44. Water + Carbon dioxide glucose + oxygen 45. Light intensity, CO 2 concentration, temperature. 46. It increases up to a point where another factor will become limiting. 47. The movement of water through a plant. 48. By active transport using energy from the soil to the cells of the root 49. By osmosis from the soil to the cells of the root then up the xylem. 50. To transport glucose up and down the plant. 51. The movement of water from high water concentration to low water concentration across a semi permeable membrane.. 52. Large surface area to increase water absorption. 53. Because fossils do not always form, because soft tissue decays, because many fossils are still to be found. 54. Suggests all vertebrates evolved from one common ancestor as there are similarities between bone structure. 55. Divide, elongate, differentiate 56.. Component Red Blood Cell Function Transport oxygen
White Blood Cell Plasma Platelets Fight infection Transport CO 2, hormones, glucose Blood clotting 57.. Carries oxygenated blood pulmonary vein, aorta, left ventricle, left atrium Carries deoxygenated blood Pulmonary artery, vena cava right ventricle, right atrium, 58. Valves 59. Thicker wall 60. Artery carries blood away from the heart, vein carries blood to the heart, capillary exchange of substances between tissues. 61. Describe the function of each of the following parts of the digestive system: Organ Mouth Oesophagus Stomach Small intestine Large intestine Pancreas Liver Gall bladder Function Food broken up into smaller pieces, mixed with saliva, starch digestion Moves food to stomach by peristalsis Mixes food with enzymes and acid Absorption of food Absorption of water Makes enzymes Makes bile, breaks down some substances Stores bile 62. Pushes food along the digestive system by muscular contraction. Peristalsis 63. Complete this table about digestive enzymes: Enzyme Group Example Function Carbohydrases Amylase Breaks starch into glucose Proteases Pepsin Breaks protein into amino acids Lipase Digests fat into glycerol and fatty acid 64. Emulsifying fats, neutralising stomach acid. 65. Large surface area, good blood supply, one layer of cells thick for efficient absorption
B2 Topic 2
B2.1 Plant and Animal Cells Plant and animal cells can be studies in greater detail using a light microscope. Light passes through a thin slice of the specimen. Lenses magnify the specimen many times. 7 Organelles Function Cell Membrane Controls movement into and out of the cell. Nucleus Contains DNA. Controls the cell Cytoplasm Where chemical reactions take place. Mitochondria Where respiration occurs. Cell Wall Made of CELLULOSE. Supports the cell. Vacuole Contains CELL SAP. Helps support the plant by keeping the cell rigid Chloroplast Contains CHLOROPHYLL. Absorbs LIGHT. Where photosynthesis takes place
B2.2 Inside Bacteria Microscopes have improved in last 350 years. Light microscopes can magnify 1500x. Electron microscopes can magnify 2000000x. Electron microscopes produce very clear images. Electron microscopes show more detail of the specimen. 2 types of DNA 4 Organelles Function Chromosomal DNA Plasmid DNA Flagella Cell Wall A giant loop of DNA containing most of the genetic material. Small loops of DNA that carry extra information. Long whip like structures that aid movement. Provides support but is more flexible than a plant. Not made of cellulose.
B2.3 DNA Key Definition A gene is a section of DNA that codes for a specific protein. DNA is made up of two strands coiled to form a double helix. The two strands are linked by complementary bases held together by weak hydrogen bonds. Adenine (A) pairs with Thymine (T) Cytosine (C) pairs with Guanine (G)
B2.4 Extracting DNA 1. Chop onion or peas into chunks. 2. Grind in a pestle and mortar. 3. Mix together with washing up liquid, salt and water and stir. 4. Incubate the mixture at 60 degrees Centigrade for 15 minutes in a water bath. 5. Filter the mixture through filter paper into a boiling tube. 6. Take ice cold alcohol and pour it slowly down the side of the boiling tube. The alcohol will form a transparent layer on top of the liquid, as the alcohol is less dense. 7. You will see the DNA between the two liquid layers.
B2.5 DNA Discovery London Maurice Wilkins & Rosalind Franklin using X rays to study DNA structure. From the patterns made they could work out how the atoms were arranged. Cambridge Watson & Crick were building a model of DNA using data from other scientists. They were given a copy of Franklins photographs which enabled them to crack the code. Franklin didn t know they had the photo. Watson and Crick published their paper with the structure of DNA but didn t acknowledge the photograph they used Watson and Crick were awarded the Nobel Prize with Maurice Wilkins but Rosalind Franklin had already died so did not get the prize.
B2.5 DNA Discovery The Human Genome Project International Project. 3 billion bases that make up the human genome were sequenced. It took 13 years and scientists collaborated using IT to store and share data. All humans have 99.9% of their DNA in common. 5 Implications of the HGP 1. Improved genetic testing for disorders. 2. New ways of finding new genes that may increase risk of certain diseases. 3. New treatments and cures for diseases. 4. New ways of looking at changes in the genome over time. 5. Personalised medicines that work with a particular genotype.
B2.6 Genetic Engineering Know this process! Definition The process of removing a gene from one organism and inserting it into the DNA of another.
B2.6 Genetic Engineering Example Advantages Disadvantages Beta carotene in golden rice to reduce vitamin A deficiency in humans The production of human insulin by GM bacteria The production of herbicide resistant crops 1. Beta carotene used to make vitamin A 2. Vitamin A will reduce death and blindness. 1. Can be used by vegans 2. Supply not affected by animal diseases 3. Supply not affected by demand for meat 4. Can be made in vast quantities 5. Cheaper 1. Could cross breed with wild rice and contaminate wild rice DNA 2. Levels of beta carotene in Golden Rice might not be high enough to make a difference 3. Can be expensive to buy 4. Produces sterile seeds so farmers have to buy them every year 1. Bacteria produce insulin slightly differently so may not work for some people 1. Reduces amount of crop spraying 1. Herbicide resistant weeds can develop 2. Cross pollination with wild plants 3. Potential loss of biodiversity
B2.7 Mitosis and Meiosis Mitosis The production of two daughter cells with identical sets of chromosomes in the nucleus as the parent cell. Results in the formation of two genetically identical diploid cells. Occurs during growth and repair and asexual reproduction Definitions Haploid Having one set of chromosomes. Diploid Having two sets of chromosomes. Gamete the sex cells (sperm and egg) Meiosis The production of four daughter cells, each with half the number of chromosomes as the parent cell. Results in the formation of genetically different haploid gametes. Occurs when making gametes only. At fertilisation, haploid gametes join to form a diploid zygote.
B2.8 Clones Cloning An example of asexual reproduction. How to produce a clone 1. Remove a diploid nucleus from a body cell 2. Enucleate an egg cell 3. Insert diploid nucleus into enucleated egg cell. 4. Stimulate the diploid nucleus to divide by mitosis. 5. Implant into surrogate mother. Enucleate Remove the nucleus
B2.8 Clones Advantages of Cloning 1. Can make a genetically identical copy of an animal with desirable characteristics. 2. Can be used to make copies of GM animals to guarantee all offspring have the trait. Disadvantages of Cloning 1. Cloned animals often die young. 2. Cloned animals often age more quickly. 3. Complicated process. Risks of Cloning 1. Very few embryos develop properly resulting in deformities.
B2.9 Stem Cells Key definitions Stem Cell An unspecialised cell that can divide to produce more stem cells or different types of specialised cell. Differentiate Become specialised. Embryonic Stem Cell Can differentiate into almost any cell type. Adult Stem Cell Can differentiate into only a few cell types. Specialised Cell a cell with a particular function e.g. neurone, red blood cell. Advantages of Stem Cell Research 1. Embryonic stem cells can develop into almost every type of human cell. 2. Bone marrow stem cells can be used to treat lukaemia. 3. Adult stem cells may be used in future instead of embryonic stem cells. Disadvantages of Stem Cell Research 1. Embryonic stem cells can come from leftover embryos from fertility treatments. 2. Risk of rejection if not from a patients own stem cells. 3. Could lead to tumours forming. Risks of Stem Cell Research 1. Technology could be used illegally. 2. Risk of the unknown long term effects may not be shown for years.
B2.10 Protein Manufacture
B2.10 Protein Manufacture Each amino acid is coded for by 3 specific bases. DNA is a triplet code. Transcription 1. DNA double helix unzips. 2. The complementary mrna strand is made in the nucleus and passes out through a pore. Translation 1. mrna attaches to the ribosome. 2. A triplet of bases on the mrna (codon) code for a specific amino acid. 3. trna transfers amino acids to the ribosome. 4. Amino acids link together to form polypeptides. RNA is single stranded but DNA is double stranded. RNA contains Uracil (U) instead of thymine (T)
B2.11 Mutations Mutation A change in the sequence of bases in the genetic code. 1. Each protein has its own specific number and sequence of amino acids. 2. This is coded for by the DNA. 3. Therefore, each protein is a different shape and has a different function e.g. an enzyme. 4. Mutations change the sequence of the bases, and therefore the shape of the protein. 5. Most mutations are harmful. 6. Radiation and some chemicals in cigarette smoke are mutagens and cause mutations.
B2.12 Enzymes Enzymes are biological catalysts. They speed up reactions. These are examples of enzyme catalysed reactions: 1. DNA Replication One enzyme unzips the two strands of DNA, the other joins the new bases together to make the new double stranded molecule. 2. Protein Synthesis RNA Polymerase makes the mrna strand from the DNA template. 3. Digestion Many enzymes break larger molecules down into smaller ones in digestion. This happens outside of the body. Stain digesting enzymes in washing powders break down stain in clothes. Microorganisms excrete enzymes onto food to break them down outside the body and then absorb the products.
B2.13 Enzymes and Temperature Enzymes are SPECIFIC to their substrate. They only catalyse specific reactions in specific conditions. They have a specific shaped active site. Factors that affect enzyme activity: 1. Temperature 2. ph 3. Substrate Concentration. Enzyme activity can be measured by measuring the speed at which a product is made e.g. a gas, or the speed at which a substrate is used up e.g. stain digestion.
B2.14 Enzyme Action As temperature increases, so does enzyme activity, up to 40 o C. After 40 o C the active site is denatured and the reaction stops. Enzymes can never be killed. They can only be denatured, which is where the shape of the active site changes. As substrate concentration increases, so does enzyme activity, up to a point where the number of active sites becomes limiting. The only way to speed up the reaction after this is to increase the number of active sites. Enzymes will only work at a specific ph. Either side of this optimum ph, the enzyme will denature and not work.
B2.14 Enzyme Action Enzymes work like a lock and key Lock and Key One key will only fit one lock. The key fits the lock. The key unlocks the lock. Wrong key won t fit the lock. Enzyme and Substrate One substrate will only fit one enzyme. The substrate fits the active site The substrate is changed in the enzyme Wrong substrate won t fit the active site.
B2.15 Aerobic Respiration. All organisms are made of cells Energy released by respiration Cells that move more need more energy. Exercise = more energy needed. Key Terms: Respiration the release of energy from food molecules that act as fuel for the cell. Diffusion when substances move from an area of high concentration to an area of low concentration. Glucose + Oxygen = Carbon Dioxide + Water Aerobic respiration = uses oxygen to release energy from glucose. How does it get delivered? Glucose and oxygen diffuse from capillaries to respiring cells Carbon dioxide diffuses from respiring cells to capillaries Capillaries smallest vessel that carries blood between cells/ one cell thick Substances move by diffusion down a concentration gradient = the diffusion pathway.
Respiring cells = oxygen and glucose levels fall as they are used up in aerobic respiration/ Carbon dioxide levels increase. Gas exchange = the transfer of gases.
B2.16 investigating The effects of exercise. Exercise = increase heart rate and has to pump blood faster to the muscles. Causes breathing rate to increase and get deeper. Why? Cells need more oxygen and glucose as they need more energy. Cells produce more carbon dioxide as a result which needs to be removed.
B2.17 Anaerobic respiration Cardiac output = stroke volume x heart rate. Glucose lactic acid Anaerobic respiration = respiration without oxygen Glucose is broken down to supply energy to the muscles Releases less energy then aerobic and produces Lactic Acid Amount of blood pumped around the body depends on the stroke volume and the heart rate. Exercise = increase in heart rate and stroke volume. Lactic Acid needs to be broken down = oxygen used to break it down into carbon dioxide and water. The requirement of this oxygen to break down the lactic acid is called excess postexercise oxygen consumption (EPOC)
B2.18 Photosynthesis. Light and chlorophyll Carbon dioxide + water glucose + oxygen Photosynthesis = plants make their own food Uses light energy to produce glucosefrom carbon dioxide and water Glucose stored as starch Starch = lots of glucose molecules joined together. Digestion breaks down starch = glucose Chlorophyll = green found in chloroplasts absorbs light for photosynthesis. Variegated leaves = the green parts of a leaf contain the chlorophyll.
2.20 Factors that effect the rate of photosynthesis. 3 factors that effect photosynthesis. Carbon dioxide Light Temperature All 3 are needed at optimum amount for photosynthesis to be at its best. The limiting factor is the one that is in short supply..you may have lots of CO 2 the right temperature but little light this means photosynthesis will be slow. Limiting factor = something can affect the rate of photosynthesis.
Adaptations of a leaf. Upper epidermis = tightly packed cells = lots of chloroplasts = lots of photosynthesis. Air spaces = provide large surface for cells to exchange with gases in the air. Lower epidermis = contain stomata. Stomata = open and close to allow gases into the leaf. Located underside of the leaf. 3 Adaptations Has stomata for gas exchange (carbon dioxide, oxygen, water vapour) Contains chlorophyll in chloroplasts to absorb light. Large surface area to absorb most amount of light. Open in response to light. Allow Carbon dioxide in and lets out oxygen and water vapour.
B2.21 Water Transport Key Definitions The loss of water from the leaves drives transpiration. Transpiration the movement of water through a plant and the loss of water throught he leaves. Osmosis = movement of water from an area of low concentration to an area of high concentration through a partially permeable membrane. Roots absorb nitrates and mineral ions dissolved in water by Active transport. This needs energy from respiration Water transported by xylem Nutrients transported by phloem Root Hair Cell Job of root = anchor plant and take up nutrients. Root hair found on surface of root. Role to absorb water and dissolved minerals. Adaptation = large surface area.
B2.22 Investigating Osmosis Osmosis Water can move across cell membranes because of osmosis. For osmosis to happen you need: two solutions with different concentrations and a partially permeable membrane to separate them
B2.23 Organisms and their environment Key Terms Environment = an organisms surroundings including the soil, air, water and other organism in the area. Biodiversity = the different plants and animals in an area. Ecosystem = an area in which all the living organisms and all the non living organism form a relationship in order to survive. Habitat = where the plants and animals are found/living. Population = the number of animals in a given area. Sampling = looking at small proportion of the plants and animals. Sampling techniques = 1) Pooter = used to catch animals. 2) Sweep net = can catch flying animals. 3) Pond net = to catch aquatic animals. 4) pit fall traps = buried in the ground the organisms fall in. 5) quadrats = used to sample the population size of plants = random sampling or systematic sampling. = placing the quadrat at regular intervals along a line.
B2 Topic 3 Common Systems
B2.25 Fossils and evolution Facts: The moon is 30 earths away The sun is 11,000 earths away Keywords Fossil record The collection of fossils identified from different periods of time that can be interpreted to form a hypothesis about the evolution of life on Earth. Fossil The preserved traces or remain of an organism which lived a very long time ago Pentadactyl five fingered organism Fossils Fossils from different periods of time show organisms have changed gradually = evolution. Fossil record has gaps Soft tissues decay not forming fossils Hard parts of organisms could have been destroyed Many fossils are buried too deep to be found Scientists using incomplete data sometimes make mistakes More fossils = more accurate conclusions Evidence for Evolution Internal bones of all vertebrate s limbs are similar Fossils of limbless vertebrates have the same five fingered structure All vertebtates evolved from one common ancestor Evolution of the limbs is due to adaptation to how the organisms lived and moved,
B2.26 Growth Keywords Percentile The value of a variable below which a certain percentage of observations fall. Stem Cell An unspecialised cell that can divide to produce more stem cells or different kinds of specialised cells Differentiate Specialise, develop into different kinds of cell, as in cells that become nerve, muscle or bone cells Elongation getting longer Facts Growth is when an organisms increases in size, length and mass To monitor growth of babies we check Head circumference Weight Height Each child is compared to a chart to determine which percentile of the population they are in. Growth involves 2 things Increase in the number of cells Increase in the size of cells Growth in Plants Grow all through their lives Cells divide in the Meristem behind the tip of the root and shoot Cells also elongate Older meristem cells differentiate to become specialised for example: Palisade leaf cell Root hair cell Growth in Animals Cell division Animals stop growing when they become adults Stem cells are undifferentiated Stem cells can specialise into all other cells Adults have very few stem cells (only in blood and skeletal tissues) Most animals cannot regrow limbs or body parts.
Components Plasma Fluid part of blood B2.27 Blood Transports carbon dioxide, hormones and waste Pale yellow Red blood cells No nucleus = more room for haemoglobin Made in the bone marrow. Contain red pigment haemoglobin which carries oxygen Oxygen + Haemoglobin Oxyhaemoglobin Oxygen is carried in the blood to the tissues for aerobic respiration Biconcave disc = large surface area to volume ratio for faster diffusion of oxygen White blood cells An important part of the immune system Some produce antibodies (proteins that bind to microbes and destroy them) Others surround and destroy foreign cells All have a nucleus Made in the bone marrow All have a nucleus Platelets Tiny fragments of cells (no nuclei) Clump together to form clots Protect the body by stopping bleeding and forming a scab to stop microbes entering.
B2.28 The heart Septum Thicker wall as it pumps blood all around the body Deoxygenated blood (low oxygen levels) Pumped to the lungs (by right ventricle) to collect oxygen Oxygenated blood returns to heart (Left side) Pumped to the body cells and tissues (by left ventricle) Left and right side work together at the same time Valves prevent backflow of blood Tendons stop valves turning inside out
B2.29 The circulatory system 3 types of blood vessel: Arteries Carry blood away from the heart Have thick muscular walls Have small internal lumen Blood under high pressure Veins Carry blood to the heart Thin walls Larger internal lumen Blood under low pressure Valves to prevent blood flowing backwards Capillaries Wall is one cell thick Very low blood pressure Allows diffusion between blood and tissues
churns B2.30 The digestive system Peristalsis Muscles contract in waves to move food along the alimentary canal ( a muscular tube running from your mouth to your anus)
B2.31 Breaking down food Keywords Enzyme a protein molecule made by living cells that speeds up the rate of a reaction Emulsion a mixture in which particles of one liquid are suspended in another liquid. Digesting proteins Digesting Carbohydrates Digesting Fats Enzyme involved Proteases (e.g. pepsin) Carbohydrases (e.g. amylase) Lipases Broken down into Amino acids Simple sugars (glucose) Glycerol and Fatty acids Where it occurs Stomach first then small intestine Mouth and small intestine Small Intestine Additional features Pepsin has an optimum ph of 2 (perfect for stomach acid) Amylase is denatured by stomach acid Bile from the gall bladder breaks down large fat globules into droplets with a larger surface area to help lipase. We say bile emulsifies the fat. Bile also neutralises the stomach acid.
B2.32 Villi Keywords Villi finger like projections in the small intestine. Diffusion movement of particles from an area of high concentration to an area of low concentration down a concentration gradient. Inside the Small Intestine 1. Digested food passes into blood by diffusion 2. Bigger surface areas = more diffusion 3. Finger like folds called Villi increase surface area of small intestine Features of a Villus to speed up diffusion 1. Good network of capillaries moving absorbed nutrients 2. Low concentration of food 3. Steep concentration gradient maintained 4. Wall is a single cell layer (shorter distance to diffuse)
B2.34 Probiotics and Prebiotics Functional foods Plant Stanol Esters Oily substances in plants Stop the small intestine absorbing cholesterol Lowers blood cholesterol Use in many foods like yogurt and spreads. Probiotics Live bacteria friendly or beneficial Bifidobacteria or Lactobacillus They produce lactic acid in your gut and companies claim they improve health NOT ENOUGH EVIDENCE to support the claims they are effective Prebiotics Substances the body cannot digest They act as food for the beneficial bacteria Oligosaccharides are a common form of prebiotic (contained in tomatoes, onions and asparagus) Also found in specially made dairy foods and sold as capsules Increasing evidence supports their positive effect on health