Biology Paper 2 Questions, 6 +11 Paper 2s, Biology Markscheme Active recall

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2. Explain how a nerve message passes from one neuron to another neuron

- Nerve impulse travels to the end of the presynaptic neuron. There, depolarization causes calcium channels in the membrane to open, and calcium diffuses into the presynaptic neuron. Allowing the vesicles with neurotranmitters to fuse with the presynaptic membrane. The neurotransmitter is released into the synaptic cleft and diffuses across to attach to the receptor on the postsynaptic neuron. The postsynaptic neuron is depolarized, causing a new acion potential. The neurotransmitter is broken down or reabsorbed

Outline the action of enzymes

A. Catalyse/speed up reactions B. Substrate-specific C. Lower the activation energy «of a chemical reaction» D. Substrate collides with/binds to active site E. Enzyme-substrate complex formed OR transition state formed OR bonds in substrate weakened

Compare and contrast mitochondria and chloroplasts in terms of substrates they use and the products they produce.

ATP produced by both/ADP used by both oxygen produced by cholorplasts and used by mitochondria co2 produced by mitochondria and used by cholorplasts the organic carbon compounds built up in choloprlasts via anabolism are broken down via catabolism in mitocondria

Explain the relationship between the structure and function of arteries, capillaries and veins

Arteries: [3 max] a. thick walls to withstand high pressure/maintain blood flow/pressure; b. collagen fibres/elastic fibres/connective tissue (in outer layer) give wall strength/flexibility/ability to stretch and recoil; c. (smooth) muscle layer (contracts) to maintain pressure; d. narrow lumen maintains high pressure; e. smooth endothelium for efficient transport/reduced friction; Capillaries: [3 max] f. wall has one layer of cells allowing (fast) diffusion of substances; g. pores to allow lymphocytes/plasma to exit / to increase permeability; h. extensive branching increases surface area for exchange of materials; i. small diameter allows them to fit between cells/perfuse tissue; j. narrow diameter increases oxygen diffusion from RBC; Veins: [3 max] k. thin walls allow (skeletal) muscles to exert pressure on veins; l. thin outer layer of collagen/elastic/muscle fibres provide structural support; m. wide lumen allows great volume of blood to pass; n. valves prevent backflow; NB Every structure requires a function for the mark.

Liver cells store extra glucose as glycogen.explain to steps that have to occur to release energy from glycogen during aerobic respiration.

Breakdown/hydrolyze glycogen to glucose to be used in glycolysis/cell respiration also break down glucose to pyruvate to enter crab cycle/mitochondria also breakdown pyruvate to carbon dioxide and water in the mitochondria to obtain a large yield of ATP.

Explain how increased atmospheric carbon dioxide concentrations can lead to coral death

Carbon dioxide dissolves in oceans/sea water, carbonic acid formed/lowers PH/makes water acidic, prevents deposition of calcium carbonate causes calcium carbonate to dissolve, skeleton of hard corals degraded, carbon dioxide is a greenhouse gas that causes warming/increases in temperatures, warmer oceans cause corals to expel, bleaching due to death expulsion of mutualistic organisms/algae

describe the causes of down syndrome

Down syndrome is caused by non-disjunction; occurs during meiosis; chromosome pairs fail to separate in meiosis I / chromatids in meiosis II / anaphase II; some gametes have an extra chromosome; can lead to zygotes/individuals with an extra chromosome / individual has 47 chromosomes; in Down syndrome this would be trisomy 21/extra chromosome 21; increased probability with increased age of mother/ages of parents;

State one function of RuBisCO

Enzyme involved in photosynthesis/carbon fixation/Calvin cycle Speeds up chemical reactions in photosynthesis Production of carbohydrate in photosynthesis/carboxylation of ruby P Addition of carbon dioxide to form glucose

State one function of RuBisCO

Enzyme involved in photosynthesis/carbon fixation/carbon cycle, speeds up chemical reactions in photosynthesis, carboxylation of Ruby P, production of carbohydrate in photosynthesis, addition of carbon dioxide from glucose in the Calvin cycle

Describe what is meant by a food chain

Food chain shows feeding/trophic relationships and shows which organism/animal eats which organism finally shows the flow of energy from producer/autotroph to top consumer/top carnivore/through trophic levels

Outline the structure and function of nucleusomes

Found in eukaryotes, consists of DNA wrapped around proteins/histones, histones are in a octamer/group of eight, are held together by another histone/protein , In linker region linker, help to super coil chromosomes slashto facilitate DNA packing, function is to regulate transcription/gene expression

Explain the importance of polysomes in protein synthesis

Group of ribosomes translating/bound to one mRNA at the same time same polypeptide/proteins synthesized in large amounts/efficient.

Describe how alpha helix is held together

Hydrogen bonds between N Dash H & C - - oh on different amino acids

Explain how energy enters, flows through and is lost from Marine food chains

Light energy is converted to chemical energy via photosynthesis Chemical energy in carbon compounds flows by means of feeding through food chains, only approximately 10% of energy is passed to the next trophic level, energy released as heat by respiration, energy is not recycled, after death energy may remain trapped as undigested detritus/fossils/fossil fuel's

Distinguish between the outcomes of a cell dividing by either mitosis or meiosis

Mitosis somatic cells 2n diploid 4 daughter cells identical Meiosis gametes n haploid 2 daughter cells not identical

The mitotic index is an important prognostic tool for predicting the response of cancer cells to chemotherapy outline how the mitotic index is calculated

Number of cells seen under the microscope undergoing mitosis divided by the total number of cells observed in sample area

State one source of carbon for marine organisms, other than feeding

Photosynthesis, absorption of dissolved carbon dioxide from the ocean

Compare and Contrast hormonal and nervous communication

Similarities a both used for communication between cells/tissues/organs/parts of the body / WTTE b. both cause a response change in specific target cells OR both use chemicals that bind to receptors / hormones and neurotransmitters are both chemicals c. both can stimulate or inhibit (processes in target cells)/WITE k over long distances/between widely separated parts of the body/WTTE e both under (overall) control of the brain/CNS / brain (has role in) sending hormones and nerve impulses 1 both use feedback mechanisms/negative feedback / both used in homeostasis Differences Hormones Nerves 9 chemical (messenger) nerve impulse/electrical (signal) in transported in blood transported by neurons slower faster carried throughout body carned to single specific cell muscle fiber k all/wide range of tissues/organs affected only muscles/glands receive signals D(usually long term (persistence/response) short duration/short-lived (responses) m. example of use of hormonal and use of nervous communication LOOK AT TABLE SCREENSHOT

State a rule of the active site of an enzyme

Site with substrate binds, catalytic site

Compare and contrast the structure of starch and cellulose

Two types of starch but one type of cellulose, both polymers of glucose/polysaccharides, starch is formed by alpha glucose while cellulose is formed by beta glucose

Outline the uses of ATP in plant cells

Used as an energy source, supplies/releases energy for a bio chemical reactions, photosynthesis/active transport/other verifiable example of reaction or process

Compare and contrast mitochondria and chloroplasts in terms of the substrates they use and the products they produce.

a ATP produced by both / ADP used by both boxygen produced by chloroplasts and used by mitochondria c. carbon dioxide produced by mitochondria and used by chloroplasts d. carbon/organic compounds built up in chloroplasts/anabolism and broken down in mitochondria/catabolism

Explain how hormones are used to control the human menstrual cycle

a FSH stimulates the development of follicles b. follicles produce estrogen c. estrogen stimulates the repair of the uterus lining d. estrogen stimulates LH secretion e. LH causes/stimulates ovulation f. LH causes/stimulates the development of the corpus luteum ✓ g. corpus luteum secretes progesterone h. progesterone causes/stimulates thickening of the uterus lining OR prepares uterine lining for implantation OR maintains the endometrium i progesterone/estrogen inhibits the secretion of LH/FSHƯ i falling progesterone levels at the end of the cycle allow FSH production/menstruation k. negative/positive feedback <control» described correctly 1. LH/FSH are pituitary hormones

Hormones are distributed throughout the body by the blood. Outline the roles of two reproductive hormones during the menstrual cycle in women.

a FSH/follicle stimulating hormone stimulates the development of follicles/follicle cell division in the ovary to produce eggs b. LH/luteinizing hormone triggers ovulation development of the corpus luteum c estrogen stimulates development of the uterine lining/endometrium d. progesterone maintains the uterine lining endometrium OR inhibits other hormones by negative feedback eg, FSH e. HCG stimulates ovary to produce progesterone sin early pregnancy f. other verifiable hormone and roles relevant to the menstrual cycle

Describe the risk to the human population of indiscriminate use of antibiotics

a antibiotics block bacterial processes b. example of bacterial process c. variations exist naturally in a population / some are naturally resistant to the antibiotic d bacteria that are not resistant to this antibiotic will die / only resistant will survive (when antibiotic given) e this characteristic could be passed to next generation 1 (natural selection) leads to changes in the proportions/frequency in the population 9. human population will be exposed to antibiotic resistant bacteria and will not have antibiotic to kill them h. (antibiotic resistant bacteria) may pass resistance to other bacteria species types by means of plasmids (so other bacteria species turn resistant too)

Broad beans are rich in starch and cellulose. Compare and contrast the structure of starch and cellulose.

a both polymers of glucose molecules / polysaccharides OR both form 1,4 glycosidic bond b. starch is formed by alpha glucose while cellulose is formed by beta glucose OR in starch C1 hydroxyl groups are found in same plane while in cellulose on different planes OR in cellulose, alternatively the beta glucose needs to be placed upside-down in order to have C1 hydroxyl groups on the same plane OR two types of starch (amylose and amylopectin) but one type of cellulose

State one function of Rubisco

Explain what happens to an enzyme if there is a change in pH.

a change in pH can cause a change in the tertiary structure of the enzyme OR enzyme denatured b. causing a change in the active site / substrate not able to bind c. the enzyme will not work as efficiently I decreased rate of reaction d. (may no longer be) the optimum/optimal pH for enzyme activity

Distinguish between osmoregulators and osmoconformers.

a concentration constant inside osmoregulators versus variable insido osmoconformers b. internal solute concentration can differ from the external environment in osmoregulators versus same/equal in osmoconformers OR osmoregulators are independent of the external environment in soluto concentration versus osmoconformers are tied to it o birds/mammals/humans/freshwater fish are osmoregulators versus starfish/mussels/crabs/jellyfish/sea squirts/squid/sharks are osmoconformers

outline the causes and consequences of blood clot formation in coronary arteries

a coronary heart disease/CHD/coronary artery disease/CAD occurs when there is reduction of oxygen to the heart muscle b. high ratio of LDL to HDL/fatty diet leads to plaque formation in arteries c. plaque breaks off causing damage that activates blood clot formation d. clots in the bloodstream> may block a coronary artery/coronary thrombosis reducing blood flow oxygen OR clots can cause heart attack/muscle death e sickle cell anemia scrisis produces blood clots that can cause coronary/arterial blockage

Outline the process of inspiration in humans.

a diaphragm and external intercostal muscles contract b. diaphragm moves down/becomes flatter OR external intercostals raise the ribcage/move the ribcage up/out e muscles/diaphragm intercostals increase volume of thorax/expand the thorax OR muscles/diaphragm intercostals decrease pressure in the thorax d. as volume «of thorax/lungs increases the pressure decreases o air enters wlungs» due to decreased pressure/higher pressure outside body f. air flows to lungs through trachea and bronchi/bronchioles

Outline the range of functions of proteins in cells.

a enzymes that catalyse/speed up/control (the rate and direction of metabolic reactions b. proteins can be hormones which are chemical messengers to cells c. proteins that transport through the membrane such as channel/carrier/pumps / that regulate what enters/leaves the cell d, hemoglobin in red blood cells that transports/binds oxygen e membrane proteins for cell/tissue recognition/cell adhesion/communication f. structural elements of muscle fibre/actin/myosin for movement OR spindle fibres move chromosomes 9. histones condense DNA into chromosomes

Outline the roles of estrogen and progesterone in females during human reproduction.

a estrogen progesterone for repair thickening development vascularisation of uterus Ining endometrium b. estrogen at high levels) stimulates LH secretion which stimulates ovulation) C. progesterone maintains the uterus lining endometrium during pregnancy prevents miscarriage d. progesteronoestrogen inhibits FSH/LH secretion o progesterone for development of breast tissue during pregnancy fall in progesterone/rise in estrogen leads to labour contractions/childbirth 9 estrogen progesterone cause pro-natal development of female reproductive organs OR h estrogen progesterone cause secondary sexual characteristics

Explain how insects excrete nitrogenous waste

a excreted as uric acid b. excretion by Malpighian tubules c. nitrogenous waste ammonia caccumulates in hemolymph d. nitrogenous wastaammonia absorbed by Malpighian tubules e. ammonia converted to uric acid f. conversion to uric acid requires energy ATP high solute concentration in Malpighian tubules OR active transport of ions/Na/Kinto Malpighian tubules h water absorbed by osmosis flushes uric acid nitrogenous wastato chindo gut i. Waterlions reabsorbed from the feces and returned to hemolymph uric acid precipitates becomes solid forms a paste so can pass out with little water k. uric acid excreted egested with the feces water conservationlosmoregulation OR reduces mass of water ein body m. uric acid is non-toxic

Explain how amino acids in casein could reach the liver, starting from the moment when the person takes a bite of pastry cream pie.

a food is mechanically physically digested in the mouth through mastication chewing b. mixed with saliva (to form the bolus) in mouth c. moved through esophagus/peristalsis d. proteins digested in the stomach (pepsin) pancreas secretes enzymes into lumen of small intestine OR (endo)peptidases/trypsin) are secreted by pancreas enzymes digest macromolecules to monomers OR endopeptidases digest polypeptides to peptides amino acids 9. villi of small intestine absorb amino acids h. amino acids carried to blood capillaries 1 blood (capillaries) carry amino acids to (hepatic portal) veinblood vessel going to liver amino acids absorbed by active transport protein pumps in the villi.

Outline how sperm are produced from diploid cells in the testis and how this production can be sustained over many decades of adult life.

a germinal epithelium divide endlessly (by mitosis giving rise to spermatagonia) b. spermatogonia are diploid/2n C. spermatogonia divide by mitosis / provide a continuous supply throughout adult life d. (some) spermatogonia enlarge forming primary spermatocytes e primary spermatocytes undergo the first division of meiosis/meiosis f. secondary spermatocytes produced are haploidin secondary spermatocytes undergo the second division of meiosis (to produce spermatids) ✓ spermatids develop tails OR spermatids differentiate into spermatozoa / spermatids associate with Sertolicells

Discuss the control of blood glucose levels and the consequences if they are not maintained.

a homeostasis is the maintenance of a constant internal environment b. the pancreas produces hormones that control the levels of glucose c. if glucose levels in blood are high, beta-cells of the pancreas» produce insulin d. «insulin causes the cells to take up labsorb glucose e liver stores excess glucose as glycogen f. if glucose levels in blood are low, alpha-cells of the pancreas» produce glucagon 9 aglucagon» causes the liver to break down glycogen into glucose h. «glucagon» increase levels of glucose in the blood i negative feedback controls the glucose levels consequences: j. if the pancreas produces little/no insulin a person can develop type 1 diabetes k a person with type 1 diabetes «usually needs/is dependent on injections of insulin type Il diabetes occurs when the body becomes resistant to insulin/cells do not respond to insulin m.type Il diabetes can sometimes» be controlled by diet and exercise n named consequence of having diabetes veg. eye damage»

Explain the role of hydrogen ions used in photosynthesis.

a hydrogen ions (and oxygen) are obtained from photolysis of water (excited) electrons (from Photosystem II) contribute to generate a hydrogen ion/proton gradient OR protons build up in the thylakoid space/inside the thylakoid C. ATP synthase generates ATP by chemiosmosis/using the proton gradient/by movement of protons from the thylakoid space to the stroma d. (two) high energy/excited electrons (from Photosystem II) are passed through an electron transport chain e. NADP accepts H (from the stroma) / electrons to produce NADPH/reduced NADP f. ATP/reduced NADP/NADPH are used by light-independent reactions/Calvin cycle in the stroma 9. (in Calvin cycle) carbon fixation to ribulose bisphosphate/RuBP produces G3P h. ATP is used to transform G3P to TP i. reduced NADP/NADPH is used to transform G3P to TP

Describe the process of spermatogenesis leading to the production of four sperm cells in a human male.

a in the seministerous tubule b. diploid cells/spermatogonia growenlarge c. two divisions of meiosis d. primary spermatocyte carries out the first division and secondary spermatocytes carry out the second division e. meiosis produces haploid cells/spermatics haploid cels/spermatis differentiate into spermatozoa/sperm cells OR develop tailflagellum helical mitochondrion acrescme sac of enzymes Sertolicells help sperm to mature differentiate

The enzyme Rubisco is used in carbon fixation during photosynthesis. Identify four other examples of proteins that illustrate the wide range of functions of this group of biochemicals in living organisms

a insulin receptors start the cellular signalling pathway/other receptor b. leptin is a hormone / other protein hormone c. immunoglobulins/antibodies defend body from disease d. rhodopsin/photosystems convert light energy to electrical impulses e. keratin/collagen/other example is a structural protein f. tubulin/microtubules part of cytoskeleton/ involved in cell division 9 ATP synthase is an enzyme that catalyzes the formation of ATP / other enzyme and function h. fibrin/fibrinogen is a protein involved in clotting ✓ i hemoglobin/sodium potassium pump/other example is a transport protein j actin/myosin/other example is involved in muscle contraction k any other named example and function a second other named example and function m. spider silk is used to form spider webs/capture prey

Plasma cells secrete antibodies against specific antigens. Outline how plasma cells become activated

a macrophages/phagocytes recognize/engulf pathogen and display antigens b. antigen binds to T cell/helper T cell/ antigen causes activation of T cell c, antigen binds to antibodies in membrane of B cells ✓ d. (activated) T cells activate B cells (that have the antigen bound to them) e activated B cells divide to produce a clone of cells active plasma cells develop from the clone of cells/from activated B cells

Describe the genetic and hormonal control of male sexual characteristics in a human.

a male if (X and Y chromosomes present bgene on Y chromosome/SRY promotes development of testes (from embryonic gonads) c. testes secrete testosterone d. testosterone stimulates sperm production/spermatogenesis e testosterone stimulates development (in fetus) of male genitals/primary sexual characteristics f. testosterone stimulates development of male secondary sexual characteristics OR testosterone causes changes to become adult male during puberty

Coughing to clear the airways is accomplished by muscle contractions. Explain muscle contraction.

a myofibrils ein muscle fibers/cells» b. sarcomeres care the repeating units in muscle/myofibrils » c. sarcomeres arranged end to end / sarcomeres shorten during muscle contraction d. actin and myosin/overlapping protein filaments/diagram to show sarcomere with actin and myosin overlapping e. dark and light bands ein sarcomeres»/diagram to show this/light bands narrower when muscle is contracted 1. thick filament is myosin and thin filament is actin/diagram to show this 19. nerve impulses stimulate contraction/cause depolarization of sarcolemma/ T-tubules/trigger release of calcium from sarcoplasmic reticulum T-tubules/trigger release of calcium h. calcium ions released from sarcoplasmic reticulum/bind to troponin i troponin causes tropomyosin to move/exposes binding sites on actin 1. myosin «heads» form cross bridges with/bind to actin k myosin heads move/change angle/swivel cock / myosin heads cause the power stroke myosin filaments pull actin towards center of sarcomere/more overlap between actin and myosin Z-lines move closer m ATP is used to provide energy»/cause cross-bridges to break/cause movement of myosin heads/cause filaments to slide/cause muscle contraction n. intercostaVabdominal diaphragm muscles contract to cough

Outline the actions taken by the body to avoid infection when the skin is cut.

a platelets/cut tissues release clotting factors b. «clotting factors» activate thrombin from prothrombin c. thrombin converts fibrinogen to fibrin d. «fibrin forms a clot/scab/mesh that seals the cut e. phagocytic white blood cells ingest pathogens

State one use of monoclonal antibodies.

a pregnancy testing kits/detection of hCG (to diagnose pregnancy) b. produce antibodies for treating arthritis C difficile/anthrax/psoriasis/ulcerative colitis/asthma/ankylosing spondylitis/Crohn's disease/multiple sclerosis/HIV/other named disease if verified/targeting tumor cells in treatment of cancer OR gives artificial/passive immunity (if injected) c. blood typing/testing urine for drugs/other verified specific use of monoclonal antibodies.

Describe the functions of valves in the mammalian heart.

a prevents backflow and ensures one-way flow controls direction of flow b. open valves allow blood to flow through OR opening and closing of valves controls timing of blood flow «during cardiac cycle c closed semilunar valves allow ventricles/chambers to fill with blood OR closed semilunar valves allow pressure in ventricles to rise «rapidly d. valves open when pressure is higher upstream/OWTTE/converse for closed valves . AV/bicuspid/tricuspidimitral valves prevent backflow from ventricle to atrium OR AV/bicuspid/tricuspidimitral valves open when pressure in atrium is higher than in the ventricle/when atrium is pumping/contracting semilunar/aortic/pulmonary valves prevent backflow from artery to ventricle OR semilunar/aortic/pulmonary valves open when pressure in ventricle is higher than in the artery/when ventricle is pumping/contracting

Outline the role of lymphocytes in defence against disease

a produce antibodies b. memory cells confer immunity c. specific immunity results from production of antibodies specific to a particular antigen d. recognize pathogens e destroy foreign cells/cancer cells

Outline how antibiotics offer protection from certain forms of infectious disease.

a protect against/kill/inhibit growth of microorganisms/bacteria/prokaryotes b. bacteria/prokaryote processes blocked but not processes in eukaryotes/other organisms c. block metabolic pathways/DNA replication/DNA transcription/translation/ribosome functioning/cell wall formation |d, do not protect against viruses as they have no metabolism/are non-living e antibiotics fail to protect if bacteria have resistance It can be used in humans/animals because antibiotics do not affect eukaryotic cells/bacterial metabolism is different

Cells produce a large variety of proteins with different sequences of amino acids. Explain how this is done.

a protein is produced when a gene is expressed / switched on b. genetic code/codons consists of three nucleotides/bases/base triplet c. genetic code in DNA is transcribed transcription (to mRNA) d. mRNA exits the nucleus e. mRNA (code) is translated/translation into a polypeptide/protein f. amino acid sequence/polypeptide formation occurs at a ribosome gone codon translates to one amino acid h. RNA carries code for specific amino acids itRNA anticodon matches with specific codon in mRNA J. amino acids joined (by peptide bonds) to form polypeptide k sequence of amino acids determined by order of bases/nucleotides/codons in DNA/mRNA proteins vary based on which amino acids are used and their order OR protein variety increases by mutations to DNA

Explain how blood solute concentrations are kept within narrow limits in the human body.

a solute concentration of blood monitored by the brain/hypothalamus b. pituitary gland secretes ADH C. ADH secreted when solute concentration/osmolarity is too high/a person is dehydrated/OWTTE d. collecting duct more permeable to water e amore aquaporins/opens aquaporins in the plasma membrane of collecting duct cells f. amore» water reabsorbed into the medulla 9 medulla is hypertonic/hyperosmotic eso water can be reabsorbed from filtrate h small volume of urine/concentrated urine produced with ADH» no/little/less ADH secreted if «blood» solute concentration is too low collecting duct less permeable to water/less water reabsorbed/large volume of urine produced dilute urine produced with low/no ADH k insulin causes blood glucose «concentration to be reduced 1 glucose stored as glycogen in the liver mglucagon causes blood glucose concentration to be increased n. negative feedback

Explain the production and role of antibodies in defense against bacterial pathogens in humans.

a specific immune response/antibody production as a consequence of the presence of bacterial antigens b. macrophage/phagocyte ingests bacterial pathogen displaying bacterial antigens on surface c. attached to major histocompatibility/MHC molecules d. helper T cell activated by presentation of antigen on surface of macrophage e. activated helper T cell binds to B cell specific to the antigen 1. stimulated B cell undergoes repeated mitotic cell divisions g. «cells enlarge and differentiate to form clone of plasma cells h. plasma cells produce specific antibodies ✓ antibodies bind to bacteria making them easier to digest by white cells OR opsonization OR agglutination (some antibodies combined with antigen) activate a complement cascade to kill bacteria directly k some antibodies act as antitoxins / neutralize toxins change chemical structure of toxins I once begun, antibody production lasts for several days until all antigens destroyed m. memory cells remain in blood giving extended immunity

Describe the structure of starch.

a starch is a carbohydrate b. starch is formed by carbon, hydrogen and oxygen C. it is a polymer/chain/polysaccharide d. formed from monosaccharides/simple sugars/glucose e linked together by condensation/dehydration f consists of amylose and amylopectin g. amylose is a long chain/unbranched n. amylopectin is branched

Describe how the structure of the chloroplast is adapted to its function in photosynthesis.

a thylakoids have a small internal volume to maximize hydrogen gradient/quickly increase concentration gradient b. many grana / thylakoids give large surface area C. (grana) contain (photosynthetic) pigments/electron carriers/ATP synthase enzymes d. (photosynthetic) pigments/chlorophyll arranged into photosystems allowing maximum absorption of light energy e. stroma has suitable pH/ enzymes of Calvin light independent cycle flamellae connect/separate grana maximizing photosynthetic efficiency

outline the uses of ATP in plant cells

a used as an energy source b. supplies/releases energy for biochemical reactions c. photosynthesis/active transport/other verifiable example of reaction or process

Explain how valves control the flow of blood through the heart

a valves open and close in response to changes in blood pressure/heart contraction/pumping b. valve prevents backflow/maintains direction of blood flow c. valves allow heart chambers to fill to empty

Outline how ventilation in humans ensures a supply of oxygen

a ventilation is exchange of gases between lungs and air b. during inhalation diaphragm contracts AND lowers c. external intercostal muscles contract, raising ribs upwards and outwards d. increase in volume AND decrease in pressure within thoracic cavity o air drawn into alveoli bringing fresh supply of oxygen 1. oxygen concentration in alveolar sacs is higher than in blood capillarios 9. coxygen concentration gradient causes oxygen to diffuse out of alveoli into red blood cells in capillaries

Rotavirus causes diarrhea and vomiting. Explain why viral diseases cannot be treated using antibiotics.

a viruses are not living b. viruses lack metabolismlackeraymes for metabolismalack coll walls c. antibioties target metabolic pathways cell wal production

Outline the functions of villi in the small intestine.

a, increase the surface area for absorption b. absorption of digested foods/nutrients c. absorption of mineral ions/vitamins

Explain the events that occur during a nerve impulse and how the impulse is propagated along an axon.

a, nerve impulses are action potentials propagated along axons of neurons b. resting potential is -70 mV OR relatively negative inside in comparison to the outside c. Na/Kt pumps maintain/re-establish the resting potential d. more sodium ions outside than inside when at the resting potentials OR more potassium ions inside than outside awhen at the resting potential e. action potential stimulates swave of depolarization along the membrane/axon f. «when neuron is stimulated if threshold potential is reached Nat channels open 9. sodium ions diffuse/move in ✓ h. «Na* move in causing depolarization / inside of the neuron becomes more positively charged than the outside of the neuron i. potassium ion channels open OR potassium ions diffuse/move out «K* move out causing repolarization local currents OR description of Nation diffusion between depolarized region and next region of axon to depolarize 1. myelination increases propagation speed/allows saltatory conduction

Outline the role of the sodium-potassium pump in maintaining the resting potential.

a, sodium/potassium pump pumps sodium ions Na' out of axon and pumps potassium ions/K' in b. requires energy/ATP/against concentration gradients/active transport c. three sodium ions pumped out for every two potassium ions pumped in d results in charge difference between inside and outside where outside is positive relative to inside

The light-dependent reactions in photosynthesis take place on the thylakoid membranes. Explain the light- [8 marks] dependent reactions

a. (chlorophyll/pigments/antenna complex) in photosystem II absorb light; b. light/photoactivation produces an excited/high energy/free electron; c. electrons pass from carrier to carrier/along electron transport chain/e.t.c.; d. protons pumped across thylakoid membrane/into thylakoid space; e. ATP produced (by the light dependent reactions); f. ATP production by chemiosmosis/by ATP synthase/ATP synthetase; g. electrons from photosystem II passed to photosystem I; h. light/photoactivation excites electrons in photosystem I (to higher energy level); i. production of NADPH/reduction of NADP(+) (using electrons from photosystem I); (reject NAD in place of NADP. Accept reduced NADP instead of NADPH) j. electrons from photolysis (needed) for photosystem II; k. oxygen from photolysis is a waste product/by-product/passes out/excreted; l. in cyclic photophosphorylation electrons from photosystem I return to it;

Outline the processes that occur during the first division of meiosis

a. (consists of) prophase, metaphase, anaphase and telophase; b. chromosome number halved/reduced/(diploid) to haploid; c. homologous chromosomes pair up/form a bivalent/synapsis in prophase; d. crossing over between non-sister chromatids/chromatids of different homologues; e. nuclear envelope breaks down (at end of prophase/start of metaphase); f. tetrads/bivalents/homologous pairs move to/align on equator/cell centre/on metaphase plate in metaphase; (accept homologous chromosomes without pairs if pairing has already been described) g. attachment of spindle fibres/microtubules to centromeres/kinetochores; h. (homologous) chromosomes separate/pulled to opposite poles in anaphase; i. nuclear envelopes reform/do not reform (because of meiosis II) in telophase; Accept the above points in a series of annotated diagrams. Reject answers with single chromatids forming pairs in metaphase or separating or moving to opposite poles in anaphase.

Outline the processes that occur during the first division of meiosis

Cell membranes separate aqueous environments in cells. Explain how the properties of phospholipids help to maintain the structure of cell membranes.

a. (labelled) phospholipid consisting of head and two tails; b. head is glycerol and phosphate; c. tails are fatty acid chains; d. head hydrophilic and tails hydrophobic; [8 marks] e. hydrophilic molecules/heads attracted to/soluble in water; f. hydrophobic molecules/tails not attracted to water but attracted to each other; g. (properties of phospholipids leads to) formation of double layer in water; h. stability in double layer because heads on outer edge are attracted to water and tails are attracted to each other in middle; i. phospholipid bilayer in fluid/flexible state because of attraction of non-polar tails to each other; j. (fluidity) allows membranes to change shape/vesicles to form or fuse with membrane/(fluidity) allows cells to divide; k. non-polar amino acid side chains attracted to (hydrophobic) tails;

Outline how depolarization of the membrane of an axon occurs.

a. (local depolarization) causes ion / sodium / voltage gated channels to open ✓ b. altering membrane permeability to sodium ions/Nat/positive ions / Nat diffuses into the cytoplasm ✓ c. membrane potential of the axon) changes from negative to positive d. a threshold potential is reached and an action potential is generated ✓

explain the causes and consequences of PKU

a. (point) mutation of gene; b. defective enzyme/phenylalanine hydroxylase (PAH); c. phenylalanine/Phe not broken down to tyrosine/Tyr; d. phenylalanine/Phe accumulates; e. (if not treated) symptoms mental retardation/seizures; f. diet free of phenylalanine/Phe to avoid symptoms;

Describe four different types of transport of substances across a membrane.

a. (simple) diffusion when molecules move down a concentration gradient directly through membrane/unaided by carrier molecule; b. (passive transport by) facilitated diffusion through (specific) channel proteins; c. osmosis of water via aquaporins/from area of low solute concentration to area of high solute concentration; d. active transport against a concentration gradient using protein pumps/ATP; e. vesicles attach to plasma membrane and release materials to exterior/ exocytosis; f. cell membrane invaginates/pinches off to bring material to interior / endocytosis / phagocytosis;

Describe the genetic code and its relationship to polypeptides and proteins

a. (the genetic code is based on) sets of three nucleotides/triplets of bases called codons; b. bases include adenine, guanine, cytosine and thymine in DNA / adenine, guanine, cytosine and uracil in RNA; (do not accept ATCG) c. each codon is code for one amino acid; d. some codons are (start or) stop codons; e. DNA is transcribed into mRNA by base-pair matching/complementary base pairing; f. mRNA is translated into a sequence of amino acids/polypeptide; g. each gene codes for a polypeptide; h. polypeptides may be joined/modified to form proteins;

Many cell functions, like synthesis of macromolecules and transport, require energy in the form of ATP. Explain how ATP is generated in animal cells.

a. ATP is a form of energy currency/immediately available for use; b. ATP is generated in cells by cell respiration (from organic compounds); c. aerobic (cell respiration) requires oxygen; d. anaerobic (cell respiration) does not require oxygen; e. glycolysis breaks down glucose into pyruvate; f. glycolysis occurs in cytoplasm; g. (by glycolysis) a small amount of ATP is released; h. ADP changes into ATP with the addition of a phosphate group/phosphoric acid / accept as chemical equation; i. in mitochondria/aerobic respiration produces large amount of ATP / 38 mols (for the cell, per glucose molecule); j. oxygen/aerobic respiration is required for mitochondrial production of ATP; k. in mitochondria/aerobic respiration pyruvate is broken down into carbon dioxide and water;

Many cell functions, like synthesis of macromolecules and transport, require energy in the form of ATP. Explain how ATP is generated in animal cells.

Describe the use of DNA profiling to determine paternity

a. DNA from child, mother and possible father(s) used to establish paternity; b. (DNA profiling is done) for legal reasons / divorce / inheritance; c. (DNA profiling is done) for personal reasons / self-esteem issues for children/fathers/parents; d. DNA copied/amplified using PCR; e. DNA cut using restriction enzymes; f. (gel) electrophoresis used to separate DNA fragments; g. pattern of bands is produced (in gel); h. analysed for matches between child with mother and possible father; i. (about) half the child's bands will match the father (while the other half will match the mother);

Explain how DNA is used to pass on genetic information to offspring accurately but also produce variation in species

a. DNA is replicated/copied semi-conservatively/from a template; b. mutations can be a source of variation / resulting protein has new or different functions; c. mutations/changes in the DNA may not result in changes in the amino acid for which the triplet codes; d. genetic code is redundant; e. genes occur as paired alleles which can be different; f. crossing-over occurs; g. recombines linked alleles producing new combinations; h. random orientation of bivalents / homologous chromosomes (in metaphase I); i. large genetic variation in (haploid) gametes / 2n / 223; j. random recombination of alleles during fertilization (leads to variation); k. different phenotypes among members of the same population; l. natural selection may lead to enhanced survival of recombinants;

Explain how DNA is used to pass on genetic info, but also include variation

Prior to cell division, chromosomes replicate. Explain the process of DNA replication in prokaryotes.

a. DNA replication is semi-conservative; b. each (molecule formed) has one new strand and one from parent molecule; c. helicase uncoils DNA; d. helicase separates the two strands by breaking hydrogen bonds between bases; (reject unzips as an alternative to uncoils but accept as alternative to separates if breakage of hydrogen bonds is included) e. RNA primase adds primer / primase adds (short) length of RNA; f. DNA polymerase III binds to/starts at (RNA) primer; g. DNA polymerase (III) adds nucleotides/bases in a 5' → 3' direction; h. bases according to complementary base pairing / A-T and C-G; i. (leading strand) built up continuously (towards the replication fork); j. (lagging strand) built up in pieces/short lengths/Okazaki fragments; k. DNA polymerase I removes RNA/primers and replaces them with DNA; l. ligase seals gaps between nucleotides/fragments/makes sugar-phosphate bonds; m. nucleoside triphosphates provide the energy to add nucleotides; Accept the above points in annotated diagrams.

Hormones such as FSH (follicle stimulating hormone) and LH (luteinizing hormone) affect the development of [6 marks] certain cells by binding to receptors in the plasma membranes. Outline the role of FSH and LH in the menstrual cycle

a. FSH stimulates estrogen secretion by follicle cells; b. at start of menstrual cycle; c. leading to development of endometrium; d. (FSH and) LH (rise to a peak and) causes egg to be released/ovulation; e. causes follicle cells to secrete less estrogen/more progesterone; f. progesterone maintains endometrium/uterine lining g. LH promotes change of follicle to corpus luteum; h. secretion of LH and FSH regulated by negative feedback; i. regulated/inhibited by high estrogen and progesterone levels; j. low progesterone levels cause menstruation;

Explain how gases are exchanged between the air in the alveolus and the blood in the capillaries.

a. O concentration in alveolar air greater than in capillary/blood prior to gas exchange OR hemoglobin in blood binds oxygen maintaining the concentration gradient b. O, gas dissolves in water lining the alveolus c. O diffuses through wall of alveolus and capillary into blood d. CO, concentration in blood greater than in alveolar air prior to gas exchange e CO2 diffuses through wall of capillary and alveolus into alveolar airspace

Explain the process of gas exchange taking place in the alveoli

a. O diffuses into blood and CO2 diffuses out from blood b. blood entering the alveoli is high in CO/low in 02 OR air in alveolus is high in O/low in CO2 c diffusion (in either direction) take place due to concentration gradients d. concentration gradients maintained by ventilation/blood flow large surface area created by many alveoli/spherical shape of alveoli for more efficient diffusion 1. rich supply of capillaries (around alveoli) allows efficient exchange type I pneumocytes are thin to allow easy diffusion/short distances h gases must dissolve in liquid lining of alveolus in order to be exchanged 1 type il pneumocytes secrete surfactants to reduce surface tension/prevent lungs sticking together type Il pneumocytes create moist conditions in alveoli

explain the cause and consequences of biomagnification using one named example.

a. a process in which chemical substances become more concentrated at each trophic level; b. valid named example (for example mercury, organophosphorous pesticides, DDT, TBT); c. these substances cannot be broken down / are broken down slowly by metabolism; d. are often stored in (adipose) tissues; e. each organism consumes large quantities of the trophic level below it; f. so substance accumulates/increases to reach toxic levels; If no example is given award [3 max].

Explain how acetylcholine initiates an action potential in a postsynaptic membrane.

a. acetylcholine binds to the receptor protein b. (causing a) change in tertiary structure / conformation of protein c diffusion/entry of ions / Na through the receptor channel protein allowed

Describe how water is carried through a flowering plant.

a. active transport of solutes from soil into roots; b. draws water by osmosis c. root hairs provide a large surface area for water uptake; d. carried through xylem vessels; e. transpiration is the loss of water (vapour) from leaves and stems / stomata; f. (transpiration) creates suction/pull/negative pressure; g. cellulose wall with rings of lignin give strength to resist (low) pressure; h. water pulled up due to capillary action/cohesion/adhesion; i. continuous column of molecules/transpiration stream;

Outline the role of amylase in digestion in humans.

a. amylase is an enzyme b. secreted by salivary glands/pancreas c. active/released into the mouth/small intestine d. acts on starch/polysaccharides e breaks a glycosidic»> bond by hydrolysis/adding water 1. converts insoluble/large molecule to soluble/small molecules g product is maltose/disaccharide/sugar molecule

Outline adaptive radiation (2 points)

a. ancestral species occupies new environment / survives natural disaster; b. different members of the species are exposed to different selection pressures; c. gives rise to new species that share common structures adapted to new environment / occupy all niches; d. example of divergent evolution/homology; e. accept valid example eg Galapagos finches, vertebrate pentadactyl limb;

Explain the roles of specific hormones in the menstrual cycle, including positive and negative feedback mechanisms.

a. anterior pituitary/hypophysis secretes FSH which stimulates ovary for follicles to develop b. follicles secrete estrogen c. estrogen stimulates more FSH receptors on follicle cells so respond more to FSH d. increased estrogen results in positive feedback on anterior pituitary e, estrogen stimulates LH secretion f. ostrogen promotes development of endometrium/uterine lining 9. LH levels increase and cause ovulation h. LH results in negative feedback on follicle cells/estrogen production i. LH causes follicle to develop into corpus luteum OR follicle cells produce more progesterone j. progesterone thickens the uterus lining k. high progesterone results in negative feedback on pituitary/prevents FSH/LH secretion I progesterone levels drop and allow FSH secretion m. falling progesterone leads to menstruation/degradation of uterine lining

Explain the evolution of antibiotic resistance in bacteria

a. antibiotics (are chemicals) used to treat bacterial diseases; b. within populations, bacteria vary in their (genetic) resistance to antibiotics/fitness; c. resistance arises by (random) gene mutation; d. when antibiotics are used antibiotic-sensitive bacteria are killed; e. (natural) selection favours those with resistance; f. resistant bacteria survive, reproduce and spread the gene / increase allele frequency of resistant bacteria; g. the more an antibiotic is used, the more bacterial resistance/the larger the population of antibiotic-resistant bacteria; h. genes can be transferred to other bacteria by plasmids; i. doctors/vets use different antibiotics but resistance develops to these as well; j. multiple-antibiotic resistant bacteria evolve/it becomes difficult to treat some infections;

Explain the evolution of antibiotic resistance in bacteria.

Describe the production of hybridoma cells

a. antigen injected into mouse/mammal/host b. B cells/B lymphocytes/plasma cells «obtained/extracted from host» c. fusion «of plasma cell with myeloma cell tumour cell ✓ d. division of hybridoma cells to produce a clone

Compare oogenesis and spermatogenesis

a. both produce haploid cells / both produce (mature/male/female) gametes; b. both have mitosis at start/in epithelium / both involve mitosis and meiosis; c. both have cell growth before meiosis; d. both involve differentiation (to produce a specialised gamete);

explain the roles of actin and myosin in muscle contraction

a. calcium/Ca2+ frees myosin binding sites on actin/thin filament; b. ATP (linked to myosin head) hydrolysed to ADP + P(i); c. myosin head cocked/assumes high energy configuration; d. myosin head binds to actin / forms a cross-bridge; e. actin filament slides towards center of sarcomere / dark band; f. combined sliding of actin filaments shortens muscle fiber / muscle; g. ATP binds to myosin head and breaks cross-bridge; Accept answers with properly annotated diagrams.

Explain the consequences of celiac disease for absorption of digested nutrients.

a. celiac disease/gluten causes) much smaller villi/flattened villi/smaller surface area (of villl) / no villi b. (smaller villi leads to) less efficientless/slower/poor absorption OR nutrients/energy lost/ fatigue/malnutrition may result c. (celiac sufferers) must eat a gluten-free diet/WTTE

Explain the role of cells in the defense against infectious disease

a. cells of skin provide a physical barrier/produce fatty acids/lactic acid/lysozyme which stops entry of microbes OR mucous membranes produce mucus to trap pathogens OR stomach cells produce hydrochloric acid which kills microbes b. platelets start the clotting process preventing access of pathogens c. (two types of) white blood cells fight infections in the body d. phagocytes ingest pathogens (by endocytosis/phagocytosis): f. production of antibodies by lymphocytes/B cells g. in response to particular pathogens/antigens h gives specific immunity i. lymphocyte/B cell makes only one type of antibody i plasma cells produce large quantity of (one type of) antibody k some lymphocytes act/remain as memory cells 1. can quickly reproduce to form a clone of plasma cells if a pathogen carrying a specific antigen is re-encountered: m. results in faster defence against second exposure to specific antigen/pathogen/disease;

Outline the role of proteins in active and passive transport of molecules through membranes

a. channel proteins allow diffusion/osmosis/passive transport; b. large/polar molecules cannot cross the (hydrophobic) membrane freely; c. facilitated diffusion involves moving molecules through proteins down their concentration gradient/without requiring ATP; d. aquaporins (specific integral membrane proteins) facilitate the movement of water molecules/osmosis; e. some proteins (for facilitated diffusion) are specific to molecule/ions; f. active transport involves moving molecules through proteins against their concentration gradient/requiring ATP; g. (some) proteins in the membrane are pumps / pumps perform active transport / sodium potassium pump;

Outline the role of proteins in active and passive transport of molecules through membranes.

Explain cladistics as a method to classify organisms

a. cladistics uses cladograms/tree diagrams; b. show clades/branches (in parallel) that begin at a point/node; c. each clade includes a (common) ancestral organism/node and all its descendents; d. members of a clade share derived/inherited characteristics; e. clades are nested/subsets of larger clades; f. cladograms show evolutionary history/origin of organisms / phylogeny; g. branch length (of clade) can indicate (relative) amount of genetic change/time; h. clades based on (objective) molecular analysis/genetic evidence / differ in amino acid sequences/DNA base changes/mutations; i. fewest number of differences/maximum parsimony determines branch separation; j. predictability of DNA base changes/mutation rates suggests evolutionary timelines; k. problems arise when gene change varies (greatly) from one gene to the next; l. cladograms may not match traditional/Linnaean classification; m. (mismatch) prompts re-examination of data / reclassification of a group; Some of the above points may be included in a correctly annotated diagram clearly stating above points.

Describe the process of blood cloting

a. clotting factor released by platelets/damaged tissue/cells; b. cascade/series of reactions; c. prothrombin (activated) to thrombin; d. soluble fibrinogen to insoluble fibrin / thrombin converts fibrinogen to fibrin; e. mesh of fibrin/fibres seals wound/traps platelets/red blood cells;

Some blood proteins are involved in defence against infectious disease. Explain the roles of named types of blood proteins in different defence mechanisms.

a. clotting factors are proteins>that initiate the clotting cascade/process b. fibrin «is a protein that permits blood clotting OR allows the formation of a clot c. «the protease thrombin converts fibrinogen to fibrin d. fibrin forms a mesh/clot that prevents the entry of pathogen/antigen into the blood e, antibodies are «specific proteins that lymphocytes make f. each antibody corresponds to a specific pathogen/antigen OR antibodies are specific «to certain pathogens/antigens>> g. antibodies create specific immunity h. plasma cells produce large amounts of «specific» antibodies OR memory cells retain the ability to produce «specific antibodies immunoglobulins are antibodies against pathogens enzymes in phagocytic white blood cells may digest pathogens

Explain the inheritance of color blindness

a. colour blindness caused by recessive allele / colour blindness is recessive; b. gene located on X chromosome/sex-linked; c. Xb is allele for colour blindness and XB is allele for normal colour vision/dominant allele; d. male has one X and one Y chromosome; e. male has only one copy of gene(s) located on X chromosome; f. X chromosome (in males) comes from female parent; g. any male receiving allele from mother will express the trait; h. XbY is genotype for colour blind male; i. many more males have colour blindness than females; j. female will express colour blindness only if is homozygous recessive/Xb Xb; k. heterozygous/XB Xb female is a carrier; l. colour blind female could be born to colour blind father and carrier mother;

Outline outcomes of the human genome project

a. complete human DNA/chromosomes sequenced; b. identification of all human genes / find position/map (all) human genes; c. find/discover protein structures/functions; d. find evidence for evolutionary relationships/human origins/ancestors; e. find mutations/base substitutions/single nucleotide polymorphisms; f. find genes causing/increasing chance of/develop test for/screen for diseases; g. develop new drugs (based on base sequences) / new gene therapies; h. tailor medication to individual genetic variation / pharmacogenomics; i. promote international co-operation/global endeavours;

outline the outcomes of the human genome project

Explain how the small intestine moves, digests, and absorbs food.

a. contraction of muscle «layers»/peristalsis helps move food OR circular muscle contraction prevents backward movement of food OR longitudinal muscle contraction moves food along gut b. peristalsis/muscle contractions mix food with intestinal enzymes c. enzymes digest macromolecules into monomers d. pancreatic enzymes/amylase/lipase/endopeptidase «chemically digest food in «lumen of» small intestine e. «pancreatic» amylase digests starch OR lipases digest lipids/fats/triglycerides OR endopeptidases/dipeptidases digest proteins/polypeptides bile/bicarbonate secreted into the small intestine creates favorable pH for enzymes OR bile emulsifies fat g. some final digestion into monomers is associated with epithelial cells/epithelium «of small intestine >> h. mucosa layer/inside surface/lining of small intestine contains villi/finger-like projections I. villi/microvilli increase surface area for better absorption j. villi absorb products of digestion/monomers/mineral «ions»>/vitamins k. glucose/amino acids enter blood «capillaries>> OR lipids enter lymph vessels/lacteals I absorption involves active transport diffusion/facilitated diffusion m different nutrients are absorbed by different transport mechanisms

Explain how the circulatory system is able to transport the blood under high pressure from the heart to the rest of the body.

a. contraction of ventricle creates high pressure b. blood at high pressure is carried out of the heart through arteries c. thick muscular walls of arteries resist pressure/prevent leaks d. elastic recoil of arterial walls helps to push blood ✓ e. narrow lumen of arteries maintain pressure

Glands are organs that secrete and release particular chemical substances. Melatonin is an important hormone secreted in the pineal gland in the brain. Describe its role in mammals.

a. controls circadian rhythms/biological clocks «in mammals >> b. production is controlled by amount of light detected by the retina c. high production/secretion in the dark OR no production/secretion in the day OR production/secretion is directly proportional to night time duration d. affects «seasonal» reproduction/sleep-wake cycles/jet lag

Outline the process of inhalation

a. diaphragm contracts / moves downwards/flattens b. external intercostal muscles contract C (muscle contraction) moves the rib cage upwards and outwards d. increases volume of the thorax/lungs o difference in pressure/decreasing pressure causes air to flow into lungs / lungs inflate

Following fertilization, cells in the developing embryo differentiate. Outline a technique for cloning using differentiated cells

a. differentiated/somatic/diploid cells taken from donor animal/sheep udder; b. (diploid) nucleus from donor cells removed; c. ova/eggs cells removed from (donor) animal/female sheep; d. (haploid) nucleus removed from eggs/ova; e. (diploid/donor's) nucleus is fused with/inserted into egg/ovum (to form zygote); f. embryo (from cell with donor nucleus and egg from surrogate) implanted in uterus of surrogate mother; g. normal pregnancy and birth is completed; h. offspring is a genetic copy/clone of the donor mother/diploid nucleus WTTE; [5 marks]

In the placenta, many substances are transported across membranes. Explain the structure and role of the [8 marks] placenta.

a. disc shaped structure b. embedded in uterus wall; c. connected to fetus by umbilical cord; d. contains fetal and maternal structures/tissues; e. placental villi/maternal intervillous space provide large surface area for exchange of materials; f. blood of fetus and mother flow close to each other (but no mixing); g. materials exchanged/diffuse (through membranes) between mother and fetal blood; h. oxygen/nutrients/antibodies/other substances diffuse (through membranes) to fetus; i. CO2 and wastes diffuse (through membranes) to mother; j. caffeine/drugs/alcohol/viruses from mother may damage fetal development; k. takes over role of corpus luteum (to produce hormones); l. produces hormones/estrogen/progesterone/HCG;

Mitochondria are thought to have evolved from prokaryotic cells. Describe two adaptations of the mitochondria, each related to its function.

a. double membrane/small intermembrane space/small gap between inner and outer membrane for a gradient of protons» to develop b. cristae/folds in inner membrane/large surface area of inner membrane for ATP synthesis/chemiosmosis/proton pumping/electron transport chains C. ATP synthase/stalked particles generates ATP from ADP + phosphate/Pi d. electron transport chains for generating a proton gradient/for releasing energy from reduced NAD e. matrix contains enzymes for Krebs cycle/link reaction/oxidation of fats/oxidation of substrates/aerobic respiration f. ribosomes/DNA for protein synthesis/replication

Explain the production of antibodies

a. each antibody corresponds to a specific antigen b. antibodies are necessary for immunity/resistance to «infectious» disease c. macrophage/phagocyte ingests/engulfs pathogen d. macrophage/phagocyte digests pathogen e. macrophage/phagocyte displays antigen from pathogen f. antigens of a pathogen correspond to a specific T lymphocytes/cells OR T lymphocytes/cells are activated by antigen binding g. T lymphocytes/cells activate B lymphocytes/cells h. «B cells» divide by mitosis to form many/clones of plasma cells i. plasma cells secrete specific antibody j. some «activated» B lymphocytes/cells act as memory cells

Explain the advantages of using hybridoma cells in the production of monoclonal antibodies.

a. endless cell divisions/unregulated mitosis (in hybridoma cells) b. large clone/population of identical cells produced c. all cells in clone) produce same type of antibody d. large amount of chosen) antibody can be produced.

Outline how a protein such as gluten is digested.

a. enzymes/protease required b. (protease/peptidase) breaks peptide bonds/bonds between amino acids c. hydrolysis adds water molecules/breaks peptide bonds between amino acids d. protein/macromolecule converted to monomer/amino acids e. endopeptidase/enzymes/protease/trypsin secreted by the pancreas

Structure and function of nucleosomes

a. found in eukaryotes; b. consists of DNA wrapped around proteins/histones; c. histones are in an octamer/group of eight; d. are held together by another histone/protein; e. in linker region; f. help to supercoil chromosomes / to facilitate DNA packing; g. (function is to) regulate transcription / gene expression;

Starting from the concept of gene pool, explain briefly how populations of early vertebrates could have evolved into different groups.

a. gene pool is all genes/all alleles b. geographic isolation OR migration to different areas OR temporal isolation OR behavioural isolation c. speciation/gene pool split if populations are reproductively isolated/do not interbreed d. in different environments there are different selection pressures/opportunities/ natural selection/adaptations/niches «to exploit >> e. allele frequencies change/diverge

Explain how spermatogenesis

a. germinal cells / spermatogonia undergo mitosis to keep a supply of germinal cells present; b. some germinal cells / spermatogonia grow larger to become primary spermatocytes; c. primary spermatocytes go through meiosis I; d. to form secondary spermatocytes; e. these secondary spermatocytes go through meiosis II; f. to produce spermatids; g. spermatids differentiate/grow a tail and reduce their cytoplasm h. spermatids associated with nurse cells (Sertoli cells); i. sperm detach from Sertoli cells and enter lumen of the seminiferous tubule; j. testosterone stimulates sperm production;

Outline how and where energy is stored in plants

a. glucose (from photosynthesis) stored as starch; b. starch stored (as granules) in chloroplast/in plastids; c. (starch stored) in seeds/storage roots/stem tubers; d. stored as lipids/oils; e. (lipid/oils storage) in seeds; f. lipids store twice as much energy per gram as starch;

state two symptoms of type 2 diabetes

a. glucose in urine; b. high blood glucose; c. frequent urination / dehydration/excess thirst; d. constant hunger; e. weight loss; f. tiredness;

Following germination of seeds, plants undergo a rapid increase in the number of cells. Describe stages in the cell cycle that result in this increase of cells.

a. growth phase/G-1: synthesis of proteins/cytoplasm/organelles; b. synthesis phase/S-phase: replication of DNA; c. second growth phase/G-2: continued growth of cytoplasm/molecular synthesis/duplication of organelles; d. prophase: chromosomes super-coil to prepare for mitosis / nuclear envelope disappears / spindle fibres form; e. metaphase: chromosomes line up at equatorial/metaphase plate / spindle fibres attach to centromeres/chromosomes; f. anaphase: chromatids move along microtubules/spindle fibres move chromatids toward opposite poles; g. telophase: nuclear membranes form around each cluster of chromosomes; h. cytokinesis: new plasma membrane forms between the nuclei / cell plate forms; i. a new cell wall forms; j. (mitosis) results in two cells with identical nuclei;

describe how the liver helps to maintain human health

a. helps regulate blood glucose level / converts glucose to glycogen and back; b. prevents excess glucose that could damage cells / lack of glucose could limit cell growth/activity / OWTTE; c. stores/recycles iron; d. stores vitamin A/vitamin D; e. synthesizes plasma proteins/cholesterol; f. provides essential substances for cell growth/hormone production; g. detoxifies substances / protects the body from damage from toxic substances (as alcohol); h. breaks down erythrocytes/hemoglobin; i. production of bile for digestion (of fats); j. (production of bile) reduces build-up of bilirubin in the blood / prevents jaundice;

Outline how males inherit hemophilia and how females can become carriers for the condition

a. hemophilia is due to a recessive allele/is a recessive trait / XH is normal allele and Xh is hemophilia allele; b. hemophilia is sex linked; c. allele/gene is on the X chromosome; Reject disease/hemophilia carried on X chromosome. d. (sex chromosomes in) females are XX while males are XY; e. Y chromosomes do not have the allele/hemophiliac males are XhY; f. males inherit their X chromosome from their mother/do not pass the allele to sons; g. males have only one copy so recessive trait/allele is not masked; h. males have a 50% chance of hemophilia/receiving the allele if mother is a carrier; i. carrier is heterozygous for the gene/is XHXh; j. dominant/normal allele masks the recessive allele (so clotting is normal); k. females inherit one X chromosome from father and one from mother; l. affected/hemophiliac males have carrier daughters; m. hemophilia allele could have been inherited from either parent; [8 marks Accept the points above explained either in text or clearly using a Punnett grid or genetic diagram, but not for simply reproducing an unlabeled Punnett grid or diagram without explanation.

Explain the possible health consequences of a diet rich in protein

a. high amount of one nutrient may cause deficiency in another one; b. excess protein not stored as protein by the body / converted to fat; c. results in weight/mass loss in many people (due to fat/carbohydrate deficiency); d. health problems such as kidney stones/other health problems; e. high protein as part of a weight/mass loss diet;

Outline how the compounds produced by chloroplasts are distributed throughout the plant

a. in phloem b. loading into sieve tubes/by active transport/by cotransport/by companion cells c. entry of water (to phloem) by osmosis/because of high solute concentration d. causes high/hydrostatic pressure e. flow from high pressure to lower pressure down pressure gradient from source to sink

Explain the mechanism of ventilation in the lungs in order to promote gas exchange for cell respiration.

a. inspiration/inhalation brings air into lungs; b. external intercostal muscles contract; c. and move rib cage upwards and outwards; d. diaphragm flattens/contracts; e. increasing thoracic volume; f. pressure decreases from atmospheric pressure so air rushes into lungs; g. expiration/exhalation forces air out; h. internal intercostal muscles contract / external intercostal muscles and diaphragm relax; i. abdominal/abdomen wall muscles contract and push diaphragm upwards; j. decreasing thoracic volume; k. increasing pressure in lungs so air is forced out; l. a concentration gradient between air sacs and blood needs to be maintained;

describe the features of alveoli in human lungs that adapt them for efficient absorption of oxygen

a. large surface area from having many alveoli; b. single/flattened layer of (thin) cells in wall; Reject one-cell membrane/thin membrane. c. (surrounded by) dense network of capillaries/capillary bed; d. short distance for gases/oxygen/carbon dioxide to diffuse; e. moist lining / film of moisture on inside of alveolus; f. moisture allows oxygen/gases to dissolve; g. diffusion of oxygen down concentration gradient;

Outline how leptin controls appetite.

a. leptin suppresses/inhibits appetite b. is secreted by adipose tissue/fat «storage» tissue c. level is controlled by amount of adipose tissue/«ongoing» food intake d. leptin targets cells in hypothalamus/appetite control centre in brain e. causes hypothalamus/control centre in brain to inhibit appetite f. if amount of adipose tissue increases, blood leptin concentration rises

outline how leucocytes defend the body against pathogens

a. leucocytes/phagocytes/macrophages can recognize pathogens/foreign matter; b. (phagocytes) engulf pathogens by endocytosis/phagocytosis; c. migration to tissues/squeezing out of capillaries; d. each pathogen has specific antigens; e. leukocytes/lymphocytes produce antibodies by reacting to specific antigen/ pathogens; f. antibody joins to (specific) antigen inactivating/destroying them; g. lymphocyte makes a clone/copies itself; h. thus increasing the total number of (specific) antibodies;

Outline the basic techniques used for the gene transfer of hemophilia treatment using Factor IX

a. mRNA/gene coding for factor IX extracted from human cell/tissue; b. mRNA copied to DNA/cDNA (using reverse transcriptase); c. plasmids used (for gene transfer); d. restriction enzyme/endonuclease used to open plasmid/cut DNA; e. complementary bases/sticky ends on gene and plasmid/link gene to plasmid; f. sealed using ligase; g. recombinant plasmid/plasmid containing desired gene taken up by bacteria; h. isolate/clone the recombinant/transformed bacteria; i. bacteria cultured/grown in fermenter to produce factor IX;

Outline how plasma cells become activated.

a. macrophages/phagocytes recognize engulf pathogen and display antigens b. antigen binds to T cell helper T cell / antigen causes activation of T cell c, antigen binds to antibodies in membrane of B cells d. (activated) T cells activate B cells (that have the antigen bound to them) e. activated B cells divide to produce a clone of cells active plasma cells develop from the clone of cells/from activated B cells

Meiosis in humans produce cells that participate in fertilization. Outline the processes involved in meiosis.

a. meiosis reduces a diploid cell into (four) haploid cell(s); b. (during prophase I) homologous chromosomes pair up/synapsis; c. chromatids (break and) recombine / crossing over d. (metaphase I) (homologous chromosomes) at the equator of the spindle / middle of cell; e. (anaphase I) (homologous) chromosomes separate and move to opposite poles; f. (telophase I) chromosomes reach poles and unwind WTTE; g. (prophase II) chromosomes (condense and) become visible, new spindles form; h. (metaphase II) chromosomes line up at the centre of the cells/equator; i. (anaphase II) sister chromatids separate; j. (telophase II) chromatids reach the poles and unwind;

Discuss the endosymbiotic theory for the origin of eukaryotes.

a. microorganisms/prokaryotes taken into cell by endocytosis; b. kept inside cell and perform respiration/photosynthesis; c. developing into mitochondria/chloroplasts; d. mitochondria/chloroplasts have double membranes (as expected in cells taken in by endocytosis); e. mitochondria/chloroplasts have (circular naked) DNA (as prokaryotes); f. mitochondria/chloroplasts have 70S ribosomes (as prokaryotes); g. mitochondria/chloroplasts grow and divide like (prokaryotic) cells;

Explain how minerals move into plants.

a. minerals bound to soil particles; b. examples of three nutrients from: phosphate, nitrate, magnesium, iron, calcium, potassium, sodium, magnesium; c. minerals dissolve in water; d. mass flow causes movement of minerals with movement of water through soil; e. minerals diffuse down a concentration gradient towards roots (as the mineral concentration next to the roots is continuously decreasing); f. minerals enter the plant through roots; g. by active transport / use of ATP; h. branching of roots increases surface area for absorption of minerals; i. root hairs increase surface area (for the absorption of minerals); j. hypha of (mutualistic) fungi may enhance movement of selected ions into roots / increase surface area; k. root hairs have many mitochondria to provide energy/ATP for active transport; l. export of H+ creates electrochemical gradient / displaces ions bound to soil/clay; m. that causes positive mineral ions to diffuse into (root) cells; n. negative mineral ions cross membrane linked to H+ ions moving down (H+) gradient;

Describe the consequences of overproduction of offspring

a. more (offspring) than the environment can support / carrying capacity reached; b. increased mortality/lower life expectancy/more deaths; c. competition (for resources) / struggle for survival; d. food/mates/nest sites/territory/other example of resource shortage / example of greater need; e. variation between members of population / example of variation; f. better adapted more likely to survive / converse; (reject Lamarckian statements such as those who adapt survive) g. better adapted reproduce / pass on (favourable) genes/traits / converse; h. natural selection / (survival of fittest) leads to evolution;

Explain the process of muscle contraction

a. muscle fibre contains many myofibrils b. made up of sarcomeres labelled diagram showing one or more sarcomeres c. nerve impulse/signal from (motor) neuron causes release of calcium (ons)/Ca d. calcium (ions Careleased from sarcoplasmic resculum e calcium (lonsyCa link to troponin tropomyosin moves to expose actin binding sites g. ATP hydrolysis/ATP to ADP and phosphate release of phosphate from ATP h. ATP binds to myosin heads and causes them to cock change angle release/gain energy L myosin heads bindform cross-bridges to actin myosin heads push on actin and then detach from actin K actin moved towards centre of sarcomer/sicing of filaments L sarcomere becomes shorter resulting in muscle contraction)

Using a named example of a genetically modifed crop, discuss ethical issues.

a. named example of verified genetically modified crop; eg, Bt corn / golden rice; Example must be verifiable. b. specific gene added / new protein synthesized by the crop plant / specific modification; eg gene from Bacillus thuringiensis / cry protein; c. biological effect of the modification; eg, makes the plant toxic to (herbivorous) insects / insect pests / corn borers; [2 max] for benefits and [2 max] for harmful effects / costs; d. a benefit of specific genetic modification; eg, increased crop yields / less land needed; e. a second benefit of this specific modification; eg, reduced need for use of chemical pesticides; f. a harmful effect of specific genetic modification; ingestion of toxin by nontarget species; g. another specific harmful effect; eg, concerns about contamination of neighbouring non-GMO crops affecting trade;

All motor neurons use acetylcholine to activate skeletal muscle. Explain the effect of neonicotinoid pesticides in insect synapses in the central nervous system.

a. neonicotinoid pesticides are similar to nicotine «chemically b. bind to nicotinic/acetylcholine receptors c. not broken down by <acetylcholinesterase OR binding is irreversible d. prevents/blocks acetylcholine binding e. blocks transmission from CNS OR blocks signals going to muscle OR muscle contraction blocked OR causes paralysis

The heart responds quickly to physical activity. Describe how heart rate is controlled to meet the increased circulatory demands.

a. nerve impulse from medulla/brain acts on heart/right atriumv b. pacemaker/sinoatrial node/SAN increases/controls contraction of heart c. epinephrine/adrenaline «rapidly increases heart rate

Explain the propagation of electrical impulses along a neuron including the role of myelin.

a. neurotransmitter attaches to receptor site, initiating transmission b. nerve impulses are action potentials propagated along the axons of neurons c. resting potential is more negative inside/-70 mV/ more positive outside the membrane OR a resting potential has greater concentration of Na ions outside than K ions inside the axon d. «volted gated >> channels open and Na ions diffuse in e. causes depolarization of the membrane/-70 mV to +40 mV f. local currents affect adjacent channels/cause action potential g. depolarization is followed by repolarization of the neuron h. «voltage gated» channels open and Kions diffuse out/repolarize the membrane i. Na-K pumps restore Na/k balance/resting potential |j. myelin around the neuron insulates the axon OR speeds the transmission k. myelin permits saltatory conduction OR permits jumping from node to node

Explain the control of body temp in humans

a. normal body core temperature constant/36.5 to 37.5°C; (accept single values within this range) b. regulated by negative feedback/homeostatic mechanisms; c. hypothalamus is the centre of thermoregulation; d. hypothalamus sends impulses to the body to increase/decrease temperatures; [8 marks] e. release of sweat (by sweat glands in the skin) if skin temperature rises; f. evaporation of water cools the body; (concept of evaporation must be mentioned) g. heat is transferred by blood; h. transfer of heat from body core in blood to surface; i. if temperature rises, increased flow of blood/heat to the skin/vasodilation of skin blood vessels/arterioles; (do not accept veins, arteries or capillaries) j. if temperature drops, decreased flow of blood/heat to the skin/vasoconstriction of skin blood vessels/arterioles; (do not accept veins, arteries or capillaries) k. shivering increases heat production (in muscles); l. example of one behavioural mechanism; (eg reducing activity (to lower body temperature) / reducing exposed surfaces (to reduce heat loss)

explain the process of photophosphorylation in chloroplasts

a. occurs in stroma (of chloroplast); b. energy/ATP and NADPH provided by the light-dependent reactions; c. Calvin cycle; d. carbon dioxide fixed to RuBP / carboxylation of RuBP/ribulose bisphosphate; e. by RuBP carboxylase/rubisco; f. forms unstable 6C compound / forms 6C compound which splits; g. glycerate 3-phosphate (is produced by carbon fixation); h. (glycerate phosphate) to triose phosphate/3C sugar by reduction/adding hydrogen; i. using NADPH/reduced NADP; j. triose phosphate/3C sugar converted to form hexose/glucose (phosphate); k. most/5/6 of triose phosphate used for regeneration of RuBP; l. ATP used to regenerate RUBP/convert glycerate 3-phosphate to triose phosphate;

Explain how the structure of the nephron and its associated blood vessels enable the kidney to carry out its functions.

a. osmoregulation/excretion of nitrogenous waste/urea «is a function of the kidney b. ultrafiltration in the glomerulus/smaller molecules filtered out in the glomerulus OR capillary walls/glomerulus permeable to smaller molecules c. basement membrane/filtration slits/podocytes act as filter/prevent loss of large>> «proteins/prevent loss of blood cells d. high «blood pressure in glomerulus due to larger afferent than efferent arteriole e. «selective>> reabsorption of glucose/useful substances in proximal convoluted tubule f. microvilli/coiling/convolutions give large surface area OR pump proteins to reabsorb specific solutes «in proximal convoluted tubule>> g. water reabsorbed in descending limb «of loop of Henle>> OR descending limb permeable to water h. active transport/active pumping of sodium ions/Nat out of ascending limb «from filtrate to medulla>> ascending limb is impermeable to water j. loop of Henle creates solute gradient/high solute concentration/hypertonic conditions in medulla k distal convoluted tubule adjusts pH/adjusts concentration of Na+/K/H I water reabsorbed in collecting duct m. collecting duct permeability to water varies due to number of aquaporins/ADH n. osmoregulation by varying the amount of water reabsorbed «in the collecting duct>

Explain the production of antibodies when a patient is infected with TB bacterium

a. phagocytes/lymphocytes are white blood cells b. TB bacterium has a specific antigen c. this antigen is recognised by white blood cells d. a clone of lymphocytes/plasma cells/B cells are produced e. antibodies are produced by lymphocytes 1. each lymphocyte produces just one type of antibody 9. (this is) specific immunity h. (part of the) antibody/immunoglobulin binds to the antigen / specific antibody binds to the specific antigen 1. antibodies are proteins/immunoglobulins j. (some) plasma cells become memory cells k. memory cells reproduce quickly 1. memory cells prevent infection in the future

Explain chemiosmosis as it occurs in photophosphorylation

a. photophosphorylation is the production of ATP; b. (some of the) light absorbed by chlorophyll / photosystem II; c. photolysis/splitting of water separation of hydrogen ion from its electron; d. the electron transport system moves the electrons through a series of carriers; e. (electron transport system occurs) in the thylakoid membrane; f. electron transport linked to movement of protons into thylakoid space; g. a proton gradient builds up (in the thylakoid space); h. small thylakoid space enhances the gradient; i. hydrogen ions move by diffusion through the ATP synthase; j. ADP + inorganic phosphate (Pi) forms ATP; k. (the kinetic energy from) movement of hydrogen ions (through ATP synthase) generates ATP; l. ATP synthase is a protein complex in the thylakoid membrane; m. formation of proton gradient / ATP synthesis linked to electron transport is chemiosmosis;

explain how the process of photosynthesis affects carbon dioxide concentrations in the atmosphere during a typical year and the likely consequences on Earth of the yearly rises in CO2

a. photosynthesis uses carbon dioxide; b. CO2 fixed/made into organic molecules/compounds by photosynthesis; c. lowering carbon dioxide level in atmosphere; d. annual/seasonal fluctuations of carbon dioxide levels could be related to photosynthesis; e. caused by increased photosynthesis during spring/summer; Consequences: [5 max] f. enhanced greenhouse effect caused by raised levels of carbon dioxide; g. causing global warming; h. rising of ocean levels / melting of polar ice caps/glaciers; i. changes in weather (patterns); j. ocean acidification; k. alter food webs; l. changes/loss of habitat; m. changes in distribution of plants and animals; n. may lead to extinction;

outline the use of named enzymes in gene transfer using plasmids

a. plasmids are removed/obtained from bacteria; b. endonuclease/restriction enzymes cut the plasmids at target sequences; c. DNA fragments of other organism are cut with the same restriction enzymes; d. in both DNA and plasmid, complementary sticky ends/staggered cut are produced; e. DNA segment added to the opened plasmid; f. spliced together by ligase; g. reverse transcriptase makes DNA copies of mRNA / DNA polymerase to increase the amount of DNA; h. recombinant plasmids inserted into new/host cells; i. cultured/cloned to produce the new genes/more genetically modified cells; Award [3 max] if no specific enzyme names are given. Do not accept the word "enzyme" on its own.

Outline the functions of the liver

a. produces bile for digestion/emulsification of fats/lipids; b. regulates blood glucose level through glucose-glycogen reaction; c. detoxification/example of detoxification (eg contains catalase for the breakdown of hydrogen peroxide); d. manufactures plasma proteins/albumins/fibrinogen; e. manufactures cholesterol; f. destroys red blood cells by phagocytosis; g. breaks down haemoglobin from red blood cells; h. stores iron; i. stores vitamin A and D; j. deaminates excess amino acids/formation of urea;

Outline the structure of proteins.

a. protein formed from amino acids OR 20 different amino acids b. linked together by peptide bonds c. may consist of one or more polypeptides linked together d. have a specific shape/conformation/folding → e shape determines function

Describe what is shown in the pyramid of energy

a. pyramid of energy shows the flow of energy from one trophic level to the next (in a community); b. units of pyramids of energy are energy per unit area per unit time/kJ m-2 yr -1; c. bar width is proportional to the energy stored (in the biomass) in that trophic level; d. the first/lowest trophic level is producers; e. second level is primary consumers/herbivores; f. third level of secondary consumers/carnivores; g. only a small amount (10 to 20 %) of energy of one level is passed to the next; h. bar width/energy stored in the trophic level decreases (proportionally) as you go up each level; i. pyramid shows that there is a limit to the length of food chains;

explain the consequences of releasing raw sewage and nitrate fertillizer into rivers

a. raw sewage contains pathogens; b. can contaminate drinking water / cause disease/death; c. nitrate fertilizers cause algal blooms/(aquatic) plant development; d. algae release toxins that can contaminate drinking water; e. more organic matter results / eutrophication; f. more oxygen required to decompose organic matter / increase in BOD; g. (leading to) death of aquatic animals/organisms; h. recovery follows since algae/plants release more oxygen

Outline the functions of rough endoplasmic reticulum and Golgi apparatus.

a. ribosomes on RER synthesize/produce polypeptides/proteins v b. proteins from RER for secretion/export/use outside cell/for lysosomes ✓ c. Golgi alters/modifies proteins/example of modification ✓ | d. vesicles budded off Golgi transport proteins «to plasma membrane» OR exocytosis/secretion of proteins in vesicles from the Golgi

Outline the changes that take place in the abiotic environment with primary succession

a. rocks begin to break down; b. minerals begin to accumulate; c. soil begins to develop; d. water retention increases; e. erosion of soil is reduced (by rhizoids and roots);

An experiment was done to test the hypothesis that temperature affects the rate of germination of the broad bean. Outline two factors apart from temperature that should be controlled in this experiment.

a. same amount/type of soil substrate / pH of soil b. same amount of water / humidity ✓ C. oxygen/aeration d. same measurement of germination/time e same number/source/age of seeds

Describe the role of ADH in human osmoregulation

a. secreted when blood/plasma is hypertonic/too concentrated/water content too low b. makes walls of collecting duct/distal convoluted tubule «more>> permeable to water c. more aquaporins in membranes «of collecting duct cells >> d. more water reabsorbed from filtrate/from urine/more water returned to blood e. small volume of concentrated urine excreted ✓

explain the interaction of short and long wave radiation with greenhouse gases in the atmosphere.

a. short wave radiation/UV «shown as having its origin in the Sun gives off light as short radiation b. short wave radiation/UV «shown as» passing through the greenhouse gases «some reflected» C. some short wave radiation/UV is absorbed by the Earth and some is reflected d. the reflected radiation is long wave radiation «reflected as heat>> e. long wave radiation/IR «shown as being unable to pass through/being absorbed/reflected by the greenhouse gases

Describe the processes involved in absorbing different nutrients across the cell membrane of villus epithelium cells lining the small intestine.

a. simple» diffusion of nutrients along/down a concentration gradient b. example of simple diffusion, eg, fatty acids c. facilitated diffusion of nutrients involves movement through channel proteins d. example of nutrient for facilitated diffusion eg, fructose e. active transport of nutrients against a concentration gradient / involving protein pumps f. example of active transport, eg: (iron) ions/glucose/amino acids g. endocytosis / by means of vesicles h. example of nutrient for endocytosis, eg: cholesterol in lipoprotein particles

Bacteria are prokaryotes that sometimes act as pathogens. Describe how the body can defend itself against pathogens.

a. skin/mucus membranes act as barrier (to pathogens); b. sebaceous glands secrete lactic acid/fatty acids/sebum / make surface of skin acidic; c. (skin/stomach) acid prevents growth of many pathogens; d. lysozyme in mucus can kill bacteria; e. pathogens caught in sticky mucus and removed from body; f. inflammatory response/inflammation can cause swelling/redness/fever (to inhibit the pathogen); g. phagocytes/macrophages/leucocytes/white blood cells (non-specifically) identify (pathogens/bacteria/fungi/viruses) as foreign; h. (phagocytes macrophages/leucocytes/white blood cells) ingest pathogens; i. specific lymphocytes recognize one specific antigen; j. (antigen-specific) lymphocytes clone themselves; k. lymphocytes/leucocytes produce antibodies; l. antigen-antibody complex formed and stimulates destruction of pathogen;

Outline how neurons generate a resting potential.

a. sodium-potassium pump b. sodium/Nat out and potassium /Kin OR sodium/Na+ concentration higher outside and potassium/K+ higher inside c. three Na+ pumped for every two K+ (hence negative inside) OR inside of axon holds negative ions/Clions/negatively charged proteins/organic anions (hence negative inside) d. by active transport / using ATP e. inside (of axon/neuron) is negative in comparison to outside OR electrochemical concentration charge difference (across the membrane) is the resting potential f. resting potential is -70mV ✓

Describe the different cell types in the seminiferous tubules that are involved in the process of spermatogenesis

a. spermatogonia «2n» are undifferentiated germ cells b. spermatogonia mature and divide «by mitosis»> into primary spermatocytes «2n>> c. primary spermatocytes divide by meiosis I into secondary spermatocytes «in» d. secondary spermatocytes divide by meiosis II into spermatids «in>> o. spermatids differentiate/mature into spermatozoa/sperm t. Sortoli/nurse colls provide nourishment/support to these developing colls g. Leydig/interstitial cells produce testosterone

Discuss ethical issues of therapeutic cloning in humans

a. therapeutic cloning involves producing embryos from which embryonic stem cells can be harvested for medical use; argument in favour: b. (to many people) any procedure that reduces pain and suffering is ethically/morally justified; c. stem cells can be used to replace organs/tissues that have been lost/damaged in a patient; d. (thus) pain and suffering can be reduced/lives can be saved/life quality improved; e. cells can be removed from embryos that have stopped developing and would have died anyway; f. cells are removed at a stage when no pain can be felt by the embryo; g. use embryos from IVF that would otherwise be destroyed; Accept up to one additional reasonable argument in favour. argument against: h. embryonic stem cells are no longer needed as adult stem cells can be used without causing loss of life; i. there is danger of embryonic stem cells developing into tumour cells/harmful effects are not yet known; j. every human embryo is a potential human with the right to development; k. more embryos may be produced than can be used and so some would be killed; l. (to many people) any procedure that harms a life/kills is unethical/morally wrong; Accept up to one additional reasonable argument against.

Outline transcription in prokaryotes.

a. transcription is the copying of a strand of DNA into RNA/RNA formation; b. RNA polymerase binds to promoter region of DNA; c. anti-sense strand as template / only one strand copied; d. RNA polymerase unwinds DNA/separates the strands; e. RNA nucleotides/nucleoside triphosphates pair with complementary bases on DNA; f. Adenine to Thymine, Cytosine to Guanine, and Uracil to Adenine; (do not accept letters alone) g. added at 3' end / strand grows 5' to 3' ; h. RNA nucleotides joined with covalent/sugar-phosphate bonds; i. RNA polymerase separates from DNA when reaches terminator/termination sequence; j. no introns/post-transcriptional modification/RNA splicing (as occurs in eukaryotes)

Some prokaryotes cause infectious disease in humans. Explain the principles of vaccination.

a. vaccines contain a dead/weakened form of the pathogen/bacteria/virus; b. vaccine introduced to the body by injection/on surface of skin/orally; c. antigens in the vaccine cause antibody production; d. antigen/pathogen engulfed by macrophage/phagocyte; e. each type of lymphocyte recognizes specific antigen; f. macrophages activate helper T-cells; g. which activate B-cells; h. B-cells divide to form clones/memory cells; i. B-cells divide to form plasma cells/antibody producing cells; j. result is (specific) immunity; k. vaccination/first exposure causes slow production of antibodies and lower level of antibodies; (this idea can be illustrated on a diagram or graph) l. contact with the disease leads to rapid production and higher level of antibodies; (this idea can be illustrated on a diagram or graph) m. second/booster shot to stimulate memory cells/more production of antibodies;

Aquatic and other environments are being affected by a global rise in temperature. Outline the consequences [6 marks] of this on arctic ecosystems

a. warming results in melting (arctic/polar) ice (cap) / loss of ice habitats; b. (warming) raises sea level / floods coastal areas / destroys coastal habitats; c. (warming) of habitat would change species/flora/fauna that can be supported (named examples can be used); d. decrease in size of population(s) / possible extinction of species; e. temperate species move into area / arctic species adapt/move; f. change in distribution of species/changes in migration patterns; g. (ecological) changes will affect higher trophic levels/food webs/food chains; h. increased rates of decomposition of detritus from (melting) permafrost; i. increased success of pest species including pathogens;

Explain the roles of specific enzymes in prokaryote DNA replication.

a. «DNA» gyrase/topoisomerase «ll» prepares for uncoiling/relieves strains in the double helix » b. helicase uncoils/unwinds the DNA/double helix c. helicase separates/unzips/breaks hydrogen bonds between the two strands of DNA d. «DNA» primase adds an RNA primer/short length of RNA e. DNA polymerase III adds «DNA» nucleotides/replicates DNA/synthesizes complementary strand in a 5' to 3' direction f. DNA polymerase III starts replication/adding nucleotides at the primer g. DNA polymerase I removes the primer OR replaces RNA with DNA h. «DNA» ligase seals the nicks OR links sections of replicated DNA OR links Okazaki fragments i. DNA polymerase /DNA polymerase III proofreads for mistakes

Describe the functioning of immunoglobulins

a. «immumoglobulins are/function as» antibodies b. variety of binding sites / variable regions for binding c. specific to antigens on bacteria/viruses/pathogens d. constant region aids destruction of the bacteria/virus/pathogen o, attracts phagocytes/macrophages to engulf pathogen f. bursting pathogen cells/agglutination/neutralizing toxins/other example of the action of antibodies

Explain how calcium is involved in muscle contraction.

action potential/nerve impulse causes release of calcium from sarcoplasmic reticulum/specialized endoplasmic reticulum binds to troponin causes tropomyosin to move/be removed from binding sites exposes myosin-binding sites on actin/allows myosin «heads» to bind to actin

Explain how ventilation and lung structure contribute to passive gas exchange.

air carried through trachea AND bronchi/bronchioles AND alveoli alveoli increase the surface area/thin walled for gas exchange gas exchange carried out through type I pneumocytes type Il pneumocytes secrete surfactant to reduce surface tension e moist surface/surfactant allows gases to diffuse in solution ventilation/moving blood maintains concentration gradients of oxygen and carbon dioxide between air in alveoli and blood in adjacent capillaries OR oxygen diffuses from alveoli to capillaries and carbon dioxide from capillaries to alveoli external intercostal muscles/diaphragm contract during inspiration lowering air pressure «in lungs/increasing thorax volume relaxation of external intercostal muscles/diaphragm enable «passive» expiration internal intercostal cand abdominal muscles» contract to force expiration I expiration due to increasing air pressure «in lungsa/decreasing thorax volume

Compare and contrast the structure of starch and cellulose

both polymers of glucose molecules polysaccharides starch is formed by alpha glucose while cellulose is formed by beta glucose there are two types of starch but one type of cellulose

State the action of the acetylcholinesterase enzyme.

breaks down acetylcholine into acetyl and choline

explain the causes of sickle cell anemia

caused by gene mutation; (sickle-cell anemia) due to a base substitution (mutation); changes the code on the DNA; which leads to a change in transcription / change in mRNA; DNA changes from CTC to CAC/GAG to GTG / mRNA changes from GAG to GUG; (accept DNA changes from CTT to CAT/GAA to GTA / mRNA changes from GAA to GUA) which (in turn) leads to a change in translation / change in polypeptide chain/ protein; (the tRNA) adds the wrong amino acid to the polypeptide chain; glutamic acid replaced by valine; produces abnormal hemoglobin; causing abnormal red blood cell/erythrocyte shape / sickle shape; which lowers the ability to transport oxygen; sickle-cell allele is codominant; homozygote/HbS HbS have sickle cell anemia/is lethal / heterozygote/HbS HbA has the sickle trait/is carrier (and is more resistant to malaria);

Define: Chromosomes, genes, alleles, and genome

chromosome: structure formed by DNA and proteins; gene: a heritable factor that controls a specific characteristic; allele: one specific form of a gene occupying the same gene locus as other alleles of the gene; genome: the whole of the genetic information of an organism;

State the type of reactions that convert monosaccharides to polysaccharides

condensation, dehydration, synthesis, anabolism

State two structural similarities between mitochondria and chloroplasts

e. (a loop of) DNA f. 70S ribosomes 9. double membrane h. electron transport chains/enzyme complexes in internal membranes 1. enzymes in a region of fluid/in stroma and matrix large area of internal membrane/cristae and thylakoids

state the source, substrate, products and optimal pH conditions for lipase in the digestive system

eg source: pancreas; substrate: triglycerides / lipids / fats / oils; product: glycerol and (three) fatty acids; (both needed) optimal pH: 8; (accept answers in the range of 7 to 8) Accept other correct examples

State one role of Rubisco

enzyme involved in photosynthesis, carbon fixation, Calvin cycle carboxylation of RuBP production of carbohydrate in photosynthesis addition of carbon dioxide to form glucose in carbon cycle

Define linked genes

genes located on the same chromosome that tend to be inherited together

Outline how the carbon compounds produced by chloroplasts are distributed throughout the plant.

in phloem loading into sieve tube by active transport by companion cells entry of water via osmosis into the pholem becuase of the high cocnentration causes high hydrostatic pressure flow from high pressure to low pressure down pressure gradient from source to sink

Many people cannot digest lactose and benefit from a diet containing no lactose. Outline the production of lactosefree milk

milk contains lactose / lactose is milk sugar; lactose is broken down to glucose and galactose; by (the enzyme) lactase; which is lacking in people with lactose intolerance; lactose-free milk is sweeter than milk containing lactose; lactase produced by small intestine / produced by yeast sometimes found in milk; can be added directly to milk; immobilized in beads / biotechnological techniques; ultrafiltration of milk to remove lactose;

Outline how mitotic index is calculated.

number of cells undergoing mitosis within a sample/ total number of cells observed in sample

Outline how cuts in the skin are sealed to prevent blood loss

platelets respond to detect skin/blood vessel damage platelets release clotting factors clotting factors trigger a chain/cascade of reactions «leading to formation of thrombin thrombin causes fibrinogen conversion into fibrin blood clot seals the wound due to fibrin network of fibres

State one possible use of hybridoma cells

produce monoclonal antibodies OR diagnosis of diseases/malaria/cancer/HIV OR treatment of rabies OR blood and tissue typing OR pregnancy testing OR targeting of cancer cells «with a chemotherapy drug OR treatment of infection if too late for vaccination/successful immune response

Explain the control mechanism of the heart rate.

sinoatrial node/SAN is a specialized group of muscle cells OR sinoatrial node/SAN is located in the right atrium acts as a pacemaker controls the heart rate OR initiates/generates the heart beat/starts the cardiac cycle sends out electrical signalimpulses/depolarisations electrical signal stimulates contraction of heart muscle signal passes through walls of atria/passes to AV node then through walls of the ventricles medulla woblongata of brain the rate can change/increase/decrease through nerves/named example of nerve/autonomic/sympathetic/parasympathetic nervous system one nerve increases the rate and the other decreases it epinephrineladrenaline increases heart rate/force of contraction epinephrine/adrenaline prepares the body for vigorous activity is part of fight or flight response

describe how human skin color is determined genetically

skin colour is an example of polygenic inheritance; many/more than two genes contribute to a person's skin colour; due to the amount of melanin in the skin; combination of alleles determines the phenotype; allows for range of skin colours / continuous variation of skin colour; phenotypes do not follow simple Mendelian ratios of dominance and recessiveness; the environment also affects gene expression of skin colour / sunlight/UV light stimulate melanin production; the more recessive alleles there are, the lighter the skin colour; (vice versa)

Outline the role of the parts of an alveolus in a human lung.

the (spherical) wall of an alveolus maximizes/allows gas exchange b. pneumocytes (optimize) gas exchange c. pneumocytes Il produce surfactant d. adjacent capillaries enclose alveolus for efficient gas exchange with blood o surfactant reduces surface tension/prevents collapse of alveolus f. (alveolar) macrophages/phagocytes help with defense/homeostasis/response to foreign substances

Outline the functions of type and type Il pneumocytes.

type: a carry out gas exchange OR diffusion of gases/C02/02 type Il b. secrete fluid/surfactant

Explain how the kidney helps to retain useful substances in the blood and eliminate substances which the body does not need.

ultrafiltration occurs in the glomerulus; basement membrane acts as a filter; preventing proteins/cells from passing; (filtered) substances pass to the Bowman's capsule; to proximal convoluted tubule (PCT); (where there is) selective reabsorption; (in PCT) all glucose/amino acids are reabsorbed; (in PCT most) water reabsorbed; surrounding the loop of Henle, is an area of high solute concentration; in distal convoluted tubule, ions are exchanged between filtrate and blood; collecting duct has role in osmoregulation; ADH regulates the amount of water reabsorbed; substances not reabsorbed are eliminated as urine;

Outline the reasons for the differences in blood concentrations between the renal artery and the renal vein.

urea/waste products lower in vein due to excretion in urines/ultrafiltration but not reabsorption oxygen lower in vein due to use in cell respiration in kidney tissue carbon dioxide higher in vein due to production by cell respiration/excretion by kidney cells glucose lower in vein due to use in cell respiration by kidney tissue sodium chloride/ion concentrations changed due to production of hypertonic/hypotonic urine OR sodium chloride/ion concentrations lower due to removal of excess ion/solute concentrations lower in vein than artery if ADH has been secreted OR ion/solute concentrations in vein vary depending on amount of water reabsorbed in the collecting duct drug/toxin concentrations lower in vein due to excretion in urine

Outline the uses of ATP in plant cells

used as an energy source supplies/releases energy for biochemical reactions photosynthesis, active transport

Outline the uses of ATP in plants

used as an energy source supplies energy for biochemical reactions photosynthesis, active transport

outline the abiotic factors that affect the distribution of plant species in an ecosystem

water (distribution) for turgor/biochemical reactions/photosynthesis; mineral / inorganic content / salinity of soil/water; temperature (max, min, range, seasonal changes) / altitude; light (intensity, duration, wavelength) for photosynthesis; pH (range, average, changes) of soil/water; wind (direction, strength);

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