Essay questions Biology Alevel 9700 PDF

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Essays

Ezz Eldin Adham

Essays How to enhance vitamin content of ….?           

vitamin A found in aleurone layer of rice (seeds) ; white rice does not contain, aleurone layer / vitamin A genes coding for vitamin A production extracted ; from, bacteria; from maize ; inserted into plasmids / plasmid used as a vector ; promoters added ; gene gun grow into adult plants ; produce seeds with, vitamin A / carotene ; in endosperm ; AVP ; e.g. ref. to Golden RiceTM

Significance of cereal crop in Human Diet:                

high, carbohydrate / starch, content ; A 70–80% source of, energy / ATP ; protein provides amino acids ; for growth ; low in fat ; A 2–4% contains essential fatty acids ; source of, vitamin B / vitamin E ; deficient in, vitamin A / vitamin D / vitamin C ; ref. to Golden Rice and vitamin A ; A ref. to other valid examples wide range / AW, of minerals ; calcium for bone development high in fibre ; for peristalsis / prevents constipation ; easily, dried / stored ; staple diet for much of the world different parts of grain have different nutrients / ref. to processing grain

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Essays

Ezz Eldin Adham

Disadvantages of using GM plants?             

GM seed could be difficult for farmers in developing countries to obtain ; high cost of buying GM seed too expensive for, people to buy might reduce efforts to relieve poverty ; may not grow well in all conditions; ref. to possible, allergic reactions in humans / toxicity of more herbicide left after use / adverse effects on the immune system ; under-developed countries becoming more dependent on other countries ; cross-pollination with, wild plants / organic crops ; new more resistant weeds / “superweeds” ; ref. to loss of traditional varieties ; loss of genetic diversity ; harm to other species ; e.g. effect on rest of food chain

How gibberellins are involved in germination of seed ?           

seed is, dormant / metabolically inactive ; water enters seed ; embryo, produces / releases, gibberellin ; gibberellin stimulates aleurone layer ; (by) affecting, gene coding / transcription of mRNA, for amylase ; to produce amylase ; amylase hydrolyses starch ; in endosperm ; maltose / glucose ; embryo uses sugars for respiration ; energy / ATP, used for growth ;

Discuss Ethical Implications of IVF:            

not natural’ / technological process ; ref. to multiple births ; (possible) birth defects ; cost to health service / only wealthy can access IVF ; some embryos discarded ; unknown effects of freezing embryos for storage ; issues regarding use of stem cells ; issues regarding selection of gender etc. ; issues regarding, single people / gay people, having children by this method ; extending age of conception of women past menopause ; issues regarding, egg donation / surrogate mothers ; ref. to psychological effects ;

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Essays

Ezz Eldin Adham

Role of hormones in maintaining human menstrual cycle:               

FSH / LH, released by anterior pituitary ; Graafian / ovarian, follicle develops / AW ; oestrogen produced by follicle (cells) ; oestrogen conc rises for first 12 days ; causes, endometrium to thicken ; A detail such as increase in blood vessels (around day 14) surge in LH / AW ; stimulates ovulation / AW ; corpus luteum develops ; produces progesterone ; causes, further development of endometrium ; if no fertilisation, secretion of FSH / LH inhibited ; corpus luteum, degenerates / AW ; progesterone conc falls ; endometrium breaks down / menstruation occurs ; negative feedback in correct context ;

Discuss ‘The organisms in kingdom protoctista can be diverse’ Similarities Differences  eukaryotic (cells) ;  single-celled or multicellular ;  nucleus / linear DNA  autotrophic or heterotrophic ;  chromosomes associated  motile or unable to move ; with histones  cell wall or no cell wall ;  golgi bodys  vacuole or no vacuole ;  80S ribosomes  different life cycles ;

Why is a species considered endangered and why ?            

fall in numbers ; danger of becoming extinct ; habitat destruction ; climate change eg: rise in temperature increase in disease ; increase in, predators / grazers ; decrease in food ; named pollutant and habitat affected ; hunting / poaching /trade in animal parts, selling rare plants increased competition ; lack of human education ; disturbance to breeding sites ;

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Essays

Ezz Eldin Adham

use of microorganisms in the extraction of metals               

ref. bioleaching ; Acidithiobacillus / A. ferrooxidans ; A Thiobacillus / T. ferrooxidans low grade ores / (mine) waste ; two metals ; e.g. copper, zinc, cobalt, uranium, lead, nickel, gold, silver insoluble ore turned into soluble products ; ore piled up ; acidic conditions created / pH low(ered) / pH 1.5 – 3 ; different bacteria at different temperatures ; chemoautotrophic ; A description oxidation (reactions) ; sulfide / S 2– to sulfate / SO4 2– ; (direct oxidation of ore) Fe 2+/ ferrous Fe 3+/ ferric ; Fe 3+ oxidise other ores ; product, drains / leaches / is washed, into pool ; metal displaced by adding scrap iron ;

Features of an organism in plant kingdom         

multicellular ; differentiated cells ; vascular tissue / xylem and phloem ; eukaryotic (cells) ; plasmodesmata most are not motile ; motile gametes only in mosses and ferns ; autotrophic nutrition / photosynthesis ; cells have: o chloroplasts ; o large / central, vacuole ; o walls made of cellulose ;

How to produce penicillin using batch fermenter        

use Penicillium (in batch fermenter) ; (main) nutrients added at start ; penicillin only produced, after growth phase / when running out of nutrients ; (penicillin) is a secondary metabolite ; fermentation is stopped ; penicillin is harvested ; fermenter is cleaned out / ref. sterility ; new culture of Penicillium is put in and started again ;

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Essays

Ezz Eldin Adham

Methods of conserving Animal species              

place in zoos ; protected against, disease / predation ; captive breeding programme ; ref. assisted reproduction / cloning / sperm banks ; released into wild ; ref. national parks / reserves ; rangers patrol parks ; human access restricted ; controlled agriculture ; controlled industry ; visitor centres / education ; habitat / breeding sites, protected ; banning sale of protected animals or their products ; banning hunting ;

Advantages of using fermenter      

Batch easy to set up culture ; can continue with minimal attention / AW ; environmental conditions easy to control ; fermenter can be used for different process afterwards ; only waste one batch if contaminated ; less chance of blockage in fermenter

Continuous

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no / less, down time / AW ; small vessels can be used ; productivity high ; cost effective ; downstream processing easier ; good for using immobilised enzymes ;

Structure of a Photosystem        

arranged in light harvesting, clusters/system ; primary pigments/chlorophyll a ; at reaction centre ; P700/P1, absorbs at 700(nm) ; P680/P11, absorbs at 680(nm) ; accessory pigments/chlorophyll b/carotenoids, surround, primary pigment centre/ chlorophyll a ; pass energy to, primary pigment/reaction centre/chlorophyll a ;

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Essays

Ezz Eldin Adham

How Photosystem functions in cyclic photophosphorylation      

P700 / PI, involved in cyclic photophosphorylation ; (light absorbed results in) electron excited/AW ; emitted from, chlorophyll/photosystem ; flows along, chain of electron carriers/ETC ; ATP synthesis ; electron returns to, P700/P1 ;

How Reduced NADP is formed      

photolysis (of water) ; releases H+ ; by, P680/PII ; e- released ; by, P700/PI ; both combine with NADP

How reduced NADP is used in light independent reaction    

reduces, GP ; A PGA to TP ; A PGAL / GALP ATP used ; NADP, regenerated/oxidised ;

Describe the structure of myelinated neuron Sensory Neuron Motor Neuron           

nucleus in cell body ; (long) dendron ; (shorter) axon ; many mitochondria (in cell body) ; many RER, (in cell body) ; synaptic knobs ; detail of synaptic knob ; (terminal) dendrites ; Schwann cells ; detail of myelin sheath ; nodes of Ranvier

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nucleus in cell body ; (short), dendrites / dendrons (axon) much longer than, dendron cell body contains, mitochondria / RER / golgi / groups of ribosomes many mitochondria at, synaptic knob / terminal branch ; synaptic vesicles ; neurotransmitter Schwann cells / myelin sheath ; nucleus in Schwann cell node of Ranvier ;

Essays

Ezz Eldin Adham

How action potential is transmitted along neuron action potential +propagation             

Na+ channels open Na+ enter cell membrane depolarised ; Na+ channels close ; K+ channels open ; K+ move out (of cell) ; inside becomes negative or membrane repolarised ; A negative figure local circuits/description ; (myelin sheath/Schwann cells) insulate axon action potential/depolarisation, only at nodes (of Ranvier)/gaps ; saltatory conduction/AW ; one-way transmission ; AVP ; e.g. hyperpolarisation/refractory period

How palisade mesophyll adaptd for photosynthesis           

closely packed to absorb (maximum) light ; vertical / at right angles to surface of leaf to reduce number of cross walls ; large vacuole pushes chloroplasts to edge of cell ; chloroplasts at edge short diffusion path for carbon dioxide ; chloroplasts at edge to absorb (maximum) light ; large number of chloroplasts to absorb (maximum) light ; cylindrical cells or air spaces to circulate gases / provide a reservoir of CO2 moist cell surfaces for diffusion of gases ; cell walls thin for (maximum) light penetration / diffusion (of gases) ; chloroplasts can move towards light to absorb (maximum) light ; chloroplasts can move away from high light intensity to avoid damage

Describe role of auxins in apical Dominance         

plant growth regulator ; synthesised in, growing tips / apical buds / meristems ; moves by diffusion from cell to cell ; also, mass flow / in phloem ; stimulates cell elongation ; R cell enlargement inhibits, side / lateral, buds / growth ; A inhibits branching plant grows, upwards / taller ; A stem elongates IAA / auxin, not solely responsible ; interaction between IAA and other plant growth regulators ;

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Essays

Ezz Eldin Adham

Describe Oxidative Phosphorylation in mitochondrion  a series of chemical reactions that occure in innermembrane of mitochondria  can be classified in to major steps: o ETC o Chemioosmosis  Starts when reduced NAD releases 2 electrons to first electron acceptor on ETC and 2 H+ ions to matrix of mitochondria regenerating NAD  electrons are transported across ETC in a redox downhill reaction from high energy level to low energy level  energy produced is used to pump H+ ions into the intermembrenal space of mitochondria  chemioosmosis: protons flow from high concentration in inter membrenal space to matrix through stalked particle down electrochemical gradient providing kinetic energy used by ATP synthase enzyme to form ATP  ADP+PiATP  At end of ETC Cytochrome oxidase enzyme is present carrying oxygen molecule which acts as final electron and proton acceptor forming H2O  Oxidative Phosphorylation produces 24-32 ATP molecules per Glucose

Endocrine glands

Nervous system

 hormones ;  chemical messengers  ductless glands / (released) into blood ;  target, organs / cells ;  ref. receptors on cell membranes ;  example of named hormone and effect ;  slow effect / ora ;  long lasting effect / ora ;  widespread effect / ora ;

 impulses / action potentials ;  along, neurones / nerve fibres ;  synapse (with target) / neuromuscular junction ;  ref. receptor / effector / sensory / motor, neurones ;

Role of Synapses          

ensure one-way transmission; receptor (proteins) only in postsynaptic, membrane / neurone ; ora vesicles only in presynaptic neurone ; ora adaptation / ACh amount reduces due to overuse of synapse ; wide range of responses ; due to interconnection of many nerve pathways ; inhibitory synapses affect other synapses ; involved in memory / learning ; due to new synapses being formed ; summation / discrimination ; 8|Page

Essays

Ezz Eldin Adham

Role of Proximal convoluted tubule                 

selective reabsorption ; pct cells have villi / microvilli / large surface area ; pct cells have many mitochondria ; Na+ leave pct cells ; by active transport ; Na+ concentration falls in (pct) cells / Na+ concentration gradient ; Na+ (diffuse) from lumen into (pct) cells ; through, transporter / carrier, proteins cotransport ; of, glucose / amino acids / vitamins / chloride ions ; (from pct cells) into intercellular fluid ; (then) diffusion into blood ; (normally) all glucose reabsorbed ; some water reabsorbed ; some urea reabsorbed ; creatinine secreted into lumen

Describe Glycolysis           

(glucose) phosphorylated by ATP ; raises energy level / overcomes activation energy ; hexose bisphosphate ; lysis / splitting, of, glucose / hexose ; R sugar splitting breaks down to two TP ; A GALP / GADP / G3P / PGAL 6C → 2 x 3C ; dehydrogenation / description ; 2 NAD reduced formed (from each TP to pyruvate formed) ; 4 ATP produced / net gain of 2 ATP ; pyruvate produced ; reduced NAD → oxidative phosphorylation / redox ;

How resting potential is maintained in an axon  axon phospholipid bilayer impermeable to K+ / Na+ ;  sodium – potassium pump ;  detail of sodium-potassium pump ; e.g. transmembrane / globular / ATP binding site  active process / ATP used / energy needed ;  3 Na+ (pumped) out / 2 K+ (pumped) in ;  K+ diffuse out / Na+ diffuse in ;  through, protein channels transport proteins ; 9|Page

Essays

Ezz Eldin Adham

 more K+ channels open than Na+ channels ;  therefore, membrane more permeable to K+ or more K+ leave than Na+ enter (axon) ;  inside relatively more negative than outside ;  –70mV  idea of leaking K+ responsible for resting potential / AW ;  electrochemical gradient ;  voltage-gated channels closed ;

How to separate chloroplast pigments by chromatography              

grind leaf with solvent ; example of solvent ; e.g. propanone leaf extract contains mixture of pigments ; ref. concentrate extract ; further detail ; e.g. pencil line drawn / extract placed on chromatography paper repetitive spotting / drying between spots paper placed (vertically) in jar of (different) solvent ; solvent rises up paper ; each pigment travels at different speed ; pigments separated as they ascend ; distance moved by each pigment is unique ; Rf value ; two dimensional chromatography ; better separation of pigments ;

Describe how the structure of chloroplast is related to it’s function ground substance / stroma ; for, light independent stage / Calvin cycle ; 3-10 μm (diameter) contains enzymes / named enzyme e.g. rubisco ; Double membrane 70s ribosomes also, sugars / lipids / starch / ribosomes / DNA ; Circular DNA internal membrane system ; for, light dependent stage ; fluid-filled sacs / thylakoids ; grana are stacks of thylakoids ; (grana) hold (photosynthetic) pigments ; (grana) have large surface area for (maximum) light absorption ; (pigments are arranged in), light harvesting clusters / photosystems ; primary pigment / reaction centre / chlorophyll a, surrounded by accessory pigments  (accessory pigments) pass energy to, primary pigment / reaction centre / chlorophyll a ;  different photosystems absorb light at different wavelengths ;  membranes hold, ATP synthase / electron carriers ;            

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Essays

Ezz Eldin Adham

 for, photophosphorylation / chemiosmosis ;

Principles of gene Therapy for treating CF             

(CF caused by) mutation ; of CFTR gene ; CF only (CFTR) protein defective ; (so) insert, normal / dominant, (CFTR) allele ; into DNA ; A chromosome in cells of respiratory system ; A named part of airway Ignore alveoli ref. to vector ; taken as spray / inhaled ; use liposomes ; use harmless virus ; not all cells take up virus ; may have unpleasant side-effects ; effects are short-lived / treatment needs repeating

Role of genetic counsellor  ref. to pedigree analysis ;  ref. to genetic screening / DNA analysis ;  detail of genetic screening ; e.g. tissue samples from adults / IVF and test embryos/ amniocentesis  explains results of tests / estimates chances of having affected child ;  (may discuss) termination ;  (may discuss) alternative, therapies / treatments ;  (may discuss) financial implications (of having affected child) ;  (may discuss) the effect of having affected child on existing siblings ;  (may discuss) ethical issues

When to go to counsellor  either has genetic disease (in family) or are carriers ;  history of recurrent miscarriages ;  older woman

Structure and role of mitochondria 0.5–1.0 μm, diameter / width ; double membrane ; inner membrane folded / cristae ; hold, stalked particles / ATP synthase / ATP synthetase ;  site of ETC ;  ref. H+ and intermembrane space ;    

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ATP production ; oxidative phosphorylation / chemiosmosis ; matrix is site of, link reaction / Krebs cycle ; enzymes in matrix ; 70S ribosomes ; (mitochondrial) DNA ;

Essays

Ezz Eldin Adham

Main Features of Bacteria (prokaryota)           

DNA not surrounded by nuclear membrane / no nucleus; (prokaryote) DNA is circular; DNA not associated with histones; A naked DNA plasmids (may) be present; no (double) membrane-bound organelles; A no, mitochondria / chloroplasts no, ER / Golgi; A ribosomes not attached to membranes ribosomes,70S / 18 nm / smaller (than eukaryotic cells); cell wall made of, peptidoglycan / murein / amino sugars / AW; (usually) unicellular; 0.5 to 5.0 μm diameter; A any value between 0.5 and 5.0 as long as μm is used AVP; (may) have, flagella / pili / capsule / slime layer

Adaptation of Rice to grow in flooded areas             

ethene (in plant); stimulates production of gibberellin; gibberellin stimulates, cell division / cell elongation / increase in stem length; leaves / flowers, above water; (so) photosynthesis can occur; (so) sexual reproduction / pollination, can occur; aerenchyma / description; assists gas diffusion (within plant); air can be trapped by specialised underwater leaves; (submerged parts of plant) carry out anaerobic respiration; produce ethanol; can tolerate high concentrations of ethanol; produce a lot of ethanol dehydrogenase;

Captive breeding Programs Advantages

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Disadvantages

can monitor health of mother; can monitor development of foetus; storage of, sperm/eggs/gametes; artificial insemination; IVF; ref. surrogate mothers; international cooperation; genetic records kept; can prevent extinction/extend range of a species/used in restoring  ecosystem;

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