B3 Essential Questions - Answers

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Tobias Harrison
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1 B3 Essential Questions - Answers M. any four from molecules / ions do not credit mineral salts move(d) through / across the cell wall / membrane against (a / the) concentration gradient by a series of chemical reactions (because) diffusion cannot occur energy (required) (supplied by) respiration oxygen required f respiration (to occur) [4] M. (a) crect names of cell components are required it = cell in sugar solution any two from: accept reverse only if clearly stated answer refers to cell in distilled water smaller vacuole smaller / less cytoplasm allow protoplasm f cytoplasm cell membrane / cytoplasm not (fully) against cell wall accept plasmolysed / flaccid / less turgid cell membrane / cytoplasm (partly) pulled away from cell wall igne reference to nucleus / water igne explanations space / liquid / sugar solution between cell membrane / cytoplasm and cell wall water passed / moved out (of cell) by osmosis / diffusion accept reverse answer if clearly refers to cell in distilled water Page

2 me concentrated (solution) outside assume reference to concentration refers to solute concentration unless answer refers to water concentration less concentrated (solution) inside lower water concentration outside accept references to hypertonic / hypotonic solutions water potential higher water concentration inside [4] M3.(a) if body temperature too high blood vessels supplying skin (capillaries) dilate / widen do not accept capillaries / veins dilate/constrict if body temperature is too low blood vessels supplying skin (capillaries) constrict / narrow do not accept idea of blood vessels moving (through skin) igne expand accept arteries / arterioles f blood vessels if no reference to skin allow blood vessels dilate and blood vessels constrict f one mark so me / less blood flows through skin (capillaries) nearer the surface of the skin must crectly relate to dilation constriction so me / less heat is lost (from the skin by radiation) must crectly relate to dilation constriction sweat released cannot evapate because of high humidity / all the water vapour in the air so less heat lost / less cooling it is evapation of sweat that cools the body [7] Page

3 M4.(a) Pancreas allow phonetic spelling any three from: max if any one process goes on in wrong gan (amino acids) broken down (amino acids) fm urea (amino acids broken down / converted urea fmed) in liver (urea / broken down amino acids) removed / filtered by kidney do not allow amino acids filtered / removed by kidney (urine / urea / broken down amino acids) sted / held in bladder do not allow amino acids sted / held in bladder 3 [4] M0. (a) (i) endocrine glands endocrine system allow a specific named gland (dissolved) in the blood(stream) plasma (i) pancreas islets of Langerhans (it insulin) lowers blood sugar level [] (by) (speeding up increasing) conversion of glucose to glycogen [] in the liver [] M7.(a) (i) A (and) speeding up increasing uptake of glucose by body cells [] (protein) molecule is large igne letters 4 [7] cannot pass through filter (protein is) too big to get through the filter = marks B is taken back into the blood B is reabsbed reabsbed completely reabsbed after filtration [8] Page 3

4 M8. any four from: use of partially permeable membrane only small molecules can pass through membrane dialysis fluid has ideal concentrations of solutes allow crect named example diffusion of waste substances out of blood accept named example eg urea waste passes from high to low concentration reference to equilibrium (between plasma & dialysis fluid) accept reference to counterflow to maintain concentration gradient 4 [7] (d) (i) any two from: kidney wks all the time dialysis wks f sht time igne enables an active life dialysis needs regular trips to hospital / regular treatment / long term treatment accept kidney transplant is one off treatment kidney maintains crect concentration all the time no build-up as between dialysis sessions no need to regulate diet crect example eg low salt / low protein / low fluid intake as with dialysis cheaper in the long term any two from: rejection / described need to use immunosuppressants need to take drugs f life allow may need later replacement susceptible to other infections hazards of operation / anaesthetic shtage of dons / match high initial cost Page 4

5 M9.(a) A ata B ventricle C atrium D vena cava igne left and right allow atria (i) (conary) artery allow arteriole stent / description accept (conary) by-pass operation allow statins allow diets low in cholesterol allow balloon (angioplasty) (iii) (stent) keeps artery open must relate to igne reference to capillary / vein (by-pass) new blood vessel / vein connecting around narrowed region; (statins / low cholesterol diet) remove some of the cholesterol blockage (balloon) widens / opens the blood vessel which allows (me) blood through allows blood to go around the blockage (c) (i) F artery accept arteriole / branch of pulmonary artery G capillary H vein H accept venule / branch of pulmonary vein; F (Pulmonary artery) has less oxygen / me carbon dioxide / me glucose / sugar accept F (Pulmonary artery) is deoxygenated accept converse f H (Pulmonary vein) It refers to F Page 5 []

6 M0. (a) fming clot at site of wound (c) size of RBC approximately same size as capillary no room f me than one cell only one can fit RBC is too big allow use of numbers do not accept capillaries are narrow (d) (i) in lungs oxygen diffuses (from the alveoli) into the blood (e) in the red blood cell, oxygen combines with haemoglobin, fming oxyhaemoglobin in tissues oxyhaemoglobin splits up, releasing oxygen, which diffuses into the cells allows cell to have me haemoglobin f oxygen transpt thin walls f sht diffusion path narrow, so have a large surface area to volume ratio M.(a) (i) diaphragm accept phonetic spelling (because) the volume (inside the jar) increases maximum two marks if no reference to crect part of model (causing) the pressure to decrease (and) air enters the balloon allow oxygen (i) (so it moves by) diffusion do not allow osmosis active transpt from a high concentration (of oxygen) to a low concentration allow down its / oxygen concentration gradient from the air to the blood (because) there is a high(er) concentration (of oxygen) in the air there is a low(er) concentration of oxygen in the blood igne reference to amount of oxygen many gill filaments must be in the crect pairs to gain marks (give a) large surface / area do not allow surface area to volume ratio thin Page 6 [0]

7 M.(a) (so) sht diffusion pathway good blood supply (to) maintain the concentration gradient water continually flows over them / continually ventilated (to) maintain the concentration gradient solution in soil is me dilute (than in root cells) concentration of water higher in the soil (than in root cells) so water moves from the dilute to the me concentrated region so water moves down (its) concentration gradient water moves from a high concentration of water to a lower concentration concentration of ions in soil less (than that in root cells) so energy needed to move ions [8] ions are moved against concentration gradient the direction of the concentration gradient must be expressed clearly accept crect reference to water potential to concentrations of water any three from: movement of water from roots / root hairs (up stem) via xylem to the leaves (water) evapates via stomata (c) (i) 0.67/0.7 accept 0.66, ⅔ 0.6 crect answer gains marks with without wking 3 if answer increct allow evidence of do not accept during the first 30 minutes f mark any one from: it was warmer it was windier it was less humid there was me water (vapour) in the leaves. Page 7

8 so there was me evapation igne water loss stomata open during first 30 minutes closed after 30 minutes () so faster (rate of) evapation in first 30 min reducing (rate of) evapation after 30 min () [] stomata / stoma / guard cells igne epidermis M3. (a) B (B has) low(est) number of stomata no stomata on upper surface only 800 (on lower surface) less transpiration / evapation / water loss owtte water (vapour) is lost via stomata only allow zero water loss if linked to no stomata on upper surface / linked to leaf B upper surface igne references to leaf surface area reduce loss / amount of water (vapour) accept converse reduced transpiration (from upper surface) do not allow no water is lost warmer above leaf accept converse wilted leaf folds over lower surface lower leaf in shade igne reference to dust less light / heat / sun on lower side [5] Page 8

9 M4.(a) (i) 76.0 / 76 crect answer with without wking gains marks allow f marks allow with extra decimal places eg f mark (c) f mark mass of fish declines (until 008) igne use of numbers allow number of fish decline (until 008) (due to an) increase in fishing / overfishing and then rises (until 00) (which could be due to) quotas / net restrictions wking allow any reasonable suggestion, such as countries swapping quotas restrictions on fishing during breeding seasons igne less fishing if no other marks awarded allow mark f a decrease in mass and an increase in mass if answer relates to sustainable fishing (fish) cannot move freely / as much (therefe) less energy loss from the fish do not allow no energy is lost igne references to less heat loss through controlling body temperature igne references to respiration (there is) me food available / better quality food / fed me often accept high-protein food (f making cells) (so) there is me energy f growth (me food) is converted to biomass [3] M5. oxygen / O accept air accept O do not allow O / O / O (iii) glucose (syrup) allow carbohydrate / sugar igne food / starch allow oxygen if oxygen / air not given in (a) Page 9

10 any two from: quicker suitable f vegetarians cheaper me efficient less land / methane igne high in protein igne sustainability unqualified igne less pollution unqualified allow less animals harmed / killed allow food chain is shter has less trophic levels allow less energy lost (from the food chain) do not allow no energy lost allow low(er) in calies (than some meat) allow low(er) in fat / healthier (than some meat) allow source of fibre / prevent constipation [5] M6. (a) 5 any four from less energy lost / used as heat lost to the atmosphere since warm indos accept temperature controlled (less energy lost) in movement since movement restricted me growth / eggs accept prevents loss of body mass gets fatter / weight gain 4 [5] M7.(a) any two from: igne CO release unqualified burning activity of microbes / microbial respiration less photosynthesis trees take in CO do not accept CO taken in f respiration less CO locked up in wood Page 0

11 CO given off by clearing machinery (i) range of different species accept idea of variety of ganisms plants animals any two from: ganisms may produce substances useful to humans do not accept if food is only example duty to preserve f future generations effect on other ganisms, eg food chain effects igne effect on human food supply loss of environmental indicats [5] M8. (a) (i) methane apply list principle allow symbols anaerobic respiration / (anaerobic) fermentation igne decay / decomposition etc (i) any two from: manure disposed of gains fertiliser (f crops) gets (free) fuel cheap supply of energy (free) cooking / heating / lighting allow converse allow not using wood / trees can sell crops at higher price in the UK allow converse arguments f Sri Lanka lower temperature not enough heat igne other fact(s) process is slower enzymes action slower igne references to efficiency / bacteria wking [6] Page

Movement of Substances in and out of Cells

Movement of Substances in and out of Cells Mark Scheme Level Subject Exam Board Unit Topic Difficulty Level Booklet GCSE Biology AQA B3 Movement of Substances in and out of Cells Gold Level Mark Scheme