Biology · May / June 2022 · Paper 42 · Question 2
0610
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The kidneys filter blood, separate useful molecules from excretory wastes and control the water content of the blood. Fig. 2.1 is a diagram of a kidney tubule and associated blood vessels. The arrows show the direction of blood flow. Fig. 2.2 is a drawing of a vertical section through a cell from the lining of region 2 of the tubule. R Q 1 2 3 P S Fig. 2.1 Fig. 2.2
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2(a)(i)[1]
glomerulus ;
2(a)(ii)[1]
any one from:
(vessel Q) is a (renal) artery / blood has not passed through any capillaries ;
blood (in Q) comes (straight) from, the heart / an artery / aorta ; (vessel Q) is narrow(er than R) ;
(vessel Q) has thick / elastic, walls ;
for (ultra)filtration ;
2(a)(iii)[2]
increase surface area ;
for faster / more, (re)absorption (of glucose / amino acids / minerals / ions / salts / water / vitamins / nutrients / (other relevant) substances) ;
2(b)[6]
any six from:
1
no protein in, region 1 / (Bowman’s / renal) capsule / protein only in, P / blood / plasma ;
2
all glucose / salts / urea, is filtered out, of P / blood plasma / into region 1 / (Bowman’s / renal) capsule ;
3
(re)absorption of, all glucose, by region 3 / loop of Henle / in tubule / in region 2 / after region 1 ; ora
4
(re)absorption of, some salts, by / at, region 3 / by loop of Henle / in tubule / in region 2 / after region 1 ;
5
urea concentration is, increased / higher in, region 3 / loop of Henle ; 6
idea that size of the substance determines what is filtered ; 7
glucose / salts / urea, filtered out of blood / plasma OR proteins, stay in blood / plasma / not filtered out, of blood / plasma ;
8
active transport, of glucose / salts (from tubule / back into blood / back into plasma) ;
9
movement of, glucose / salts, against a concentration gradient / through proteins (in membranes) ;
10 (active transport) uses energy from, respiration / mitochondria ; 11 (most) water (re)absorbed by osmosis (in region 3 / loop of Henle) ; 12 urea concentration increases as a result of reabsorption of water ; 13 urea / excess salt, is, an excretory substance / waste product (of metabolism) / toxic ;
14 urine contains salts and urea ;
2(c)(i)[1]
homeostasis ;
2(c)(ii)[3]
any three from:
1
(blood) glucose concentration, is low / decreases ;
2
(causing) glucagon, secretion / production ;
3
glucagon, released from / produced in, pancreas ;
4
(glucagon stimulates) breakdown of glycogen / release of glucose (into the blood) ;
5
from liver / muscle ;
6
(blood) glucose concentration, goes (back) up / returns to normal / stays within limits ;
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