A-LevelBiologyHomeostasis9700/42 · May/June 2023 · Q615 Marks

(a) Fig. 6.1 is a photomicrograph of a section through a Bowman's capsule and a glomerulus. [Figure 6.1]

(a)On Fig. 6.1, use label lines and letters to label: F – the location of the glomerular filtrate P – the location of the blood plasma.[2]
(b)The glomerular filtration rate (GFR) is the rate at which fluid filters from the blood in the glomerulus into the Bowman's capsule. Fig. 6.2 shows the mean GFR values for healthy males and females of different age groups. [Figure 6.2]
(b)(i)Use Fig. 6.2 to calculate the yearly rate of decrease in mean GFR from the 20–29 age group to the 80–89 age group for females. Show your working. Give your answer to one decimal place and include units. answer [3][3]
(b)(ii)The age of a person and whether they are male or female can affect GFR. Suggest and explain other factors that can affect GFR.[3]
(c)The glomerular filtrate passes from the Bowman's capsule to the proximal convoluted tubule, where selective reabsorption takes place. Describe the process of selective reabsorption.[7]

This question uses a diagram from the original paper, which isn't shown here. Open the full paper from the past papers archive to see it.

Mark scheme

Marking points from the official mark scheme (May/June 2023). The mark or mark type is shown in brackets.

[2] F - in Bowman's capsule space / outside glomerulus capillaries, P - inside glomerulus capillaries
[3] 118-52 / 60 or 118-52 / 69 or 118-52 / 51 ; 1.1 or 1.0 or 1.3; cm³ min-1 y-1; A cm³ min-1 / year A year(s) -1 R yr or yrs or mins
[3] any three from: 1 high(er), hydrostatic / blood, pressure causes higher GFR ; ora 2 water / solute, potential gradient between glomerulus and Bowman's capsule affects GFR ; 3 kidney disease / named, decreases GFR ; e.g. damage to nephron or basement membrane / cancer 4 dehydration / lower water potential of blood, decreases GFR ; ora 5 high altitude decreases GFR ; ora 6 drugs / named, affects GFR ; e.g. diuretics / beta blockers / vasodilators / NSAIDS / ACE inhibitors 7 larger difference between afferent arteriole lumen and efferent causes higher GFR ; ora
[7] any seven from: 1 Na+, actively transported / pumped, out of cells; 2 Na+ enter blood; 3 Na+ concentration in cells decreases or Na+ concentration gradient (between pct lumen and cytoplasm) / described ; 4 Na+ enter cells from, filtrate / lumen ; 5 by facilitated diffusion ; 6 cotransport of, glucose / amino acids ; I secondary active transport 7 water potential of cells decreases ; 8 water enters cells from (filtrate / lumen) by, osmosis / down the water potential gradient ; 9 glucose / amino acids, leave cells by, (facilitated) diffusion / described ; 10 glucose / amino acids, reabsorbed or move into, tissue fluid / blood ; 11 AVP; e.g. other named ions reabsorbed

On Oracle Prep you can write or photograph your own answer and have it marked by AI against this mark scheme, with feedback on what you missed.