excretion

Question 1

suggest why older patients have more uncertain diagnosis’

Answer 1

uncertain diagnosis because
idea that older people may have more complex medical
problems ;

Question 2

how does the function renal dialysis differ to artifical membrane

Answer 2

it can perform , active transport / facilitated diffusion ;

Question 3

why does some dialsysis contain dextrose instead of water alone

Answer 3

1 idea that (dialysis is replicating function of kidney and)
part of kidney’s function is to remove
(excess) water from blood ;
2 (dextrose / sugar) reduces , water potential / 
(of dialysis fluid)
or
(dextrose / sugar , solution)
has a lower , water potential /  (than water) ;

3 water moves from blood (into dialysis fluid)
by osmosis
or
prevents water moving into the blood
(from dialysis fluid) by osmosis ;
4 (if it was water alone) cells would , swell / burst ;

Question 4

why does some dialysis require replacement 4 times a day versus 3 times a week

Answer 4

1 peritoneal dialysis can remove
less (named) waste
(than haemodialysis) ;
2 idea that
in haemodialysis dialysis fluid is constantly ,
refreshed / changed
(but not in peritoneal dialysis) ;
3 haemodialysis uses counter-current flow ;
4 idea that
haemodialysis maintains concentration gradient
or
in peritoneal dialysis the concentration gradient ,
reduces / is lower ;
5 (in peritoneal dialysis) the fluid reaches equilibrium
with the blood

Question 5

What condition was being tested for in this 59-year-old patient?

Answer 5

diabetes (mellitus) ;

Question 6

Why was it important that the patient had not eaten for at least eight hours before the test?

Answer 6

idea that time needed ,
to restore normal (blood) glucose concentration /
for insulin to act (fully) ;

Question 7

) The patient was sent for a further blood test, known as the haemoglobin A1C (HbA1C) test.
• Glucose combines with haemoglobin in the bloodstream to form a ‘glycosylated haemoglobin’ molecule, HbA1C.
• The concentration of HbA1C is directly proportional to the mean concentration of glucose in the blood over an eight to twelve week period.
Suggest why a single HbA1C test cannot indicate accurately the mean blood glucose concentration for a period longer than twelve weeks

Answer 7

1 HbA1C / glycosylated Hb , contained within ,
red blood cell(s) / erythrocyte(s) ;
2 red blood cells / erythrocyte(s) ,
have limited life span / live for 8 to 12 weeks
or
red blood cells / erythrocyte(s) ,
break down after , 12 weeks / 3 months ;
3 HbA1C / glycosylated Hb , broken down ,
in liver / by hepatocytes / by Kupffer cells ;

Question 8

Explain how the longer loop of Henle is able to assist the desert kangaroo rat in preventing excessive water loss.

Answer 8

1 more (sodium and chloride) ions pumped ,
out of ascending limb / into medulla ;
2 builds up greater water potential gradient ;
3 allows , reabsorption / removal , of more water from ,
collecting duct / M ;

Question 9

Discuss whether it is ethical for live donors to be used as a source of kidneys for transplantation.

Answer 9

general
1 idea that people should have a right to choose
(freely) what to do with their kidney ;
perceived donor advantages
2 idea that donors / donors’ families ,
can benefit from money raised
(by selling a kidney) ;
3 people can donate a kidney to family member ;
4 idea that people can donate without payment ;
perceived donor disadvantages
5 idea of exploiting people’s poverty ;
6 idea of exploitation of , children / minors ;
recipient issues
7 idea that people should receive transplants
irrespective of wealth ;
8 idea that it is wrong that recipients are being
charged excessively ;
9 AVP ;

Question 10

Explain the changes in fluid composition of urine passing kidney

Answer 10

1 large molecules / proteins / blood cells ,
cannot , leave blood / enter the filtrate
or
(named) small molecules can ,
leave blood / enter filtrate;
2 endothelium / fenestrations /
basement membrane ,
prevents , large molecules / erythrocytes ,
reaching , renal / Bowmans capsule ;
3 all glucose / glucose completely , reabsorbed at the ,
proximal convoluted tubule / PCT ;
4 all amino acids / amino acids completely , reabsorbed
at the , proximal convoluted tubule / PCT ;
5 (some / not all) ions , reabsorbed / move into blood
(at any part of , nephron / tubule) ;
6 urea / ion , concentration increases
(between filtrate and urine) because ,
movement (of urea / ion) into tubule /
water removed ;
QWC
endothelium / endothelial fenestration(s)
basement membrane Bowmans capsule
reabsorb (or derived term) proximal convoluted tubule

Question 11

Name the part of the adrenal gland that releases aldosterone

Answer 11

cortex ;

Question 12

explain the role of the loop of Henle in the production of urine.

Answer 12

role of loop of Henle is to
cause a decrease in water potential in /
establish water potential gradient going down , medulla ;
(as) in ascending limb active transport outwards of ,
solutes / (sodium and chloride) ions ;
(walls of) descending limb permeable to water ;
water removed from descending limb ;
water potential of tissues surrounding collecting duct is
low(er) than fluid inside it ;
water removed from , filtrate / urine (in collecting duct) ;

Question 13

Name the organ that produces urea.

Answer 13

liver

Question 14

Suggest why a high intake of protein in the diet will be likely to result in a high concentration of urea in urine.

Answer 14

1 (high intake of protein) leads to a large amount of
amino acids ;
2 (excess) amino acids cannot be stored ;
3 amino acids deaminated
or
amine group / NH2 , removed / converted to ammonia ;
4 (large amount of) ammonia enters ornithine cycle
(for conversion to urea) ;
5 increased , blood / plasma , concentration of urea
(leads to more urea in , filtrate / urine) ;
6 high concentration of , amino acids / urea , in blood
increases water absorption from urine ;

Question 15

Suggest what condition is indicated by the presence of glucose in a person’s urine.

Answer 15

diabetes mellitus

Question 16

State the substance that is being tested for in urine when a pregnancy test is carried out

Answer 16

(human) chorionic gonadotrop(h)in / hCG;

Question 17

Using your knowledge of how a test stick works, suggest how the test stick in Fig. 2.1 can be used to indicate a positive result for LH in urine.

Answer 17

1 LH binds to ,
anti-LH / its complementary (free / mobile / with dye) ,
antibodies ;
2 this (LH-anti-LH) antibody complex moves along
(test stick together with urine) ;
3 this (LH-anti-LH) antibody complex binds (only) with ,
immobilised antibodies specific to them /
lower band of immobilised antibodies ;
4 (only) control antibodies bind with,
immobilised antibodies specific to them /
upper band of immobilised antibodies ;
5 idea that binding of antibody (with dye to its
immobilised anti-antibody) produces coloured line ;
6 2 lines indicates , positive result / presence of LH
or darker line = more
LH
or
‘control’ / top , line indicates the strip is working
(correctly)
or only control’ / top line indicates no LH ;

Question 18

Explain how the glomerulus is able to perform its function.

Answer 18

1 afferent arteriole ,
has diameter greater than that of / is wider than ,
efferent arteriole ;
2 build up of / high , hydrostatic / blood , pressure ;
3 endothelium / wall , of , capillary / glomerulus ,
has , (small) pores / fenestrations ;
4 (these allow) ultrafiltration ;

Question 19

what are the specialised cells in the glomerulus called

Answer 19

podocyte(s)

Question 20

Suggest the effects of complete kidney failure on the composition of the blood.

Answer 20

if kidney cannot filter so substances remain in blood
1 increase / high , in urea ;
2 increase / high , in , (named) ions / (named) salts ;
3 increase / high , in water ;
4 AVP ;
OR
if problems cause substances to be lost indiscriminately
5 decrease / low , in , protein / blood cells ;
6 decrease / low , in , (named) ions / (named) salts ;
7 decrease / low , in , glucose / amino acids / vitamins ;
8 decrease / low , in water

Question 21

Explain the need for close matching of the donated kidney to the recipient.

Answer 21

if not closely matched
1 donated kidney will be recognised as ,
 foreign / non-self ;
2 antigens / glycoproteins , (on donated kidney)
 will be different ;
3 causing rejection ;
4 (response) by immune system ;
5 use of immuno-suppressant drugs ;
6 ref to need for suitable size in specific case
 (e.g. if recipient is a small child) ;

Question 22

Describe the features of the glomerulus and Bowman’s capsule that allow them to perform their function effectively.

Answer 22

1 ultrafiltration ;
2 afferent arteriole is wider than efferent arteriole ;
3 high blood pressure in glomerulus /
high(er) hydrostatic pressure in glomerulus
(than in Bowman’s capsule) ;
4 idea that endothelium / wall of capillary , has gaps to ,
allow / prevent , passage (of substances / cells) ;
5 idea that basement membrane stops removal of ,
large molecules / cells ;
6 podocytes / epithelial cells of Bowman’s capsule ,
have (finger-like) projections / processes ;
7 (projections) ensure gaps to allow passage
(of substances) ;

Question 23

nephritis - tissue of glomerulus and proximal convoluted tubule becomes inflamed and damaged. Suggest two differences in the composition of the urine of a person with nephritis when compared to the urine of a person with healthy kidneys.

Answer 23

1 (large) protein / amino acids , present ;
2 blood (cells) present ;
3 glucose present ;
4 more water present / more dilute ;
5 more , ions / salts / electrolytes , present ;
6 (more) vitamins present ;

Question 24

With reference to Fig. 5.2, suggest two ways in which the structure of this aquaporin prevents the passage of ions.

Answer 24

1 the ions (in solution) are
 too large to pass through the channel
 or
 the channel is too narrow for the ions (in solution)
 to pass through ;
2 shapes not compatible ;
3 idea that positive charge (in the channel) repels the
 (positively charged) ions ;

Question 25

Suggest where ADH is removed from the blood and describe what then happens to the ADH molecule.

Answer 25

how ADH is dealt with as a protein: 
1. in , liver / hepatocytes ;
2. hydrolysis / acted on by protease ;
3. deamination / amine group removed /
 formation of ammonia / formation of NH3 ;
4. ornithine cycle /
 formation of urea / formation of CO(NH2)2 ;
5. amino acids / keto acids ,
used in (named) metabolic pathway ;

how ADH or urea is dealt with as a small molecule:
6. in kidney ;
7. (ultra)filtered from blood / moves from blood into nephron ;
8. (because) small molecule ;
9. urea not (all) reabsorbed / ADH not reabsorbed /
(ADH or urea) present in urine ;
10. excreted ;

Question 26

A pregnancy testing kit contains a testing ‘stick’ to detect a hormone in the urine.Explain how the stick detects this pregnancy hormone.

Answer 26

1. (testing for) human chorionic gonadotrophin / hCG ;
2. hormone small so can pass from blood into filtrate
   (at Bowman’s capsule) ;
3. monoclonal / immobilised ,
   antibodies / immunoglobulin , on stick ;
4. antibodies attached to , marker / dye ;
5. hormone , binds / complementary , to antibody ;
6. (triggers) appearance of colour / line becomes visible ;

Question 27

Name the process by which the fluid passes from the glomerulus into the renal tubule.

Answer 27

ultrafiltration

Question 28

Name the tissue that lines the proximal convoluted tubule.

Answer 28

(cuboidal) epithelium / epithelial ;

Question 29

explain how these observed changes in concentration are brought about by the proximal convoluted tubule.

Answer 29

selective reabsorption ;
of glucose and amino acids ;
co-transport / facilitated diffusion / uptake described ;
water follows by osmosis so concentration of,
ions / nitrogenous waste / urea / remaining substances ,
increases ;