NGT persons always tend to be below 9 mmol/L even after oral intake of glucose
.Persons with IGT's glucose levels will generally be above 9 mmol/L after oral
intake of glucose.
Persons with IGT2 tend to have a higher plasma glucose level than persons with
IGT1 over the same period of time.
Glucagon and insulin work in a negative feedback system to control blood glucose
concentration.
Insulin is responsible for activating the GLUT4 transport protein, which leaves the
cytoplasm to travel to the cell surface membrane. This allows decrease of blood
glucose concentration by allowing intake of glucose into body cells.
Glucagon increases the amount of glucose in the blood by converting stored glycogen
in the liver into glucose. It can also synthesize new glucose from fats and proteins in a
process called gluconeogenesis.
Insulin is secreted by beta cells in the pancreas and glucagon is secreted by alpha
cells.
The presence of glucose in urine indicates the likelihood of diabetes or damage
to the kidneys. Glucose is usually selectively reabsorbed by the proximal convoluted
tubule.
Ethylene is gaseous, meaning that it diffuses easily through the air to access fruits
easily and allow uniform ripening.
It has a low melting point and high boiling point, so it remains a gas even at low temperatures.
The particles move rapidly and spread over large areas.
Ethylene allows fruits to ripen, leading them to have brighter colours, be sweeter in taste
(increase in edibility) and releases aromatic compounds for a pleasant smell. All of this
increases the fruit's commercial worth.
5.
(a)
An athlete loses a considerable amount of water by sweating during training, after which he
has a high intake of fluids. Explain the mechanism by which water balance is maintained
in this athlete’s body.
..............................................................................................................................................
1. Osmoreceptors (sensory neurones) in the hypothalamus detect water potential of blood.
..............................................................................................................................................
2. If the blood does not contain enough water, osmoreceptors secretes more ADH into the blood
..............................................................................................................................................
from the posterior pituitary gland.
..............................................................................................................................................
3. ADH increases the permeability for water in the DCT and collecting ducts in the nephron.
..............................................................................................................................................
It does this by moving aquaporins to membranes.
..............................................................................................................................................
4. As a result, more water is reabsorbed into the blood from collecting ducts. The urine is more
..............................................................................................................................................
concentrated with urea and salts (darker, yellow colour).
5. If the blood has too much water, less ADH is secreted (or ADH is suppressed).
..............................................................................................................................................
6. As a result, the collecting duct cells become less permeable to water.
..............................................................................................................................................
7. Urine becomes diluted (clearer) and a larger volume is excreted, thus reducing water
..............................................................................................................................................
content in blood.
..............................................................................................................................................
8. This process is known as osmoregulation and helps maintain the water potential of the
..............................................................................................................................................
blood due to negative feedback mechanisms.
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[8 marks]
02207020/CAPE 2018
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DO NOT WRITE IN THIS AREA DO NOT WRITE IN THIS AREA DO NOT WRITE IN THIS AREA - 18 -
r
2.
-l
-8(a)
Figure 3 is a stained section through the medulla of the kidney showing cross sections
through some functional regions of the nephron and associated ducts.
I
III
II
Figure 3. Section through the medulla of the kidney
Source:http://apbrwww5.apsu.edu/thompsonj/Anatomyok20&o%20Physiolog,'/2020/2020%
2 0 Exam%o2 0 Rev i ew s/ Exam% 2 0 4 /col le c t i ngo/o2 0 duc t0 2. bmp
(i)
Identify the cross sections labelled I and II and for EACH, state ONE observable
feature which justifies the given identification.
I
II
Thick region of loop of Henle. Cell to cell borders are difficult to distinguish.
Collecting duct. Wider cross section and cells bulge towards lumen.
Cell to cell borders are easier to distinguish.
[4 marks]
(ii)
Comment on the main function of the region labelled III
(III is the thin section of the Loop of Henle)
Creates a high solute concentration of sodium and chloride ions, which establishes an
osmotic gradient to reabsorb water.
[1 mark]
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02207020|CAPE.2017
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0220702008
J
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-19(b)
-|
Outline the general principles of hormonal action in animals and discuss the role of
hormones in the regulation of blood glucose concentration.
Hormones are chemical messengers secreted from endocrine glands into the bloodstream.
They are transported to target cells to allow performance of specific actions, and usually
have a role in homeostasis, e.g. insulin and ADH.
REGULATION OF BLOOD GLUCOSE CONCENTRATION
- Insulin and glucagon are the two hormones involved in blood glucose regulation.
- When blood glucose level increases above the norm, the beta cells in the pancreas
secrete insulin into the blood.
- Insulin activates enzymes in the liver to facilitate uptake of glucose from the blood.
It also activates enzymes necessary for the synthesis of glycogen from glucose.
- When blood glucose level falls below the norm, the alpha cells in the pancreas
release glucagon into the blood.
- Glucagon binds to receptors on liver cells and stimulates breakdown of glycogen
to glucose, as well as fats and proteins into glucose to be released into the blood.
[7 marksl
Total 15 marks
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02207020/cAPF.2017
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0220702019
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(b)
Figure 3 is a photomicrograph of a section through the medulla ofthe kidney of a mammal
A
Loop of Henle
(thin section)
B
Loop of Henle
(thick region)
c
Collecting duct
Figure 3. Section of a mammalian kidney
Source: http://quizlet.com/535 t 362/urinary-ond-reproductive-histologrt-fiash-cards/
(i)
Identify the regions of the nephron labelled A, B and C.
A
B
Loop of Henle (thin region)
Loop of Henle (thick region)
Collecting duct
C:
[3 marksl
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022070201cAP8 2016
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0220702010
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(ii)
Outline the process of urea formation and suggest a reason why urea in the form
of nitrogenous waste is produced in mammals.
Deamination of amino acids occur in the liver to form ammonia.
The ammonia is then combined with carbon dioxide in the liver to form urea.
The reasons for converting ammonia to urea is because of its lowered
toxicity. Urea also requires less water for elimination (via urine) than ammonia.
[4 marksl
Total 15 marks
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02207020/CAPE 2016
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0220702011
J
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-17(a)
Define the term 'hormone'. With reference to insulin and glucagon, explain how hormones
function in the coordination of activities in mammals.
A hormone is a molecule or compound that is made in the body, released by
endocrine glands (into the bloodstream) to target cells to produce a specific response.
INSULIN - If blood glucose level increases beyond set point, the islets of Langerhans in
the pancreas signal for beta cells to secrete more insulin. Insulin targets cells, allowing
uptake of glucose from blood.
GLUCAGON - If blood glucose level decreases beyond set point, alpha cells in pancreas
detect the change and facilitate glucagon secretion. This increases the rate of glycogen
breakdown to form glucose, or synthesis of glucose from amino acids.
[8 marks]
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02207020tcAP8 2016
L
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0220702017
I
- 16 5.
(a)
(b)
(i)
Give a brief explanation of the concept of ‘homeostasis’.
[2 marks]
(ii)
A homeostatic system consists of at least three key components: a receptor, a set point
and an effector. Discuss the roles of these THREE key components in a homeostatic
system.
[6 marks]
Collecting ducts play an important role in kidney function and the activity of these ducts is
under hormonal control.
(i)
Briefly describe the structure of a collecting duct and comment on its role in kidney
function.
[4 marks]
(ii)
Explain how the antidiuretic hormone, ADH, regulates the function of the collecting
ducts.
[3 marks]
Total 15 marks
Write the answer to Question 5 here.
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02207020/CAPE 2013
- 17 Write the answer to Question 5 here.
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02207020/CAPE 2013
- 18 Write the answer to Question 5 here.
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02207020/CAPE 2013
-17f,.
(a)
(b)
t2.oz.o2-
(i)
Explain what is meant by the term 'synaptic transmission'.
(ii)
Outline the MAIN steps in the chemical transmission of an action potential across a
synapse. (No diagrams required.)
[5 marks]
(D
Outline the TWO MAJOR functions of the human kidnev.
(ii)
The kidney accomplishes its functions by three separate but related processes:
ultrafiltration, selective re-absorption and secretion. Discuss the significance of
EACH of these processes in relation to the functions stated in (b) (i) above.
[6 marks]
[2 marks]
[2 marks]
Total 15 marks
Write the answer to Question 5 here.
Osmoregulation:
- Maintenance of water and solute solutes in optimal proportions
- Conservation of water
Excretion:
Removal of unwanted and excess waste products of metabolism, e.g., toxins and hormones.
Ultrafiltration: The blood is filtered at high pressure - production of filtrate from blood for
processing for excretion / osmoregulation .
Selective Reabsorption: Useful parts of the filtrate are returned to the blood. - osmoregulation.
Secretion: Further substances not required by the body are secreted into the filtrate. e.g., ions, drugs,
hormones, urea - excretion.
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022070201cAP8 2012
- 7 (b)
A nephron is a tubule which is divided into distinct regions, each of which serves a specific
function. Figure 4 is a diagrammatic representation of the loop of Henlé of a nephron.
Figure 4. Diagrammatic representation of the loop of Henlé
(i)
Using arrows labelled A, B, and C, indicate on Figure 4 where
a)
A – water leaves the loop of Henlé by osmosis
b)
B – sodium ions and chloride ions leave the loop of Henlé by diffusion
c)
C – sodium ions and chloride ions leave the loop of Henlé by active transport.
[3 marks]
(ii)
Account for the large number of mitochondria in the cells in the region of the loop of
Henlé that is labelled C.
Sodium ions and chloride ions leave the loop of Henlé by active transport
___________________________________________________________________
which requires energy ATP
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[1 mark]
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02207020/CAPE/2011
- 8 (iii)
How does the concentration of the urine of small mammals inhabiting a desert differ
from that of small mammals inhabiting a moist tropical forest? Suggest ONE structural
modification of the loop of Henlé that may be responsible for this difference.
___________________________________________________________________
___________________________________________________________________
Inhabitants of the desert would produce more concentrated urine.
___________________________________________________________________
Long loop of Henle
___________________________________________________________________
[2 marks]
(iv)
Protein and glucose were found to be present in a sample of human urine. Identify
the regions of the nephron which may NOT have been functioning as they should,
therefore resulting in the presence of these substances in the urine.
Protein: Bowman's Capsule
___________________________________________________________________
Glucose: Proximal Convoluted Tubule (PCT)
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[2 marks]
Total 15 marks
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02207020/CAPE/2011