Paper 2 Exam Questions Flashcards
Explain, using insulin as an example, what is meant by negative feedback.
higher blood sugar level results in increased secretion of insulin
effect of insulin is to lower blood sugar
which in turn reduces rate of insulin secretion
overall result is to keep fluctuations in sugar level to a minimum
Explain how the body of a healthy person restores blood sugar level if the level drops too low.
* increased secretion of glucagons
* by pancreas
* results in increases rate of conversion of glycogen into glucose
Suggest why sugar is recommended for a ‘hypo’(low glucose levels), rather than a starchy food.
sugar soluble
therefore absorbed
quicker than starch
which has to be digested
Explain why there is too little sugar in the blood if the person exercises more than usual.
* muscles use more glucose from blood
* in respiration
* to release energy needed for exercise
Explain why there is too little sugar in the blood if too much insulin is taken.
* increase in rate of conversion
* of glucose to glycogen
* in liver
Many diabetics need to take insulin.
(i) Explain why.
* blood sugar rises because
* insufficient insulin secreted by body
A doctor suggests that person A has diabetes.
Give two pieces of evidence from the graph to support this suggestion.
- high(er) concentration (of blood glucose) (anywhere / any time)
accept 115 not 88
139 not 99
- large(r) increase (in concentration after the drink)
accept increase by 24 not 11 / their b(i)
- fast(er) / steep(er) rise
accept it takes 3 hours not 1 ¼ hours to get back to original level
accept it takes a long time to get back to normal
- slow(er) fall
Give one reason for the fall in blood glucose concentration in person B, shown in the graph.
any one from:
- insulin present / produced
accept glucagon not produced
- (used in) respiration
allow exercise
- taken into cells
allow converted to glycogen
allow taken into liver (cells) / muscle (cells)
allow produce / make energy
Some people have kidney failure.
Doctors may treat patients with kidney failure by either:
* dialysis
* a kidney transplant.
Explain two biological reasons why most doctors think that a kidney transplant is a better method of treatment than dialysis.
Do not refer to cost or convenience.
changes in concentrations / levels of substances / urea are minimised
allow no change in concentration / level of substances / urea
allow correctly named substances
1
(so) less / no chance of causing damage to body cells / tissues
allow eg less / no osmotic stress or not poisoned by urea
1
not repeatedly puncturing skin or blood not in contact with machine
allow blood does not leave the body
1
(so) less / no chance of infection or less / no chance of blood clots or no need to take anti-clotting drugs
allow less / no chance of microorganisms entering body
allow only one operation so less chance of infection for 2 marks
allow dialysis requires anti-clotting drugs and so may lose more blood if cut for 2 marks
A man is walking across a desert.
The man has used up his supply of drinking water.
Explain how the gland you named in part (a) and the kidneys reduce water loss.
high(er) concentration of blood causes (more) ADH / hormone release
allow low(er) water potential of blood causes (more) ADH / hormone release
allow alternative descriptions in terms of – eg low(er) water concentration / level or high(er) osmotic pressure or high(er) solute concentration / level
1
(and hormone / ADH causes) increased permeability of kidney tubules (to water)
allow increased permeability of collecting duct / distal convoluted tubule
1
(so) increased water reabsorption
allow more water taken back into blood
ignore reference to urine
A person with diseased kidneys may be treated by dialysis.
Explain how dialysis trexatment restores the concentrations of dissolved substances in the blood to normal levels.
use of partially permeable membrane or only small molecules can pass through membrane
- dialysis fluid has ‘ideal’ concentrations of solutes
allow correct named example
- diffusion of waste substances out of blood
accept named example – eg urea
or
waste passes from high to low concentration
- reference to equilibrium (between plasma & dialysis fluid)
accept reference to counterflow to maintain concentration gradient
