Brainscape's Knowledge GenomeTM

Browse over 1 million classes created by top students, professors, publishers, and experts.


See full index

A Level Biology Exam Questions > topic 6-c homeostasis > Flashcards

topic 6-c homeostasis Flashcards

You may prefer our related Brainscape-certified flashcards:
AP® Biology flashcards Biology 101 flashcards
1
Q

Explain how the loop of Henle maintains the gradient of ions which allows water to be reabsorbed from the filtrate in the collecting duct.

A

epithelial cell of tubule cells carry out active transport;
transport sodium ions out (of filtrate);
against concentration gradient;
into surrounding tissue / tissue fluid;
creates / maintains water potential gradient for water reabsorption

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
2
Q

Explain how ADH is involved in the control of the volume of urine produced.

A

if water potential of blood falls, detected by receptors in hypothalamus;
leads to ADH released from pituitary gland;
ADH makes cells of collecting duct / distal convoluted tubule permeable to water;
water leaves filtrate by osmosis;
smaller volume of urine produced;

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
3
Q

explain how the autonomic reflex arc is different from a simple reflex arc involving voluntary muscle

A

autonomic ganglion involved;
extra synapse outside the spinal cord;
inhibitory rather than excitatory neurone;
more neurones involved

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
4
Q

Exenatide is a drug used for treating Type 2 diabetics. Scientists investigated the effects of exenatide on insulin production.
The scientists used three groups of volunteers who were treated in the following ways.
Group 1: healthy, non-diabetics who were injected with exenatide in salt solution
Group 2: Type 2 diabetics who were injected with exenatide in salt solution
Group 3: Type 2 diabetics who were injected with salt solution.
Three hours after these injections, the scientists injected the same amount of glucose into the blood of each volunteer.
The scientists measured the rate of insulin production by each person before and after injecting the glucose.
(a) (i) Group 1 and Group 3 were control groups in this investigation.
Explain why each group was used.

The scientists measured the rates of insulin production per unit body mass.
Explain why.

Suggest how exenatide could help people with Type 2 diabetes

A

Group 1: To see ‘normal’ response / non-diabetic response / as comparison with diabetic response;
Group 3: To ensure any difference was due to exenatide/ not due to salt / as comparison to show effect of exenatide on diabetes / to ensure effect was not psychosomatic / to see placebo effect

Different mass of person → different amount insulin secreted /
larger person secretes more insulin

Increases sensitivity of pancreas cells to glucose;
Increases insulin secretion (by pancreas) / similar insulin production
as healthy / non-diabetic / Group 1;
So more stimulation of cells / of liver / of muscles;
Causes more glucose uptake (from blood) / blood glucose level
lowered / kept at normal level / can control blood glucose conc.;
Person can consume more carbohydrate / glucose / doesn’t need
special diet / will not develop symptoms of diabetes;

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
5
Q

Explain how the evidence from the graph shows one function of

(i) the kidneys
(ii) the liver

A

(i) (Kidneys) function: removes urea from blood, evidence from graph: when kidneys not working the level of (blood) urea rises;
(ii) (Liver) function: makes urea / adds urea to blood, evidence from graph: no rise in urea (when liver not working) OR when working, urea not removed, so level rises;

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
6
Q

Describe how insulin reduces the concentration of glucose in the blood.

A

insulin binds to specific receptors (on membranes);
insulin activates carrier proteins / opens channels / causes more channels to form;
insulin increases the permeability of liver / muscle cells / tissues to glucose;
insulin action results in glucose conversion to glycogen / glycogenesis;

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
7
Q

Suggest two reasons why the concentration of glucose decreased after 1 hour even though this man’s blood contained no insulin.

A

glucose is used in cell respiration / as energy source / in metabolism;
(must qualify how glucose is used)
glucose enters cells / converted to glycogen in cells;
glucose is excreted / in urine

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
8
Q

Explain the advantage of injecting both slow acting and fast acting types of insulin before breakfast for a diabetic person

A

fast acting insulin reduces blood glucose from breakfast;
slow acting insulin reduces blood glucose from other meals
before the evening meal / eliminates the need to inject at lunch

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
9
Q

a diabetic man did not eat a midday meal. Suggest one reason why his blood glucose concentration did not fall dangerously low even though he had injected himself with the mixture of insulin before breakfast.

A

glucagon is still active;
glycogen converted to glucose / glycogenolysis;
insulin injected at breakfast causes cells to take up glucose
too slowly for levels to become dangerously low;
person is not active so little glucose used in respiration;

DO NOT TALK ABT LARGE BREAKFASTS

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
10
Q

What is meant by homeostasis?

A

maintaining a constant internal environment;

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
11
Q

Giving one example, explain why homeostasis is important in mammals.

A

temperature / pH must be kept at optimum levels for enzymes as pH and temperature affect enzyme activity;

OR

water potential / blood glucose;
has an effect of osmotic / blood glucose imbalance on cells

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
12
Q

Cross-channel swimmers may suffer from muscle fatigue during which the contraction mechanism is disrupted. One factor thought to contribute to muscle fatigue is a decrease in the availability of calcium ions within muscle fibres. Explain how a decrease in the availability of calcium ions could disrupt the contraction mechanism in muscles.

A

cannot move tropomyosin from binding sites on actin;
(reject active sites)
myosin(heads) do not bind
does not activate ATPase / energy not released from ATP

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
13
Q

Which hormone causes the decrease in the water content in the distal convoluted tubule?

A

ADH

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
14
Q

Explain the drop in the amount of glucose in the PCT ( proximal convoluted tube )

A

reabsorption / passes back into blood;

by active transport

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
15
Q

Explain the temporary increase of sodium ions in the loop of Henle

A

(sodium) ions pumped out of ascending limb;
water passes out of descending limb (into high concentration in tissue fluid / interstitial fluid);
some sodium ions re-enter descending loop (by diffusion);
high concentration at base of loop / some ions diffuse out near base increasing concentration outside loop;

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
16
Q

Negative feedback in living organisms. ( essay )

A

principle of negative feedback – departure from a norm initiates changes which restore a system to the norm.
importance in homeostasis; principles of detection of change, role of receptors, corrective response, role of effectors.
regulation of blood glucose; roles of receptors in pancreas, secretion of insulin or glucagon; effect of insulin on surface membrane
receptors / carrier proteins in stimulating uptake of glucose and
glycogenesis; role of glucagon in glycogenolysis.
regulation of blood water potential; role of receptors in hypothalamus;
secretion of ADH from pituitary; effect of ADH on permeability of
d.c.t. and collecting duct; role of loop of Henle in maintaining high
ion concentration in the medulla; effect on urine concentration.
control of ventilation; stimulation of chemoreceptors in medulla;
effect on inspiration; stimulation of stretch receptors in lungs;
stimulation of expiratory cells in medulla.
control of heartbeat; roles of chemoreceptors and pressure receptors;
inhibitory and acceleratory centres in medulla; effect on SAN and rate
of heartbeat; effect of change in rate on pH / pressure of blood.
metabolic pathways; examples of build-up of a product in a metabolic
pathway resulting in inhibition of its formation.
population stability; effect of increasing competition / predation on
increasing population size and restoration of balance.
(selection – stabilising selection resulting in constancy of species)

In a good essay the description of the changes in a system should be
clearly related to the principles of negative feedback, with sufficient
detail for the relationship to be explained.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
17
Q

describe lizard in heat :D

A

moves to 40 °C side, then later to 20 °C;
gets warmer in hot side and colder in cool side;
warmer as it absorbs heat / colder as it loses heat;
by conduction / convection / radiation;

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
18
Q

Suggest the advantage to the lizard of the way they maintain their temp

A

lizard finds favourable environment;
(helps it to) maintain constant body temperature;
advantage of this, e.g. for enzyme activity

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
19
Q

Name the gland which releases ADH.

A

Pituitary

Ignore any reference to lobe / hypothalamus.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
20
Q

Explain how the structure of protein molecules allows them to form channels through which only water molecules can pass. ( nephron )

A

Each protein has a tertiary structure;
Gives specific / correct shape / size to (inside of) channel / pore;
More negative / lower WP (inside tubule cells);
accept Ψ symbol / down a WP gradient
Water enters / moves by diffusion / osmosis

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
21
Q

) Apart from water and glucose, name two substances which will be present in the glomerular filtrate.

A

urea / amino acids / fatty acids / glycerol / ion / small protein

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
22
Q

Explain how the cells of the collecting duct are able to absorb water from the filtrate through the protein channels in their plasma membranes.

A

blood pressure decreased;

(less pressure) forms less filtrate;

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
23
Q

Selective reabsorption from the glomerular filtrate occurs in the proximal convoluted tubule. Explain two ways in which the cells of the proximal convoluted tubule are adapted for reabsorption.

A

microvilli provide large surface area;
carrier proteins (in membrane) for active transport;
channel proteins for facilitated diffusion;
specific carriers for specific molecules / sodium pumps;
(many) mitochondria for active transport

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
24
Q

A person with diabetes may have a plasma glucose concentration greater than the threshold value for glucose reabsorption. Explain what causes this raised plasma glucose concentration

A

decrease in insulin production / receptors not responsive to insulin

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
25
Q

Explain the role of the loop of Henle in the absorption of water from the filtrate

A

In the ascending limb sodium(ions) actively removed;
Ascending limb impermeable to water;
In descending limb sodium(ions) diffuse in;
Descending limb water moves out / permeable to water;
Low water potential / high concentration of ions in the medulla / tissue fluid;
The longer the loop / the deeper into medulla, the lower the water potential in medulla / tissue fluid;
Water leaves collecting duct / DCT;
By osmosis / down water potential gradient;

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
26
Q

Explain the role of ADH in the production of concentrated urine.

A

When water potential of the blood too low;
Detected by receptors in the hypothalamus;
Pituitary secretes / releases (more) ADH;
ADH increases the permeability / recruitment of aquaporins / opens channels for water in the DCT / collecting duct;
More water is reabsorbed / leaves the nephron moves into the blood;
By osmosis down the water potential gradient

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
27
Q

A species of crayfish lives in fresh water. This crayfish does not have kidneys but it does have an organ which excretes nitrogenous waste and controls the amount of water in its body. [ in case it comes up in mocks / friday test ]

A

Ammonia not urea;
Ammonia (into labyrinth) enters by diffusion, not (ultra) filtration;
Reabsorption of glucose from labyrinth, not PCT / no reabsorption in PCT;
All salt reabsorbed / no salt in urine, comparison to humans;
Concentrated urine not produced;

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
28
Q

Suggest how the production of large amounts of dilute urine enables the crayfish to survive in fresh water

A

Water potential lower in cytoplasm of cells / fresh water higher water potential than cells / idea of water potential gradient;
(Removal of excess water) prevents osmotic damage;

or

All salts reabsorbed (because difficult to replace);
Take in excess water and need to remove it;

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
29
Q

Where does ultrafiltration occur?

A

Renal capsule / Bowman’s capsule / glomerulus / basement membrane;

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
30
Q

Give one component of the blood which is not normally present in the filtrate

A

blood cells / platelets / proteins / named plasma protein;

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
31
Q

Reabsorption of glucose takes place in the proximal tubule. Explain how the cells of the proximal tubule are adapted for this function.

A

(Many) mitochondria provide ATP / energy for active transport;
(Many) carrier proteins for active transport / channel proteins for facilitated diffusion;
Microvilli / brush border provide large surface area (for absorption);

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
32
Q

Name two polymers present in mammals and fish that contain nitrogen.

A

protein / haemoglobin

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
33
Q

Describe how urea is removed from the blood.

A

hydrostatic pressure / description of pressure;
causes ultrafiltration at Bowman’s capsule / glomeruli / renal capsule;
through basement membrane;
enabled by small size of urea molecule;

34
Q

Explain how urea is concentrated in the filtrate.

A 
reabsorption of water;     [water out]
by osmosis;
at the PCT / descending LoH;
at the DCT / CD;
active transport of ions / glucose creates gradient
35
Q

By what process does urea enter the fluid in the abdominal cavity from the blood?

A

by (simple) diffusion

36
Q

Explain why the fluid is changed every five hours

[ in case it comes up on the mocks you’ll recognise it when u see it ]

Fluid of the composition shown in the table is used instead of distilled water

A

to maintain concentration gradients

ions, glucose and amino acids would diffuse into the dialysate;
because of their concentration gradients;
Causing deficiency in these substances

37
Q

what is secreted when a fall in blood glucose is detected

A

glUcagOn

38
Q

when glucagon is secreted, glycogen breaks down in what organ

A

liver

39
Q

Explain why the events shown in the diagram can be described as an example of negative feedback

A

A change to the normal level initiates a response which

reduces the effect / reverses / acts against the change;

40
Q

Describe and explain the effect of ADH on the volume and concentration of urine produced by the kidney

A

Lower volume AND higher concentration;
ADH increases water re-absorption (in 2nd convoluted tubule / collecting duct) / increases water permeability / adds aqua porous;

Evidence: observe increasing concentration (of dissolved substances) (in 2nd convoluted tubule / collecting duct) / concentration increased c.f. ADH absent

41
Q

Glomerulosclerosis is a disease in which the glomeruli of the kidney are damaged. Explain why protein is not normally present in the urine of a healthy person but may be present in the urine of a person with glomerulosclerosis.

A

Protein molecule too large (to cross filter in healthy person);
Protein can cross if filter is damaged / protein from damaged glomerulus enters filtrate

42
Q

Many diabetics require regular injections of insulin. Describe how bacteria can be genetically modified to produce human insulin

A
  1. Use m-RNA + reverse transcriptase to produce gene / (c)-DNA;
  2. Restriction enzyme to cut open plasmid;
  3. Add sticky ends (to insulin gene and to plasmid);

OR
Allow:
1. Cut out insulin gene / cut open plasmid with restriction enzyme;
2. Use same restriction enzyme on second DNA;
3. Reference to (complementary) sticky ends;
4. Use ligase to join 2 DNA molecules;
5. Modified plasmid taken up by bacteria

43
Q

Describe what is meant by negative feedback.

A

where a change triggers a response which reduces the effect of a change

44
Q

Water is removed from the body via the kidneys. Give two other ways in which water is removed from the body.

A

sweating, breathing, defaecating

45
Q

Name the part of the brain which acts as the coordinator in the control of water balance.

A

hypothalamus

46
Q

From which gland is ADH released

A

pituitary

47
Q

to explain how ADH increases the movement of water from the lumen of the collecting duct into the blood

A

ADH causes vesicles containing aquaporins / aquaporins to be inserted into membrane / collecting duct wall / plasma;
water enters cell through aquaporins;
by osmosis / diffusion / down a water potential gradient;
(from cell) to capillary;
via interstitial fluid;

48
Q

The gene for the ADH receptor proteins is found on the X chromosome. One allele of this gene causes a non-functioning receptor protein to be made. This allele is recessive and is one cause of the condition called diabetes insipidus.
What would be the most obvious symtom of diabetes insipidus?

A

excessive urination / drinking / diluted urine / thirst

49
Q

The gene for the ADH receptor proteins is found on the X chromosome. One allele of this gene causes a non-functioning receptor protein to be made. This allele is recessive and is one cause of the condition called diabetes insipidus.
Suggest why diabetes insipidus is more common in males

A

because males only have one X chromosome / do not have Y chromosome;
a single copy of the recessive allele will be expressed

50
Q

A recessive allele which has harmful effects is able to reach a higher frequency in a population than a harmful dominant allele. Explain how.

A

recessive alleles can be carried by individuals without showing effects / dominant allele always expressed;
organism that are carriers more likely to reproduce / affected organism less likely to reproduce;
therefore recessive alleles are more likely to be passed on / dominant alleles less likely to be passed on

51
Q

The kangaroo rat is a small desert mammal. It takes in very little water in its food and it rarely drinks. Its core body temperature is 38 °C.
The kangaroo rat takes in some water by feeding and drinking. Describe another method by which the kangaroo rat could obtain water.

A

metabolic water / from respiration;

aerobic / use of oxygen

52
Q

Describe how urea is removed from the blood.

A 
Hydrostatic pressure 
Causes ultrafiltration 
 at Bowman’s capsule / glomeruli / renal capsule;
Through basement membrane;
Enabled by small size urea molecule
53
Q

Describe how ultrafiltration produces glomerular filtrate

A
  1. Blood pressure / hydrostatic pressure;
  2. Small molecules / named example;
  3. Pass through basement membrane / basement membrane acts as filter;
  4. Protein too large to go through / large so stays behind;
  5. Presence of pores in capillaries / presence of podocytes;
54
Q

Some people who have diabetes do not secrete insulin. Explain how a lack of insulin affects reabsorption of glucose in the kidneys of a person who does not secrete insulin.

A
  1. High concentration of glucose in blood;
  2. High concentration in tubule / in filtrate;
  3. Reabsorbed by facilitated diffusion / active transport;
  4. Requires proteins / carriers;
  5. These are working at maximum rate / are saturated;
  6. Not all glucose is reabsorbed / some is lost in urine;
55
Q

Some desert mammals have long loops of Henle and secrete large amounts of antidiuretic hormone (ADH). Explain how these two features are adaptations to living in desert conditions

A
  1. More water (from filtrate) reabsorbed / returned to blood / less lost in urine;
  2. By osmosis;
  3. From collecting duct / from end of second convoluted tubule;
  4. Due to longer loop of Henle;

For loop of Henle, maximum 2 marks:

  1. Sodium / chloride ions absorbed from filtrate in ascending limb;
  2. Gradient established in medulla / concentration of ions increases down medulla;
  3. Acts on collecting duct / distal convoluted tubule / second convoluted tubule;
  4. Makes cells more permeable / inserts aquaporins in plasma membranes;
56
Q

a girl who took part in this investigation was being successfully treated with insulin. on some occasions, the concentration of glucose in her blood was very high. Suggest why

A

Eaten;
food Containing carbohydrate

Glucose absorbed from intestine / into blood;

Long time after insulin injection / needs more insulin / has not taken insulin;

Does not convert glucose to glycogen / glucose not taken up from blood;

57
Q

Use the graph to evaluate the use of the urine test as a measure of blood glucose concentration

in case it comes up on mocks

A

Shows positive correlation / directly proportional;
A range of results for a particular value / values (for different colours) overlap;
Urine test only an arbitrary scale / not directly related to concentration / colour is subjective / few colour values;

58
Q

Sucrase is an enzyme. It hydrolyses sucrose during digestion. Name the products of this reaction.

A

Glucose;

Fructose

59
Q

Sucrase does not hydrolyse lactose. Use your knowledge of the way in which enzymes work to explain why

A

Lactose has a different shape / structure;

Does not fit / bind to active site of enzyme / sucrase;

60
Q

A glucose biosensor is an instrument used to measure glucose concentration. It contains an enzyme called glucose oxidase

A glucose biosensor detects only glucose. Use your knowledge of the way in which enzymes work to explain why.

A

Enzyme / active site has a (specific) tertiary structure;
Only glucose has correct shape / is complementary / will bind / fit to active site;
(Forming) enzyme-substrate complex;

61
Q

It is better to use a biosensor than the Benedict’s test to measure the concentration of glucose in a sample of blood. Suggest two reasons why

A

(Only detects glucose whereas) Benedict’s detects (all) reducing sugars / named examples;
Provides a reading / is quantitative / Benedict’s only provides a colour / doesn’t measure concentration / is qualitative / semiquantitative;
Is more sensitive / detects low concentration;
Red colour / colour of blood masks result;
Can monitor blood glucose concentration continuously;

62
Q

Diabetes mellitus is a disease that can lead to an increase in blood glucose concentration. Some diabetics need insulin injections. Insulin is a protein so it cannot be taken orally. Suggest why insulin cannot be taken orally

A

Broken down by enzymes / digested / denatured (by pH) too large to be absorbed;

63
Q

A drug company produced a new type of insulin. Scientists from the company carried out a trial in which they gave this new type of insulin to rats. They reported that the results of this trial on rats were positive. A newspaper stated that diabetics would benefit from this new drug. Suggest two reasons why this statement should be viewed with caution

A

Study not carried out on humans / only carried out on rats;
Long-term / side effects not known;
Scientists have vested interest;
Study should be repeated / further studies / sample size not known;

64
Q

A laboratory worker suspected she had type 2 diabetes but did not have a glucometer.
Instead she added a drop of her blood to a test strip and used a colour chart to estimate her blood glucose concentration as 140 mg 100 cm–3.

A
  1. Diabetics have (blood glucose) concentration greater than 140 mg cm−3 / than her estimate / estimate suggests she is pre-diabetic;
  2. Colour change is subjective / blood on test strip masks colour change;
  3. Concentration given as a range / estimation is not reliable;
  4. May not have fasted;
  5. May not have had a drink with 75 g glucose;
  6. Only one test carried out;
65
Q

Adrenaline or insulin binds to receptors in the plasma membranes of liver cells. Explain how this causes the blood glucose concentration to increase.

A 
Adenylate cyclase activated / cAMP produced / second messenger produced;
Activates enzyme(s) (in cell so) glycogenolysis / gluconeogenesis occurs / glycogenesis inhibited;
66
Q

The rats were not fed for at least 6 hours before their blood glucose concentration was measured. Explain why

A

Glucose / sugar in food would affect the results;
Accept references to starch / carbohydrate

Or

  Food / eating would affect blood glucose (level); Or

  (Allows time for) blood glucose (level) to return to normal;
67
Q

The rats used in an investigation had type I diabetes. This form of gene therapy may be less effective in treating rats that have type II diabetes. Explain why.

A

Type 2 diabetes is a failure to respond to insulin / still produces insulin / is not insulin-dependent;

68
Q

Research workers have suggested that treating diabetes in humans by this method of gene therapy would be better than injecting insulin. Evaluate this suggestion.

A

(For) – 3 max

  1. Avoids injections / pain of injections;
  2. Long lasting / permanent / (new) cells will contain / express gene;
  3. Less need to measure blood sugar / avoids the highs and lows in blood sugar;
  4. Less restriction on diet;

(Against) – 3 max

  1. Rats are different to humans;
  2. May have side effects on humans;
  3. Accept: virus may be harmful / disrupt genes / cause cancer
  4. Long(er) term effects (of treatment) not known / may have caused effects after 8 months;
  5. (Substitute) insulin may be rejected by the body;
69
Q

When insulin binds to receptors on liver cells, it leads to the formation of glycogen from glucose. This lowers the concentration of glucose in liver cells.
Explain how the formation of glycogen in liver cells leads to a lowering of blood glucose concentration

A
  1. Glucose concentration in cell / liver falls below that in blood (plasma) which creates / maintains glucose concentration / diffusion gradient;
  2. Glucose enters cell / leaves blood by facilitated diffusion / via carrier(protein) / channel (protein);
    Not just diffusion
70
Q

Before the glucometer was available, diabetics used test strips to measure the concentration of glucose in their urine as a means of measuring their blood glucose concentration.
Give two reasons why this method of testing urine would not give an accurate measurement of blood glucose concentration.

A
  1. Concentration is given as a range (for each colour) / measurement is not precise;
  2. Only measures glucose concentration above normal / above 170 (mg 100 cm−3) (in blood);
  3. 170 (mg 100 cm−3) is an average figure / concentration for loss to urine varies (between people);
  4. Difficult to match colour against chart / colour match is subjective;
71
Q

Identify all the substances located at where blood is dropped on a glucometer on the test strip before a drop of blood is added

A

Glucose oxidase and peroxidase;

Dye (with colour A);

72
Q

adding an inhibitor of amylase to the food will lead to a lower blood glucose concentration.

Use your knowledge of digestion to suggest how the addition of the inhibitor could lead to a lower blood glucose concentration.

A
  1. Fewer E-S complexes formed;
  2. (With inhibitor) less / no starch digested to maltose ;
    Require knowledge that maltose comes from starch
  3. (So) less / no glucose from maltose;
    Require knowledge that glucose comes from maltose
    Accept no glucose
  4. (So) less absorption of glucose (from gut
73
Q

Scientists investigated the control of blood glucose concentration in mice. They kept a group of normal mice without food for 48 hours. After 48 hours, the blood glucose concentrations of the mice were the same as at the start of the experiment.

 Explain how the normal mice prevented their blood glucose concentration falling when they had not eaten for 48 hours.
A
  1. Release of glucagon;
  2. Leads to formation of glucose in liver (cells);
    Reject: glucagon breaks down glycogen, or any other biological molecule
  3. From non-carbohydrates / amino acids / fatty acids.
    Accept: gluconeogenesis / references to glycogen as source of glucose
74
Q

Give the location of osmoreceptors in the body of a mammal

A

Hypothalamus.

75
Q

When a person is dehydrated, the cell volume of an osmoreceptor decreases.
Explain why

A
  1. Water potential of blood will decrease;

2. Water moves from osmoreceptor into blood by osmosis.

76
Q

Stimulation of osmoreceptors can lead to secretion of the hormone ADH. Describe and explain how the secretion of ADH affects urine produced by the kidneys

A
  1. Permeability of membrane / cells (to water) is increased;
  2. More water absorbed from / leaves distal tubule / collecting duct;
  3. Smaller volume of urine;
  4. Urine becomes more concentrated
77
Q

Creatinine is a breakdown product of creatine found in muscle tissues. Apart from age and gender, give two factors that could affect the concentration of creatinine in the blood.

A

Muscle / body mass
Ethnicity
Exercise
Kidney disease

78
Q

Give two ways in which people with type 1 diabetes control their blood glucose concentration.

A

Treat with insulin (injection/infusion);

(Control) diet/control sugar intake

79
Q

Diabetes can damage the nervous system. The response of the rats with diabetes is different from the response of the healthy rats. Use your knowledge of the control of heart rate by the nervous system to suggest an explanation for these results

A
  1. Damage to autonomic (nervous) system in diabetic rats;
  2. (Could be) pressure receptors/baroreceptors (in arteries/aorta/carotid body) don’t work as well;
  3. Damage to medulla
80
Q

The regulation of the formation of helper T cells by interferon gamma is an example of positive feedback.
Explain why it is an example of positive feedback

A
  1. Causes more helper T cells to form;

2. (So) more interferon (gamma) production (by helper T cells);

81
Q

Synapses are unidirectional. Explain how acetylcholine contributes to a synapse being unidirectional

A
  1. (Acetylcholine) released from / in presynaptic side;

2. Receptors in postsynaptic (side) / binds on postsynaptic (side);

A Level Biology Exam Questions (8 decks)

Brainscape helps you reach your goals faster, through stronger study habits.
© 2024 Bold Learning Solutions. Terms and Conditions