12 Homeostasis Flashcards
EQ
Explain how the formation of glycogen in liver cells leads to a lowering of blood glucose concentration. (2)
(Formation of glycogen)
1. Glucose concentration in cell/liver falls;
2. Below that in blood (plasma)/ higher in blood;
3. Creates/maintains glucose
concentration/diffusion gradient;
4. Glucose enters cell/leaves blood by facilitated
diffusion/via carrier(protein)/channel (protein);
EQ
The girl who took part in this investigation was being successfully treated with insulin.
The graph shows that on some occasions, the concentration of glucose in her blood
was very high. Suggest why. (2)
Eaten;
Containing carbohydrate/sugar;
Glucose absorbed from intestine/into blood;
Long time after insulin injection/needs more insulin/has
not taken insulin;
EQ
Diabetic people who do not control their blood glucose concentration may become
unconscious and go into a coma. A doctor may inject a diabetic person who is in a
coma with glucagon. Explain how the glucagon would affect the person’s blood
glucose concentration. (2)
Glycogen to glucose/glycogenolysis;
By activating enzymes;
Gluconeogenesis;
Adrenaline binds to receptors in the plasma membranes of liver cells. Explain how this
causes the blood glucose concentration to increase. (2)
1. Adenylate cyclase activated / cAMP produced / second messenger produced; 2. Activates enzyme(s) (in cell); 3. (So) glycogenolysis/ gluconeogenesis occurs / glycogenesis inhibited;
Scientists made an artificial gene which codes for insulin. They put the gene into a
virus which was then injected into rats with type I diabetes. The virus was harmless to
the rats but carried the gene into the cells of the rats.
The treated rats produced insulin for up to 8 months and showed no side-effects. The
scientists measured the blood glucose concentrations of the rats at regular intervals.
While the rats were producing the insulin, their blood glucose concentrations were
normal.
The rats were not fed for at least 6 hours before their blood glucose concentration was
measured. Explain why. (1)
The rats used in the investigation had type I diabetes. This form of gene therapy may
be less effective in treating rats that have type II diabetes. Explain why. (1)
1. Glucose/sugar in food would affect the results; 2. Food/eating would affect blood glucose (level); 3. (Allows time for) blood glucose (level) to return to normal;
Type 2 diabetes is a failure to
respond to insulin / still produces
insulin / is not insulin-dependent;
Scientists made an artificial gene which codes for insulin. They put the gene into a
virus which was then injected into rats with type I diabetes. The virus was harmless to
the rats but carried the gene into the cells of the rats.
The treated rats produced insulin for up to 8 months and showed no side-effects. The
scientists measured the blood glucose concentrations of the rats at regular intervals.
While the rats were producing the insulin, their blood glucose concentrations were
normal.
Research workers have suggested that treating diabetes in humans by this method of
gene therapy would be better than injecting insulin. Evaluate this suggestion. (4)
1. Avoids injections / pain of injections; 2. Long(er) 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 5. Rats are different to humans; 6. May have side effects on humans; 7. Long(er) term effects (of treatment) not known / may have caused effects after 8 months; 8. (Substitute) insulin may be rejected by the body;
Suggest how each of the following responses helps to maintain core body temperature.
The change in water intake as environmental temperature increases (increase). (1)
The change in food intake as environmental temperature decreases (decrease). (1)
Explain the change in milk production as environmental temperature increases (decrease). (1)
Water intake linked to sweating /
panting;
- Food intake linked to
(increased) respiration; - Food intake linked to
heat/energy release /
maintaining body
temperature;
1. Increased sweating so less water available (for milk production); 2. Less food so less energy/nutrients available (for milk production); 3. Enzymes not working at optimum temperature;
The rectal temperatures of cows are recorded to monitor heat stress. This is a better
measurement of core body temperature than measuring the temperature of the skin.
Explain why. (2)
(Skin temperature) 1. Varies/fluctuates more / more heat lost/gained / (can be) further from core; 2. (As) more affected by environment / sweating / conduction / convection / radiation;
Explain one way in which a suit with water circulating in it at 38 ºC causes hyperthermia. (2)
Suitable reason with explanation;; Eg Suit prevents loss of sweat; So heat of evaporation not lost; OR Water (initially) at higher temperature than skin/body/blood; (So) heat gained/less lost (by conduction/convection);
Why did the rate of oxygen consumption increase as body temperature increased? (2)
- Increased temperature leads to
faster enzyme activity; - Faster rate of respiration (and
oxygen consumption);
Define ectotherms
organisms that derive heat from outside their bodies
Give 3 ways in which ectotherms regulate their body temperature (in accordance with external environment)
Exposing themselves to Sun Gain heat from ground Metabolism/respiration Taking shelter Colour variations - dark absorbs more heat, light absorbs less heat
Define endotherms
organisms that derive heat from inside their bodies
Give 4 ways in which endotherms conserve heat energy in cold environments.
Small surface area to volume ratio
Vasoconstriction - arterioles near skin surface constrict, less blood flow, less heat loss by radiation
Raising of hair - traps layer of air next to skin - insulation
Reduced sweating - decreased evaporating
Shivering - metabolic heat
Increased metabolic rate
Give 4 ways in which endotherms lose heat energy in warm environments.
Large surface area to volume ratio
Vasodilation - arterioles near skin surface dilate, more blood flow, more heat loss by radiation
Lowering of hair
Increased sweating - increased evaporation
