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
Control of body temperature:
Too hot? (3)
- Thermoreceptor detects rise in temperature
- Increases frequency of nerve impulses to the hypothalamus/thermoregulatory centre (heat loss centre)
- Stimulates heat loss mechanisms
Control of body temperature:
Too cold? (3)
- Thermoreceptor detects fall in temperature
- Increases frequency of nerve impulses to the hypothalamus/thermoregulatory centre (heat gain centre)
- Stimulates heat conservation mechanisms
Where are hormones produced?
Endocrine glands
Describe the second messenger model (3)
- Hormone (first messenger) binds to specific receptors on membrane of target cells forming hormone-receptor complex.
- Enzyme inside cell activated producing chemical (second messenger).
- Produces response.
Pancreas:
What does it produce? (2)
What are islets of Langerhans?
Difference between alpha and beta cells? (4)
digestive enzymes (amylase, protease, lipase) hormones insulin and glucagon
groups of pancreatic cells that produce hormones
alpha - glucagon, lager
beta - insulin, smaller
Sources of glucose? (3)
- Diet - from breakdown of carbohydrates
- Glycogenolysis = breakdown of glycogen to glucose
- Glycogen stored in liver/muscle cells.
- Glycogenesis = excess glucose converted into glycogen. - Gluconeogenesis = production of new glucose
Beta cells and insulin:
How do beta cells/insulin lower blood glucose? (3)
This results in? (3)
by activation of?
Once lowered?
- Beta cells detect rise in blood glucose concentration
- Secrete insulin into blood plasma
- Binds to glycoprotein receptors on membranes of body cells
Change in tertiary structure of/increase in number of glucose protein channels - more absorbed into cells
Increase in rate of glycogenesis - more converted to glycogen
Increase in respiratory rate - more glucose taken from blood
enzymes
beta cells reduce insulin secretion (=negative feedback)
Alpha cells and glucagon:
How do alpha cells/glucagon increase blood glucose? (3)
This results in? (2)
by activation of?
Once increased?
Alpha cells detect fall in blood glucose concentration
Secrete glucagon into blood plasma
Binds to receptors on membranes of liver cells
Increase in rate of glycogenolysis
Increase in rate of gluconeogenesis
enzymes
alpha cells reduce glucagon secretion (=negative feedback)
Role of adrenaline in regulating blood glucose level:
Produced by?
How does adrenaline increase blood glucose? (2)
by activation of?
Adrenal glands
Increase in rate of glycogenolysis.
Decreases rate of glycogenesis
enzymes
Type 1 (insulin dependent) diabetes
problem?
due to?
treatment?
Type 2 (insulin idependent) diabetes
problem?
due to?
treatment?
Unable to produce insulin Due to autoimmune response Insulin injections (oral would be digested)
Glycoprotein receptors lose responsiveness to insulin
Due to obesity
Control of carbohydrate in diet and exercise
Define homeostasis
the maintenance of a more or less constant internal environment.
Why is homeostasis important for?
Enzymes? (2)
Water potential? (2)
Independence?
Sensitive to change in pH/temp
Denature if not at optimum
Constant blood glucose level = constant water potential
No osmosis in/out of cell
Makes organism more independent of external environment, greater geographical range, greater chance of survival.
Control mechanisms:
Define set point
Order? (6)
The desired level, or norm, at which the system operates.
Input, receptor, controller, effector, output, feedback loop
