Homeostasis - Blood Glucose

Question 1

Homeostasis in mammals involves physiological control systems that [1] the internal [2] within restricted limits.

Answer 1

[1] maintain

[2] environment

–

Question 2

What internal factors should be kept stable to avoid negatively affecting enzyme activity.

Answer 2

core temperature

blood pH

Question 3

Explain the importance of maintaining a stable core temperature in relation to enzyme activity.

Answer 3

To maintain optimum temperature for enzyme activity;

If too high enzymes may dentature = permanent change to tertiary structure;

Active site no longer complementary to substrate / no enzyme substrate complexes form;

Question 4

Explain the importance of maintaining a stable blood pH in relation to enzyme activity

Answer 4

to maintain optimum pH for enzyme activity;

If too low OR too high enzymes may dentature = permanent change to tertiary structure;

Active site no longer complementary to substrate / no enzyme substrate complexes form;

Question 5

Explain the importance of maintaining a stable blood glucose concentration

Answer 5

Glucose is a key respiratory substrate;
Required for both aerobic and anaerobic respiration to produce ATP;
OR

Increased levels of glucose also lowers the water potential of blood;
This increases volume of urine produced and leads to symptoms such as dehydration / thirst

Question 6

Explain the importance of maintaining a stable water potential of blood

Answer 6

To maintain blood pressure;

Avoids osmostic damage to cells e.g. swelling / lysis OR loss of water from cells;

Question 7

______________ feedback restores systems to their original level.

Answer 7

Negative

Question 8

During [1] feedback, the response involves producing more of the [2].

Answer 8

[1] positive

[2] stimululs

Question 9

exam q

Answer 9

(Insulin stimulates release of osteocalcin – no mark)

1. Osteocalcin causes more release of insulin;
2. (More) insulin causes more inactive osteocalcin to be released;

Question 10

The control of blood glucose concentrations involves which type of feedback.

Answer 10

negative

Question 11

What increases blood glucose concentration?

Answer 11

Consumption of carbohydrate-rich foods;

e.g. fruits which contain monosaccharides AND/OR
foods such as potatoes, pasta and rice which contain high concentrations of the polysaccharide starch;

Question 12

What decreases blood glucose concentration?

Answer 12

Exercise;

by increasing cellular uptake of glucose for aerobic and anaerobic respiration;

Question 13

Hormone produced in response to increases in blood glucose concentration

Answer 13

insulin

Question 14

Specialised cells of pancreas that synthesise and secrete insulin

Answer 14

Beta cells

Question 15

Insulin is a small modified protein with a specific [1] structure that is [2] to its receptor.

Answer 15

[1] tertiary

[2] complementary

Question 16

Location of insulin receptors

Answer 16

Cell surface membrane of liver and muscle cells

Question 17

Hormone that causes glycogenesis

Answer 17

insulin

Question 18

Glycogenesis

Answer 18

Conversion of (alpha) glucose into glycogen

Question 19

Decribe how insulin reduces blood glucose concentration (3)

Answer 19

1. Binds to receptors with a specific and complementary shape
2. Increases facilitated diffusion of glucose into cells by increasing the number of glucose channel proteins in the cell-surface membrane
3. Activates enzymes involved in the conversion of glucose to glycogen (glycogenesis)

Question 20

exam q

Answer 20

box 4

Question 21

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 (2 marks).

Answer 21

1. Glucose concentration in liver cells falls below that in blood (plasma) which creates / maintains glucose concentration / diffusion gradient;
2. Glucose enters cell / leaves blood by facilitated diffusion via channel protein;

Question 22

Neonatal diabetes is a disease that affects newly born children. The disease is caused by a change in the amino acid sequence of insulin.

This change prevents insulin binding to its receptor.

Explain why this change prevents insulin binding to its receptor (2 marks).

Answer 22

1. Changes tertiary structure;
2. No longer complementary to receptor

Question 23

examm q

Answer 23

1. Less/no AKT activated;
2. Fewer/no vesicles move to membrane

OR Fewer/no (channel) proteins in membrane;

3. Less/no glucose diffuses into cell (so high blood glucose);

Question 24

Binding of insulin to its receptors leads to an increase in the rate of respiration in target cells.

Explain how (2 marks).

Answer 24

1. Leads to more glucose channel proteins in cell surface membrane
2. More glucose enters the cell for respiration / glycolysis;

Question 25

Hormone produced in response to decreases in blood glucose concentration

Answer 25

glucagon

Question 26

Specialised cells of pancreas that synthesise and secrete glucagon

Answer 26

alpha cells

Question 27

Glucagon is a small modified protein with a specific [1] structure that is [2] to its receptor.

Answer 27

[1] tertiary [2] complementary

Question 28

Location of glucagon receptors

Answer 28

Cell surface membrane of liver and muscle cells

Question 29

Hormones that causes glycogenolysis

Answer 29

glucagon adrenaline

Question 30

Define glycogenolysis

Answer 30

Glycogen is broken down / hydrolysed into (alpha) glucose

Question 31

Hormone that causes gluconeogenesis

Answer 31

glucagon

Question 32

Define gluconeogenesis

Answer 32

Amino acids / fatty acids / glycerol converted into glucose

Question 33

Decribe how glucagon increases blood glucose concentration (3).

Answer 33

1. Binds to receptors on the cell-surface membrane; 2. Activates enzymes involved in the conversion of glycogen to glucose (glycogenolysis); 3. **Activates enzymes **involved in the conversion of glycerol / fatty acids / amino acids into glucose (gluconeogenesis);

Question 34

Describe the role of glucagon in gluconeogenesis (2)

Answer 34

1. Binds to receptors on target cells 2. Activates enzymes that convert; 3. Glycerol/amino acids/fatty acids into glucose;

Question 35

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 (2 marks).

Answer 35

1. Release of glucagon; (Binds to receptors on liver cells) 2. Activates enzymes; 3. Which convert glycerol / fatty acids / amino acids into glucose (gluconeogenesis)

Question 36

Adenylate cyclase converts ATP into ___________

Answer 36

cAMP

Question 37

Describe the second messenger model for glucagon / adrenaline (3)

Answer 37

1. Adrenaline OR glucagon (“1st messenger”) bind to receptors 2. Activates adenylate cyclase 3. Adenylate cyclase converts ATP into cAMP = “2nd messenger” 4. cAMP activates protein kinase which leads to conversion of glycogen into glucose (glycogenolysis) Note: 2nd messengers lead to an increase in enzyme controlled reactions, amplifying the effect of the 1st messanger binding to its receptor

Question 38

Cause of type 1 diabetes

Answer 38

No / less production of insulin by beta cells

Question 39

Treatment(s) for type 1 diabetes

Answer 39

Insulin pump / injections; Constant monitoring of blood glucose levels Improve diet e.g. less carbohydrates / high GI foods Increased exercise Transplants involving beta cells (whole pancreas OR specific tissues with beta cells)

Question 40

Cause of type 2 diabetes

Answer 40

Insulin insensitivity i.e. still produce insulin but target cells become ‘resistant’ or ‘insensitive’; Binds to receptors but does not have usual effects i.e. no addition of glucose channels, no glycogenesis; unable to lower blood glucose concentration;

Question 41

Treatment(s) for type 2 diabetes

Answer 41

Improve diet e.g. less carbohydrates / high GI foods Increased exercise Drugs that improve insulin sensitivity OR replace action of insulin

Question 42

Metformin is a drug commonly used to treat type II diabetes. Metformin’s ability to lower the blood glucose concentration involves a mechanism that increases a cell’s sensitivity to insulin. Explain how increasing a cell’s sensitivity to insulin will lower the blood glucose concentration (2 marks).

Answer 42

1. (More) insulin binds to receptors; 2. (Stimulates) uptake of glucose by channel/transport proteins OR Activates enzymes which convert glucose to glycogen;

Question 43

Metformin is a drug commonly used to treat type II diabetes. Metformin’s ability to lower the blood glucose concentration involves a mechanism that inhibits adenylate cyclase. Explain how inhibiting adenylate cyclase may help to lower the blood glucose concentration (2 marks).

Answer 43

1. Less/no ATP is converted to cAMP; 2. Less/no protein kinase activated; 3. Less/no glycogen is converted to glucose OR Less/no glycogenolysis;

Question 44

Each year, a few people with type I diabetes are given a pancreas transplant. Pancreas transplants are not used to treat people with type II diabetes. Give two reasons why pancreas transplants are not used for the treatment of type II diabetes (2 marks).

Answer 44

1. Type II produce insulin; 2. Cells / receptors less sensitive (to insulin) OR faulty (insulin) receptors; 3. Treated / controlled by diet / exercise;

Question 45

Give two reasons why a weight-loss programme could be used to treat type II diabetes but not type I diabetes.

Answer 45

1. Type l do not produce insulin OR type lI do produce insulin 2. In type II receptors/cells less sensitive/responsive to insulin OR In type II receptors/cells are insulin ‘resistant’; Accept ‘In Type II faulty/fewer receptors’.