Homeostasis - blood glucose

Question 1

Define homeostasis (1)

Answer 1

The maintenance of a stable/constant internal environment within strict limits

Question 2

Advantages of organisms controlling their own internal environment (3)

Answer 2

More independent of their environment
Leads to greater geographical range so can colonise more habitats and ecosystems
Greater chance of finding food, shelter and mates

Question 3

Define negative feedback (2)

Answer 3

When there is an increase/decrease from the set point, the opposite effect is instigated - produces a response that returns the value to the norm

Question 4

Define positive feedback (2)

Answer 4

Occurs when a deviation from an optimum causes even greater deviation from normal

Question 5

Define thermoregulation (1)

Answer 5

Regulation of body temperature

Question 6

How do endotherms thermoregulate (1)

Answer 6

Maintain body temperature by both physiological and behavioural means

Question 7

How do ectotherms thermoregulate and give examples (4)

Answer 7

Maintain body temperature by behavioural means only
Exposing themselves to the sun
Taking shelter
Gaining warmth from the ground

Question 8

Why is it important that blood glucose concentration remains stable? (2)

Answer 8

Maintains constant blood water potential - prevent osmotic lysis of cells
Maintain constant concentration of respiratory substrates - allows organisms to maintain constant level of activity regardless of environmental conditions

Question 9

Suggest why coordinators analyse inputs from several receptors before sending an impulse to effectors (2)

Answer 9

Receptors may send conflicting information
Optimum response may require multiple types of effectors

Question 10

Why is there a time lag between hormone production and response by an effector? (3)

Answer 10

Takes time to:
Produce hormone
Transport hormone in the blood
Cause required change to the target protein

Question 11

Name the factors that affect blood glucose concentration (3)

Answer 11

Amount of carbohydrate digested from diet
Rate of glycogenolysis
Rate of gluconeogenesis

Question 12

Define glycogenesis, glycogenolysis, gluconeogenesis (3)

Answer 12

Glycogenesis - liver converts glucose into the storage polymer glycogen
Glycogenolysis - Liver hydrolyses glycogen to produce glucose
Gluconeogenesis - Liver makes glucose from organic compounds such as amino acids

Question 13

What organ controls blood glucose concentration and why? (3)

Answer 13

Pancreas
Has glucose receptors which monitor the concentration of blood glucose
Has endocrine cells called the islets of Langerhans which secrete hormone

Question 14

What are the Islets of Langerhans (1)

Answer 14

Endocrine cells in the pancreas which secrete hormones

Question 15

Name the hormone used to reduce blood glucose levels to the normal range and where is it secreted from? (2)

Answer 15

Insulin
Secreted by beta cells in the Islets of Langerhans in the pancreas

Question 16

Outline the role of insulin in reducing blood glucose levels to normal range (3)

Answer 16

Insulin binds to complementary receptors on cell surface membrane of target cells
This controls the uptake of glucose by regulating the inclusion (addition) of glucose carrier proteins in the surface membrane of target cells
Also activates enzymes that stimulate glycogenesis. This therefore reduces blood glucose concentration

Question 17

Name the hormone used to increase blood glucose levels to the normal range and where is it secreted from? (2)

Answer 17

Glucagon
Secreted by alpha cells in the Islets of Langerhans in the pancreas

Question 18

Outline the role of glucagon in increasing blood glucose levels to normal range (3)

Answer 18

Glucagon binds to complementary receptors on cell surface membrane of target cells (liver)
Activates enzymes for glycogenolysis and gluconeogenesis . This therefore increases blood glucose concentration

Question 19

Describe the role of glycogen formation and its role in lowering blood glucose levels (4)

Answer 19

Glucose concentration in cell/liver falls
Below that in blood plasma
Maintains glucose concentration
Glucose enters cell/leaves blood by facilitated diffusion/via carrier/channel proteins

Question 20

Describe how blood glucose levels can be increased using hormones (3)

Answer 20

Release of glucagon from alpha cells
Leads to formation of glucose in liver cells
From non-carbohydrates/amino acids/fatty acids

Question 21

Describe how insulin leads to a decrease in blood glucose concentration (3)

Answer 21

Increases permeability of cells to glucose
Increases glucose concentration gradient
Triggers inhibition of enzymes for glycogenolysis

Question 22

How does insulin increase permeability of cells to glucose (2)

Answer 22

Increases number of glucose carrier proteins
Triggers conformational change which opens glucose carrier proteins

Question 23

How does insulin increase glucose concentration gradient (2)

Answer 23

Activates enzymes for glycogenesis
in liver and muscles
Stimulates fat synthesis in adipose tissues

Question 24

Outline the role of adrenaline and glucagon in increasing blood glucose levels to normal range (4)

Answer 24

Both bind to specific transmembrane protein receptors on the surface of the target cell membrane (liver cell) - first messenger
Hormone-receptor complex forms
Hormone-receptor complex activates adenylate cyclase that results in the conversion of ATP into cyclic AMP - second messenger
The cAMP is the second messenger and activates protein kinase enzymes which produce a cascade of chain of reaction that catalyse the conversion of glycogen to glucose

Question 25

Explain the cause of Type 1 diabetes and how it can be controlled (3)

Answer 25

Body cannot produce insulin due to autoimmune response which attacks beta cells
Treat by injecting insulin

Question 26

Explain the cause of Type 2 diabetes and how it can be controlled (3)

Answer 26

Glycoprotein receptors are damaged or become less responsive to insulin
Strong positive correlation with poor diet/obesity
Treat by controlling diet and exercise regime

Question 27

Name some signs and symptoms of diabetes (5)

Answer 27

High thirst due to osmosis of water from cells to the blood, which has a low water potential
Larger volume of urine production due to excess water in blood
Poor vision due to osmotic loss of water from the eye lens
Tiredness due to loss of glucose in urine and poor uptake of glucose by liver and muscle cells
Muscle wasting due to gluconeogenesis caused by increased glucagon

Question 28

Why is it important that core temperatures remain stable (3)

Answer 28

Maintain stable rate of enzyme-controlled reactions and prevent damage to membranes
Too low - less KE - Less ESC
Too high - enzymes denature

Question 29

Why is it important that blood pH remains stable (2)

Answer 29

Maintain stable rate of enzyme controlled reactions
Any change away from pH alters tertiary structure