L18: Glucose homeostasis

Question 1

role of glucose

Answer 1

source of energy
required for synthetic reactions
pentose phosphate pathway

Question 2

advantages of glucose

Answer 2

water soluble
can cross BBB
oxidised anaerobically

Question 3

disadvantages of glucose

Answer 3

low yield of ATO
osmotically actice
high conc- can damage cells

Question 4

sources of blood glucose

Answer 4

• diet
• liver glycogen
• liver gluconeogenesis

Question 5

role of glycogen in the liver

Answer 5

maintain blood glucose under control of insulin and glucagon

Question 6

what is muscle sensitive to?

Answer 6

adrenaline, calcium, AMP, ATP

Question 7

Product of glycogen synthesis - ‘activation’ of glucose

Answer 7

UDP GLUCOSE

Question 8

product of glycogen breakdown

Answer 8

glucose + Pi

Question 9

2 controls in the pathway of regulation of glucose metabolism

Answer 9

Allosteric control, hormonal control

Question 10

regulation of glycogen metabolism by glucagon/ adrenaline and function of hormones

Answer 10

hormone binds cell surface receptor & activates internal signalling pathway that activates protein kinase

Question 11

gluconeogenesis

Answer 11

glucose is synthesised from non-carbs sources in the liver

Question 12

which sources can glucose be synthesised from during gluconeogenesis

Answer 12

• lactate
• glycogenic amino acids
• glycerol

Question 13

why can’t glucose be synthesised from free fatty acids

Answer 13

pyruvare dehydrogenase is irreversible

Question 14

what are the irreversible reactions in glycosis catalysed by?

Answer 14

• hexokinase/glucokinase
• phosphofructokinase
• pyruvate kinase

Question 15

what enzymes are involved in the reversal of hexokinase & phosphofructokinase reactions ?

Answer 15

glucose-6-phosphatase
fructose 1,6-biphosphatase

Question 16

2 steps of reversal of pyruvate kinase reaction

Answer 16

1. pyruvate carboxylated in pyruvate carboxylate, yielding oxaloacetate, requiring ATP
2. oxaloacetate converted into PEP by PEP carboxykinase, requiring GTP which releases CO2

Question 17

what does pyruvate carboxylase reaction allow of glucose

Answer 17

Regeneration of glucose from pyruvate

Question 18

describe the ‘cori cycle’

Answer 18

lactate from muscle is converted to glucose in the liver, and glucose is returned to muscle and used in glycolysis

Question 19

what enzyme converts lactate to pyruvate?

Answer 19

lactate dehydrogenase

Question 20

role of blood glucose maintenance

Answer 20

maintain physiological blood glucose concs needed to preserve function of brain & other tissues dependent on glucose

Question 21

role of insulin, glucagon, glucose and adrenaline in blood glucose maintenance

Answer 21

signal & coordinate activities of liver, adipose tissue, muscle tissue

Question 22

Is insulin a anabolic/catabolic hormone

Answer 22

anabolic

Question 23

is glucagon an anabolic/catabolic hormone

Answer 23

catabolic

Question 24

define anabolic pathway

Answer 24

requires energy; build up large molecules from smaller ones

Question 25

define catabolic pathway

Answer 25

releases energy; break down large molecules into smaller ones

Question 26

what does insulin promote

Answer 26

promote synthesis & storage

Question 27

what does glucagon promote?

Answer 27

promotes degradation of stored fuel

Question 28

metabolic effects of insulin in liver

Answer 28

• activates glycogen synthesis
• increase amino acid uptake
• increase fatty acid synthesis
• inhibits gluconeogenesis

Question 29

metabolic effects of insulin in muscle

Answer 29

• activates glycogen synthesis
• increase amino acid uptake

Question 30

metabolic effects of glucagon

Answer 30

• increase in blood glucose
• increase in circulating fatty acids & ketone bodies
• decrease in plasma amino acids