metabolism of feasting and fasting

Question 1

what does skeletal muscle allow?

Answer 1

direct motion
adipose tissue stored and releases energy in the form of fat which serve as fuel throughout the body

Question 2

what role does the liver play

Answer 2

processing and distributing role in metabolism and furnishes all other organs and tissues with and appropriate mix of nutrients via the bloodstream

Question 3

the neurons of the adult human brain use what as fuel?

Answer 3

glucose and oxygen

Question 4

what happens in the fasting state

Answer 4

glucose from glycogen and muscle amino acid degeneration
glucose oxidation for energy
can form lactate to the liver for gluconeogenesis

Question 5

what are the 3 mechanism of metabolic control

Answer 5

intra-cellular mechanisms
availability of substrates
inhibition by end-product

Question 6

name the 2 inter-cellular (hormonal) mechanisms

Answer 6

changed activity of existing enzyme-fast acting
changed amount of enzyme-slow acting

Question 7

name the 3 glycolytic enzymes catalyse spontaneous reactions

Answer 7

hexokinase
phosphofructokinase
pyruvate kinase

Question 8

how is hexokinase controlled

Answer 8

by the concentration of the inhibitory reaction product glucose-6-phosphate

Question 9

what is glucokinase
when is it activated

Answer 9

a variant of hexokinase found in the liver, has a high Km for glucose
only be activated at high levels of glucose
low affinity of glucokinase for glucose in the liver gives the brain and muscles first call on glucose when the supply is limited

Question 10

what are the two ways in which the activity of enzymes can be changed?

Answer 10

allosteric regulation
covalent modification

Question 11

what is phosphofructokinase

Answer 11

is usually the rate-limiting step of the glycolysis pathway

Question 12

what is phosphofructokinase inhibited by

Answer 12

ATP

Question 13

at high and low levels of concentration what happens to ATP in phosphofructokinase

Answer 13

low concentration, ATP binds only at the active site
high concentration, ATP binds at a low affinity

Question 14

insulin has 3 actions in adipose tissue in the fed state,
name the 3 stages

Answer 14

stimulation of glucose uptake induction of lipoprotein lipase (LPL)
inhibition of hormone-sensitive lipase (HSL)
cAMP produced in response to glucagon and adrenaline-stimulated PKA which activates HSL

Question 15

what are the 5 phases of glucose homeostasis

Answer 15

absorptive phase
post-absorptive phase
early starvation phase
intermediate starvation phase
prolonged starvation phase

Question 16

what happens at the absorptive phase (4)

Answer 16

when food is digested and absorbed
blood glucose concentrations tend to rise
liver and muscles convert glucose to glycogen
transported to adipose tissue for storage

Question 17

what happens at the post-absorptive phase

Answer 17

the pancreatic alpha-cells secrete glucagon and this promoted the breakdown of liver glycogen which contributes to the blood glucose.

Question 18

what happens in the early starvation phase

Answer 18

glucose being used is derived from glycogen and gluconeogenesis
glucose derived from glycogen continues to decline whereas glucose derived from gluconeogenesis

Question 19

what happens in the intermediate starvation phase

Answer 19

after 32 hours
the liver’s glycogen reserves are exhausted
resorts to the hormone cortisol which is a steroid
breaks down proteins in muscle and other tissues to form energy

Question 20

what happens in the prolonged starvation phase

Answer 20

an average person with access to water might survive another 24 days without food
during the final phase glucose is only provided by gluconeogenesis which helps to fuel the brain

Question 21

what is the fasting state characterised by

Answer 21

low glucose and low insulin, high glucagon

Question 22

what is used to mobilise to supply fuel to the various tissues

Answer 22

TAG

Question 23

the liver maintains blood glucose concentrations at 5 mm which helps to supply to what organ in the body

Answer 23

the brain

Question 24

what is the normal fasting blood glucose concentration maintained at

Answer 24

3.5 and 5 mm
63-90 mg/100ml