Metabolism

Question 1

what is metabolism
anabolism
catabolism

Answer 1

all the chemical reactions in the body which cost energy
synthesis reactions which need energy
break down of larger molecules releasing energy

Question 2

what are the 4 phases of metabolism

Answer 2

absorptive - dealing with a meal
post absorptive maintaining homeostasis between meals
fasting - dealing with the challenge of longer periods without food
intense exercise - responding t dramatic increases in demand

Question 3

give examples of the difference between acute and longer term time scales

Answer 3

acute - regulation of plasma glucose 
long term - maintenance of stores 
turnover of proteins and cells 
growth 
reproduction

Question 4

what molecule do muscles store for very short term energy production

Answer 4

phosphocreatine

Question 5

what is amp

Answer 5

a marker of a low energy state and regulates a number of metabolic enzymes allosterically

Question 6

how many molecules of ATP can be made from one 1-3DPG molecule anaerobically

Answer 6

2

Question 7

how many molecules of ATP do we get from 1 pyruvate

Answer 7

18

Question 8

describe carbohydrates as a store

Answer 8

release energy quickly
bind lots of water and inefficient as a store
stored as polymers mainly glycogen in liver and muscle
short lived energy store
liver can release glucose from glycogen into circulation

Question 9

describe fat as a store

Answer 9

don’t bind much water and contain little oxygen
can’t be synthesised back into glucose and energy is rebased slower
liver can convert fatty acids into ketone bodies during starvation

Question 10

describe protein as a store

Answer 10

not ideal as a source of energy as mainly stored as functional proteins so catabolism inmapirs cellular function
the liver converts most amino acids to glucose
muscle cells can convert protein to alanine and glutamine which can be exported for gluconeogenesis

Question 11

describe the metabolic needs for erythrocytes

Answer 11

anaerobic respiration which inefficient but do not have high demand for energy themselves

Question 12

describe the metabolic needs for the brain

Answer 12

brain tissue does not have mitochondria but has high metabolic demand
bbb limits entry
relies on steady glucose conc which if drops below 3mM can lead to unconsciousness and death
during fasting ketone bodies are crucial supply

Question 13

describe the metabolic needs for adipocytes

Answer 13

insulin sensiitve uptake of glucose and glucagon sensitive release of free fatty acids and glycerol
high glucose periods - convert glucose to triglyceride

Question 14

describe the metabolic actions of the liver

Answer 14

insulin sensitive uptake and glucagon sensitive release of glucose
high glucose = glycogen
low glucose = catabolism of glycogen
gluconeogenesis using lactate glycerol and amino acids
ketone body production from acetyl CoA

Question 15

describe the metabolic needs of the cardiac muscle

Answer 15

highly aerobic tissue up to 40% mitochondria and abundant in myoglobin
main energy source is fatty acids but can also use lactate or ketone bodies

Question 16

describe th metabolic demands of skeletal muscle type 1
type 2b
type 2a

Answer 16

highly aerobic - mainly for postural muscle and uses fatty acids

fast twitch muscle and quick fatigue - white with few myoglobin or mitochondria - use PCr
rely on anaerobic glycolysis

middle between the two - can use many different stores depending the situation

Question 17

why can’t we have constant high plasma glucose

Answer 17

osmotic effects
glucose lost in urine which would be a waste
glycation of proteins and later cross linking which leads to peripheral neuropathy, micro/macrovascular disease