Integration Of Metabolism Flashcards
Muscle
Relies upon carbohydrate and fatty acid oxidation
Have periods of very high ATP requirement
Brain and nervous system
Cannot utilise fatty acids as a fuel source
Uses 20% of resting metabolic rate —> has continuous high ATP requirement
Adipose tissue
Long term storage site for triglycerides
Heart
Can oxidise fatty acids and carbohydrates
10% of resting metabolic rate
Liver
Main carbohydrate store
Source of blood glucose
20% resting metabolic rate
Source of ketone bodies (from fatty acids)
What does the brain require a continuous supply of?
Glucose
(Ketone bodies can partially substitute for glucose)
What can the brain not metabolise?
Fatty acids
In the brain what does too little and too much glucose cause?
Too little = hypoglycaemia —> fairness and coma
Too much = hyperglycaemia —> irreversible damage
In the muscle how are requirements met during light contraction?
OxPhos
—> O2 and blood borne glucose and fatty acids used as fuel
In the muscles how are requirements met during vigorous contraction?
Glycogen breakdown
Lactate formation
When ATP consumption > than ATP supply rate by OxPhos
—> O2 becomes a limiting factor
Metabolic features of the heart
Completely aerobic metabolism —> rich in mitochondria
Utilises TCA substrates —> free fatty acids, ketone bodies e.g.
Loss of O2 —> cell death —> myocardial infarction
What happens during extreme exercise?
ATP demand > ATP production
—> lactate produced
What happens during fasting?
Instead of entering TCA cycle —> acetyl CoA results in ketone body production
What happens if glucose levels fall below 3 mM?
Body enters a hypoglycaemic coma
How is hypoglycaemia avoided?
Breakdown of liver glycogen stores —> maintain plasma glucose levels
Release free fatty acids from adipose tissue
Convert acetyl CoA into ketone bodies via the liver
What reaction can directly enter pathway to increase oxaloacetate for gluconeogenisis?
Transamination of amino acids
—> carbon skeleton enters the cycle
Why must some redactions on gluconeogenisis be bypassed?
The forward reactions are essentially irreversible under cellular conditions
Why can’t the muscle produce glucose via gluconeogenisis?
It doesn’t have the enzyme (glucose-6-phosphatase) to bypass the reaction
Why is it important that the muscle doesn’t have glucose-6-phosphatase?
It ill reverse the reaction —> set up a futile cycle
What are glucogenic amino acids used for?
Generate glucose via gluconeogenisis
What are ketogenic amino acids used for?
Synthesis fatty acids and ketone bodies
Fats as a fuel source
Triglycerides —> fatty acids and glycerol
Fatty acid —> ketone bodies
Glycerol —> DHAP —> enter gluconeogenisis
Energy stores and consumption - Aerobic respiration
Contractions increase ATP demand
Contractions increase glucose transport
Muscle glycolysis increases (adrenalin)
Gluconeogenisis increases (adrenalin)
Fatty acids increase (adrenalin)
Energy stores and consumptions - Anaerobic respiration
ATP demand not matched by O22 delivery
Transport cannot keep up with the demand for glucose
Muscle glycogen breakdown increases
Lactate increases
Liver uses lactate to form glucose (recovery) —> replenishes NAD+ levels