Lipolysis and substrate use! @

Can TG enter blood?

No that’s why broken into FFA’s

What determines concentrations of FFA in bloodstream?

Determined by the rate at which it is mobilized/released into circulation & uptaken from circulation

How does fatty acid mobilization increase?

Typically when the body enters into a hypoglycemic state due to fasting or an increase in PA

* TG broken down

What stimulate fatty acid mobilization? How is it carried?

Catecholamines (epinephrine & norepinephrine) & Glucagon stimulate FA mobilization from adipocytes

* FFA is released in bloodstream & carried by albumin

Lipolysis vs esterification?

Lipolysis: TG broken into FFA, enter blood, then tissue

Esterification: FFA into TG, stored in adipose tissue

What does lipolysis involve and how is it done?

Involves breakdown of triglycerides

* releases the attached FFA from the glycerol backbone

Hydrolysis

* using H2O to hydrolyze TG and FFA is detached from backbone one by one

What are the 3 components of lipolysis or aerobic system (lipid)?

1) Lipolysis & FFA uptake in skeletal muscle

2) Beta-oxidation

3) Oxidative phosphorylation

* when acetyl-CoA enters TCA cycle

What are per molecule of oxygen ratio in carbs vs fat oxidation? Result?

Carb oxidation (glucose)

* C6 H12 O6 + 6 O2 ➞ 6 CO2 + 6 H 2O
* 32 ATP created per 12 oxygen
* this equals 2.67 per molecule/unit of oxygen ratio

FFA oxidation (stearic acid)

* C 18H 36O2 + 26 O2 ➞ 18 CO2 + 18 H 2O
* 120 ATP created per 52 oxygens
* equals 2.31 P/O ratio

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More oxygen is needed to get same amount of ATP from lipids compared to carbs

Which molecule produces more ATP? What about in molecule/unit per oxygen?

Fat & then carbs

What is fat and carb oxidation like in exercise?

With higher intensity, more carbs used & less fat and vice versa

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* the major shift in balance of substrates used for oxidation during exercise grossly around 50% of maximal aerobic capacity
* this is the crossover, where carb utilization passes over fat

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* at crossover point, carbs represent more than 70% of sources of energy for the exercising body
* 30% of fat is only used

What stores more?

Fat stores are far greater than carbohydrate stores