Energy Production II

Protein CHO Fat

PyruvateAmino Acids

Fatty Acids

Acetyl-CoA

TCA Cycle and Electron TS

ATP produced

ATP produced

Carbohydrate

Muscle glycogen (250-300g).

Stored in muscle and used there, it is not transported in the blood.

2. Blood glucose (90 mg/100ml blood) = 5g = 1 tsp.

Not used much by most tissues except after a meal, reserved for the brain and "special" situations

At rest: 250 mg glucose/min = 20 min of glucose in blood at any one time.

.

During long, hard exercise can use 2g blood glucose/min = 2.5 min unless replaced

3. Liver glycogen (60-100g).

Breakdown of

glycogen plus gluconeogenesis

(new glucose formation from amino acids,

lactate), replaces blood glucose being used

to maintain normal blood glucose levels.

glycogen pyruvate lactate + 2ATP

glucose carbon dioxide +

water + 30-36 ATP

blood glucose

glucose glycogen

MUSCLE

LIVER

FAT

Most fatty acids used for exercise are transported from adipose tissue to muscle.

Some fat stored is stored in muscle (intramyocellular lipid or IMCL) and can be mobilized for use.

1. Requires a lot of oxygen A 16 carbon fatty acid requires 23 oxygen molecules vs. 6 O2 for glucose

2. Need to transport from adipose tissue makes fat use minimal early in exercise.

3. Cannot sustain high-intensity exercise.

4. Slow – fat must undergo beta oxidation in order to generate acetyl CoA for TCA cycle.

ProteinOnly 5-10% of energy derived from oxidation of protein. Use of protein depends heavily on:

1. Energy balance (deficit = more PRO used)2. CHO available (low = more PRO used)

Amino acids derived from body protein can be used to produce:

a. energy, via entry into TCA cycleb. glucose, via gluconeogenesis

No true storage of protein. Protein used in excess of dietary intake causes loss of lean body mass.

Consequences of extended reliance on a lot of protein for energy (e.g. for weeks, months)?

Protein CHO Fat

PyruvateAmino Acids

Fatty Acids

Acetyl-CoA

TCA Cycle and Electron TS

ATP produced

ATP produced

SummaryGoal of CHO, fat and protein breakdown is to generate ATP, the body’s energy currency.

Non-oxidative metabolism occurs in the cytosol of the cell, oxidative metabolism occurs in the mitochondria.

Acetyl CoA is the common entry point of all 3energy sources into the TCA cycle (oxidative metabolism)=