2. Fat-Metabolism
Fat, in the form of TG, is the major shortage
form of energy in humans(adipose cells).
Excellent shortage fuel for several reasons:
→ Energy-dense fuel yielding 9.13 kcl/gm.
→ TG is stored dry(unlike CHO).
→ Fat supplies can last for weeks.
TG=1 Glycerol & 3 Fatty acids.
→ (Palmitic acid, Steric acid)
4. Fat-Metabolism
Comparing Pathways:
Catabolic and Anabolic Pathways
involving the same product are not same
Some steps may be common to both
Metabolic Pathways are Multi-step
pathway
This also allows regulation Mechanisms to
turn on pathways and other turned off
6. Fat-Metabolism
Fatty Acid Metabolism:
Synthesis and degradation are reciprocally
regulated
starvation – degradation occurs because
epinephrine & glucagon stimulate lipolysis
fed state – insulin inhibits lipolysis
ACC also influences degradation
malonyl CoA inhibits carnitine acetyltransferase
limits beta oxidation in mitocondria
Long-term control mediated by sythesis
and degradation of key enzymes
adaptive control
7. Fat-Metabolism
Unsaturated Fat Metabolism
special enzymes needed to convert cis bonds in fatty
acids to trans bonds
Regulation of Fat Metabolism
Transport is rate-limiting
Regulation of carnitine acyl transferase
off by fat synth products
high NADH
8. Fat-Metabolism
General
80% of carbohydrates ingested contain glucose;
remainder: fructose, galactose
glucose is the body's preferred carbohydrate
energy source
Fate of carbohydrates -- depends on needs of body
cells
ATP production
Amino acid synthesis
Glycogenesis
Lipogenesis
Excretion in urine (minimal)
Carbohydrate Metabolism:
9. Fat-Metabolism
Comparison of Fat Metabolism per gram and CHO per
gram:
Fats provide about 9 kilocalories per gram and
carbohydrates provide about 4 kilocalories per gram.
Using nutritional units, that is 9 Calories/gram for fats
and 4 Calories/gram for carbohydrates.
CHO provide energy more quickly
Fats are good fuel for endurance events, but not
sprints
