Discuss the roles of hormone-sensitive lipase and lipoprotein lipase in the metabolism of fats

Question

What will be an ideal response?

Answer 1

When meals deliver more energy than the body needs, the excess is stored as fat in the adipose cells for later use. An enzyme—lipoprotein lipase (LPL)—hydrolyzes triglycerides from circulating lipoproteins, releasing fatty acids, diglycerides, and monoglycerides into the adipose cells. Enzymes inside the adipose cells reassemble these fatty acids, diglycerides, and mono-glycerides into triglycerides again for storage.

After meals, the blood delivers chylomicrons and VLDL loaded with triglycerides to the body's cells for energy. Fat supplies about 60 percent of the body's ongoing energy needs during rest.

During prolonged light to moderately intense exercise or extended periods of food deprivation, fat may make a slightly greater contribution to energy needs. During energy deprivation, several lipase enzymes (most notably hormone-sensitive lipase) inside the adipose cells respond by dismantling stored triglycerides and releasing the glycerol and fatty acids directly into the blood. Energy-hungry cells anywhere in the body can then capture these compounds and take them through a series of chemical reactions to yield energy, carbon dioxide, and water.

A person who fasts (drinking only water) will rapidly metabolize body fat. Even with abundant fat supplies, the person has to obtain some energy from lean protein tissue because the brain, nerves, and red blood cells need glucose—and without carbohydrate, only protein and the small glycerol molecule of a triglyceride can be converted to glucose; fatty acids cannot be. Still, in times of severe hunger and starvation, a fatter person can survive longer than a thinner person thanks to this energy reserve.