Page 67 - الكيماء الحيوية

?الكيمياء الحيوية?

Digestion, Absorption, and Transport of Lipids
Special arrangements are made in the digestion of lipids. This is due
to the hydrophobic nature of lipids. Lipids tend to separate from the

watery fluids of digestion. Digestive enzymes are hydrophilic, or
water loving. Bile from the liver emulsifies lipids. Enzymes are then

.able to break down lipids to monoglycerides and fatty acids
Lipid Digestion A.

.In the mouth, the salivary glands release lingual lipase .1
Muscle contractions in the stomach disperse fat into smaller .2

.droplets. Fat is exposed to gastric lipase enzyme
In the Small Intestine .3

.Cholecystokinin (CCK) signals the gallbladder to release bile a.
Pancreatic and intestinal enzymes hydrolyze lipids to b.
.monoglycerides and fatty acids
.Phospholipids are hydrolyzed c.
.Sterols are absorbed as is d.
Bile’s Routes .4
Enterohepatic circulation – reabsorbed and recycled a.

Soluble fibers are effective in trapping some bile and excreting it b.
.from the body through the large intestine
Lipid Absorption B.

Glycerol and short- and medium-chain fatty acids diffuse and are .1
.absorbed directly into the bloodstream

Monoglycerides and long-chain fatty acids form micelles, are .2
absorbed, and are reformed into new triglycerides. With protein they

.are transported by chylomicrons
Lipid transport is made possible by a group of vehicles known as C.

.lipoproteins
Chylomicrons .1
Largest of the lipoproteins a.
Least dense b.
Get smaller as triglyceride portion is removed by the cells c.
VLDL (Very-Low-Density Lipoproteins) .2
Composed primarily of triglycerides a.
Made by the liver b.
Transport lipids to the tissues c.
Get smaller and more dense as triglyceride portion is removed d.
LDL (Low-Density Lipoproteins) .3
Composed primarily of cholesterol a.
Transport lipids to the tissues b.
HDL (High-Density Lipoproteins) .4
Composed primarily of protein a.
Transport cholesterol from the cells to the liver b.
Health Implications .5
High LDL is associated with higher risk of heart attack and is a.
.known as “bad” cholesterol
High HDL seems to have a protective effect and is known as b.
.“good” cholesterol
Factors that lower LDL and raise HDL c.
Weight control .1
Replace saturated fat with monounsaturated fat and .2
polyunsaturated fat in the diet
Soluble fibers .3
Phytochemicals .4
Moderate alcohol consumption .5
Physical activity .6
.Genes influence lipoprotein activity d.