7/30/2019 5- Lipids 2

1/4

Lipids

Lipids 2: phospholipids andcholesterol, lipid digestion,

lipoprotein types, blooddistribution

Phospholipids

Phospholipids

Are composed of Glycerol backbone

2 fatty acids

Phosphate

Have a detergent quality

Are manufactured in our bodies so they arenot required in our diet

Phospholipids Question

Cholesterol is an essential nutrient andmust be consumed in the diet to survive.

A. True

B. False

Sterols Functions of Cholesterol

Critical component of cell membranes

Can be made de novo in the liver

In the diet found only in animalproducts

Serves as a substrate for thesynthesis of important hormones Estrogen, testosterone, vitamin D

Precursor to bile acids

7/30/2019 5- Lipids 2

2/4

Digestion of Fats and Oils

Digestion of Fat in the Stomach

Gastric lipase Activated by an acidic environment

Acts on triglycerides containing short- &medium-chain fatty acids

Digestion of Fat in the SmallIntestine

Primary site of fat digestion

Hormone Cholecystokinin (CCK) Stimulates release of pancreatic lipase

Fat is broken down To monoglycerides and free fatty acids

Phospholipids digested by enzymes Phospholipases also secreted by pancreas

Free cholesterol not affected by digestion

Cholesterol esters hydrolyzed

Absorption of Fat

95% of dietary fat is absorbed formedinto a micelle

Diffused into the absorptive cells down aconcentration gradient higher to lower

Inside absorptive cell long-chain fattyacids re-form into triglycerides not water-soluble

Incorporated, along with phospholipids &cholesterol into lipoproteins known aschylomicrons more water-soluble Enter the lymphatic system and then blood

Fat AbsorptionIs fat digestion necessary for absorption?

Orlistatnews

7/30/2019 5- Lipids 2

3/4

Transportation of Absorbed Fatty Acids

Chylomicrons deliver lipid load totissues

Lipoprotein lipase Breaks down triglycerides in the

chylomicrons fatty acids diffuse intocells

Chylomicron remnant Delivered to the liver

Lipoproteins

Question

The major component of low-densitylipoproteins (LDL) is cholesterol whereasthe major component of high-densitylipoprotein is protein.

A. True

B. False

Composition and Roles ofLipoproteins

pg.192

Return

Transportation of SynthesizedFat

Made primarily by the liver

Very-Low-Density Lipoprotein (VLDL) Low-Density Lipoprotein (LDL)

High-Density Lipoprotein (HDL)

7/30/2019 5- Lipids 2

4/4

Total Blood Cholesterol Value

TC = LDL-C + HDL-C + (TG/5)

TC =total cholesterol

LDL-C =LDL cholesterol decrease

HDL-C =HDL cholesterol - increase

TG=triglyceride which is VLDL cholesterol