BIOCHEM | Cholesterol and Lipoproteins

Cholesterol

a waxy, fat-like steroid found in cells of animals that can be synthesized in the liver or acquired through diet

Structure of Cholesterol

a steroid with a hydroxyl group at one end and a hydrocarbon tail at the other; one ring has a complex ring structure has a double bond

Properties of Cholesterol

amphipathic, but mostly hydrophobic; insoluble in blood and can form lumps and plaques; embedded within the lipid bilayer

Functions of Cholesterol

• maintains membrane fluidity and stability

• helps produce hormones as a precursor to hormones

• produces vitamin D and bile acids (for digestive aid)

Lipoproteins

complex of lipids and proteins; transport vehicles for lipids throughout the body to compensate for lipids’ hydrophobic nature

Functions of Lipoproteins

• cholesterol transport

• energy distribution

• atherosclerosis risk

Apolipoprotein

an amphipathic outer shell of phospholipids, free cholesterol, and proteins that stabilizes the lipoprotein in blood and is a recognition site for cell surface receptors

Core of Lipoprotein

hydrophobic core with triglycerides and esterified cholesterol

Lipoprotein Classification

classified based on density, or the lipid:protein ratio; higher proteins means higher density

Chylomicrons

largest and least dense lipoproteins that transport dietary triglycerides and cholesterol from intestines to other tissues; are quickly cleared from the blood after a meal

Very Low-Density Lipoproteins

produced by the liver, and transport endogenous triglycerides and cholesterol from liver to tissues

Low-Density Lipoproteins

responsible for delivering cholesterol to cells (adipose tissue) throughout the body and can increase risk of heart disease and stroke through plaque formation in arteries

High-Density Lipoproteins

maintains cholesterol balance by transporting excess cholesterol from tissues to the liver in a process called “reverse cholesterol transport",” decreases chances of heart disease and stroke

Ideal Levels of HDL

higher levels are desirable; >60 mg/dL is protective

Ideal Levels of LDL

lower levels are desirable; <100 mg/dL is optimal

Risk Factors for High Cholesterol

age, weight, gender, genetics, lifestyle choices

Diet

consume whole grains, fat-/low-fat dairy products, egg whites, fresh fruits and veggies

Exercise

engage in 20-30 mins of moderate exercise daily

Lifestyle Modifications

avoid alcohol, smoking, and an unhealthy weight