Unit 6 Lipids: Fats & Cholesterol

very-low-density lipoprotein(VLDL)

lipoprotein that transports a high proportion of lipids in the bloodstream

high-density lipoprotein (HDL)

lipoprotein that transports cholesterol away from tissues and to the liver, where it can be eliminated, increased HDL cholesterol is good

atherosclerosis

long-term disease process in which plaque builds up inside arterial walls, causing hardening of the arteries

lipase

enzymes that breakdown lipids

Dietary Guidelines for fat/cholesterol

less than 10% from saturates, trans fat "low as possible", less than 300mg/day cholesterol

arterial plaque

lipid-filled patch that builds up within the wall of an artery

Essential Fatty acids

lipids that must be supplied by the diet

Low-density lipoprotein (LDL)

lipoprotein that carries cholesterol to tissues

lipoprotein

structure that transports lipids through the bloodstream and lymph

3rd function of fat

Fat is essential to many body functions: cell membrane structure, nerve cell transmissions, protection of internal organs, insulation to retain body heat

Lipid Digestion

Fats are not digested and absorbed easily because they are insoluble in water, digestion begins in the small intestine

Monounsaturated fatty acids (MUFA) Sources

Found in large amounts in: canola oil, olives and olive oil, peanuts, peanut oil and peanut butter. Nuts such as pecans, almonds and cashews. As well as avocados

Saturated Fatty Acids (SFAs) Sources

Found in large amounts of fats: butter, lard, bacon fat. Also found in large amounts in some vegetable oils: tropical oils- palm and coconut oil

Trans Fatty Acids

Found in processed foods: crackers, cookies, cakes, margarine, frozen pizza, fast food, coffee creamer

Dietary Cholesterol

Found only in animal products. Limit to 200-300 mg/day

4th step of lipid digestion

Glycerol, fatty acids, and monoglycerides are the major products of lipid digestion.

1st step of lipid digestion

In response to the presence of the fatty chyme in the duodenum, the gallbladder releases bile into the chyme. Bile contains bile salts, which emulsify the lipids

Polyunsaturated fatty acids (PUFAs)

Lack hydrogen atoms in multiple sites, more than one double bond

Monounsaturated fatty acids (MUFAs)

Lack oxygen atoms in one part, one double bond

Lecithin

Lecithin is the major phospholipid in food

5th function of fat

Makes us feel satiated (full) because it is more energy dense and takes longer to digest

Beneficial Fats

Omega-3 found in fish, walnuts, soy, canola, and flax seeds

3rd step of lipid digestion

Pancreatic lipase digests fat by removing two fatty acids from each triglyceride molecule. This action converts most fat into monoglycerides and "free" fatty acids Monoglyceride is a lipid that has a single fatty acid attached to the glycerol backbone of the molecule

Hydrogenation

Adding H atoms to unsaturated fatty acids: creates trans fatty acids and saturated fatty acids, increases risk for cardiovascular disease

2nd function of fat

Carrier for fat-soluble vitamins (vitamins A, D, E, and K) Fat is required for their transport

Dietary Cholesterol Sources

Egg yolk, meat, fish and shell fish, poultry, dairy products

1st function of fat

Energy, 9kcal per gram, major energy used during rest and during exercise, energy storage

2nd step of lipid digestion

The presence of chyme in the small intestine also stimulate the pancreas to secrete pancreatic lipase. Pancreatic lipase gains greater access to the fat molecules because of the action of bile salts. As a result, the lipase digests the molecules more easily.

Types of lipids

Triglycerides, sterols (cholesterol), phospholipids

alpha-linolenic acid

an essential omega-3 fatty acid

linoleic acid

an essential omega-6 fatty acid

5th step of lipid digestion

bile salts surround the fatty acids and monoglycerides to form a water-soluble particle called a micelle. Michelles transport the lipids to the edge of the absorptive cell. These cells remove the monoglycerides and fatty acids from the micelles. The used bile salts that remain can continue to form new micelles.

Ways to monitor risk of CVD

blood tests: total cholesterol below 200mg/dl is normal

Lipids

cell membrane maintenance

angina

chest pain that results from lack of oxygen to heart muscle tissue

triglyceride

composed of 3 fatty acid molecules attached to glycerol "backbone" molecule

Polyunsaturated sources

corn oil, sesame safflower, sunflower, and soybean, fish (omega-3s)

stroke

loss of blood flow to a region of the brain, causing the death of brain cells in that area

heart attack

loss of blood flow to a section of the heart muscle, causing the tissue to die

Saturation

saturated fatty acids (SFAs); hydrogen atoms surrounding every carbon in the chain; no double bonds

chylomicrons

type of lipoprotein that's formed in the absorptive cells

4th function of fat

Provides flavor and texture to foods by giving it taste, smell and adds to tenderness to foods

pancreatic lipase

digestive enzyme that removes two fatty acids from each triglyceride molecule

emulsifier

substance that helps fat-soluble and water-soluble compounds mix together

phospholipid

type of lipid needed to make cell membranes and for proper functioning of nerve cells

Choline

vitamin-like compound in lecithin;nerves use choline to produce acetylcholine, a chemical that transmits messages between nerve cells