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