lipids

Question 1

Describe the three classifications of lipids and explain the differences in the structure of triglycerides, phospholipids, and cholesterol.

Answer 1

• 3 types of lipids
  o Triglycerides (fats) = 3 fatty acids + glycerol. Function =
  o Phospholipids= 2 fatty acids (hydrophobic) + phosphate + glycerol (hydrophilic)
  Function = building blocks of cell membranes
  o Sterols: structure = 4 hydrocarbon rings. Function = cell membrane structure, precursor of important compounds in body like vit D, not required in diet cause body makes all it needs

Question 2

fat digestion

Answer 2

• Mouth: chewing and lingual lipase start digestion
• Stomach: gastric lipase breaks down fat into diglyceride and one fatty acid (lipid hydrolysis in stomach stops when 10-30% of free fatty acids have been released from TG
• Small intestine: most digestion and absorption occurs here
  o Bile: emulsify fat, break fat globules into smaller pieces
  o Pancreatic lipase: breaks down to two fatty acids and monoglyceride
  o Lecithin in bile is packaged with monoglycerides and fatty acids to create micelles (small carriers) for absorption

Question 3

fat absorption

Answer 3

Mature chylomicrons are secreted into the lacteals where they join lymph to become chyle. Lymphatic vessels carry chyle to lymph ducts before they join the venous return of the systemic circulation via subclavian veins. Chylomicron remnants are taken up by the liver

Question 4

fat transportation

Answer 4

• after mixing with blood in heart, fat could be transported to every tissue of the body
• lipoproteins transport fat through lymph and blood
  o chylomicrons: carry digested fat through lymph into blood stream
  o Very LDL: deliver fat made in liver to cells
  o LDL: deposit cholesterol on walls of arteries, density of cholesterol = 50% and protein = 25%
  o HDL: remove cholesterol from body and deliver to liver for excretion, density of cholesterol = 20% and protein = 50%
  o Lipoprotein lipase (LPL): degrades circulating triglycerides in blood
• Endogenous lipoprotein pathway: starts in liver with formation of VLDL where the triglycerides carried in the VLDL are metabolized in muscle & adipose by lipoprotein lipase releasing free fatty acids and IDL are formed

Question 5

functions of fat

Answer 5

energy storage, insulation, transport proteins in blood, cell membrane structure. and phospholipids contribute to satiety

Question 6

Define the dietary recommendations for total fat, the essential fatty acids, saturated fat, cholesterol, and trans fats.

Answer 6

total fat: 20-35% of total daily calories
essential fatty acids: Should be consuming 1:1 to 1:4 ratio of omega 3/6
saturated fat: less than 7-10%
cholesterol: Limit dietary cholesterol to less than 300 mg daily
trans fats: as little as possible

Question 7

major sources of essential fatty acids

Answer 7

fatty fish, pasteurized poultry & eggs, vegetable oils, seeds
omega 3 - nuts, vegetable oils, red meat, and dairy

Question 8

major sources of saturated fats

Answer 8

fatty meats, cheese, butter, cream, coconut oil

Question 9

major sources of trans fats

Answer 9

margarine, processed foods, fried and fast foods,

Question 10

major sources of unsaturated fats

Answer 10

vegetable oils, soy beans, walnuts, peanut butter

Question 11

Compare the different fat substitutes currently used in food products

Answer 11

Fat substitutes: are designed to provide all the creamy properties of fat with fewer calories and total fat, they can be carb/protein/fat based
- most are carb based and use plant polysaccharides

Question 12

Describe the development of atherosclerosis, including its role in the risk of heart disease.

Answer 12

• heart disease starts with the buildup in arteries
• atherosclerosis: narrowing of arteries due to plaque buildup
• increases chance of blood clots which can cause heart attack and stroke

Question 13

Explain the dietary changes you can make to maintain healthy blood cholesterol levels and reduce your risk of heart disease.

Answer 13

• Eat less: cholesterol, fats, trans fats
• Eat more: fish, plant foods, antioxidant and phytochemical rich foods
• Exercise and manage weight
• Moderate consumption of alcohol
• Whole is greater than the sum of its parts

Question 14

types of fatty acids

Answer 14

saturated: single bonds, solid
monounsaturated: one double bond, semi liquid
polyunsaturated: over 1 double bond, liquid

Question 15

phytosterols

Answer 15

lower LDL by competing with cholesterol for absorption in GI tract