Chapter 5

Question 1

Lipids Composition

Answer 1

Composition: Lipids are made of carbon (C), hydrogen (H), and oxygen (O), including triglycerides, phospholipids, and sterols.

Question 2

Triglycerides

Triglycerides and Fatty Acids:

Answer 2

Triglycerides: The most abundant type of fat in food and the body. Made of glycerol and three fatty acids.

Question 3

Fatty Acids

Triglycerides and Fatty Acids:

Answer 3

Fatty Acids: Vary in length (4-24 carbons, with 18-carbon fatty acids being the most common). Can be:

Saturated: No double bonds between carbons.
Unsaturated: One (monounsaturated) or more (polyunsaturated) double bonds.

Question 4

Omega-3 (linolenic) and Omega-6 (linoleic) fatty acids

Triglycerides and Fatty Acids:

Answer 4

Omega-3 (linolenic) and Omega-6 (linoleic) fatty acids: Essential polyunsaturated fatty acids important for creating longer-chain fatty acids involved in blood pressure regulation, blood clotting, etc.

Question 5

Characteristics of Fats and Oils:

Answer 5

Firmness: Degree of unsaturation determines whether fats are solid or liquid at room temperature.

Polyunsaturated fats (e.g., vegetable oils) tend to be liquid, while saturated fats (e.g., animal fats) are solid.

Stability: Unsaturated fats spoil faster due to oxidation (rancidity), while saturated fats are more stable.

Question 6

Hydrogenation

Answer 6

Hydrogenation: A process that adds hydrogen to unsaturated fats, making them more saturated and stable. Partial hydrogenation can produce trans fats, which change the configuration of hydrogen atoms from “cis” (same side of the double bond) to “trans” (opposite sides).

Question 7

Trans fats

Answer 7

Trans fats: Common in processed foods, raise LDL (bad cholesterol) and lower HDL (good cholesterol).

Question 8

Phospholipids

Answer 8

Structure: Glycerol, two fatty acids, phosphate group, and choline. They have both fat-soluble and water-soluble properties, making them useful as emulsifiers.

Roles: Part of cell membranes, help fat-soluble vitamins and hormones pass into cells.

Food sources: Eggs, liver, soybeans, peanuts.

Question 9

Sterols

Answer 9

Cholesterol: Found in animal foods; a structural component of cell membranes and precursor to bile acids, sex hormones, adrenal hormones, and vitamin D.

Plant sterols: Can interfere with cholesterol absorption, offering health benefits.

The body produces cholesterol (endogenous), but excess can lead to plaque in arteries, increasing heart disease risk.

Question 10

Lipid Digestion:

Answer 10

Goal: Break down triglycerides into monoglycerides, glycerol, and fatty acids. Fats are hydrophobic, while digestive enzymes are hydrophilic, requiring emulsification for digestion.

Process: Begins in the mouth (minor role), continues in the stomach (with gastric lipase), and mostly occurs in the small intestine with the help of bile and pancreatic lipase.

Question 11

Lipid Absorption

Answer 11

Lymphatic System: Lipids are packaged into chylomicrons (lipoproteins) and absorbed into the lymph before entering the bloodstream.

Question 12

Lipoprotein

Answer 12

Types:

LDL (Low-Density Lipoprotein): “Bad” cholesterol, associated with plaque formation.
HDL (High-Density Lipoprotein): “Good” cholesterol, helps remove excess cholesterol from the body.

Health: Lowering LDL and raising HDL can be achieved through weight management, dietary changes (e.g., replacing saturated fats with unsaturated fats), increasing soluble fiber, and physical activity.

Question 13

Roles of Triglycerides

Answer 13

Provide energy, store fat in adipose tissue, insulate skin, absorb shock, and form cell membranes.

Question 14

Essential Fatty Acids and Eicosanoids

Answer 14

Omega-6 (linoleic) and Omega-3 (linolenic) fatty acids: Required for producing eicosanoids, hormone-like compounds that regulate various body processes (e.g., inflammation, blood pressure).

Eicosanoids from omega-3 fats tend to be more beneficial (e.g., reducing inflammation).

Question 15

Health Effects of Saturated Fats and Trans Fats:

Answer 15

Cardiovascular Disease (CVD): Excess saturated and trans fats raise LDL cholesterol and increase the risk of heart disease.

Trans fats: Particularly harmful, raising LDL and lowering HDL.
Saturated fats: Promote LDL cholesterol, contributing to heart disease.

Cancer and Obesity: High-fat diets may promote certain types of cancer and contribute to obesity, though low-fat foods may have hidden sugars and calories.

Question 16

Dietary Recommendations

Answer 16

Fat intake: 20-35% of daily energy from fat, with less than 10% from saturated fats. Minimize trans fats as much as possible.

Essential Fatty Acids: Include enough linoleic acid (5-10% of energy) and linolenic acid (0.6-1.2% of energy).

Question 17

Sources of Healthy Fats

Answer 17

Olive oil, nuts, and fish (rich in omega-3 fatty acids) promote heart health.

Mediterranean diet: Features whole foods, healthy fats (mono- and polyunsaturated fats), limited meat, and high consumption of fiber-rich foods (vegetables, legumes, fruits), offering benefits for heart disease prevention.