Unit 3: Lipids

Question 1

What are triglycerides?

Answer 1

A class of lipids. Made up of 3 fatty acids and a glycerol backbone.

Question 2

What are phospholipids?

Answer 2

A class of lipids. Contain 2 fatty acids, 1 phosphate group with a molecule of choline and a glycerol backbone.
Both water and fat soluble. In cell membranes, act as emulsifiers and generate signals in response to insulin.
Ex: Lecithin in egg yolk, liver, peanuts.

Question 3

How do you increase the stability of fatty acids?

Answer 3

Hydrogenation will make fatty acids more firm at room temperature and protect against oxidation.
Can create trans-fatty acids.

Question 4

What are sterols?

Answer 4

A class of lipids. Large molecules consisting of interconnecting rings of carbon atoms with side chains of carbon, hydrogen and oxygen.
Found in meat, eggs, fish, poultry and dairy.
Ex: Cholesterol, vitamin D, sex hormones

Question 5

What are plant sterols?

Answer 5

Phytochemicals that interfere with cholesterol absorption in the intestinal tract, thus lower cholesterol levels and not affecting the HDL levels.
Found in vegetable oil, nuts, cereals and legumes.

Question 6

What do high levels of low density lipoproteins (LDL) do?

Answer 6

High LDL levels increase the risk for heart disease.
High intakes of staurated and trans fat can increase LDL.
To lower LDL levels: maintain a healthy body weight, increase intake of soluble fibre and reduce intake of saturated and trans fat.

Question 7

What do high levels of high density lipoproteins (HDL) do?

Answer 7

High HDL levels are associated with a low risk of heart disease.
To increase HDL levels: maintain a healthy body weight, engage in regular physical activity and quit smoking.

Question 8

What can we replace to lower heart disease risk?

Answer 8

Replace saturated and trans fat with monosaturated fatty acids and polyunsaturated fatty acids (EPA and DHA).

Question 9

What are EPA and DHA?

Answer 9

Omega-3 fatty acids. Found abundantly in the oils of certain fish (salmon, char, cod) and human milk.

Question 10

What is hypertriglyceridemia?

Answer 10

Elevated blood triglycerides. Liver accelerates very low density lipoprotein (VLDL) production in response to obesity.
Caused by being overweight, high alcohol intake, high blood glucose and a diet high in sugar, fat and calories.
Healthy body weight, physical activity, restricting alcohol, eating fish, eating foods low in saturated and trans fat and limiting refined carbohydrates and simple sugars are some of the treatments.

Question 11

What is the daily recommended intake for lipids?

Answer 11

20-35% of energy from dietary fat and

Question 12

What is the daily recommended intake for polyunsaturated fatty acids?

Answer 12

5-10% energy from linoleic acids (omega-6)

0.6-1.2% energy from linolenic acids (omega-3)

Question 13

What is the daily recommended intake of cholesterol?

Answer 13

To minimize intake within the context of a healthy diet.
Only 1/3 of the population responds to lowering dietary cholesterol.
Limit eggs, shellfish, liver.

Question 14

What are fat cells’ role in the body?

Answer 14

Provide energy. Virtually unlimited capacity to store fat unlike glycogen, which is limited.
Secrete hormones that help regulate appetite and influence other body functions.
Padding, insulation, cell membranes and raw materials for conversion of hormones, bile and vitamin D as needed.

Question 15

What is a saturated fatty acid?

Answer 15

When every available carbon in a fatty acid chain is filled to capacity with hydrogen atoms. Only single bonds.

Question 16

What is an unsaturated fatty acid?

Answer 16

When there are double bonds present and thus there are are missing hydrogens. Can be mono- or poly-unsaturated. Causes a bend in the chain.

Question 17

What characteristics of fat make it melt more readily?

Answer 17

Shorter chains or more unsaturations make it melt more readily.

Question 18

What are the essential fatty acids?

Answer 18

The fatty acids the body cannot synthesize itself and must be obtained from food. Linoleic acid and linolenic acid (polyunsaturated fatty acids)

Question 19

What is linoleic acid?

Answer 19

Omega-6 fatty acid. Found in the seeds of plants and in the oils produced by seeds.

Question 20

What is linolenic acid?

Answer 20

Omega-3 fatty acid. Found in fish oils. EPA and DHA.

Question 21

How can cholesterol leave the liver?

Answer 21

It can be incorporated into bile, stored in the gallbladder and delivered to the intestine.
It may travel, via the bloodstream to all the body cells.
Bile may absorbed and reused but rest is excreted in feces.

Question 22

What are lipoproteins?

Answer 22

Cholesterol that is packaged with other lipids and proteins and leaves the liver via the arteries and is transported to the body tissues by the blood.

Question 23

How does obesity lead to insulin resistance?

Answer 23

Obesity is associated with reduced secretion of adiponectin (hormone that promotes insulin sensitivity and glucose tolerance). Adipose cells also release larger amounts of resistin (hormone that promotes insulin resistance).
Enlarged adipose cells also activate local macrophages which secrete cytokines which induce inflammation and blood coagulation.