Chapter 5 - Lipids

Question 0

What is the AMDR recommendation for fat?

Answer 0

20-35% of energy consumed

Question 1

What are lipids?

Answer 1

• a group of organic molecules, most of which don’t dissolve in water
• contribute to texture, flavour, aroma of food
• incl. fatty acids, triglycerides, phospholipids, sterols

Question 2

What is “good” cholesterol? What is “bad” cholesterol?

Answer 2

"good" = high density lipoproteins (HDL) cholesterol
"bad" = low density lipoproteins (LDL) cholesterol

Question 3

What kind of an impact does soluble fibre have on LDL cholesterol?

Answer 3

fibre lowers LDL b/c it binds to it

Question 4

What are triglycerides?

Answer 4

The major form of lipid in food & in the body

• consist of 3 fatty acids attached to a glycerol molecule
• these fatty acids determine the physical properties & health effects of the triglycerides we consume

Question 5

What are fatty acids?

Answer 5

organic molecules made up of a chain of carbons linked to hydrogen atoms w. an acid group at one end

Question 6

What are phospholipids?

Answer 6

type of lipid containing phosphorous

ex. phosphoglyceride

Question 7

What are sterols?

Answer 7

types of lipids w. a structure composed of multiple chemical rings

Question 8

What is a saturated fatty acid?

Answer 8

a fatty acid in which the carbon atoms are bound to as many hydrogens as possible, and which, therefore, contains no carbon-carbon double bonds
- associated w. increased risk of cardiovascular disease

Question 9

What are monounsaturated fatty acids?

Answer 9

contains 1 carbon-carbon double bond (i.e. some carbons that are not saturated w. hydrogens)
- ex. oleic acid (i.e. olive oil, canola oil)

Question 10

What are polyunsaturated fatty acids?

Answer 10

contains 2+ carbon-carbon double bonds

- ex. linoleic acid (i.e. corn oil, safflower oil, soybean oils)

Question 11

What are omega-3 fatty acids?

Answer 11

contains a carbon-carbon double bond b/w the 3rd & 4th carbons from the omega end
- ex. alpha-linolenic acid, EPA, DHA

Question 12

What are omega-6 fatty acids?

Answer 12

contains a carbon-carbon double bond b/w the 6th & 7th carbons from the omega end
- ex. linoleic acid (safflower, corn oils), arachidonic acid (meat & fish)

Question 13

What is the ‘cis’ configuration of fatty acids?

Answer 13

when both hydrogen atoms are on the same side of the double bond
- most unsaturated fats

Question 14

What is the ‘trans’ fatty acid configuration?

Answer 14

when the hydrogen atoms are on opposite sides of the double bond
- trans fats

Question 15

What is hydrogenation?

Answer 15

the process whereby atoms are added to the carbon-carbon double bonds of unsaturated fatty acids, making them more saturated
- most trans fats come from this process

Question 16

What are phosphoglycerides?

Answer 16

a class of phospholipids consisting of a glycerol molecule, 2 fatty acids, and a phosphate group
- soluble in both water & fat --> important for many functions in the body

Question 17

What are emulsifiers?

Answer 17

substances that allow water & fat to mix by breaking large fat globules into smaller ones

• ex. egg yolks in cake batter
• an important component of cell membranes in the body

Question 18

What is a lipid bilayer?

Answer 18

2 layers of phosphoglyceride molecules oriented so that the fat-soluble fatty acid tails are sandwiched b/w the water-soluble phosphate-containing heads
- forms the barrier of a cell that helps regulate which substances can pass into and out of the cell

Question 19

What is lecithin?

Answer 19

a phosphoglyceride composed of a glycerol backbone, 2 fatty acids, a phosphate group, and a molecule of choline

• req’d for optimal function of cell membranes, memory
• found in eggs & soybeans

Question 20

What is cholesterol?

Answer 20

a lipid that consists of multiple chemical rings and is made only by animal cells

• a sterol
• necessary in the body, but not in the diet b/c liver manufactures it

Question 21

What can plant sterols do?

Answer 21

• reduce cholesterol levels in the body by decreasing cholesterol absorption from the diet

Question 22

What are lipases?

Answer 22

lipid-digesting enzymes

- digestion of dietary fat in small intestine

Question 23

What are micelles?

Answer 23

particles formed in the small intestine when the products of fat digestion are surrounded by bile acids
- facilitate the absorption of fat

Question 24

What are lipoproteins?

Answer 24

• transport lipids in the blood

Question 25

What is the post-prandial state?

Answer 25

the time following a meal when nutrients from the meal are being absorbed

Question 26

What are chylomicrons?

Answer 26

lipoproteins that transport lipids from the mucosal cells of the small intestine and deliver triglycerides to other body cells

Question 27

What is lipoprotein lipase?

Answer 27

an enzyme that breaks down triglycerides into fatty acids and glycerol as chylomicrons circulate in the blood
- attached to the cell membranes that line the blood vessels

Question 28

What are VLDLs?

Answer 28

very-low-density lipoproteins

- assembled by the liver; carry lipids from the liver & deliver triglycerides to body cells

Question 29

What are LDLs?

Answer 29

low-density lipoproteins

• transport cholesterol to cells
• elevated LDL cholesterol increases risk of cardiovascular disease

Question 30

What is an LDL receptor?

Answer 30

a protein on the surface of cells that binds to LDL particles and allows their contents to be taken up for use by the cell

Question 31

What are HDLs?

Answer 31

high-density lipoproteins

• pick up cholesterol from cells and transport it to the liver so that it can be eliminated from the body (reverse cholesterol transport)
• high level of HDL decreases risk of cardiovascular disease
• “good” cholesterol

Question 32

What is adipose tissue?

Answer 32

tissue found under the skin and around body organs that is composed of fat-storing cells

• most of the lipids in the human body are triglycerides stored in this tissue
• also insulates the body from changes in temp & provides a cushion to protect internal organs against shock

Question 33

What are essential fatty acids?

Answer 33

fatty acids that must be consumed in the diet b/c they cannot be made by the body or cannot be made in sufficient quantities to meet needs

• ex. omega-3 fatty acids, omega-6 fatty acids
• essential to the formation of the phospholipids that give cell membranes their structure & functional properties

Question 34

What are eicosanoids?

Answer 34

regulatory molecules (incl. prostaglandins & related compounds) that can be synthesized from omega-3 and omega-6 fatty acids
- help regulate blood clotting, blood pressure, immune function, other body processes

Question 35

What is beta-oxidation?

Answer 35

• 1st step in the production of ATP from fatty acids
• breaks the carbon chain of fatty acids into 2-carbon units that form acetyl-CoA & releases high-energy electrons that are passed to the electron transport chain

Question 36

What is hormone-sensitive lipase?

Answer 36

an enzyme present in adipose cells that responds to chemical signals by breaking down triglycerides into free fatty acids & glycerol for release into the bloodstream
- when less energy is consumed than is needed

Question 37

What is the glucose/fatty-acid-cycle?

Answer 37

the inverse relationship b/w blood glucose & free fatty acids

• when blood glucose levels are high, as in the post-prandial state, free-fatty-acid levels are low
• in the fasting state when blood glucose levels decline, free-fatty-acid levels increase

Question 38

What is essential fatty acid deficiency?

Answer 38

a condition characterized by dry scaly skin & poor growth that results when the diet does not supply sufficient amounts of the essential fatty acids
- rare

Question 39

What is atherosclerosis?

Answer 39

• a type of cardiovascular disease

- build up of fatty material in the artery walls, reducing their elasticity and eventually blocking blood flow

Question 40

What is atherosclerotic plaque?

Answer 40

cholesterol-rich material that is deposited in the arteries of individuals with atherosclerosis
- consists of cholesterol, smooth-muscle cells, fibrous tissue & eventually calcium

Question 41

What is oxidized LDL cholesterol?

Answer 41

• formed when cholesterol in LDL is oxidized by reactive oxygen molecules
• key in the development of atherosclerosis b/c it contributes to the inflammatory process