Lipids

Question 1

Lipids are

Answer 1

heterogenous organic molecules that exist in a few different forms and have several purposes

Question 2

Give 3 functions of lipids

Answer 2

• a stored form of energy
• a structural component of cell membranes
• needed as enzyme cofactors
• used in hormones
• used for the synthesis of Vitamins A, D, E and K
• used as signalling molecules

Question 3

What are the major lipid classes?

Answer 3

• fatty acids
• triacylglycerides
• phospholipids

Question 4

What are fatty acids?

Answer 4

Hydrocarbon chains with a carboxylic group at one end

• can be saturated or unsaturated
• nomenclature defines which is which

Question 5

What are the four types of fatty acids?

Answer 5

Essential fatty acids - must be obtained from plants

Good fats - high in polyunsaturated fatty acids

Bad fats - high in saturated fatty acids

Really bad fats - trans fatty acids

Question 6

Give an example of an essential fatty acid

Answer 6

• Linoleic acids

- A-Linoleic acids

Question 7

Give an example of a good fat

Answer 7

Plant oils e.g. sunflower oil

Question 8

Give an example of a bad fat

Answer 8

Stearic acid

Question 9

Give an example of a really bad fat

Answer 9

Margarine

Question 10

Essential fatty acids must be obtained via

Answer 10

our diet, since humans cannot introduce double bonds beyond carbon nine

Question 11

What are triacylglycerides?

Answer 11

Esters of fatty acids and glycerol - water insoluble

• coalesce into droplets in water
• major component of adipose tissue
• act as insulation and dietary fuel

Question 12

What are phospholipids?

Answer 12

Glycerol bonded to two fatty acids and a phosphate group

• amphipathic
• form basic structure of the cell membrane

Question 13

What is the main dietary lipid?

Answer 13

Triglycerols

Question 14

Where does most digestion of triglycerols take place? Through the use of what?

Answer 14

Small intestine

pancreatic enzymes, emulsification by bile salts and peristalsis

Question 15

Most triglycerols are digested by ___ into ___

Answer 15

pancreatic lipase

monoacylglycerol and two fatty acids

Question 16

Cholesterol esters are broken down to

Answer 16

cholesterol and a fatty acid

Question 17

Phospholipids are hydrolysed to

Answer 17

a fatty acid and lysophospholipid

Question 18

Mixed micelles release their contents when they

Answer 18

approach the brush border

Question 19

The intestinal cells repackage ___
into ___
which are released ___

Answer 19

TAG, fatty acids and cholesterol esters

chylomicrons

into the blood via the lymphatic system

Question 20

When lipids reach the tissues, TAG is hydrolysed to ___

by ___

Answer 20

fatty acids and glycerol

lipoprotein lipase

Question 21

The resulting free fatty acids are used for ___

or ___

Answer 21

energy

re-esterified into TAG for storage

Question 22

Free fatty acids are transported in lipoproteins in a complex with

Answer 22

serum albumin

Question 23

Fats are also transported in

Answer 23

high and low density lipoproteins

Question 24

LDLs carry

Answer 24

cholesterol from the liver to other tissues

Question 25

HDLs

Answer 25

pick up cholesterol from tissues and bring it back to the liver for elimination

Question 26

The beta-oxidation pathway degrades ___ | to form ___

Answer 26

fatty acids two carbons at a time Acetyl CoA, NADH and FADH2

Question 27

The beta-oxidation pathway occurs in the

Answer 27

mitochondrial matrix

Question 28

What are the three stages of the beta-oxidation pathway?

Answer 28

- activation - transport - degradation

Question 29

What happens in the activation stage of the beta-oxidation pathway?

Answer 29

The fatty acids are activated to form fatty acyl CoA in the cytoplasm

Question 30

What happens in the transport stage of the beta-oxidation pathway?

Answer 30

- carnitine shuttle transfers long chain fatty acyl CoA from the cytoplasm to inside the mitochondrion - carnitine is a non-essential amino acid - carnitine fatty-acyl transferase is inhibited by malonyl CoA, used in fatty acid synthesis - therefore synthesis and degradation cannot occur simultaneously

Question 31

What happens in the degradation stage of the beta-oxidation pathway?

Answer 31

- fatty acyl CoA is dehydrogenated to form FADH2 and another intermediate - this intermediate is then hydrated - the resulting intermediate is dehydrogenated again to form NADH - finally, thiolysis occurs to form Acetyl CoA that feeds into the CAC

Question 32

Each beta-oxidation cycle forms

Answer 32

- 1 Acetyl CoA - 1 NADH - 1 FADH2 - Carbon species 2 carbons shorter than the original

Question 33

No fatty acid is

Answer 33

gluconeogenic

Question 34

During fasting or starvation, glucose supplies run low and so excess Acetyl CoA from fat metabolism can be made into

Answer 34

ketone bodies

Question 35

What cells can use ketone bodies?

Answer 35

- cardiac muscle cells - skeletal muscle cells - brain cells during times of starvation

Question 36

Ketogenesis occurs in the

Answer 36

liver

Question 37

What is also produced in ketogenesis?

Answer 37

Acetone (but is expelled during expiration)

Question 38

What are the main ketone bodies?

Answer 38

Acetoacetate | 3-Hydroxybutarate