Energy Release From Fat

Question 1

What are the main functions of lipids? (3)

Answer 1

Components of cell membranes (phospholipids and cholesterol)

Hormone precursors

Long-term fuel stores (triglycerides)

Question 2

What type of hormones are formed from cholesterol?

Answer 2

Steroid hormones

Question 3

What type of hormones are formed from arachidonic acid?

Answer 3

Prostaglandins

Question 4

How much fat does the average adult have?

Answer 4

11-15kg

Question 5

How much energy does 1g of fat store?

Answer 5

38kJ

Question 6

Order the following in ascending amount of energy stored:

Protein, carbohydrate, fat

Answer 6

Carbohydrate

Protein

Fat

Question 7

What is another name for triglycerides?

Answer 7

Triacylglycerols

Question 8

What is the structure of a triglyceride?

Answer 8

3 fatty acids with ester bonds to glycerol

Question 9

Give three examples of saturated fatty acids and state their C:C=C ratio

Answer 9

Stearic acid 18:0

Palmitic acid 16:0

Myristic acid 14:0

Question 10

Give four examples of unsaturated fatty acids and state their C:C=C ratio

Answer 10

Oleic acid 18:1

Linoleic acid 18:2

Linolenic acid 18:3

Arachidonic acid 20:4

Question 11

What type of enzyme breaks down lipids?

Answer 11

Lipases

Question 12

Describe how triglycerides are broken down into their components

Answer 12

Removal of one fatty acid at a time

Question 13

What enzymes are used in the breakdown of triacylglycerol?

Answer 13

Triacylglycerol lipase

Diacylglycerol lipase

Monoacylglycerol lipase

Question 14

How do fatty acids travel in the blood stream?

Answer 14

Bound to albumin (as water-insoluble)

Question 15

How does glycerol travel in the blood stream?

Answer 15

Diffusion/free in plasma

Question 16

How many carbons are in glycerol?

Answer 16

3

Question 17

What activates triacylglycerol lipase?

Answer 17

Glucagon

Adrenaline

Question 18

What happens to glycerol in most tissues?

Answer 18

Enters glycolysis as dihydroxyacetone phosphate

Question 19

What happens to glycerol in the liver/during starvation?

Answer 19

Enters glycolysis as dihydroxyacetone phosphate

Converted to glucose by gluconeogenesis

Question 20

What is the name of the process of fatty acid breakdown?

Answer 20

Beta oxidation

Question 21

Where do the reactions of beta oxidation occur?

Answer 21

Mitochondrial matrix

Question 22

How is the biological energy of fatty acids conserved?

Answer 22

Transfer of 2 hydrogen atoms to NAD+ or FAD

Question 23

How many steps are there in beta oxidation?

Answer 23

4

Question 24

What is the result of one cycle of beta oxidation?

Answer 24

Removal of one 2C unit (acetyl CoA)

One NADH and one FADH2 formed

Question 25

What must occur before the fatty acid is transported into the mitochondrion?

Answer 25

Activation using ATP

Question 26

Where does fatty acid activation occur?

Answer 26

Cytosol

Question 27

What is the reaction of fatty acid activation?

Answer 27

Fatty acid --> fatty acyl CoA Catalysed by fatty acyl CoA synthetase/synthase ATP --> AMP + PPi

Question 28

Describe how fatty acyl CoA is moved into the mitochondrial matrix

Answer 28

Diffuses through permeable outer mitochondrial membrane into intermembrane space CoA swapped for carnitine by carnitine palmitoyl transferase I Fatty acyl carnitine moved into matrix by translocase Carnitine swapped for another CoA by carnitine palmitoyl transferase II

Question 29

What are the four steps of beta oxidation?

Answer 29

1. Removal of 2H atoms 2. Addition of water across C=C 3. Removal of 2H atoms 4. Removal of 2C/acetyl unit

Question 30

What is the first reaction of beta oxidation?

Answer 30

Fatty acyl CoA --> enoyl CoA Acyl CoA dehydrogenase FAD --> FADH2

Question 31

What is the second reaction of beta oxidation?

Answer 31

Enoyl CoA --> hydroxyacyl CoA Enoyl CoA hydratase

Question 32

What is the third reaction of beta oxidation?

Answer 32

Hydroxyacyl CoA --> b-ketoacyl CoA Hydroxyacyl CoA dehydrogenase NAD+ --> NADH + H+

Question 33

What is the fourth reaction of beta oxidation?

Answer 33

b-ketoacyl CoA --> fatty acyl CoA + acetyl CoA b-ketoacyl CoA thiolase

Question 34

What happens to the products of beta oxidation?

Answer 34

Fatty acyl CoA re-enters cycle Acetyl CoA goes into TCA cycle

Question 35

How many cycles of beta oxidation would a 16C fatty acid go through for complete breakdown?

Answer 35

7

Question 36

How many NADH, FADH2 and acetyl CoA does a cycle of beta oxidation produce?

Answer 36

1 of each

Question 37

How much ATP is formed from the use of one acetyl CoA molecule (TCA and oxidative phosphorylation)?

Answer 37

10

Question 38

Where are odd-numbered carbon fatty acids often found?

Answer 38

Shellfish

Question 39

How would a three carbon fatty acid be metabolised?

Answer 39

Propionyl CoA carboxylase adds carbon dioxide using ATP hydrolysis Methyl malonyl CoA mutase converts methyl malonyl CoA to succinyl CoA Succinyl CoA enters TCA cycle

Question 40

What is the name for ketone body formation?

Answer 40

Ketogenesis

Question 41

When does ketogenesis occur?

Answer 41

When fat metabolism is the main source of energy in starvation and type I diabetes

Question 42

Why does ketogenesis occur?

Answer 42

Beta oxidation in hepatocytes leads to high concentrations of acetyl CoA which exceeds capacity of TCA cycle So excess acetyl CoA converted to ketone bodies in liver

Question 43

What are two examples of ketone bodies?

Answer 43

Acetoacetate b-hydroxybutyrate

Question 44

Why can the liver not use ketone bodies?

Answer 44

Lacks enzymes to convert them into TCA cycle intermediates to prevent a futile cycle

Question 45

Why can the brain not use fatty acids?

Answer 45

Cannot pass blood-brain barrier

Question 46

Why can red blood cells not use fatty acids or ketone bodies?

Answer 46

No mitochondria