lecture 29 - fatty acids as fuel molecules

Question 1

What is the preferred fuel source for red muscle?

Answer 1

fat

Question 2

What is the preferred fuel source for white muscle?

Answer 2

glucose

Question 3

What is the primary energy reserve in mammals?

Answer 3

Fats - as Triacylglycerols

Question 4

What is excess energy consumed as glucose stored as in mammals?

Answer 4

As fat - TAGs

Question 5

Why is fuel stored as fats rather than carbohydrates in the body?

Answer 5

They take up less space, and are more reduced than carbohydrates (more energy stored in the chemical bonds that is released when oxidised in pathways)

Question 6

What form are fats delivered into the blood from adipose tissue when used for fuel?

Answer 6

Passively diffuses at free fatty acids and glycerol into the blood stream

Question 7

In what form are free fatty acids transported in the blood?

Answer 7

They are hydrophobic, so travel bound to albumin as Albumin-FFA

Question 8

Is delivery of fatty acids from the blood to tissues passive or active?

Answer 8

Passive

Question 9

What form are fatty acids found in once transported into cells for use as fuel?

Answer 9

Bound to fatty acid binding proteins (FABP) as the cytosol is aqueous and FFA are hydrophobic.

Question 10

Are fatty acids activated before or after beta-oxidation?

Answer 10

Before - before the FFA enters the mitochondria

Question 11

How are free fatty acids activated?

Answer 11

Attached to CoA to make a fatty acyl-CoA

Question 12

What provides the energy to activate fatty acids by adding CoA?

Answer 12

The hydrolysis of ATP to AMP (energy equivalent of 2 ATP)

Question 13

What is the difference between a fatty acyl-CoA and an acetyl-CoA?

Answer 13

Fatty acyl-CoA has a carbon chain of any length, while acetyl-CoA always has a 2 carbon chain (and is therefore a type of fatty acetyl-CoA)

Question 14

Where does fatty acid oxidation occur?

Answer 14

In the mitochondrial matrix

Question 15

How does fatty acyl-CoA pass through the outer mitochondrial membrane?

Answer 15

Via a fatty acyl-CoA carrier

Question 16

How does fatty acyl-CoA pass through the inner mitochondrial membrane?

Answer 16

Is converted to fatty acyl-carnitine, then passes through a carrier protein

Question 17

What does the carnitine acyltransferease reaction facilitate?

Answer 17

The transport of fatty acyl-CoA from the inter-membrane space into the mitochondrial matrix by converting it to fatty acyl-carnitine

Question 18

What enzyme catalyses the formation of fatty-acyl carnitine from fatty acyl-CoA and carnitine?

Answer 18

Carnitine acyltransferase

Question 19

What are the reactants of the reversible carnitine acyltransferase reaction?

Answer 19

Fatty acyl-CoA and carnitine

Question 20

What are the products of the reversible carnitine acyltransferase reaction?

Answer 20

Fatty acyl-carnitine and free CoA

Question 21

what happens to a fatty acyl-CoA during the carnitine acyltransferase reaction?

Answer 21

Exchange of CoA and carnitine on a fatty acid

Question 22

In what form must fatty acids be to undergo beta-oxidation?

Answer 22

Have an even number of carbons that are saturated (no double bonds)

Question 23

Do fatty acids have an even or odd number of carbons when undergoing beta oxidation?

Answer 23

Even

Question 24

Are fatty acids saturated or unsaturated when undergoing beta oxidation?

Answer 24

Saturated - no double bonds

Question 25

Is ATP made in Beta-oxidation?

Answer 25

No (see exam diagram and there is no ATP included)

Question 26

Where is energy released in beta-oxidation transferred?

Answer 26

To the coenzymes NAD and FAD

Question 27

What happens to the fatty acid carbon chain during each round of Beta-oxidation?

Answer 27

Carbon chain split into 2

Question 28

What is the final product of Beta-oxidation, and what happens to it?

Answer 28

Acetyl-CoA - is further oxidised in the citric acid cycle

Question 29

What are the 4 stages of beta-oxidation?

Answer 29

Oxidation (1), Hydration (2), Oxidation (3), Cleavage (4)

Question 30

What happens during the first reaction (oxidation) of Beta-oxidation?

Answer 30

Loss of 2 hydrogens to form a double bond - FAD reduced to FADH2

Question 31

What happens during the second reaction (hydration) of Beta-oxidation?

Answer 31

H2O split across double bond adding a hydrogen and a hydroxyl group

Question 32

What happens during the third reaction (oxidation) of Beta-oxidation?

Answer 32

Hydroxyl group converted to carbonyl group and NAD+ reduced to NADH and H+

Question 33

What happens during the fourth reaction (cleavage) of Beta-oxidation?

Answer 33

Cleavage of molecule to release acetyl-CoA and add CoASH (free CoA) to remaining carbon chain, creating a 2 carbon shorter fatty acyl-CoA which enters the next round

Question 34

What are the carbon products of beta-oxidation, one of which renters the cycle?

Answer 34

acetyl-CoA, 2 carbon shorter fatty acyl-CoA

Question 35

How can the number of rounds of beta-oxidation undertaken by a fatty acid be calculated?

Answer 35

n(C)/2 -1 (the number of carbons, divided by 2, -1)

Question 36

How many rounds of beta-oxidation is undertaken by palmitic acid (with 16 carbons)?

Answer 36

7

Question 37

What are the products of each round of B-oxidation, excluding the carbon chain that enters the next round?

Answer 37

1NADH, 1FADH2, 1 acetyl-CoA

Question 38

What are the overall products of the 7 rounds of beta-oxidation of palmitic acid?

Answer 38

7 NADH, 7FADH2, 8 acetyl-CoA