L16: Energy release from fat

Question 2

3 biological functions of lipids

Answer 2

1. Components of cell membranes
2. Precursors of hormones
3. Long term fuels

Question 3

3 efficiency of tryglycerides as fuel

Answer 3

1. Compact storage
2. Large body stores
3. Weight

Question 4

How is triacylglycerol formed?

Answer 4

3 fatty acids linked to a glycerol backbone via ester bond

Question 5

Describe breakdown of stored triglyceride fat in adipose tissue

Answer 5

1) Triaglycerol broken down by triacylglycerol lipase to give diacylglycerol , fatty acid travels in plasma bound to albumin

2) Diacylglycerol broken down by DAG lipase to give monoacylglycerol, fatty acid travels

3) Monoacylglycerol broken down by MAG lipase to give glycerol, fatty acid also travels

Question 6

What happens to glycerol when it enters glycolysis pathway?

Answer 6

Conversion to pyruvate, into TCa cycle for oxidation to CO2

Question 7

What happens to glycerol when it enters liver in starvation?

Answer 7

Converted to glucose by gluconeogenesis

Question 8

What bonds does CoA form with carboxylic acids?

Answer 8

Thioester bonds

Question 9

How many ATP does activation of fatty acids require?

Answer 9

2

Question 10

What does activation of fatty acids results in the production of?

Answer 10

AMP from ATP

Question 11

What does the carnitine shuttle represent?

Answer 11

Mechanism where a long-chain acid, impermeable to mitochondrial membrane, are transported into the mitochondrial matrix for beta-oxidation & energy production

Question 12

What does the carnitine shuttle system transport?

Answer 12

Long-chain fatty acids (fatty acyl CoA) from the cytosol into the mitochondria

Question 13

Describe the transporty of fatty acyl-CoA into mitochondria by the carnitine shuttle

Answer 13

1) Fatty acyl-CoA diffuses across outer mitochondrial membrane

2) Fatty acid group transferred to carnitine by carnitine acyltransferase I to create FA carnitine

3) FA carnitine crosses inner membrane via translocase

4) Carnitine switched back for CoA by carnitine acyltransferase II, recreating fatty acyl-CoA

5) Carnitine back to intermembrane space

Question 14

Why is beta-carbon called beta-oxidation?

Answer 14

beta-carbon undergoes oxidation to produce a carbonyl group (c doubled-bonded to o2)

Question 15

What does 1 round of beta-oxidation produce?

Answer 15

Acetyl-CoA & a FACoA that is 2C shorter

Question 16

Beta-Oxidation Pathway

Reaction 1: Removal of 2H atoms

Answer 16

Dehydrogenation of 2 H+ atoms, catalysed by acyl-CoA dehydrogenase

Question 17

Beta-Oxidation Pathway

Reaction 2: Addition of H2O

Answer 17

Hydration catalysed by enoyl-CoA hydratase

Question 18

Beta-Oxidation Pathway

Reaction 3: Removal of 2H atoms

Answer 18

Dehydrogenation catalysed by 3-hydroxylacyl-CoA dehydrogenase, generating NADH

Question 19

Beta-Oxidation Pathway

Reaction 4: Removal of 2C units

Answer 19

Thiolytic cleavage catalysed by beta-ketoacyl-CoA thiolase splits acetyl-CoA to form new fatty acyl-CoA (2C atoms shorter)

Question 20

How many repeats of beta-oxidation pathway does fatty acids with 16C atoms pass through?

• How many NADH produced?
• How many FADH2 produced?

Answer 20

7 repeats
7 NADH
7 FADH2

Question 21

How many acetyl CoA enters the TCA cycle from fatty acids with 16C atoms?

Answer 21

8 acetyl CoA

Question 22

What is the final oxidation product of odd-chain fatty acid?

Answer 22

Propionyl CoA

Question 23

What is propionyl CoA further converted to succinyl CoA by?

Answer 23

3 enzymes

Question 24

Define ketogenesis

Answer 24

Organisms produce ketone bodies by breaking down fatty acids & ketogenic amino acids

Question 25

When does ketogenesis occur?

Answer 25

When fat metabolism is the main source of energy

• In starvation
• In Type I diabates

Question 26

What is excess Acetyl CoA converted into in the liver?

Answer 26

Ketone bodies