B-Oxidation

Question 1

What is the process of producing energy using fatty acids

Answer 1

b-oxidation

Question 2

What is b-oxidation

Answer 2

Metabolic pathway responsible for breaking down fatty acids to generate energy.
A series of 5 enzyme-catalyzed reactions that cleaves carbon atoms 2 at a time from the carboxyl end of a fatty acid and feeds it into the TCA

Question 3

What is the principal storage form of energy for most animals

Answer 3

fatty acids in triglycerides - they store energy in

Question 4

What is the difference between the ATP yield of b-oxidation and glycolysis

Answer 4

The energy yield per gram of fatty acid oxidized is greater than that per gram of carbohydrate oxidized
Steric acid (18:0) C18
ATP:C = 8:1

Glycolysis (C6)
ATP:C = 6:1

Question 5

Why is the oxidation of water soluble glucose preferred over oxidation of FA

Answer 5

Much more energy is produced per mole of lipid however water soluble glycoses is still the preferred method because it can be moved around in aqueous solutions and can be transported with molecules easily. Where as lipids require lipoproteins to carry them from one place to another which requires energy itself.

Question 6

What reaction pathway occurs after B-oxidation

Answer 6

citric acid cycle

Question 7

What enzyme is used to break down lipids

Answer 7

Lipases are the key enzymes

Question 8

How are triglycerides broken down initially

Answer 8

Triglycerides from adipocytes are emulsified (bile salts) and then lipases enzymatically cleave the fatty acid chains from the triglyceride proceeding TAG –> DAG –> MAG –> glycerol

Question 9

What is the substances put into b-oxidation

Answer 9

Fatty acid and CoA

Question 10

What is the product of B-oxidation

Answer 10

multiple Acetyl-CoA

Question 11

how many steps are in b-oxidation

Answer 11

5 steps

Question 12

From the b-oxidation of steric acid (C18) how much ATP is produced

Answer 12

146

Question 13

How do the FA molecules get into the mitochondria matrix

Answer 13

carnitine shuttle

Question 14

What energy molecules are used and produced in b-oxidation

Answer 14

Used - ATP, NAD, FAD
Produces , NADH, FADH2

Question 15

Which step of b-oxidation is an oxidation and how is it an oxidation

Answer 15

Step 2 - as it involves the loss of 2 hydrogens to form a double carbon bond (C=C)
Step 4

Question 16

What are the carnitine shuttles

Answer 16

Step 1 occurs in the cytosol and carnitine shuttles are a mechanism which transports the FA acyl CoA (activated FA) into the mitochondria

Question 17

What is step 1 of b-oxidation

Answer 17

Investment Phase
-The fatty acid is added onto Coenzyme A resulting in a high energy thioester bond to the Fatty acid
- This is an investment phase as ATP is required to be hydrolyzed into AMP to release energy
- The product is known as a fatty acid acyl CoA
- This step happens only once

Question 18

How many times does step 1 of B-oxidation occur

Answer 18

once

Question 19

What is used to transport FA into the mitochondria

Answer 19

Carnitine Shuttles

Question 20

What is step 2 of b- oxidation

Answer 20

Oxidation
-Oxidation of the fatty acid acyl CoA which results in the loss of 2 hydrogens and the formation of a double bond between the alpha and beta carbons
- Uses Acyl CoA dehydrogenase (loss of hydrogens)
- FAD is reduced to FADH2 using the 2 hydrogens lost, this will enable ATP to be harvested as the reduced electron carrier FADH2 will continue to produce ATP through oxidative phosphorylation

Question 21

What is step 3 of b-oxidation

Answer 21

Hydration
Water is added across the carbon double bond between the a and b carbon

Question 22

What is step 4 of b-oxidation

Answer 22

Oxidation
- Oxidation at the site of the b carbon
- NAD+ is reduced to NADH which will harvest energy from the reduced electron carrier NADH in oxidative phosphorylation where ATP will be created

Question 23

What is step 5 of b-oxidation

Answer 23

Cleavage Reaction
- the release of the 2C acetyl group from the original carrier CoA
- C2 is attached to a second CoA
- Significant energy will be harvested when the Aceryl-CoA passed into TCA
- The remaining FA chain (n-2) is grafted onto the original CoA

Question 24

What occurs with the shortened fatty acyl CoA at the end of step 5

Answer 24

further oxidized by cycling through reactions 2-5 until the fatty acid carbon chain is completely degraded to acetyl CoA (removed 2 carbons each cycle)

Question 25

What is the general reaction of each step in b-oxidation

Answer 25

1. Investment of ATP
2. Oxidation
3. Hydration
4. Oxidation
5. Cleavage

Question 26

What step/s is the investment stage

Answer 26

step 1

Question 27

What steps is harvesting reactions

Answer 27

2-5

Question 28

What stage is cleavage reactions

Answer 28

5

Question 29

Where does step 1 of b-oxidation occur

Answer 29

investment = cytosol

Question 30

Where does harvesting steps 2-5 of b-oxidation occur

Answer 30

mitochondria matrix

Question 31

Where does cleave step 5 of b-oxidation occur

Answer 31

mitochondria matrix

Question 32

How many acteyl CoA is produced from b-oxidation

Answer 32

For every n-carbon fatty acid we produce n/2 acetyl CoA to send to the TCA

Question 33

How many times does a FA go around the b- oxidation

Answer 33

(n/2 -1) times

Question 34

What is the role of CoA in b-oxidation

Answer 34

• Activates the fatty acid by forming acyl-CoA
• Acyl-CoA serves as the substrate for the enzymes involved in b-oxidation

Question 35

How much ATP does 1 cycle of b-oxidation produce

Answer 35

17
FADH2 –> 2 ATP
NADH –> 3 ATP
Acetyl CoA –> 12 ATP