Lipids 2

Question 1

Where does beta oxidation occur?

Answer 1

Mitochondrial matrix

Question 2

What is produced from B-oxidation?

Answer 2

• Degrades FA 2 C at a time

- Produces acetyl CoA and also NADH and FADH2 which are sources of energy

Question 3

What are the 3 stage of B-oxidation and where do they occur?

Answer 3

• Activation of FA: cytosol
• Transport into the mitochondria
• Degradation to 2 C fragments: mitochondrial matrix

Question 4

What is FA activated to form?

Answer 4

Fatty acyl CoA I the cytoplasm

Question 5

What mechanism is used in the transport of fatty acyl CoA to the mitochondrial matrix?

Answer 5

The Carnitine shuttle

Question 6

Why is the carnitine shuttle used?

Answer 6

CoA is very big and can diffuse through the outer membrane but not the inner membrane

Question 7

What does carnitine palmitoyl transferase I do?

Answer 7

Transfers FA from FA acyl CoA to carnitine

Question 8

What enzyme aids the movement of FA carnitine across the membrane?

Answer 8

Translocase

Question 9

What does carnitine palmitoyl transferase II do?

Answer 9

Transfers FA from FA carnitine to acyl CoA

Question 10

What enzyme moves carnitine back to its original position?

Answer 10

Translocase

Question 11

What inhibits carnitine palmitoyl transferase?

Answer 11

Malonyl CoA

Question 12

What does malonyl Co do?

Answer 12

Prevents synthesis and degradation occurring simultaneously

Question 13

Where do we get carnitine from/

Answer 13

Mainly our diet or can be made from lysine or methionine in the liver/kidney

Question 14

What is occurs during carnitine palmitoyl transferase deficiency?

Answer 14

• No B-oxidation occurs which results in hypoglycaemia
• Coma on overnight fast
• Improved with IV glucose
• Give medium chain FA which do not require CPT1 for mitochondrial transport

Question 15

What is acarnitine palmitoyl transferase deficiency?

Answer 15

A carnitine associated defect in liver DA B-oxidation which impairs the liver’s capacity to use FA as fuels, putting extra burden on its capacity to generate glucose through gluconeongensis

Question 16

What are the 4 main stages in degradation?

Answer 16

-Dehydrogenation
-hydration
Dehydrogenation
Thiolysis

Question 17

What does the dehydrogenation (stage 1) produce?

Answer 17

FADH2 from FAD

Question 18

What does the dehydrogenation (step 3) produce?

Answer 18

NADH from NAD

Question 19

What does thiolysis (step 4) produce?

Answer 19

Acetyl CoA which feeds into TCA cycle

Question 20

What does each cycle of B-oxidation produce?

Answer 20

One acetyl CoA and a species 2 carbon atoms shorter than the original

Question 21

What happens to very long chain fatty acids before B-oxidation?

Answer 21

Undergoes a preliminary B-oxidation in peroxisomes

Question 22

Why is B-oxidation in peroxisomes less energy efficient?

Answer 22

The first step doe not produce FADH2

Question 23

What happens to the shortened FA after B-oxidation in the peroxisome?

Answer 23

It is linked to carnitine and diffuses out of the peroxisome into the mitochondria for further oxidation

Question 24

What do defects in the B-oxidation pathway in peroxisomes result in?

Answer 24

VLC-FA accumulation in blood and tissue

Question 25

Why can animals not convert FA to glucose?

Answer 25

- No FA is gluconeogenic | - They are unable to convert CoA into glucose due to thermodynamically irreversible pyruvate to acetyl CoA step

Question 26

What happens to excess Acetyl CoA?

Answer 26

Form ketone bodies

Question 27

What affect does acetyl CoA have on enzymes?

Answer 27

- Inhibits pyruvate dehydrogenase | - Activates pyruvate carboxylase

Question 28

What does the amount of ketogenesis depend on?

Answer 28

The availability of acetyl CoA

Question 29

When is acetyl CoA converted to ketone bodies?

Answer 29

During fasting or starvation, when glucose is decreased

Question 30

What uses ketone bodies as an energy source?

Answer 30

Cardiac and skeletal muscles

Question 31

When can ketone bodies fuel brain cells?

Answer 31

During starvation

Question 32

Where are ketone bodies found?

Answer 32

Formed in the liver in the mitochondrial matrix and is transported with the blood to other cells where it is used as fuels

Question 33

What can the liver not do in regards to ketone bodies?

Answer 33

Use them as a fuel source

Question 34

What can lead to very high ketone body concentrations in the blood?

Answer 34

-Uncontrolled diabetes or starvation

Question 35

What happens when the rate of ketone body production exceeds utilisation?

Answer 35

Ketonemia, ketonuria and acidemia

Question 36

When does diabetic ketosis result?

Answer 36

When insulin is absent

Question 37

Why can Acetyl CoA not be processed after B-oxidation?

Answer 37

Due to a lack of glucose derived oxaloacetate