Lipids 2

Question 1

Can fatty acids be converted to glucose?

Answer 1

No because pyruvate to acetyl conenzyme A is irreversible

Question 2

What does the beta-oxidation pathway do?

Answer 2

Degrades fatty acids two carbons at a time, producing acetyl coenzyme A, NADH and FADH₂

Question 3

Where does beta-oxidation occur?

Answer 3

Mitochondiral matrix

Question 5

Why can red blood cells not perform beta-oxidation?

Answer 5

They have no mitochondria

Question 6

What are the 3 stages of beta-oxidation?

Answer 6

1. Activation of fatty acid in cytosol
2. Transport into the mitochondria
3. Degradation to two carbon as acetyl coenzyme A

Question 7

What do fatty acids form when they are activated?

Answer 7

Fatty acyl coenzyme A

Question 8

Where does the activation of fatty acids occur?

Answer 8

The cytosol

Question 9

What does the reaction of the activation of a fatty acid looking like?

Question 10

Can fatty acyl coenzyme A pass the membrane without help?

Answer 10

No, it needs to use the carmitine shuttle

Question 11

What is the process of the carnitine shutle?

Answer 11

1. Carnitine reacts with acyl coenzyme A to produce acyl carnitine which crosses the mitochondrial membrane
2. Inside the mitochondria acyl carnitine reactions with coenymze A to produce acyl conenzyme A
3. Carnitine crosses the membrane and returns to the cytosol to be used again

Question 12

What does the carnitine shuttle look like?

Question 13

What enzymes are used in the carnitine shuttle?

Answer 13

Carnitine palmityl transferase I and II

Question 14

What can inhibit carnitine polmityl transerase?

Answer 14

Malonyl coenzyme A when their is enough broken down fatty acids

Question 15

What does malonyl coenzyme A ensure?

Answer 15

That synthesis and degradation do not happen at the same time

Question 16

Where does carnitine come from?

Answer 16

The diet

Made from lysine or methionine

Question 17

What does carnitine palmitoyl transferase dificiency lead to?

Answer 17

No beta-oxidation (hypoglycemia)

Coma

Question 18

What is the treatment of carnitine palmitoyl transferase difficiency?

Answer 18

Eating medium and short chain fatty acids that do not require the carnintine shuttle

Question 19

What are the stages of the degradation of beta-oxidation occurs in four stages?

Answer 19

1. Dehydrogenation to produce FADH₂
2. Hydration
3. Dehydrogenation to produce NADH
4. Thiolysis (cleaved) to produce acetyl coenzyme A

Question 20

What does each beta-oxidation cycle produce?

Answer 20

1 acetyl coenzyme A

Spieces of carbon 2 carbons shorter than the original

Question 21

What would 7 beta-oxidation pathways produce?

Answer 21

8 acetyl coenzyme A

7 NADH

7 FADH₂

Question 22

What is the total net energy yield of beta-oxidation?

Answer 22

129 ATP molecules

Question 23

What do very long chain fatty acids (>22 carbons) need to undergo before beta-oxidation?

Answer 23

Preliminary beta-oxidation in peroxisomes

Question 24

How are very long chain fatty acids (>22 carbons) degraded?

Answer 24

1. Preliminary beta-oxidation in peroxisomes, does not produce FADH₂ so not as efficient as shorter chains
2. Shortened fatty acid links to carntine and diffuses into the mitochondria for beta-oxidation

Question 25

Why are very long chain fatty acids not as efficient as shorter ones?

Answer 25

Preliminary beta-oxidation in peroxisomes does not produce FADH₂

Question 26

What happens during starving/fasting?

Answer 26

1. Liver flooded with acetyl coenzyme A 2. Acetyl coenzyme A inhibits pyruvate dehydrogenase (pyruvate to acetyl coenzyme A) and activates pyruvate carboxylase (pyruvate to oxaloacetate) 3. Oxaloacetate is used to produce glucose for gluconeogenesis

Question 27

What happens to excess acetyl coenzyme A during fasting?

Answer 27

Converted into ketone bodies

Question 28

What tissues can use ketones for fuel?

Answer 28

Cardiac and skeletal muscle

Question 29

When can brain cells use ketones for fuel?

Answer 29

During starvation

Question 30

Where are ketone bodies made?

Answer 30

In the liver (mitochondrial matrix) and then transported in the blood to other tissues

Question 31

What cannot use ketones for energy?

Answer 31

The liver

Question 32

What cannot use fatty acids for energy?

Answer 32

The brain

Question 33

Why do ketones not need albumin or lipoprotein to transport in the blood?

Answer 33

They are soluble

Question 34

What leads to high ketone concentration?

Answer 34

Uncontrolled diabetes or starvation

Question 35

What happens when the rate of ketone production becomes greater than the rate they are used?

Answer 35

Body becomes acid (ketosis) which causes a fruity oddur in breath due to acetone

Question 36

What ensure that fatty acid synthesis and degradation do not happen at the same time?

Answer 36

Inhibition and the two happening in different places