Lipid Metabolism

Question 1

What are the functions of lipids?

Answer 1

Membrane structure, fuel for energy metabolism, hormone action, electron transfer, antioxidant

Question 2

Where does beta-oxidation of fatty acids occur?

Answer 2

Liver, heart, muscle cells, in mitochondria

Question 3

How to long chain fatty acids enter beta-oxidation?

Answer 3

Coenzyme A attached to the fatty acid to make fatty acetyl CoA

Question 4

What is the product of beta-oxidation and where does it go?

Answer 4

Acyl CoA, can enter TCA cycle/ox. phos. or be used for ketone formation

Question 5

How is beta-oxidation regulated on a whole body scale and on a cellular scale?

Answer 5

Whole body: Hormonal release of fatty acids from adipose tissue
Cellular: Entry of fatty acyl CoA into mitochondria is regulated

Question 6

What metabolic diseases can be caused by beta-oxidation?

Answer 6

Bovine ketosis, equine hyperlipidemia, diabetes mellitus

Question 7

How much ATP is required to activate a fatty acid and what energy is produced?

Answer 7

2 ATP consumed, AMP is produced

Question 8

How does the fatty acyl CoA enter mitochondria to partake in beta-oxidation?

Answer 8

CoA attaches fatty acyl to the carnitine shuttle, which brings fatty acyl into mitochondria and binds with another CoA while the carnitine shuttle recycles

Question 9

What occurs in the first step of beta-oxidation?

Answer 9

Acyl CoA is dehydrogenated via Acyl CoA dehydrogenase and the hydrogen is used to reduce FAD+ to FADH2 and create a double bond

Question 10

What occurs in the second step of beta-oxidation?

Answer 10

Water is added via hydratase which adds a hydroxyl group to the beta carbon

Question 11

What occurs in the third step of beta-oxidation?

Answer 11

Molecule is oxidized again, NAD+ reduced to NADH via hydroxacyl CoA dehydrogenase

Question 12

What occurs in the final step of beta-oxidation?

Answer 12

Thiolase cleaves the molecule to get acetyl CoA and acyl CoA (Which goes around the cycle again).

Question 13

How does beta-oxidation change for polyunsaturated fatty acids?

Answer 13

Requires more enzymes to oxidize double bonds, requires 5 ATP per extra double bond

Question 14

What happens to excess acetyl CoA in the liver?

Answer 14

Forms ketone bodies, secreted to blood and used in other tissues

Question 15

What triggers lipid catabolism?

Answer 15

Glucagon, adrenaline

Question 16

What inhibits the carnitine shuttle?

Answer 16

Malonyl CoA

Question 17

Under what conditions and in which locations is fatty acid anabolism performed?

Answer 17

High energy conditions, in liver, adipose tissue, mammary tissue

Question 18

What is the substrate for fatty acid anabolism and how is it carried out of the mitochondria?

Answer 18

Acetyl CoA, moved out by citrate shuttle

Question 19

What is the primary product of fatty acid anabolism?

Answer 19

Palmitoyl CoA, 16 carbon chain

Question 20

Where can palmitic acid be elongated?

Answer 20

Endoplasmic reticulum or mitochondria

Question 21

When does fatty acid synthesis occur?

Answer 21

Times of high energy intake, increased insulin, decreased glucagon, and high glucose

Question 22

How is acetyl CoA carboxylase regulated?

Answer 22

Stimulated by citrate (Substrate), inhibited by palmitoyl acid (Product), insulin/glucagon