Lipid Metabolism

Question 1

Explain Fat catabolism:

Answer 1

diet and Fat cells -> fatty acids -> acetyl-CoA-> CO2 + H2O

Question 2

What is a triacylglycerol?

Answer 2

three fatty acids esterified to glycerol “backbone”

Question 3

What is the advantage of lipids for energy storage?

Answer 3

-very highly reduced
–large amount of energy per molecule
-they are insoluble
–can store large amounts of energy without associated water

Question 4

What is the problem with lipids for catabolism?

Answer 4

-they are insoluble
-lipases: enzyme that hydrolyze lipids

Question 5

What are the processing of dietary lipids?

Answer 5

-emulsified with bile salts
-hydrolyzed by pancreatic lipase
-taken up by intestinal cells
-re-esterified to triacylglycerol
-combined with proteins to form chylomicrons
-released into the lymphatic systems
-eneters bloodstream via the lymphatic duct

Question 6

What is orlistat?

Answer 6

-pancreatic lipase inhibitor
-prevents some fat uptake

Question 7

Difference between LDL and HDL.

Answer 7

LDL: carries cholesterol to tissues (bad)
HDL: carries cholesterol away from tissues to liver (good)

Question 8

What is the fate of chylomicrons?

Answer 8

Chylomicron TAG hydrolyzed by lipoprotein lipase
-adipose tissue- re-esterified and stored
-other tissues- oxidized
-depends on nutritional state
Remnant chylomicrons- liver

Question 9

What is lipolysis?

Answer 9

-occurs when fasting and prolonged exercise
-yields 3 fatty acids and 1 glycerol

Question 10

When is adipose tissue triacylglycerol used?

Answer 10

when needed (fasting prolonged excercise)
-hydrolyzed by lipase in the adipocyte
-resulting in fatty acids transported in the blood bound to albumin
-glycerol metabolized in the liver
-fatty acids oxidized in other tissues as needed

Question 11

Give an overview of fatty acids (B-oxidation).

Answer 11

-first FA is activated with CoA to form fatty acyl-CoA
-transported into mitochondria, involves carnitine
-B-oxidation removes two carbons at a time, each as acetyl-CoA
-Acetyl-CoA oxidized in the Krebs cycle

Question 12

What enzyme oxidizes fatty acid activation?

Answer 12

fatty acyl-CoA synthetase

Question 13

What transports the fatty acid into the mitochondria?

Answer 13

carnitine

Question 14

Steps of FA transport into mitochondria:

Answer 14

1. Fatty acyl-CoA converted to fatty acyl-carnitine outer membrane
2. Fatty acyl-carnitine transported across inner mitochondrial membrane
   3.Fatty acyl-carnitine converted back to fatty acyl-CoA inner membrane

Question 15

Overview of fatty acid oxidation:

Answer 15

-carbons removed two at a time, as acetyl-CoA
-oxidized in the Krebs cycle

Question 16

Explain B-Oxidation:

Answer 16

-occurs in 4 steps
-has a spiral
-each turn of the spiral yields 1 FADH2, 1 NADH, and 1 acetyl-CoA

Question 17

How do some animals generate water?

Answer 17

Fat oxidation

Question 18

Discuss Fatty acid Vs. Glucose oxidation.

Answer 18

-during fasting:
–oxidation of FFA inhibits glucose oxidation
–spares glucose for the brain
–glucose-fatty acid cycle

Question 19

What is a ketone body?

Answer 19

-formed under conditions of high rates of fatty acid metabolism
-happens during prolonger fasting, very low carbohydrate diet, untreated diabetes