Lipid Metabolism

Question 1

Purpose of Fatty Acid Metabolism

Answer 1

Fatty acid synthesis (lipogenesis) takes place in liver and adipose cells where excess acetyl CoA that builds up when glucose levels are high.

(ANABOLISM)

Fatty acid oxidation is responsible for providing energy to cells when glucose levels are low.

(CATABOLISM)

Question 2

B-Oxidation Reactions of Fatty Acids

Answer 2

3 steps to break down fatty acids to make energy

1. Fatty acid must be activated: bond to coenzyme A 2. Fatty acid must be transported into mitochondria 3. Fatty acid repeatedly oxidized produces Acetyl

CoA, FADH2, & NADH

Question 3

Digestion of Lipids

Answer 3

Lingual and gastric lipases initiate lipid digestion by hydrolyzing ingested fat to free fatty acids and glycerol

Most lipid digestion occurs in small intestine

Pancreatic enzymes digest the lipids: • lipase

• cholesterol ester hydrolase

Question 4

Digestion of Lipids

Answer 4

Final products of fat digestion are hydrophobic and therefore the process of absorption is complex

Question 5

Breakdown of Triglycerides

Answer 5

Broken down by Lipases

Question 6

Degradation of Phospholipids

Answer 6

Phospholipase A removes 1 fatty acid from carbon 2

lysophospholipase

2
leaving a lysophospholipid

Question 7

What is glycolysis? What does glucose get converted into during glycolysis?

Question 8

Why do you need complicated TCA cycle to oxidize acetate?

Question 9

TCA cycle is a complicated way to oxidize acetate units to CO2. True

or False

Question 10

Describe the first entry step to TCA cycle.

Question 11

What are the most important take home points about TCA cycle?

Question 12

What are fatty acids primarily stored as?

Answer 12

Efficient way to cleave C-C bonds as normal methods do not work to ALSO generate carbon dioxide for the body AND energy

Energy comes from the release of NADH/FADH and ATP

Oxidation forms carbon dioxide

Regeneration forms oxaloacetate

Both acetyl CoA and oxaloacetate are generated from pyruvate, condense to form citric acid

Question 13

What is the role of catabolism of fatty acids? What is the role of fatty acid anabolism?

Answer 13

Fatty acids are stored as triglycerides and can be stored/released depending on glucose levels

Fatty acid oxidation occurs when glucose levels are low (catabolism)

Fatty acid synthesis (lipogenesis) occurs when glucose levels are high, takes place in the liver and adipose cells where excess acetyl coA that builds up

Question 14

What are the primary enzymes involved in digestion of lipids?

Answer 14

Lingual/gastric lipase helps to initiate lipid digestion by hydrolyzing ingested fat to free fatty acids/glycerol

Most lipid digestion occurs in the small intestine

Pancreatic enzymes: lipase, cholesterol ester hydrolase

Question 15

How are the three primary group of lipids digested?

Answer 15

Triglycerides

Require lingual, gastric, pancreatic lipase

Yields a monoglyceride and two FA

Cholesterol ester

Cholesterol ester hydrolase

Yields a cholesterol and a FA

Phospholipid

Uses phospholipase A2

Yields lysolecthin and FA

Question 16

Explain the role of bile.

Answer 16

Bile is works to emulsify dietary fats

Bile covers the fat as it has hydrophobic sides facing the fat and a hydrophilic side that covers the rest of the body

Question 17

Step wise explain the absorption of lipids in the intestine.

Answer 17

Final products of fat digestion are hydrophobic SO fat is covered with bile to form micelles

These micelles move to the epithelial cells of the small intestine (enterocytes)

Inside, these are re-esterfied into their original lipids and packaged into chylomicrons

Chylomicrons are very large transporters so they move through the lymphatic capillaries

Go to the thoracic duct and into the blood stream

Question 18

What is the primary role of CCK and secretin in controlling lipid digestion?

Answer 18

CCK is produced in the presence of lipids and partially digested proteins

Causes the stomach to slow gastric motility, signals the release of bile, and the pancreas to release lipase

Secretin is released in response to low pH

Causes the contents of the gastric system to neutralize by signaling the pancreas and liver to release bicarbonate

Question 19

What happens to fat anabolism and catabolism when glucagon or insulin is high?

Question 20

Explain the role of insulin in triggering fat storage during fed state? What does the enzyme lipoprotein lipase do?

Question 21

Explain the role of glucagon in fasting state. What is adipocyte lipase?

Question 22

What is the difference between the role of lipoprotein lipase and

adipocyte lipase?

Question 23

What is ketogenesis?

Question 24

Describe how acetyl CoA is in the crossroads of the different metabolism pathways.