Fatty Acid Oxidation

Question 1

T or F: fatty acids are a major source of energy for all tissue.

Answer 1

False

Question 2

What is the consequence of fats being more reduced than carbohydrates?

Answer 2

They produce more high energy molecules

Question 3

In what cellular compartments does oxidation of fatty acids occur?

Answer 3

Mitochondria: ß-oxidation
Peroxisome: alpha and ß-oxidation
Endoplasmic reticulum: omega oxidation

Question 4

T or F: the stored fats used in fatty acid oxidation are pulled out of chylomicrons to enter the target tissue.

Answer 4

False

• While its true that chylomicrons carry DIETARY fatty acids to tissues, STORED fatty acids are released from fat cells via serum albumin

Question 5

What is the upper limit for fatty acids that the mitochondria can handle, where does oxidation of larger fatty acids occur?

Answer 5

20 carbons = Arachindonate

• any larger than 20 they go to peroxisomes

Question 6

What are the essential fatty acids (fatty acids that we can’t synthesize ourselves from others)?

Answer 6

omega 3

omega 6

Question 7

Why do fat cells have to produce all of their glycerol 3-phosphate from glucose instead of just using glycerol from the environment?

Answer 7

• they lack the Glycerol kinase enzyme

Question 8

What is another name for the hormone sensitive lipase, what hormones is it sensitive to?

Answer 8

• Triacyglycerol lipase

- glucagon and epinephrine (lipolytic hormones)

Question 9

What is an antilipolytic hormone?

Answer 9

• Insulin

- works by decreasing adipocyte cAMP

Question 10

Why do people with type I diabetes have a high risk for ketoacidosis?

Answer 10

• They lack insulin to down regulate Triacylglycerol lipase. With this active fatty acids are constantly being created by TG breakdown, these go into the liver to become ketone bodies.

Question 11

What are the activated transport intermediates in fatty acid uptake?

Answer 11

FACoA and FAcarnitine

Question 12

How are fatty acids mobilized by fat tissue?

Answer 12

1. Glucagon or Epinephrine binds to GPCR stimulating cAMP cascade
2. TAG lipase is phosphorylated and activated
3. TAG is converted to diacylglycerol which is broken down further to Fatty acids and Glycerol by other lipases
4. Fatty acids are then bound to serum albumin once transported out of adipose tissue

Question 13

How are fatty acids activated in the cytosol?

Answer 13

Fatty acyl CoA synthase converts fatty acids to the activated Fatty Acyl CoA and pyrophosphate

Question 14

What is the function of pyrophosphatase?

Answer 14

converts pyrophosphate into 2 organic phosphates

Question 15

What are the 3 metabolic routes of Fatty acyl CoA?

Answer 15

1. Energy (ß-oxidation and ketogenesis)
2. Membrane Lipid Formation (phospholipids and sphingolipids)
3. Storage (as TAGs)

Question 16

T or F: short and medium chain fatty acids can cross the inner mitochondrial membrane.

Answer 16

True

Question 17

What must fatty acyl CoA be converted to to cross the inner mitochondrial membrane and by what?

Answer 17

Fatty acylcarnitine by CPT-I

-CPT-1 replaces CoA with carnitine

Question 18

What moves fatty acylcarnitine across the inner mitochondrial membrane?

Answer 18

a translocase

Question 19

What is the carnitine cycle?

Answer 19

1. CPT-1 converts FACoA to FA carnitine
2. Translocase move FAcarnitine through inner membrane
3. Matrix CPT-II converts FA carnitine back to FACoA
4. Carnitine is transported back to make another cycle

Question 20

What the the two main ways beta oxidation is regulated?

Answer 20

• Malonyl CoA

- High ATP (which negatively affects ETC)

Question 21

What is the major energetic difference between saturated and unsaturated ß-oxidation?

Answer 21

• No FADH2 is produced because acyl CoA dehydrogenase is bypassed
• If doubly unsaturated
• NADPH must be used (energetically costly) - FADH2 producing step is bypassed a second time

Question 22

How is the problem of odd chain fatty acid oxidation solved?

Answer 22

• Propionyl CoA is left over
• A carbon is added by proponyl CoA carboxylase creating succinyl CoA
• Succinyl CoA can then enter the TCA cycle

Question 23

What is the difference in first step of long chain fatty acid oxidation and very long chain fatty acid breakdown

Answer 23

• Peroxide instead of FADH2 is produced in VLCFA breakdown because it takes place in the peroxisome

Question 24

When does omega oxidation of fatty acids occur?

Answer 24

Happens only when medium chain fatty acids build up in individuals

NOTE: This is a sign that ß-oxidation of fatty acids is compromised in an individual