Fatty Acids

Question 1

What are the role of fatty acids between meals and during periods of increased demand, such as exercise?

Answer 1

During overnight
fasting, fatty acids become the major fuel for cardiac muscle, skeletal
muscle, and liver.

Question 2

In the liver, ketone bodies are converted to what?

Answer 2

The liver converts fatty acids to ketone bodies (acetoacetate
and !-hydroxybutyrate), which also serve as major fuels for tissues

Question 3

Can the brain use fatty acids for fuel?

Answer 3

NO, however, the brain, which does not have a significant capacity for fatty acid oxidation,
can use ketone bodies as a fuel during prolonged fasting.

Question 4

How are fatty acids classified in terms of length?

Answer 4

They are classified in terms of length by the number of Carbons present in the chain.

Question 5

How many carbons typically make up a “very long-chain” fatty acid?

Answer 5

> 20 Carbons

Question 6

How many carbons typically make up a “long-chain” fatty acid?

Answer 6

12-20 Carbons

Question 7

How many carbons typically make up a “medium-chain” fatty acid?

Answer 7

6-12 Carbons

Question 8

How many carbons typically make up a “short long-chain” fatty acid?

Answer 8

4 Carbons

Question 9

What pathway generates ATP during the oxidation of fatty acids?

Answer 9

Adenosine Triphosphate (ATP) is generated from oxidation of fatty acids in the pathway of beta-oxidation.

Question 10

Between meals and during overnight fasting, what kind of fatty acids are released from adipose tissue?

Answer 10

Between meals and during overnight fasting, long-chain fatty acids are released from adipose tissue triacylglycerols.

Question 11

How do triacylglycerols circulate in the blood?

Answer 11

Triacylglycerols travel through the blood stream to their destinations by binding to albumin, which is their carrier.

Question 12

Once in the cell, what happens to triacylglycerol?

Answer 12

In cells, a stepwise process occurs to convert the triacylglycerol into usable energy.
1. they are converted to fatty acyl coenzyme A (fatty acyl-CoA)
2.The activated acyl group is transported into the mitochondrial matrix bound to carnitine, where fatty acyl-CoA is regenerated.
3.Beta-oxidation of the fatty acyl group is sequentially oxidized
to yield FAD(2H), NADH, and acetyl-CoA.
4.Subsequent oxidation of NADH
and FAD(2H) in the electron-transport chain, and oxidation of acetyl-CoA
to CO2 in the tricarboxylic acid (TCA) cycle, generates ATP from oxidative
phosphorylation.

Question 13

In general how are ketone bodies formed?

Answer 13

In the liver, much of the acetyl-CoA generated from fatty acid oxidation is
converted to ketone bodies, acetoacetate and Beta-hydroxybutyrate, which enter the blood and travel to other tissues for use.

Question 14

In general how to tissues use ketone bodies?

Answer 14

In tissues ketone bodies are converted to acetyl-CoA, which is oxidized in the TCA cycle.

Question 15

Where does ketone body synthesis occur?

Answer 15

The liver synthesizes

ketone bodies but cannot use them as a fuel.

Question 16

How is the rate of fatty acid oxidation determined?

Answer 16

The rate of fatty acid oxidation is linked to the rate of NADH, FAD(2H), and acetyl-CoA oxidation and, thus, to the rate of oxidative phosphorylation and ATP use.

Question 17

What is an additional regulator of fatty acid oxidation?

Answer 17

Additional regulation occurs through malonyl-CoA, which inhibits formation of the fatty acyl carnitine derivatives.

Question 18

How do hormones influence the use of fatty acid and ketone bodies for fuel?

Answer 18

Fatty acids and ketone bodies are used as fuel when their level increases in the blood, which is determined by hormonal regulation of adipose tissue lipolysis.

Question 19

Where are adipose tissue triacylclylcerols derived from?

Answer 19

Adipose tissue
triacylglycerols are derived from two sources: dietary lipids and triacylglycerols
synthesized in the liver.

Question 20

What are the three major fatty acids oxidized in humans?

Answer 20

The major fatty acids oxidized are the long-chain fatty
acids, palmitate, oleate, and stearate, because they are highest in dietary lipids and
are also synthesized in the human.

Question 21

During fasting how do hormones effect lipolysis?

Answer 21

Between meals, a decreased insulin level and increased levels of insulin counterregulatory
hormones (e.g., glucagon) activate lipolysis, and free fatty acids are
transported to tissues bound to serum albumin.

Question 22

What is the main link between fatty acid oxidation and the TCA cycle?

Answer 22

The acetyl-CoA produced from fatty acid oxidation is principally oxidized in the tricarboxylic
acid (TCA) cycle.

Question 23

If acetyl-CoA does not enter the TCA cycle, where does it go?

Answer 23

Acetyl-CoA is converted to ketone bodies in the liver.

Question 24

What does the body do with excess ingestion of glucose?

Answer 24

Adipose tissue triacylglycerols also contain fatty acids synthesized in the
liver, principally from excess ingestion of glucose.

Question 25

What is the product of the fatty acid synthesis pathway?

Answer 25

The pathway of fatty acid synthesis generates palmitate, which can be elongated to form stearate or can be unsaturated to form oleate.

Question 26

How are palmitate, stearate, or oleate transported to adipose tissue?

Answer 26

These fatty acids are assembled into triacylglycerols and transported to adipose tissues as the lipoprotein very low-density lipoprotein (VLDL).

Question 27

Why do long-chain fatty acids need to be bound to a carrier protein for transport in the blood?

Answer 27

Long-chain fatty acids are hydrophobic, water insoluble, and are toxic to cells because they can disrupt the hydrophobic bonding between amino acid side chains in proteins. Consequently, they are transported in the blood and in cells bound to proteins.

Question 28

How do fatty acids enter a cell?

Answer 28

Fatty acids enter cells both by a saturable transport process and by diffusion through the lipid plasma membrane.

Question 29

What activates fatty acids for a metabolic pathway?

Answer 29

Acyl-CoA. The process of activation involves an acyl-CoA synthetase (also called a thiokinase) that uses ATP energy to form the fatty acyl-CoA thioester bond.

Question 30

Where is the acyl-CoA synthetase for long chain fatty acids located?

Answer 30

The acyl-CoA synthetase that activates long-chain fatty acids is present in three locations in the cell: the endoplasmic reticulum, outer mitochondrial membranes, and peroxisomal membranes

Question 31

Where is the acyl-CoA synthetase for very long chain fatty acids located?

Answer 31

The synthetase for activation of very long-chain fatty acids is present in peroxisomes,

Question 32

Where is the acyl-CoA synthetase for medium chain fatty acids located?

Answer 32

The medium-chain-length fatty acid–activating enzyme is present only in the mitochondrial matrix of liver and kidney cells.

Question 33

What protein serves as the carrier for activated long-chain fatty acyl groups into the mitochondria

Answer 33

Carnitine palmitoyl transferase I (CPTI; also called carnitine acyltransferase I, CATI), the enzyme that transfers long-chain fatty acyl groups from CoA to carnitine, is located on the outer mitochondrial membrane

Question 34

How is carnitine obtained?

Answer 34

Carnitine is obtained from the diet or synthesized from the side chain of lysine by a pathway that begins in skeletal muscle and is completed in the liver.

Question 35

What cofactors are needed for carnitine synthesis?

Answer 35

The reactions use S-adenosylmethionine to donate methyl groups, and vitamin C (ascorbic acid) is also required for these reactions.

Question 36

Where is carnitine stored?

Answer 36

Skeletal muscles have a high-affinity | uptake system for carnitine, and most of the carnitine in the body is stored in skeletal muscle.

Question 37

What is the energy yield of beta-oxidation?

Answer 37

The total energy yield from the oxidation of 1 mol of palmityl-CoA to 8 mol of acetyl-CoA is 28 mol of ATP: 1.5 for each of the 7 FAD(2H), and 2.5 for each of the 7 NADH.

Question 38

How many carbons long is palmitic acid?

Answer 38

16 Carbons

Question 39

How many beta-oxidation spirals must palmitic acid undergo to be completely converted to acetyl-CoA?

Answer 39

7 spirals are needed.

Question 40

What is the major fat in the human diet?

Answer 40

Triacylglycerols are the major fat in the human diet, consisting of three fatty acids esterified to a glycerol backbone.

Question 41

Where does the main breakdown of dietary fats occur?

Answer 41

In the intestine the fats are emulsified | by bile salts that are released from the gallbladder.

Question 42

What are the two products of metabolized dietary fats?

Answer 42

Free fatty acids and 2-monoacylglycerol

Question 43

What hormone is released by the intestine to signal the gall-bladder and pancreas to release digestive enzymes in the presence of fats?

Answer 43

Cholecystokinin