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Biochemistry > Fatty Acids > Flashcards

Fatty Acids Flashcards

1
Q

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

A

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

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2
Q

In the liver, ketone bodies are converted to what?

A

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

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3
Q

Can the brain use fatty acids for fuel?

A

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.

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4
Q

How are fatty acids classified in terms of length?

A

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

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5
Q

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

A

> 20 Carbons

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6
Q

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

A

12-20 Carbons

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7
Q

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

A

6-12 Carbons

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8
Q

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

A

4 Carbons

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9
Q

What pathway generates ATP during the oxidation of fatty acids?

A

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

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10
Q

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

A

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

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11
Q

How do triacylglycerols circulate in the blood?

A

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

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12
Q

Once in the cell, what happens to triacylglycerol?

A

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.

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13
Q

In general how are ketone bodies formed?

A

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.

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14
Q

In general how to tissues use ketone bodies?

A

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

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15
Q

Where does ketone body synthesis occur?

A

The liver synthesizes

ketone bodies but cannot use them as a fuel.

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16
Q

How is the rate of fatty acid oxidation determined?

A

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.

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17
Q

What is an additional regulator of fatty acid oxidation?

A

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

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18
Q

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

A

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.

19
Q

Where are adipose tissue triacylclylcerols derived from?

A

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

20
Q

What are the three major fatty acids oxidized in humans?

A

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.

21
Q

During fasting how do hormones effect lipolysis?

A

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.

22
Q

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

A

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

23
Q

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

A

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

24
Q

What does the body do with excess ingestion of glucose?

A

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

25
Q

What is the product of the fatty acid synthesis pathway?

A

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

26
Q

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

A

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

27
Q

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

A

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.

28
Q

How do fatty acids enter a cell?

A

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

29
Q

What activates fatty acids for a metabolic pathway?

A

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.

30
Q

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

A

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

31
Q

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

A

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

32
Q

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

A

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

33
Q

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

A

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

34
Q

How is carnitine obtained?

A

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.

35
Q

What cofactors are needed for carnitine synthesis?

A

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

36
Q

Where is carnitine stored?

A

Skeletal muscles have a high-affinity

uptake system for carnitine, and most of the carnitine in the body is stored in skeletal muscle.

37
Q

What is the energy yield of beta-oxidation?

A

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.

38
Q

How many carbons long is palmitic acid?

A

16 Carbons

39
Q

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

A

7 spirals are needed.

40
Q

What is the major fat in the human diet?

A

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

41
Q

Where does the main breakdown of dietary fats occur?

A

In the intestine the fats are emulsified

by bile salts that are released from the gallbladder.

42
Q

What are the two products of metabolized dietary fats?

A

Free fatty acids and 2-monoacylglycerol

43
Q

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

A

Cholecystokinin

Biochemistry (2 decks)

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