Lipid Metabolism: Fatty Acid Synthesis; Fatty Acid Oxidation; Special Lipids

Front 1

Most common fatty acids in human systems contain an even number of carbon atoms. True or False?

Back 1

True

Front 2

Where do fatty acids most commonly occur?

Back 2

Primary occur as esters of of glycerol as mono-, di- or triacylglycerols (TAGs)

Front 3

Why are TAGs efficient energy stores?

Back 3

1. On a weight basis, TAGs yield 2.5x more energy than glycogen
2. TAGs are anhydrous, stored without associating with water
3. Their FA's are more reduced than amino acids or monosaccharides
4. Saturated or monounsaturated forms are relatively inert (non-reactive)

Front 4

What is mobilisation (of triacylglycerols)?

Back 4

Hydrolysis of triacylglycerols in adipose tissue and release of fatty acids into the bloodstream

Front 5

What are triacylglycerols broken down into?

Back 5

Monoacylglycerol + 3 free fatty acids

Front 6

What is B-oxidation?

Back 6

The biochemical pathway that degrades fatty acids to acetyl CoA removing two carbons at a time and tielding energy.

Front 7

Where does B-oxidation occur?

Back 7

Occurs in the mitochondrial matrix

Front 8

What is fatty acid transport?

Back 8

Carnitine is the acyl group transporter ("carnitine shuttle system"), where FAs are transported across the inner mitochondrial membrane in the form of acyl carnitine

Front 9

Name the 4 steps of B-oxidation.

Back 9

Step 1: Oxidation (dehydrogenation)
Step 2: Hydration
Step 3: Oxidation (dehydrogenation)
Step 4: Chain Cleavage (thiolysis)

Front 10

What does the length of the FA determine in B-oxidation?

Back 10

- determines the number of oxidations
- the total number of acetyl CoA groups

Front 11

The oxidation of most unsaturated FA's require what two enzymes?

Back 11

1. isomerase
2. reductase
(in addition to those required for the oxidation of saturated fatty acids)

Front 12

What is the product of the final thiolytic cleavage of odd-chain fatty acids?

Back 12

Propionyl CoA (CoA with a C3 acyl group)

Front 13

What is the product of the final thiolytic cleavage of even-chain fatty acids?

Back 13

Acetyl CoA (CoA with a C2 acyl group)

Front 14

What can the propionyl group, derived from B-oxidation of an odd chain fatty acid, be converted to and why?

Back 14

Glucose, because in mammals, propionyl CoA can be converted to succinyl CoA (TCA intermediated), succinyl CoA can be metabolised to oxaloacetate and then to glucose (oxaloacetate is a substrate of gluconeogenesis)

Front 15

What does activation of a fatty acid require?

Back 15

2 ATP

Front 16

What does one cycle of oxidation of a fatty acid produce?

Back 16

1 NADH = 2.5 ATP equivalents
1 FADH2 (CoQH2) = 1.5 ATP equivalents
1 Acetyl CoA = 10 ATP equivalents (TCA)

Front 17

How many ATP molecules does 5 cycles of B-oxidation yield?

Back 17

78 ATP

Front 18

How many ATP molecules does the oxidation of glucose to CO2 and water yield? (Glycolysis -> Pyruvate-Acetyl CoA -> TCA)

Back 18

30 ATP

Front 19

What happens where there is too much acetyl-SCoA for the TCA to process?

Back 19

Ketone bodies are formed

Front 20

What are Ketone bodies?

Back 20

Compounds produced in the liver that can be used as fuel by muscle and brain tissue

Front 21

What is Ketogenesis?

Back 21

The synthesis of ketone bodies from acetyl-SCoA

Front 22

During prolonged starvation, the brain will switch from glucose to what, to meet up to 75% of its energy needs?

Back 22

Ketone bodies

Front 23

What is a highly volatile ketone?

Back 23

acetone

Front 24

What is Ketosis?

Back 24

A condition in which ketone bodies are produced faster than they are utilised (occurs in diabetes)

Front 25

What is ketonuria?

Back 25

The presence of ketone bodies in the urine

Front 26

What is Ketonemia?

Back 26

The presence of ketone bodies in the urine

Front 27

What is ketoacidosis?

Back 27

Increased concentrations of ketone bodies in the blood.

*The ACID part of the name refers to the fact that two of the ketone bodies are carboxylic acids.

Front 28

What happens in the body/manifestations of ketoacidosis?

Back 28

- Blood buffers are overwhelmed and blood pH drops
- Dehydration due to increased urine flow
- Laboured breathing because acidic blood is a poor oxygen carrier
- Depression
- (if untreated) coma and death

Front 29

What is lipogenesis?

Back 29

The biosynthesis of fatty acids from acetyl-SCoA

Front 30

What provides a link between carbohydrate, lipid, and protein metabolism?

Back 30

Lipogenesis

Front 31

Lipogenesis is the exact reverse of the beta-oxidation pathways. True or False?

Back 31

False: The reverse of an energetically favourable pathway is energetically unfavourable; lipogenesis is not.

Front 32

What is an Acyl-carrier protein?

Back 32

ACP complex that carries the growing fatty acid chain over a number of enzymes (collected into a multi enzyme complex called fatty acid synthase), each of which catalyses a specific reaction

Front 33

What two reactions need to occur before lipogenesis is able to begin?

Back 33

(1) transfer of an acetyl group from acetyl-SCoA to an acyl carrier protein (ACP)
(2) conversion of acetyl-SCoA to malonyl-SCoA in a reaction that requires investment of energy from ATP; the malonyl-SCoA is then transferred to the acyl carrier protein (ACP)

Front 34

In lipogenesis, what occurs occurs at each repetition?

Back 34

Fatty acids with up to 16 carbon atoms are produced by a series of 4 reactions that lengthen the growing fatty acid chain by 2C atoms with each repetition

Front 35

What are the names of the 4 reactions that lengthen the fatty acid chain?

Back 35

(1) Condensation
(2) Reduction
(3) Dehydration
(4) Reduction

Front 36

Why do we have to gain the essential unsaturated fatty acids linoleic and linolenic acid from our diet?

Back 36

- In humans and animals, enzymes can only introduce a doube bond between C4 and C5 and between C9 and C10, using desaturases that act on palmitoyl CoA and stearoyl CoA
- Mammalian cells do not contain a desaturase that acts beyond the C9 position