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BMS07 > Energy Release From Fat > Flashcards

Energy Release From Fat Flashcards

1
Q

What are the main functions of lipids? (3)

A

Components of cell membranes (phospholipids and cholesterol)

Hormone precursors

Long-term fuel stores (triglycerides)

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2
Q

What type of hormones are formed from cholesterol?

A

Steroid hormones

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3
Q

What type of hormones are formed from arachidonic acid?

A

Prostaglandins

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4
Q

How much fat does the average adult have?

A

11-15kg

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5
Q

How much energy does 1g of fat store?

A

38kJ

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6
Q

Order the following in ascending amount of energy stored:

Protein, carbohydrate, fat

A

Carbohydrate

Protein

Fat

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7
Q

What is another name for triglycerides?

A

Triacylglycerols

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8
Q

What is the structure of a triglyceride?

A

3 fatty acids with ester bonds to glycerol

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9
Q

Give three examples of saturated fatty acids and state their C:C=C ratio

A

Stearic acid 18:0

Palmitic acid 16:0

Myristic acid 14:0

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10
Q

Give four examples of unsaturated fatty acids and state their C:C=C ratio

A

Oleic acid 18:1

Linoleic acid 18:2

Linolenic acid 18:3

Arachidonic acid 20:4

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11
Q

What type of enzyme breaks down lipids?

A

Lipases

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12
Q

Describe how triglycerides are broken down into their components

A

Removal of one fatty acid at a time

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13
Q

What enzymes are used in the breakdown of triacylglycerol?

A

Triacylglycerol lipase

Diacylglycerol lipase

Monoacylglycerol lipase

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14
Q

How do fatty acids travel in the blood stream?

A

Bound to albumin (as water-insoluble)

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15
Q

How does glycerol travel in the blood stream?

A

Diffusion/free in plasma

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16
Q

How many carbons are in glycerol?

A

3

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17
Q

What activates triacylglycerol lipase?

A

Glucagon

Adrenaline

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18
Q

What happens to glycerol in most tissues?

A

Enters glycolysis as dihydroxyacetone phosphate

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19
Q

What happens to glycerol in the liver/during starvation?

A

Enters glycolysis as dihydroxyacetone phosphate

Converted to glucose by gluconeogenesis

20
Q

What is the name of the process of fatty acid breakdown?

A

Beta oxidation

21
Q

Where do the reactions of beta oxidation occur?

A

Mitochondrial matrix

22
Q

How is the biological energy of fatty acids conserved?

A

Transfer of 2 hydrogen atoms to NAD+ or FAD

23
Q

How many steps are there in beta oxidation?

A

4

24
Q

What is the result of one cycle of beta oxidation?

A

Removal of one 2C unit (acetyl CoA)

One NADH and one FADH2 formed

25
Q

What must occur before the fatty acid is transported into the mitochondrion?

A

Activation using ATP

26
Q

Where does fatty acid activation occur?

A

Cytosol

27
Q

What is the reaction of fatty acid activation?

A

Fatty acid –> fatty acyl CoA

Catalysed by fatty acyl CoA synthetase/synthase

ATP –> AMP + PPi

28
Q

Describe how fatty acyl CoA is moved into the mitochondrial matrix

A

Diffuses through permeable outer mitochondrial membrane into intermembrane space

CoA swapped for carnitine by carnitine palmitoyl transferase I

Fatty acyl carnitine moved into matrix by translocase

Carnitine swapped for another CoA by carnitine palmitoyl transferase II

29
Q

What are the four steps of beta oxidation?

A
  1. Removal of 2H atoms
  2. Addition of water across C=C
  3. Removal of 2H atoms
  4. Removal of 2C/acetyl unit
30
Q

What is the first reaction of beta oxidation?

A

Fatty acyl CoA –> enoyl CoA

Acyl CoA dehydrogenase

FAD –> FADH2

31
Q

What is the second reaction of beta oxidation?

A

Enoyl CoA –> hydroxyacyl CoA

Enoyl CoA hydratase

32
Q

What is the third reaction of beta oxidation?

A

Hydroxyacyl CoA –> b-ketoacyl CoA

Hydroxyacyl CoA dehydrogenase

NAD+ –> NADH + H+

33
Q

What is the fourth reaction of beta oxidation?

A

b-ketoacyl CoA –> fatty acyl CoA + acetyl CoA

b-ketoacyl CoA thiolase

34
Q

What happens to the products of beta oxidation?

A

Fatty acyl CoA re-enters cycle

Acetyl CoA goes into TCA cycle

35
Q

How many cycles of beta oxidation would a 16C fatty acid go through for complete breakdown?

A

7

36
Q

How many NADH, FADH2 and acetyl CoA does a cycle of beta oxidation produce?

A

1 of each

37
Q

How much ATP is formed from the use of one acetyl CoA molecule (TCA and oxidative phosphorylation)?

A

10

38
Q

Where are odd-numbered carbon fatty acids often found?

A

Shellfish

39
Q

How would a three carbon fatty acid be metabolised?

A

Propionyl CoA carboxylase adds carbon dioxide using ATP hydrolysis

Methyl malonyl CoA mutase converts methyl malonyl CoA to succinyl CoA

Succinyl CoA enters TCA cycle

40
Q

What is the name for ketone body formation?

A

Ketogenesis

41
Q

When does ketogenesis occur?

A

When fat metabolism is the main source of energy in starvation and type I diabetes

42
Q

Why does ketogenesis occur?

A

Beta oxidation in hepatocytes leads to high concentrations of acetyl CoA which exceeds capacity of TCA cycle

So excess acetyl CoA converted to ketone bodies in liver

43
Q

What are two examples of ketone bodies?

A

Acetoacetate

b-hydroxybutyrate

44
Q

Why can the liver not use ketone bodies?

A

Lacks enzymes to convert them into TCA cycle intermediates to prevent a futile cycle

45
Q

Why can the brain not use fatty acids?

A

Cannot pass blood-brain barrier

46
Q

Why can red blood cells not use fatty acids or ketone bodies?

A

No mitochondria

BMS07 (7 decks)

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