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GI 2018 > Metabolic pathways: Lipid catabolism > Flashcards

Metabolic pathways: Lipid catabolism Flashcards

1
Q

Why is lipid metabolism important?

A

It is associated with human disease

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2
Q

What are essential fatty acids?

A

Body cannot produce them

Deficiencies can lead to membrane disorders, increased skin permeability, mitochondrial damage

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3
Q

What are the fat soluble vitamins?

A

A
D
E
k

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4
Q

What are simple lipids?

A

Fatty acids, triglycerides, waxes

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5
Q

What are compound lipids/

A

Phospho- glyco-lippids, lipoproteins

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6
Q

What are steroids

A

Cholesterol, steroid hormones

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7
Q

Are lipids soluble in water?

A

NO

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8
Q

Why are triglycerides important?

A

Main energy storage form in adipose tissue

Compact
-dont require concomitant storage of water

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9
Q

What do triglycerides consist of?

A

Glycerol and three fatty acids

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10
Q

How are esters and fatty acids linked?

A

Ester linkage

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11
Q

What is the structure of fatty acids?

A

Straight chained

Alipathic- no rings

Even number of C atoms

Some are branches and have odd numbers

  • Saturated
  • Unsaturated
  • Polyunsaturated
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12
Q

What is the configuration double bonds in the fatty acid chains?

A

Cis configuration- chain continues in the same direction from the double bond (left and right below the double bond)

Trans- two side chains are at opposing sides of the double bond

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13
Q

Where is cis configuration found?

A

Naturally occurring fats

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14
Q

Why are polyunsaturated fatty acids important?

A

Essential

Cannot be synthesised

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15
Q

What is an omega three fatty acid?

A

A fatty acid with a double bond three carbons away from its omega carbon

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16
Q

What is an omega carbon

A

The last carbon

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17
Q

Which carbons are liquid at room temperature?

A

Carbons with up to 8C, longer ones are solid

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18
Q

Do double bonds increase the melting point?

A

No they decrease it

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19
Q

Why are plant fats liquid?

A

They have large proportions of unsaturated fatty acids

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20
Q

Why are animal fats solid?

A

Contain mostly palmitic and stearic acid

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21
Q

What does digestion of fats produce?

A

Glycerol
Fatty acids
Mono-glycerides

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22
Q

Where do products of fat digestion go?

A

Absorbed into mucosal cells of intestine

23
Q

What happens to short and medium length fatty acids?

A

Enter portal blood

24
Q

What happened to longer chain FAs and monoglycerides?

A

Resynthesised to triglycerides which are coated with proteins, phospholipids and cholesterol forming chlyomicrons which enter lymph and then bloodstream

25
Q

What happens to chylomicrons within muscle and adipose tissue?

A

Attacked and cleaved by lipoprotein lipase

26
Q

What happens to free fatty acids at adipose tissue?

A

Resynthesised to triaglycerols for storage

27
Q

What happens to free fatty acids in muscle?

A

Oxidised to produce energy

28
Q

What does oxidation of fatty acids depend upon?

A

How many fatty acids are available

29
Q

What happens to stored fat during times of starvation?

A

Broken down in lipolysis by hormone sensitive lipases

30
Q

What does initial cleavage by hormone sensitive lipase cause?

A

Release of free fatty acids and glycerol

31
Q

What happens to a fatty acid if it is required for energy?

A

Activated by linking to Co-enzyme A in the cytoplasm of cells (requiring 2ATP). This forms an acyl-CoA

32
Q

What is the difference between acyl-CoA and acetyl CoA

A

Acyl-CoA= uncertain number of carbons

Acetyl-CoA= 2 carbons

33
Q

What is the difficulty with fatty acid oxidation?

A

Acyl-CoA has to be transported from cytoplasm to mitochondrial matric

34
Q

How does the carnitine shuttle work?

A

Acyl-CoA fatty acid is transferred onto carnitine forming acyl-carnitine which can be transported to the matric

35
Q

What happens to acyl-carnitine when it reaches the matrix?

A

The fatty acid is cleave off again, reforming Acyl-CoA and allowing the cycle to continue

36
Q

What is the net result of the carnitine shuttle?

A

Acyl-CoA located in mitochondrial matrix, CoA is NEVER transported across

37
Q

What is B Oxidation?

A

Cycle of reactions in the mitochondrial matrix with Acyl-CoA as its substrate

38
Q

Describe the reactions in B oxidation?

A

Four steps in each cycle- the acyl CoA is shortened by two carbons, producing 1 Acetyl-CoA, a shortened Acyl-CoA, 1 FADH2, 1NADH + H+

39
Q

How many times will B oxidation occur in stearic acid (C18)? What are the products?

A

Repeated 8 times

  • 8 FADH2, 8 NADH + 8H+
  • 9 acetyl-CoA molecules which are oxidised to CO2 in the TCA cycle
40
Q

What is the yield for 9 acetyl-CoA in the TCA cycle?

A

-9 FADH2, 27 NADH, 27 H + 9 GTP

41
Q

What is the P/O ratio?

A

The amount of ATP we can obtain for the reduction of a single oxygen atom to water

42
Q

What is the P/O ration of FADH2?

A

1.5

43
Q

What is the P/O ratio of NADH + H+ ?

A

2.5

44
Q

What oxidation reactions involve additional enzymes?

A

Unsaturated fatty acids

Odd-Chain fatty acids

Branched-chain fatty acids

45
Q

What happens to glycerol following hydrolysis of fats?

A

Activated to glycerol-3-phosphate by glycerol kinase (present in liver and kidney)

Dehydrogenated to dihydroxyacetone phosphate (normal intermediate of carbohydrate metabolism)

46
Q

When does the formation of ketone bodies occur normally?

A

In liver mitochondria from acetyl-CoA from B oxidation

47
Q

What are the 3 ketones?

A

Acetoacetate
Acetone
a-2-hydroxybutrate

48
Q

What happens to ketone bodies?

A

Diffuse into blood stream and to peripheral tissues

Concerted back to acetyl-CoA which enters TCA cycle

49
Q

What are ketone bodies important for?

A

Important molecules of energy metabolism for heart muscle and renal cortex

50
Q

What happens in starvation and diabetes?

A

Oxaloacetate is consumed for gluconeogenesis- liver produced new glucose which removes oxaloacetate.

Fatty acids are oxidised to provide energy which produces acetyl-CoA which enter the TCA cycle due to lack of oxaloacetate?

51
Q

What happens to acetyl-CoA that cannot enter the TCA cycle?

A

Converted to ketone bodies

52
Q

Why is ketone body accumulation bad?

A

Ketone bodies are moderate acids

Accumulation leads to severe acidosis- blood can’t buffer anymore

Impairs tissue function, particularly CNS

53
Q

How can ketosis be identified?

A

Smell of acetone in breath

GI 2018 (10 decks)

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