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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
What happens to chylomicrons within muscle and adipose tissue?
Attacked and cleaved by lipoprotein lipase
26
What happens to free fatty acids at adipose tissue?
Resynthesised to triaglycerols for storage
27
What happens to free fatty acids in muscle?
Oxidised to produce energy
28
What does oxidation of fatty acids depend upon?
How many fatty acids are available
29
What happens to stored fat during times of starvation?
Broken down in lipolysis by hormone sensitive lipases
30
What does initial cleavage by hormone sensitive lipase cause?
Release of free fatty acids and glycerol
31
What happens to a fatty acid if it is required for energy?
Activated by linking to Co-enzyme A in the cytoplasm of cells (requiring 2ATP). This forms an acyl-CoA
32
What is the difference between acyl-CoA and acetyl CoA
Acyl-CoA= uncertain number of carbons Acetyl-CoA= 2 carbons
33
What is the difficulty with fatty acid oxidation?
Acyl-CoA has to be transported from cytoplasm to mitochondrial matric
34
How does the carnitine shuttle work?
Acyl-CoA fatty acid is transferred onto carnitine forming acyl-carnitine which can be transported to the matric
35
What happens to acyl-carnitine when it reaches the matrix?
The fatty acid is cleave off again, reforming Acyl-CoA and allowing the cycle to continue
36
What is the net result of the carnitine shuttle?
Acyl-CoA located in mitochondrial matrix, CoA is NEVER transported across
37
What is B Oxidation?
Cycle of reactions in the mitochondrial matrix with Acyl-CoA as its substrate
38
Describe the reactions in B oxidation?
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
How many times will B oxidation occur in stearic acid (C18)? What are the products?
Repeated 8 times - 8 FADH2, 8 NADH + 8H+ - 9 acetyl-CoA molecules which are oxidised to CO2 in the TCA cycle
40
What is the yield for 9 acetyl-CoA in the TCA cycle?
-9 FADH2, 27 NADH, 27 H + 9 GTP
41
What is the P/O ratio?
The amount of ATP we can obtain for the reduction of a single oxygen atom to water
42
What is the P/O ration of FADH2?
1.5
43
What is the P/O ratio of NADH + H+ ?
2.5
44
What oxidation reactions involve additional enzymes?
Unsaturated fatty acids Odd-Chain fatty acids Branched-chain fatty acids
45
What happens to glycerol following hydrolysis of fats?
Activated to glycerol-3-phosphate by glycerol kinase (present in liver and kidney) Dehydrogenated to dihydroxyacetone phosphate (normal intermediate of carbohydrate metabolism)
46
When does the formation of ketone bodies occur normally?
In liver mitochondria from acetyl-CoA from B oxidation
47
What are the 3 ketones?
Acetoacetate Acetone a-2-hydroxybutrate
48
What happens to ketone bodies?
Diffuse into blood stream and to peripheral tissues Concerted back to acetyl-CoA which enters TCA cycle
49
What are ketone bodies important for?
Important molecules of energy metabolism for heart muscle and renal cortex
50
What happens in starvation and diabetes?
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
What happens to acetyl-CoA that cannot enter the TCA cycle?
Converted to ketone bodies
52
Why is ketone body accumulation bad?
Ketone bodies are moderate acids Accumulation leads to severe acidosis- blood can't buffer anymore Impairs tissue function, particularly CNS
53
How can ketosis be identified?
Smell of acetone in breath

GI 2018 (10 decks)

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