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2.1 Biochemistry of Metabolism > Sean - Fatty Acid Catabolism > Flashcards

Sean - Fatty Acid Catabolism Flashcards

1
Q

What are lipids?
(5)

A

Group of chemically diverse, naturally occurring molecules
Macromolecules
Hydrophobic molecules
Compartmentalised molecules (in vivo)
Bound to hydrophilic molecules (in vivo)

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2
Q

What are the three main functions of lipids?

A

Cell structure
Energy storage
Intracellular messengers

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3
Q

In vivo lipids are compartmentalised, what does this mean?

A

They are membrane associated

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4
Q

In vivo lipids are bound to hydrophilic molecules, give an example of such a case.

A

Lipoproteins

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5
Q

Where are phospholipids often found?

A

Often found in structure

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6
Q

Where are glycolipids found and what is their main function?
(3)

A

They are lipids with a carbohydrate attached

They are used in cell signalling

They are found on the surface of cells to relay messages

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7
Q

What does saturated mean?

A

No double bonds

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8
Q

What does unsaturated mean?

A

There is at least one double bond

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9
Q

What does monounsaturated mean?

A

There is one double bond

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10
Q

What does polyunsaturated mean?

A

More than one double bond

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11
Q

How do you go about naming a fatty acid?

A

Count the number of carbons
Count the number of double bonds
Delta designates the position of the first C atom involved in the double bond

e.g. 16:1 (delta 9)

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12
Q

Classify unsaturated fatty acids

A

Cis and Trans fatty acids

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13
Q

What are trans fatty acids?
(4)

A

Synthetically produced unsaturated fatty aids

Produced by fermentation in the rumen of dairy animals

Hs are located on the opposite sides of the double bond

They pack in an orderly way to produce solid fats

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14
Q

What are Cis fatty acids?
(5)

A

Unsaturated fatty acids

Hs are on the same side of the double bond

Creates a kink or bend in the chain

Nearly all naturally occurring unsaturated fatty acids have this conformation

Do not contribute to the build up of cholesterol -> increase of LDL

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15
Q

Why do trans fatty acids increase risk of cardiovascular disease but not cis fatty acids?

A

Trans can pack in an organised fashion while cis cannot due to the ‘kink’ they produce in their carbon chain

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16
Q

Explain the risk associated with saturated fats and cardiovascular disease

A

Saturated fats lead to the increase of LDL (bad cholesterol) and increase in HDL (good cholesterol)

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17
Q

Give a source of saturated fat

A

Partially hydrogenated vegetable oils

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18
Q

How do mammals store fatty acids?

A

Triacylglycerols

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19
Q

Describe the structure of a triacylglycerol.

A

3 fatty acids linked to a glycerol (3C) by ester bonds

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20
Q

What is the main function of triacylglycerols?

A

Storage

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21
Q

What are the principle short term source of energy in humans?

A

Carbhydrates

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22
Q

What are the principle short term source of energy in humans?

A

Carbohydrates

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23
Q

What happens to excess glucose in the body?

A

It is converted into glycogen and stored in the liver

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24
Q

How much glycogen do humans store?

A

Only enough for a single day of energy

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25
Q

What happens to glycogen when glucose is needed?

A

Glycogen is broken down into glucose

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26
Q

What is the energy from tracylglycerols used for?

A

It’s used to sustain cellular activity

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27
Q

What are the three main sources of fatty acids?

A

They can be synthesised in one type of cell and can be transported to another

They can be consumed in the diet -> these are digested and degraded for energy/stored as triacylglycerols (exogenous reaction)

They can be stored as triacylglycerols in lipid droplets in adipocytes in adipose tissue (endogenous reaction)

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28
Q

Lipids are water insoluble but must be transported around the body, how is this done?

A

They are carried in blood plasma attached to proteins (lipoproteins)

These lipoproteins express signalling proteins so they can interact and coordinate with each other

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29
Q

What do lipoproteins consist of?
(5)

A

Apolipoproteins
Phospholipids
Cholesterol
Cholesteryl esters
Triacylglycerols

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30
Q

What are apolipoproteins?

A

A specific type of carrier proteins

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31
Q

How are lipoproteins classified?

A

Based on their density

32
Q

What are the five main classifications of lipoproteins?

A

Chylomicrons

Very Low Density Lipoproteins (VLDL)

Intermediate Density Lipoproteins (IDL)

Low Density Lipoproteins (LDL)

High Density Lipoproteins (HDL)

33
Q

What proteins is responsible for transporting fatty acids?

34
Q

Write a note on albumin.
(3)

A

Synthesised in the liver

Makes up half of all proteins in the blood

Binds up to 20 fatty acids

35
Q

How does albumin transport fatty acids?

A

Up to 10 fatty acids bind to albumin

At target tissues these fatty acids dissociate from albumin

They then move across specific transporters in the plasma membrane into cells -> fuel

36
Q

What is the first step in the processing of dietary lipids?
(2)

A

Bile salts emulsify dietary fats in the small intestine

Forming mixed miscelles

37
Q

What is the second step in the processing of dietary lipids?

A

Intestinal lipases degrade triacylglycerols

38
Q

What is the third step in the processing of dietary lipids?

A

Fatty acids and other breakdown products are taken up by the intestinal mucosa and converted into triacylglycerols

39
Q

What is the fourth step in the processing of dietary lipids?

A

Triacylglycerols are incorporated with cholesterol and apolipoproteins into chylomicrons

40
Q

What forms chylomicrons?

A

Triacylglycerols incorporated with cholesterol and apolipoproteins

41
Q

What is the fifth step of the breakdown of dietary lipids?

A

Chylomicrons move through the lymphatic system and bloostream to tissues

42
Q

What is the sixth step in the digestion of dietary fatty acids?

A

Lipoprotein lipase is activated by apoC-II in the capillary

This converts triacylglycerols to fatty acids and glycerol

43
Q

What activates lipoprotein lipase?

44
Q

What does lipoprotein lipase do?

A

Converts triacylglycerols to fatty acids and glycerol

45
Q

What is the seventh step in the breakdown of dietary fatty acids?

A

Fatty acids enter the cells

46
Q

What is the eight step in the breakdown of dietary fatty acids?

A

Fatty acids are oxidised as fuel or reesterified for storage

47
Q

What are chylomicrons?

A

A droplet of fat present in the blood or lymph after absorption from the small intestine

48
Q

Describe the structure of a fat droplet
(4)

A

Triacylglycerols are stored within

A monolayer of amphiphatic phospholipids surrounds the droplet

Perilipins (proteins) protect the surface of the droplet

Perilipins restrict lipase access to the lipid droplets (prevents unnecessary release of fatty acids)

49
Q

What signals the release of fatty acids?

A

Hormones such as glucagon and adrenaline

50
Q

What causes signals for the release of fatty acids to be initiated?

A

The need for metabolic fuel
The fatty acids are then released and transported from adipose tissue to the energy requiring tissue

51
Q

What is the first step in the release of fatty acids from triacylglycerols?
(3)

A

Blood glucose concentration falls

Glucagon is released

Glucagon binds its receptor to the adipocyte membrane

52
Q

What is the second step in the release of fatty acids from triacylglycerols?

Glucagon has bound it’s receptor to the adipocyte membrane.

A

This binding stimulates adenylyl cyclase to produce cAMP

53
Q

What does adenylyl cylase produce?

54
Q

What produces cAMP?

A

Adenylyl/adenyl cylase

55
Q

What does adenylyl cyclase produce?

56
Q

What is the third step in the release of fatty acids from triacylglycerols?

cAMP has just been produced
(2)

A

cAMP activates PKA

PKA phosphorylates the hormone-sensitive lipase and perilipin molecules on the surface of the lipid droplet

57
Q

What does cAMP activate?

58
Q

What does PKA do?

A

It phosphorylates lipase and perilipin molecules on the surface of the lipid droplet

59
Q

What is the fourth step in the release of fatty acids from triacylglycerols?
(2)

A

Perilipin is activated/phosphorylation

This permits lipase access to the surface of the lipid droplet

60
Q

What is the fifth step in the release of fatty acids from triacylglycerols?

Lipase has just gotten access to the surface of the lipid droplet

A

Lipase hydrolyses triacylglycerols to free fatty acids

61
Q

What is the sixth step in the release of fatty acids from triacylglycerols?
(3)

Triacylglycerol has just been hydrolysed by lipase

A

Fatty acids leave the adipocyte

They then bind to serum albumin in the blood

They are then carried in the blood

62
Q

What is the seventh step in the release of fatty acids from triacylglycerols?

Fatty acids have bound to albumin and are being transported in blood
(3)

A

The fatty acids are released from the albumin

They enter a cell where energy is needed

They enter through a specific fatty acid transporter

63
Q

What is the eight step in the release of fatty acids from triacylglycerols?

The fatty acids have just entered a cell in need of energy

A

The fatty acids are broken down in a process called B-oxidation

64
Q

Where does B oxidation take place?

A

Mitochondria

65
Q

What are the three stages to fatty acid utilisation in cells?

A

Activation

Transport

B oxidation

66
Q

What happens during fatty acid activation?

A

Fatty acids are converted into fatty acyl-coenzyme A

67
Q

What happens during fatty acid transport?

A

Import of the fatty acyl-coenzyme A into mitochondria

68
Q

What happens during B-oxidation of fatty acids?

A

The conversion of a fatty acyl-coenzyme A into acetyl-CoA with the release of energy

69
Q

What catalyses the activation of fatty acids?

A

Acyl-CoA synthase

70
Q

Write a note on the activation of fatty acids. (Step 1 of utilisation of fatty acids)
(6)

A

Acyl-CoA synthase catalyses the formation of a thioester bond between the carboxyl group of the fatty acid and sulphydryl group (-SH) of coenzyme A

This generates a high energy fatty acyl-coenzyme A (CoA)

Acyl-CoA then goes through one of two pathways:
- transported into mitochondria and oxidised to release energy
- used in the cytosol to generate membrane lipids

Both reactions are driven by ATP hydrolysis in a coupled reaction

71
Q

Write a note on the transport of fatty acyl-CoA into the mitochondria
(Phase 2 of the utilisation of fatty acids by cells)
(4)

A

Fatty acyl-CoA molecules forms on the cytosolic side of the outer mitochondrial membrane

There are no specific transporters present here to transport the molecules

Instead they use ‘the carnitine shuttle’

The fatty Co A molecules attach to carnitine and move through the carnitine transporter present on inner mitochondrial membranes

The OH group of carnitine interacts with the C=O group of the fatty acyl Co A

Coenzyme A is released and a fatty acyl-carnitine forms (catalysed by carnitine acyltransferase I/CAT I)

A transport protein present on the inner mitochondrial membrane allows cytosolic fatty acyl-carnitine to be swapped for mitochondrial carnitine (Fatty acyl-carnitine now present in the mitochondrial matrix)

Carnitine acyltransferase II (CATII) found on the inner mitochondrial membrane catalyses the conversion of fatty acyl-carnitine to fatty acyl-CoA (reverse affect of CAT I

Carnitine released is then recycled by exchange back to the cytosol

Fatty acid B-oxidation then occurs in the mitochondrial matrix

72
Q

What catalyses the release of Coenzyme A from acetyl CoA to form fatty acyl-carnitine?

A

Carnitine acyltransferase I (CATI)

73
Q

How does fatty acyl-carnitine get into the mitochondrial matrix?

A

A transport protein present on the inner mitochondrial membrane allows cytosolic fatty acyl-carnitine to be swapped for mitochondrial carnitine (Fatty acyl-carnitine now present in the mitochondrial matrix)

74
Q

What does CAT I and II stand for?

A

Carnitine acyltransferase I and II

75
Q

What does CAT II do?
(2)

A

Carnitine acyltransferase II (CATII) catalyses the conversion of fatty acyl-carnitine to fatty acyl-CoA

It’s the reverse affect of CAT I

76
Q

Where is CAT II found?

A

Found on the inner mitochondrial membrane

2.1 Biochemistry of Metabolism (21 decks)

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