Essential Fatty Acids, TAG Metabolism and the Carnitine Shuttle.

Question 1

What 2 factors about fatty acids will lead to an increase in melting point?

Answer 1

Chain length.

Degree of unsaturation (double bonds).

Question 2

How many carbons and double bonds does palmitate have and what is its melting point?

Answer 2

16 carbons.

No double bonds.

63C.

Question 3

How many carbons and double bonds does stearate have and what is its melting point?

Answer 3

18 carbons.

No double bonds.

70C.

Question 4

How many carbons and double bonds does oleic acid have and what is its melting point?

Answer 4

18 carbons.

1 double bond.

13C.

Question 5

How many carbons and double bonds does linoleic acid have and what is its melting point?

Answer 5

18 carbons.

2 double bonds.

-9C.

Question 6

How many carbons and double bonds does alpha lonoleic acid have and what is its melting point?

Answer 6

18 carbons.

3 double bonds.

-17C.

Question 7

How many carbons and double bonds does arachidonic acid have and what is its melting point?

Answer 7

20 carbons.

4 double bond.

-50C.

Question 8

How many carbons and double bonds does EPA have and what is its melting point?

Answer 8

20 carbons.

5 double bonds.

-54C.

Question 9

How many carbons and double bonds does DHA have and what is its melting point?

Answer 9

20 carbons.

6 double bond.

-45 to -50C.

Question 10

What lipids are usually found at position 1 on the glycerol backbone in phospholipids?

Answer 10

Palmitate and stearate.

Question 11

What is formed when animals introduce a double bond into palmitate and stearate?

Answer 11

Palmitoleate and oleate.

Question 12

What end of a fatty acid will carbon 1 be at?

Answer 12

The carboxyl end.

Question 13

Where can animals introduce double bonds in fatty acids?

Answer 13

9 carbons away from the carboxyl end.

Question 14

What carbons is the double bond placed at when palmitoleate and oleate are formed?

Answer 14

Between carbons 9 and 10.

This is written as Δ9.

Question 15

Can animals place double bonds in fatty acids near the methyl end?

Answer 15

No, only 9 carbons away from the carboxyl end.

Question 16

What kind of double bonds will always be formed by animals?

Answer 16

Cis double bonds.

Question 17

How can animals obtain fatty acids with bonds beyond Δ9?

Answer 17

From the diet.

Question 18

What are essential fatty acids?

Answer 18

Fatty acids with bonds beyond Δ9 that are obtained in the diet.

Question 19

What organisms form essential fatty acids?

Answer 19

Plants.

Question 20

Can animals alter essential fatty acids?

Answer 20

They can elongate them but they cannot change the location of the double bond.

Question 21

How can animals form bonds that are beyond carbon 9 in an essential fatty acid?

Answer 21

By elongating the fatty acid.

They can never move the bond.

Question 22

How is the family of an essential fatty acid is determined?

Answer 22

By counting backwards from the methyl end until the 1st double bond is reached.

Question 23

The methyl end of an essential fatty acid is known as what carbon?

Answer 23

The ω carbon.

Question 24

What determines the family of an essential fatty acid?

Answer 24

The number of carbons between the methyl end and the 1st double bond will determine the family.

Question 25

What family of essential fatty acid is linoleic acid?

Answer 25

Omega-6.

Question 26

What family of essential fatty acid is α linolenic acid

Answer 26

Omega-3.

Question 27

At what end will carbons be added when animals are elongating an essential fatty acid?

Answer 27

To the carboxyl end.

Question 28

Why does the family of essential fatty acid not change after elongation?

Answer 28

Because the number of carbons between the methyl end and the 1st double bond does not change.

Question 29

Can animals introduce any double bonds into an essential fatty acid?

Answer 29

They can introduce double bonds between the carboxyl end and Δ9.

Question 30

If animals introduce double bods to an EFA will it change the family?

Answer 30

No because animals introduce them at the carboxyl end and not at the methyl end.

Question 31

Arachidonic acid is what family of EFA?

Answer 31

Omega 6.

Question 32

Linoleic acid is elongated to form what fatty acid in humans?

Answer 32

Arachidonic acid.

Question 33

What will humans use arachidonic acid for?

Answer 33

To make eicosanoids.

Question 34

How many carbons do eicosanoids have?

Answer 34

20 carbons.

Question 35

Where do we get omega 3 fatty acids from?

Answer 35

From fish who get them from the consumption of algae.

Question 36

How do fish store alpha linolenic acids?

Answer 36

As eicosapentaenoic acid, 20:5, (EPA).

Question 37

How do humans alter EPA when they obtain it from fish?

Answer 37

They elongate it to docosahexaenoic acid, 22:6, (DHA).

Question 38

Where is DHA usually found?

Answer 38

In phospholipids in the brain.

Question 39

DHA is important for what in humans?

Answer 39

Brain and retina function. It will protect against heart disease.

Question 40

Why are TAGs synthesised?

Answer 40

To store free fatty acids so that they do not damage cells

Question 41

What is the structure of a TAG?

Answer 41

A glycerol backbone that is bound to 3 fatty acids.

Question 42

What group is removed from fatty acids when they are placed into TAGs?

Answer 42

The hydroxyl group.

Question 43

What is the common intermediate that is formed during TAG synthesis?

Answer 43

Phosphatidic acid.

Question 44

How is phosphatidic acid formed?

Answer 44

When a glycerol 3-phosphate molecule from glycolysis is combined with 2 fatty acyl CoAs.

Question 45

What can phosphatidic acid be used to form?

Answer 45

Phospholipids, DAGs and TAGs.

Question 46

Where does TAG synthesis occur?

Answer 46

In the liver, intestinal mucosal and fat cells.

Question 47

When does the liver synthesise TAGs?

Answer 47

When blood sugar levels are high.

Question 48

What happens to TAGs that are synthesised in the liver?

Answer 48

They are placed inside a VLDL transport protein and released into the blood to be delivered to fat cells.

Question 49

What does VLDL stand for?

Answer 49

Very low density lipoprotein.

Question 50

What hormone activates TAG synthesis in the liver?

Answer 50

Insulin.

Question 51

When are TAGs synthesised in the intestinal mucosal cells?

Answer 51

When the intestinal mucosal cells will join a MAG to 2 free fatty acids to form a TAG.

Question 52

TAGs formed in the intestinal mucosal cells are transported in what transport molecule?

Answer 52

A chylomicron.

Question 53

When is insulin present in the body?

Answer 53

When blood glucose levels are high.

Question 54

Will the TAGs that are stored in adipose tissue ever leave the fat cell?

Answer 54

No.

Question 55

Why will TAGs be degraded?

Answer 55

To provide energy for the body when glucose levels are low.

Question 56

When will TAGs be degraded?

Answer 56

During fasting and in fight or flight scenarios.

Question 57

What enzyme degrades TAGs?

Answer 57

Hormone sensitive lipase.

Question 58

When is HSL active?

Answer 58

When it is phosphorylated.

Question 59

What activates the phosphorylation of HSL?

Answer 59

Epinephrine or low levels of insulin.

Question 60

What is formed when TAGs are broken down?

Answer 60

3 free fatty acids and glycerol.

Question 61

What parts of a TAG are used for energy?

Answer 61

The fatty acids.

Question 62

What happens to glycerol when it is released from a TAG?

Answer 62

It is recycled or excreted.

Question 63

What is the difference in site of synthesis for hormone sensitive lipase and pancreatic lipase?

Answer 63

Hormone sensitive lipase = Fat cells. Pancreatic lipase = Pancreatic cells.

Question 64

What is the difference in site of action for hormone sensitive lipase and pancreatic lipase?

Answer 64

Hormone sensitive lipase = Fat cells. Pancreatic lipase = Lumen of small intestine.

Question 65

What is the difference in mode of action for hormone sensitive lipase and pancreatic lipase?

Answer 65

Hormone sensitive lipase = Cleaves TAGs to 3 free fatty acids and glycerol. Pancreatic lipase = Cleaves TAGs to MAGs and 2 free fatty acids.

Question 66

What is the difference in mode of activation for hormone sensitive lipase and pancreatic lipase?

Answer 66

Hormone sensitive lipase = Phosphorylation, low insulin levels, epinephrine and high cortisol. Pancreatic lipase = Conjugated bile salts and procolipase.

Question 67

Cleaved fatty acids will bound to what in the blood?

Answer 67

They will be non-covalently bound to albumin.

Question 68

Where are cleaved fatty acids transported to once they are in the bloodstream?

Answer 68

To the liver and other tissues.

Question 69

What happens when cleaved fatty acids arrive at cells from the bloodstream?

Answer 69

They will be taken up for beta oxidation.

Question 70

What happens to glycerol that is formed by TAG cleavage during fasting?

Answer 70

It will be used by an enzyme to make glycerol 3-phosphate that can be used in gluconeogenesis.

Question 71

What enzyme converts cleaved glycerol to glycerol 3-phosphate in the fasting state?

Answer 71

Glycerol kinase.

Question 72

Can gluconeogenesis and beta oxidation occur at the same time?

Answer 72

Yes.

Question 73

What gives the liver enough energy to carry out gluconeogenesis?

Answer 73

The beta oxidation of fatty acids. NADH. ACoA.

Question 74

What is the hearts preferred fuel?

Answer 74

Fatty acids.

Question 75

What is done to reduce the detergent characteristics of fatty acids before they are released to give energy to cells?

Answer 75

They are converted to fatty acyl CoA and then esterified.

Question 76

What enzyme will activate and esterify free fatty acids?

Answer 76

Fatty acyl CoA synthase.

Question 77

What will fatty acyl CoA synthase use as its substrates?

Answer 77

A free fatty acid. ACoA. ATP.

Question 78

Where will fatty acyl CoA synthase activate and esterify free fatty acids?

Answer 78

In the outer mitochondrial membrane.

Question 79

Is the reaction that is catalysed by fatty acyl CoA synthase reversible?

Answer 79

No. It is irreversible.

Question 80

Why is the activation and esterification of fatty acids irreversible?

Answer 80

So that free fatty acids cannot be randomly formed as they would damage the cell.

Question 81

The activation and esterification depends on the availability of what molecule?

Answer 81

CoA.

Question 82

Where does the CoA used for fatty acid activation come from?

Answer 82

The rapid turnover of activated fatty acids mean that CoA can be recycled and re-used for fatty acid activation.

Question 83

What happens to fatty acyl CoA molecules?

Answer 83

They can be used for energy. To create phospholipids or sphingolipids. They can be re-syntheised as TAGs.

Question 84

What happens when fatty acyl CoA reaches adipose tissue or a cell membrane?

Answer 84

They can be esterified and the CoA can be removed and recycled.

Question 85

Can long chain fatty acids enter the inner mitochondrial membrane?

Answer 85

No.

Question 86

Where does the beta oxidation of fatty acids occur?

Answer 86

In the mitochondrial matrix.

Question 87

What fatty acids can cross the inner mitochondrial membrane?

Answer 87

Medium and short chain fatty acids.

Question 88

What is the carnitine shuttle used for?

Answer 88

To transport long chain fatty acids across the inner mitochondrial membrane.

Question 89

What organ is the carnitine shuttle particularly important in?

Answer 89

The heart.

Question 90

What fatty acid is used to power the heart?

Answer 90

Palmitoyl CoA.

Question 91

The oxidation of Palmitoyl CoA will generate how much ATP?

Answer 91

131 ATP.

Question 92

How will the heart gain TAGs after a meal?

Answer 92

From TAGs that are found in lipoproteins.

Question 93

How will the heart gain TAGs in the fasting state?

Answer 93

From the breakdown of TAGs in fat cells.

Question 94

What will the liver use as an energy source during fasting?

Answer 94

Only fatty acid oxidation.

Question 95

The NADH and ACoA that are produced in the beta oxidation of fats will are used by the liver for what?

Answer 95

As allosteric regulators of gluconeogenesis.

Question 96

What happens if the carnitine shuttle in the liver is inhibited?

Answer 96

It will result in severe hyperglycaemia.

Question 97

What happens in step 1 of the carnitine shuttle?

Answer 97

Fatty acyl CoAs cross into the intermembranous space and are joined to a carnitine molecule to make fatty acylcarnitine and free CoA.

Question 98

Where are fatty ACoAs synthesised?

Answer 98

In the outer membrane of the mitochondria.

Question 99

What enzyme joins fatty acyl CoA and carnitine in the intermembranous space?

Answer 99

Carnitine palmitoyl transferase-1.

Question 100

Where is carnitine palmitoyl transferase-1 found?

Answer 100

In the intermembranous space bound to the outer membrane.

Question 101

What is the susbtrate of carnitine palmitoyl transferase-1 found?

Answer 101

Fatty acyl CoA and carnitine.

Question 102

What is the product of carnitine palmitoyl transferase-1 found?

Answer 102

Fatty acylcarnitine and free CoA.

Question 103

What happens in step 2 of the carnitine shuttle?

Answer 103

A translocase enzyme takes fatty acylcarnitine across the inner mitochondrial membrane and delivers it into the mitochondrial matrix.

Question 104

What is the translocase enzyme in step 2 of the carnitine shuttle called?

Answer 104

Carnitine acyl carnitine translocase.

Question 105

How is free carnitine removed from the matrix?

Answer 105

As carnitine acyl carnitine translocase returns to the inter-membranous space it will transport free carnitine out of the matrix.

Question 106

What does carnitine acyl carnitine translocase do?

Answer 106

It transports free carnitine into the inter membranous space.

Question 107

What happens in step 3 of the carnitine shuttle?

Answer 107

An enzyme uses CoA to form fatty acyl CoA and free carnitine.

Question 108

What enzyme is used in step 3 of the carnitine shuttle to form fatty acyl carnitine and free CoA in the mitochondrial matrix?

Answer 108

Carnitine palmitoyl transferase 2 (CPT-2).

Question 109

What will fatty acyl CoA used for when it is in the mitochondrial matrix?

Answer 109

Beta oxidation.

Question 110

What is the substrate for CPT-7?

Answer 110

Fatty acylcarnitine and free CoA.

Question 111

What is the product for CPT-7?

Answer 111

Fatty acyl CoA and free carnitine.

Question 112

What must be inhibited when fatty acids are being synthesised?

Answer 112

The carnitine shuttle.

Question 113

What will inhibit the carnitine shuttle?

Answer 113

The presence of manolyl CoA in the cytosol.

Question 114

The presence of manolyl CoA in the cytosol will lead to what?

Answer 114

Fatty acid synthesis.