L17

Front 1

What are the biological functions of lipids?

Back 1

1. Components of cellmembranes(phospholipids & cholesterol)

2. Precursors of hormonescholesterol steroid hormonesarachidonic acid prostaglandins

3. Long term fuels(triglycerides)

Front 2

Where are triglycerides stored?

Back 2

Compact storage - triglyceridesstored as large fat droplets inthe fat cells of adipose tissue

• Large body stores -70 kg adult has:

11 kg fat (as TG)

120 g glycogen in liver

10 g glucose

Front 3

What is the efficiency of fats on a weight basis?

Back 3

Efficiency on weight basis

–1 g fat yields 38 kJ

1 g protein 21 kJ

1 g carbohydrate 17 kJ

Front 4

What are some common fatty acids?

Back 4

palmitic acid C 16:0

stearic acid C 18:0

oleic acid C 18:1

linoleic acid C 18:2

linolenic acid C 18:3

Front 5

What is lipase activated by?

Back 5

Lipaseactivated byadrenaline& glucagon

Front 6

How do free fatty acids travel in the plasma?

Back 6

Free fatty acidstravel in plasmabound to albumin

Front 7

What do the fatty acids act as?

Back 7

Act as fuelsfor muscles,heart & liver

Front 8

What happens to the glycerol in the breakdown of triacylglycerides?

Back 8

Glyceroldiffuses inblood streamto all tissues

Front 9

How are triglycerides broken down?

Back 9

Front 10

Why can glycerol be taken up by all cells?

Back 10

Glycerol is water soluble & is taken up by alltissues

Front 11

What happens to glycerol in most tissues?

Back 11

Enters glycolysispathway for conversionto pyruvate, theninto TCA cycle foroxidation to CO2

Front 12

What happens to the glycerol in liver or in starvation?

Back 12

Enters glycolysispathway and isconverted to glucose bygluconeogenesis

Front 13

Where does Fatty acid metabolismby B-oxidation pathway take place?

Back 13

all reactions occur in the mitochondrial matrix(* transport across membrane)

Front 14

What are the intermediates in this pathway?

Back 14

intermediates present as CoA thioesters

Front 15

How is the biological energy of fatty acids conserved?

Back 15

biological energy of fatty acid molecule isconserved as the transfer of 2 H atoms to thecofactors NAD+ and FAD to form NADH & FADH2(no direct ATP synthesis)

Front 16

How is acetyl CoA removed?

Back 16

series of four enzyme reactions results in removalof two carbon unit as acetyl CoA

Front 17

What happens when the fatty acid is activated?

Back 17

Fatty acyl-CoA synthetase(cytosol)

Coenzyme A forms thioesterbonds with carboxylic acids

Front 18

How are fatty acids Transported intomitochondria?

Back 18

Front 19

What moves the carnitine across the inner mitochondrial membrane?

Back 19

Translocase

Front 20

What happens in reaction 1?

Back 20

Reaction 1 - Removal of 2 H atoms

acyl-CoAdehydrogenase

Front 21

What are the 4 reactions in B-oxidation of fatty acids?

Back 21

Front 22

What happens in reaction 2?

Back 22

Reaction 2 – Addition of water

Enoyl-CoA hydratase

Front 23

What happens in reaction 3?

Back 23

Reaction 3 – Removal of 2 H atoms

Hydroxyacyl-CoAdehydrogenase

Front 24

What happens in reaction 4?

Back 24

Reaction 4 - Removal of 2 C units

B-Ketoacyl-CoA thiolase

Front 25

What happens to the shorter fatty acid?

Back 25

Shorter fatty acid re entersreactions 1 - 4

Front 26

what is a summary of the B-oxidation pathway?

Back 26

Fatty acid with 16 C atomswill pass through 7 repeatsof B-oxidation pathwayproducing 7 NADH& 7 FADH2

Front 27

How many acetyl CoA will a fatty acid with 16 C atoms give rise to?

Back 27

Fatty acid with 16 Catoms will give riseto 8 acetyl CoA whichenter the TCA cycle

Front 28

What is the Energy yield from fatty acid oxidation?

Back 28

Fatty acid with 16 C atoms goes through 7 repeats of-oxidation producing 7 NADH & 7 FADH2

ATP yield = 7 x 2.5 + 7 x 1.5 = 28

Fatty acid with 16 C atoms produces 8 acetyl CoAATP yield from complete oxidation of acetyl CoAby TCA cycle = 8 x 10 ATP = 80

TOTAL = 80 + 28 = 108 – 1 = 107

Front 29

What activates lipase enzyme?

Back 29

Release of fatty acids from adipose tissueadrenaline & glucagon activate lipase enzyme

Front 30

What determines the rate of entry of fatty acid into mitochondria?

Back 30

Rate of entry into mitochondria via carnitineshuttle

Front 31

What determines the rate of reoxidation of cofactors NADH and FADH2?

Back 31

Rate of reoxidation of cofactors NADH & FADH2by cytochrome chain

Front 32

What happens in the metabolism of odd numbered fats?

Back 32

Front 33

When does ketogenesis occur?

Back 33

Ketogenesis occurs when fat metabolism is the main sourceof energy:

– in starvation

– in Type I diabetes

Front 34

What does fatty acid oxidation in hepatocytes lead to?

Back 34

Fatty acid oxidation in hepatocytes leads to highconcentrations of Acetyl Co A - exceeds capacity of the TCAcycle.

Front 35

What happens to the excess Acetyl CoA?

Back 35

Excess Acetyl CoA is converted into ‘ketone bodies’ in liver

Front 36

What are the ketone body compounds?

Back 36

Acetoacetate

B-Hydroxybutyrate

Front 37

What are the ketone bodies used for?

Back 37

Ketone bodies can be utilised for energy bymost (but not all) tissues

Front 38

What happens to the acetoacetate and β hydroxybutyrate?

Back 38

acetoacetate and β hydroxybutyrate are released into thebloodstream.

Front 39

What happens in most tissues?

Back 39

In most cell types they can be converted back into TCA cycleintermediates (acetyl CoA and succinate).

Most tissues oxidise a mixture of fatty acids and ketonebodies

Front 40

Liver cannot utilise ketone bodies – WHY?

Back 40

Ketone bodies cannot be used as fuel by the liver, because the liver lacks the enzyme β-ketoacyl-CoA transferase, also called thiophorase.

Front 41

Brain cannot utilise fatty acids – WHY?

Back 41

Cannot pass through Blood-Brain barrier

– uses glucose and small amount of ketone bodies (‘emergency fuel’)

Front 42

Red blood cells cannot utilise fatty acids or ketone bodies, useglucose only – WHY?

Back 42

No mitochondria