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42 Cards in this Set

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What are the biological functions of lipids?

1. Components of cellmembranes(phospholipids & cholesterol)


2. Precursors of hormonescholesterol steroid hormonesarachidonic acid prostaglandins


3. Long term fuels(triglycerides)

Where are triglycerides stored?

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

What is the efficiency of fats on a weight basis?

Efficiency on weight basis


–1 g fat yields 38 kJ


1 g protein 21 kJ


1 g carbohydrate 17 kJ

What are some common fatty acids?

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

What is lipase activated by?

Lipaseactivated byadrenaline& glucagon

How do free fatty acids travel in the plasma?

Free fatty acidstravel in plasmabound to albumin

What do the fatty acids act as?

Act as fuelsfor muscles,heart & liver

What happens to the glycerol in the breakdown of triacylglycerides?

Glyceroldiffuses inblood streamto all tissues

How are triglycerides broken down?



Why can glycerol be taken up by all cells?

Glycerol is water soluble & is taken up by alltissues

What happens to glycerol in most tissues?

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

What happens to the glycerol in liver or in starvation?

Enters glycolysispathway and isconverted to glucose bygluconeogenesis

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

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

What are the intermediates in this pathway?

intermediates present as CoA thioesters

How is the biological energy of fatty acids conserved?

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)

How is acetyl CoA removed?

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

What happens when the fatty acid is activated?

Fatty acyl-CoA synthetase(cytosol)


  Coenzyme A forms thioesterbonds with carboxylic acids

Fatty acyl-CoA synthetase(cytosol)




Coenzyme A forms thioesterbonds with carboxylic acids

How are fatty acids Transported intomitochondria?

What moves the carnitine across the inner mitochondrial membrane?

Translocase

What happens in reaction 1?

Reaction 1 - Removal of 2 H atoms




acyl-CoAdehydrogenase

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

What happens in reaction 2?

Reaction 2 – Addition of water


Enoyl-CoA hydratase

What happens in reaction 3?

Reaction 3 – Removal of 2 H atoms


Hydroxyacyl-CoAdehydrogenase

What happens in reaction 4?

Reaction 4 - Removal of 2 C units




B-Ketoacyl-CoA thiolase

What happens to the shorter fatty acid?

Shorter fatty acid re entersreactions 1 - 4

what is a summary of the B-oxidation pathway?

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

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

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

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

What is the Energy yield from fatty acid oxidation?

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

What activates lipase enzyme?

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

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

Rate of entry into mitochondria via carnitineshuttle

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

Rate of reoxidation of cofactors NADH & FADH2by cytochrome chain

What happens in the metabolism of odd numbered fats?

When does ketogenesis occur?

Ketogenesis occurs when fat metabolism is the main sourceof energy:


– in starvation


– in Type I diabetes

What does fatty acid oxidation in hepatocytes lead to?

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

What happens to the excess Acetyl CoA?

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

What are the ketone body compounds?

Acetoacetate


B-Hydroxybutyrate

What are the ketone bodies used for?

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

What happens to the acetoacetate and β hydroxybutyrate?

acetoacetate and β hydroxybutyrate are released into thebloodstream.

What happens in most tissues?

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

Liver cannot utilise ketone bodies – WHY?

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

Brain cannot utilise fatty acids – WHY?

Cannot pass through Blood-Brain barrier




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

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

No mitochondria