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Biochemistry > Fat metabolism > Flashcards

Fat metabolism Flashcards

1
Q

How is most energy in the body stored?

A

As fat

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2
Q

What are the long term energy stores in the body?

A

Lipids and ketone bodies

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3
Q

Why is fat such a good storage of energy?

A

High density of energy can be stored in a small space

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4
Q

What are the break down products of lipids?

A

Fatty acids and glycerol

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5
Q

How do fatty acids produce ATP? Where does lipid break down occur and under what conditions?

A

They are oxidised
location: muscle and liver
Conditions: aerobic

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6
Q

Where are fatty acids converted into keton bodies and under what conditions?

A

Location: liver
Condition: Aerobic

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7
Q

Name the two mechanisms outside of lipolysis that lead to the break down of fatty acids

A

B-oxidation

Ketogenesis

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8
Q

Where does lipolysis mainly occure? What conditon does it need to occur? What are the products?

A

Location: liver and muscle
Condition: Aerobic
Products: Acetyl-CoA and glyceral

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9
Q

Which mechanism does Acetyl-CoA feed into?

A

Start of the TCA cycle

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10
Q

Which enzymes regulates lipolysis?

A

Hormone sensitive lipase

Adipose triglyceride lipase

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11
Q

How is Hormone sensitive lipase regulated?

A

Activated by glucagon and adrenaline, cAMP,

Inhibited insulin

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12
Q

How does cAMP activate HSL

A

cAMP activates kinases which phosphorylates HSL making it active

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13
Q

How does insulin inhibit HSL?

A

Insulin blocks cAMP activity and keeps HSL inactive (de-phosphorylated)

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14
Q

How does Adipose triglyceride regulate lipase

A

Breaks down triglycerides into diglycerides and fatty acids

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15
Q

How is fatty acid converted to acetyl Co- A?

A

Free fatty is bound to albumin in the blood
1. FA —-> Fatty acytl CoA
Enzyme: Acyl CoA synthase
Uses ATP-AMP
2. Fatty acyl CoA is transported into the mitochondria by carnitine shuttle
3. B-oxidation of fatty acyle CoA to acetyle CoA + NADH (TCA cycle)

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16
Q

Describe the carnitine shuttle

A
  1. Fatty acyle Co-A is linked to a carnitine molecule using ATP
    Enzyme: CAT1 (mitochondria)
  2. Acyl-CoA and carnitine complex is transfered to the matrix
    Enzyme:Translocase
  3. Acyl-CoA is seperated from complex inside the matrix. Carnitine is is shuttled out
    Enzyme: CATII
17
Q

Regulation of FA breakdown short and long term

A

Transport of FA into mitochondria is:
Inhibited by: malonyl Co-A
Activated: glucagon through cAMP signalling to transport more Fatty acyl-coA into the mitochondria
allosteric
Long term regulation: Changes to CATI/CPTI gene expression

18
Q

Describe the B-oxidation of Acyl-coA

Which requires more enzymes, saturated or unsaturated fatty acids?

A

2 Carbons removed from each turn of FA during the spiral reaction to produce acetyl-coA
Catalysed by many enzymes

Saturated fatty acids

19
Q

What is the product of beta oxidation?

A

Acetyl-co A

1 NADH and1 FADH

20
Q

Where does beta oxidation not occur? Why?

A

Brain- albumin can not pass BBB

red blood cells- no mitochondria

21
Q

What is lipid synthesis?

A

The conversion of glucose into fatty acid to for fat

22
Q

Describe the stages of lipid synthesis

A
  1. Glucose is converted to pyruvate
  2. Pyruvate is used in the TCA cycle
  3. Citrate leaves the TCA cycle
  4. Citrate is converted into acetyle co-A-malonyl-coA
  5. Acetyle co-A-malonyl-coA is converted into malonyl co- A.
  6. Malonyl co- A is added to a growing chain of fatty acids (fatty acid synthase)
  7. FA produced
23
Q

Where does lipid synthesis occur?

A

Liver, white adipose tissue, lactating mammary glands

24
Q

How is lipid synthesis regulated?

A

The conversion of Acetyle co-A into malonyl co A. is regulated by the enzyme acetyl coA carboxylase

Malonyl co-A is an allosteric inhibitor of carnitine shuttle. It inhibits the shuttling of FA into the mitochondria so it can not be broken down

25
Q

How is acetyl coA carboxylase regulsted?

A

Polymerisation activates it- this only occurs in the presence of citrate

Phosphorylation by a kinase also makes it inactive

Long term- Gene/protein expression level

26
Q

What are ketone bodies?

A

The name of the 3 molecules produced during fatty acid break down:
Acetone
Acetoacetate
2 hydroxybutyric acid

27
Q

State 2 main properties of keton bodies

A

Water soluable- easier to transport

Can be used by many organs to generate energy

28
Q

Where and how are keton bodies made?

A

Liver only
Produced from acetyl coA
During ketogenesis

29
Q

Describe how keton bodies are produced (ketogenesis)

A

In the liver-
3 acetyle-CoA joint to form HMG- CoA by HMG- CoA synthase
HMG- CoA is them broken down into acetoacetate which can be converted into 2 hydroxybutyric acid

30
Q

How is ketogenesis regulated?

A

Formation of HMG- CoA by HMG- CoA synthase is
short term regulation: Acetylation
Long term: Gene expression by FOXA2 and PPARA
(lipid activated transcription factor)

31
Q

How are ketones used for energy?

A

Ketone bodies leave the liver, enter the blood, where they are trasported to other tissues.

They are converted to acetyle-CoAand used in the TCA cycle to make ATP

32
Q

Key feature of ketone use during starvation

A

brain uses 50% ketones only during starvation

33
Q

Which organs always use ketone bodies

A

Heart, muscles

34
Q

Which organ can not use ketone bodies are why?

A

Liver

does not have the enzyme to break it down

35
Q

Use of ketone bodies in new born babies?

A

New born babies have an absolute requirement for keton bodies

36
Q

How is fatty acid transported in the blood?

A

Bound to albumin

37
Q

What is metabolic flexibility? Which type of individuals have good metabolic flexibility? Which type of individuals do not have good metabolic flexibility and why?

A

The ability to switch from glucose to fats as a source of energy as a response to the changes in metabolic demands (exercise vs fasting)
People who exercise regularly tend to have good metabolic flexibility
Metabolic inflexibility tends to occur in obese and diabetic people
Have decreased ability to burn fat

Biochemistry (7 decks)

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