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Science for Medicine > Lipids 2 > Flashcards

Lipids 2 Flashcards

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1
Q

Where does beta oxidation occur?

A

Mitochondrial matrix

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2
Q

What is produced from B-oxidation?

A
  • Degrades FA 2 C at a time

- Produces acetyl CoA and also NADH and FADH2 which are sources of energy

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3
Q

What are the 3 stage of B-oxidation and where do they occur?

A
  • Activation of FA: cytosol
  • Transport into the mitochondria
  • Degradation to 2 C fragments: mitochondrial matrix
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4
Q

What is FA activated to form?

A

Fatty acyl CoA I the cytoplasm

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5
Q

What mechanism is used in the transport of fatty acyl CoA to the mitochondrial matrix?

A

The Carnitine shuttle

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6
Q

Why is the carnitine shuttle used?

A

CoA is very big and can diffuse through the outer membrane but not the inner membrane

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7
Q

What does carnitine palmitoyl transferase I do?

A

Transfers FA from FA acyl CoA to carnitine

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8
Q

What enzyme aids the movement of FA carnitine across the membrane?

A

Translocase

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9
Q

What does carnitine palmitoyl transferase II do?

A

Transfers FA from FA carnitine to acyl CoA

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10
Q

What enzyme moves carnitine back to its original position?

A

Translocase

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11
Q

What inhibits carnitine palmitoyl transferase?

A

Malonyl CoA

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12
Q

What does malonyl Co do?

A

Prevents synthesis and degradation occurring simultaneously

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13
Q

Where do we get carnitine from/

A

Mainly our diet or can be made from lysine or methionine in the liver/kidney

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14
Q

What is occurs during carnitine palmitoyl transferase deficiency?

A
  • No B-oxidation occurs which results in hypoglycaemia
  • Coma on overnight fast
  • Improved with IV glucose
  • Give medium chain FA which do not require CPT1 for mitochondrial transport
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15
Q

What is acarnitine palmitoyl transferase deficiency?

A

A carnitine associated defect in liver DA B-oxidation which impairs the liver’s capacity to use FA as fuels, putting extra burden on its capacity to generate glucose through gluconeongensis

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16
Q

What are the 4 main stages in degradation?

A

-Dehydrogenation
-hydration
Dehydrogenation
Thiolysis

17
Q

What does the dehydrogenation (stage 1) produce?

A

FADH2 from FAD

18
Q

What does the dehydrogenation (step 3) produce?

A

NADH from NAD

19
Q

What does thiolysis (step 4) produce?

A

Acetyl CoA which feeds into TCA cycle

20
Q

What does each cycle of B-oxidation produce?

A

One acetyl CoA and a species 2 carbon atoms shorter than the original

21
Q

What happens to very long chain fatty acids before B-oxidation?

A

Undergoes a preliminary B-oxidation in peroxisomes

22
Q

Why is B-oxidation in peroxisomes less energy efficient?

A

The first step doe not produce FADH2

23
Q

What happens to the shortened FA after B-oxidation in the peroxisome?

A

It is linked to carnitine and diffuses out of the peroxisome into the mitochondria for further oxidation

24
Q

What do defects in the B-oxidation pathway in peroxisomes result in?

A

VLC-FA accumulation in blood and tissue

25
Q

Why can animals not convert FA to glucose?

A
  • No FA is gluconeogenic

- They are unable to convert CoA into glucose due to thermodynamically irreversible pyruvate to acetyl CoA step

26
Q

What happens to excess Acetyl CoA?

A

Form ketone bodies

27
Q

What affect does acetyl CoA have on enzymes?

A
  • Inhibits pyruvate dehydrogenase

- Activates pyruvate carboxylase

28
Q

What does the amount of ketogenesis depend on?

A

The availability of acetyl CoA

29
Q

When is acetyl CoA converted to ketone bodies?

A

During fasting or starvation, when glucose is decreased

30
Q

What uses ketone bodies as an energy source?

A

Cardiac and skeletal muscles

31
Q

When can ketone bodies fuel brain cells?

A

During starvation

32
Q

Where are ketone bodies found?

A

Formed in the liver in the mitochondrial matrix and is transported with the blood to other cells where it is used as fuels

33
Q

What can the liver not do in regards to ketone bodies?

A

Use them as a fuel source

34
Q

What can lead to very high ketone body concentrations in the blood?

A

-Uncontrolled diabetes or starvation

35
Q

What happens when the rate of ketone body production exceeds utilisation?

A

Ketonemia, ketonuria and acidemia

36
Q

When does diabetic ketosis result?

A

When insulin is absent

37
Q

Why can Acetyl CoA not be processed after B-oxidation?

A

Due to a lack of glucose derived oxaloacetate

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