Lipids 2 Flashcards

1
Q

In the beta oxidation pathway, how many fatty acid carbons does it break down at a time?

A

2

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2
Q

What are the products of beta oxidation?

A

Acetyl CoA, NADH, and FADH2 all sources of energy for ATP

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3
Q

Where does beta oxidation occur?

A

In the mitochondrial matrix

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4
Q

What does FA released from an adipocyte bind to?

A

Albumen

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5
Q

What are the stages for fatty acid to undergo beta oxidation?

A

Activation, transport and degradation (explain each)

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6
Q

How is the fatty acid released from adipocytes?

A

lipolysis

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7
Q

How does the fatty acyl co a cross the mitochondrial walls?

A

Fatty acyl co a diffuses across the first membrane. The carnitine shuttle is responsible for the movement of the fatty acyl co a across the second membrane- Co a component of the molecule is removed, remaining molecule then binds to carnitine and passes over the membrane with help from translocase. Carnitine is removed and fatty acyl co a is reformed

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8
Q

What is the effect of malonyl co a?

A

Malonyl is needed for FA synthesis - therefore prevent the synthesis and degradation happening at the same time.

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9
Q

What is the effect of carnitine fatty acyl tranferase or carnitine palmitoyl transferase deficiency?

A

No beta oxidation
Hypoglycemia

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10
Q

What are the steps of degradation?

A

Dehydrogenation - produces FADH2
Hydration - Requires H20
Dehydrogenation- To produce NADH
Thyolysis- Cleaved to produce acetyl co a

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11
Q

What is the precursor of FADH2 and NADH

A

FADH2 = FAD
NADH = NAD+

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12
Q

What happens to acetyl co a produced?

A

Joins TCA cycle (citric acid cycle)

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13
Q

What carbon products are produced after every beta oxidation cycle?

A

A carbon species two carbons shorter than the original + acetyl co a

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14
Q

How much ATP does each of the following molecules give / use?
FADH2
NADH
Acetyl Co A

A

FADH2 = 2 ATP
NADH = 3 ATP
Acetyl Co a = 12 ATP

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15
Q

Where does a preliminary beta oxidation of very long fatty acids take place?

A

Peroxisomes

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16
Q

Why is the first step (dehydrogenation) less energy efficient?

A

No FADH2 is produced

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17
Q

What happens to the FA linked to the carnitine?

A

Diffuses from peroxisome to mitochondria for further oxidation

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18
Q

What happens to acetyl co a levels during fasting / starvation?

A

Liver flooded with acetyl co a

19
Q

What is the effect of high acetyl co a levels on pyruvate dehydrogenase?

A

Pyruvate dehydrogenase is inhibited reducing further acetyl co a formation

20
Q

What is the effect of high acetyl co a levels on pyruvate carboxylase?

A

Activates pyruvate carboxylase and therefore increases the oxaloacetate present

21
Q

What does the amount of ketogenesis depend on?

A

The amount of acetyl co a, excess is converted into ketone bodies

22
Q

What muscles use ketone bodies as an energy source?

A

The skeletal muscles, and the cardiac muscles

23
Q

What important organ can ketone bodies also provide energy for?

A

The brain

24
Q

Where are ketone bodies formed?

A

The liver, although the liver cannot actually use them!

25
Q

How are ketone bodies transported from the liver?

A

In the blood to other tissues, they are soluble and do not need albumen or lipoprotein

26
Q

What can lead to very high levels of ketone bodies in the blood?

A

Starvation or uncontrolled diabetes

27
Q

What can result from a higher build to use ratio of etone bodies?

A

Ketonemia, ketonuria and acidosis
fruity breath odour due to acetone

28
Q

What is the initial trigger for lipolysis?

A

‘The fasted state’ - glucagon production due to low blood glucose levels

29
Q

Describe the process of lipolysis?

A

Triglycerides are broken down by Lipase enzymes into 3 free fatty acids released into the blood and glycerol

30
Q

Functions of oxidation of fatty acids in the liver

A

energy for liver, ketone body production

31
Q

Which pathway is favoured for fatty acid metabolism during fasted state?

A

Beta-Oxidation and (increased lipolysis)

32
Q

Which pathway is favoured for fatty acid metabolism during fasted state?

A

Triglyceride synthesis and (decreased lipolysis)

33
Q

Steps of Beta-oxidation

A
  1. Long fatty acids >22 carbons broken down by peroxisomes
  2. Dehydration - FADH2
  3. Rehydration
  4. Dehydration - NADH + H+
  5. Breaking bond by introducing CoA - Acetyl group + original molecule -2 carbons
34
Q

What causes ketone body production?

A

Fasting state, Glycogon

35
Q

What happens when acetyl-CoA is produced during fasting state and what can this lead to?

A

Excessive acetyl-CoA is stored as ketone bodies which are acidic and can lead to ketoacidosis

36
Q

Where does fatty acid synthesis occur?

A

Mostly in cytosol of liver (also in lactating mammary gland and adipose tissue)

37
Q

What is the key molecule needed to add on 2 carbons to a fatty acid during FA synthesis

A

Malonyl CoA (Formed from Acetyl-CoA)

38
Q

What is the purpose of the citrate shuttle?

A

To transfer Acetyl CoA from TCA cycle across mitochondrial membrane into the cytosol (By combining with oxaloacetate then removing when across the membrane)

39
Q

How is Acetyl-CoA converted into Malonyl-CoA

A

Acetyl-CoA carboxylase + 1 ATP

40
Q

What does malonyl CoA react with to synthesis FAs

A

Acyl carrier protein (ACP)

41
Q

What FA is produced at the ens of FA synthesis

A

palmitate (C16)

42
Q

Where does triglyceride synthesis occur?

A

Endoplasmic reticulum (contains enzymes to synthesise triglycerides from fatty acid CoAs)

43
Q

Can FA synthesis and degradation occur at the same time?

A

No