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PODT > Lecture 23 > Flashcards

Lecture 23 Flashcards

1
Q

How are lipids transported in circulation?

A

As lipoproteins

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2
Q

What are the components of lipoproteins?

A

Triglycerides, phospholipids, cholesterol, cholesterol ester, apolipoproteins.

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3
Q

What are some functions of apolipoproteins?

A

Solubilize the proteins, enzyme activation and receptor binding

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4
Q

What makes up a triglyceride?

A

1 Glycerol and 3 Fatty acids chains

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5
Q

What is a fatty acid?

A

Unbranched hydrocarbon chains with a carboxyl group at one end.

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6
Q

How are fatty acids stored?

A

Stored in adipose tissue s triglyceride, used as a source of energy and converted to ketone bodies in liver

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7
Q

What is more energy efficient fat or glucose?

A

Fat

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8
Q

How are fatty acids used as energy?

A

They enter the Beta-oxidation pathway to provide energy.

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9
Q

Why is it called Beta-oxidation?

A

Because it is the Beta carbon atom that is oxidised.

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10
Q

What does the Beta-oxidation of fatty acyl CoA produce?

A

One molecule of Acetyl CoA and reduced nucleotides.

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11
Q

What then happens to the acetyl CoA?

A

It enters the TCA cycle

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12
Q

What is the net product of ATP from the complete oxidation of a C16 fatty acid?

A

129ATPs

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13
Q

What can happen if excess Acetyl CoA is present?

A

It can be converted into ketone bodies - this is known as ketogenesis. It occurs in liver mitochondria.

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14
Q

What happens to the ketone bodies?

A

They enter the blood and travel to other tissues where they can be oxidised to provide energy

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15
Q

Can ketone bodies be converted back to acetyl CoA

A

Yes

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16
Q

What can carbohydrates be metabolised to?

A

They can be metabolised to acetyl CoA - which then undergo lipogenesis, this is the process by which acetyl CoA is converted to fatty acids and subsequently triglycerides

17
Q

How many steps is lipogenesis?

A

3 steps:

  1. Activation
  2. Elongation
  3. Termination
18
Q

How do you supply acetyl CoA for lipogenesis?

A

It combines with oxaloacetate to form citrate and CoA

19
Q

What is the next stage?

A

Citrate is then transported into the cytoplasm via a membrane transporter and cleaved to form acetyl CoA

20
Q

What is step 1 of the process?

A

Activation:

In the cytoplasm, Acetyl CoA is carboxylated to malonyl-CoA which is catalysed by acetyl-CoA carboxylase

21
Q

What is the rate limiting step of lipogenesis?

A

Step 1: Activation

22
Q

What is stage 2 of lipogenesis?

A

Step 2: Elongation

The next stage is catalysed by the fatty acid synthase complex

23
Q

What is fatty acid synthase?

A

Homodimer - two identical polypeptides with 7 different enzymes attached.

24
Q

What does fatty acid synthase do?

A

It adds two carbons atoms at a time from malonyl-CoA to the growing fatty acid carbon chain wit the los of CO2. This repeats 6 times.

25
Q

What is the 3rd step of Lipogenesis?

A

Step 3: Termination

Is the net reaction. Put in equation when doing proper notes

26
Q

What are the things for Beta-Oxidation?

A
  1. Occurs in mitochondria
  2. Separate enzymes
  3. Required NAD and FAD
  4. Energy yield - 129ATP
  5. Regulation - Acetyl CoA availability
27
Q

What are the things for Synthesis?

A
  1. Occurs in cytoplasm
  2. Multifunctional enzyme
  3. Required NADPH
  4. Energy requirement
  5. Regulation - Acetyl CoA carboxylase
28
Q

What are the components of cholesterol?

A

Precursor for synthesis of bile acids, steroid hormones, fat soluble vitamins such as A, D, E & K

29
Q

Describe cholesterol?

A

4 ring steroid structure, 27 carbons

30
Q

Describe cholesterol synthesis

A

All cells can synthesis cholesterol but the liver can synthesise the most, ALL 27 carbons come from Acetyl CoA, and synthesis occurs in the cytoplasm and ER

31
Q

What is the rate limiting step of cholesterol synthesis?

A

HMG-CoA reductase

PODT (24 decks)

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