23-Lipid synthesis and Lipid formation

Question 1

What are lipoproteins?

Answer 1

Particles that transport lipids

Question 2

What are lipoproteins made up of?

Answer 2

Triglyceride
Phospholipids
Cholesterol 
Cholesterol ester
Apolipoproteins

Question 3

What are the three functions of apolipoproteins?

Answer 3

Interact with lipid component and help solubilize the particles
Enzyme activation or inhibition
Receptor binding

Question 4

What are triglycerides broken down to during digestion?

Answer 4

Three fatty acids and glycerol

Question 5

How are fatty acids stored?

Answer 5

Stored in adipose tissue as triglyceride

Question 6

What fatty acids used for?

Answer 6

Used as a source of energy

Converted to ketone bodies in liver

Question 7

What is beta oxidation?

Answer 7

Beta carbon atom on the fatty acid is what is being oxidised

Question 8

What happens during beta oxidation of fatty acids?

Answer 8

4 step cyclic process taking off two carbons each cycle

Question 9

What does one beta oxidation cycle release?

Answer 9

One molecule of acetyl CoA and reduced nucleotides

Question 10

What is the net gain of ATP from the complete oxidation of C16?

Answer 10

129 ATPs

Question 11

What happens if there is excess acetyl- CoA? Where does this occur and what is it known as?

Answer 11

Acetyl CoA can be converted to ketone bodies
Occurs in liver mitochondria
Known as Ketogenesis

Question 12

What is the role of ketone bodies?

Answer 12

Ketone bodies enter the blood and travel to other tissue where they can be oxidised to provide energy.
Can be converted back to acetoacetyl-CoA and then acetyl-CoA

Question 13

People with diabetes often have a strong smell on the breath what is this from?

Answer 13

Acetotacetate decarboxylates to acetone

Question 14

What is lipogenesis?

Answer 14

Fatty acid formation

The process by which acetyl-CoA is converted to fatty acids, and subsequently triglycerides

Question 15

Where does fatty acid synthesis take place?

Answer 15

Cytosol

Question 16

What is the first step in fatty acid synthesis catalysed by?

Answer 16

Acetyl-CoA carboxylase

Question 17

What are the enzymes involved in fatty acid synthesis?

Answer 17

7 enzymes joined by a polypeptide chain called fatty acid synthesis

Question 18

How is the growing fatty acid chain elongated?

Answer 18

The sequential addition of two carbon units derived from acetyl CoA, and the active donor of this 2 carbon unit is malonyl- CoA

Question 19

What is the reductant in fatty acid synthesis?

Answer 19

NADPH

Question 20

When does the elongation of the fatty acid complex stop?

Answer 20

When there is a C16 - palmitate

Question 21

What are the 3 steps of fatty acid synthesis?

Answer 21

Activation
Elongation
Termination

Question 22

Where is Acetyl CoA generated?

Answer 22

Mitochondria and cannot cross the inner mitochondrial membrane

Question 23

How is acetyl- CoA supplied for lipogenesis?

Answer 23

Acetyl- CoA combines with oxaloacetate to produce citrate

Question 24

What is meant by the term elongation which happens during lipogenesis?

Answer 24

Chain elongation mainly occurs in the ER by ezymes called fatty acid elongases.
2C are added at a time from malonyl-CoA and the reductant is again NADPH

Question 25

What is meant by desaturation which happens during lipogenesis?

Answer 25

Desaturase enzymes located in the ER membrane introduce specific bonds at specific postitions in the fatty acid chain.
This requires NADP and O2

Question 26

What is cholesterol?

Answer 26

Biological lipid made up of 27 carbons

Question 27

What is the rate limiting step during cholesterol synthesis?

Answer 27

HMG-CoA reductase

Question 28

What happens in the rate limiting step in cholesterol synthesis?

Answer 28

HNG-CoA becomes mevalonate

Question 29

What happens when cholesterol levels are high?

Answer 29

Result in decreased HMG-CoA reductase transcription- caused reduced cholestrol production

Question 30

What happens when cholesterol levels are too low?

Answer 30

Increased HMG-CoA reductase transcription - caused increased cholesterol production

Question 31

What are satins used for?

Answer 31

Inhibit HMG- CoA reductase and reduce cholesterol biosynthesis