PoH: Lipids

Question 1

Name the 4 types of fatty acids

Answer 1

Saturated
Mono-unsaturated
Poly-unsaturated
Trans fats

Question 2

Name the 4 major lipid classes

Answer 2

Triacylglycerol
Phospholipid
Glycolipid
Steroids

Question 3

What is triacylglycerol made of, and why do we need them?

Answer 3

Esters of FAs and glycerol
Provide dietary fuel and insulation

Question 4

Are phospholipids water-soluble, fat-soluble or both? What 3 functions do they perform in the body

Answer 4

Both - amphipathic

Membranes
Lipid droplets
Local signalling molecules

Question 5

What sort of ring system do steroids have? Provide 3 examples of steroids in the body

Answer 5

4 Ring system

Cholesterol – starting material for synthesis of bile salts, steroid hormones and other components

Steroid hormones – serve as chemical messengers (corticosteroids, sex hormones)

Bile salts – sodium salts of steroid use for emulsification

Question 6

Describe the 2 functions of cholesterol

Answer 6

Component of cell membranes, e.g. plasma lipoproteins

Precursor to sterol hormones, vitamin D, bile acids and protein modification

Question 7

Describe the structure of cholesterol

Answer 7

C27H46O
It has a central sterol nucleus of four hydrocarbon rings

Question 8

What is eicosanoid derived from?

Answer 8

Oxidation of 20-carbon unsaturated fatty acids (omega 3 or 6)

Question 9

What 2 functions do eicosanoids have, and what’s their half-life like?

Answer 9

They’re signalling molecules

Precursors to prostaglandins

Short half life

Question 10

What is a steroid lipid made from and what is it a starting material for?

Answer 10

From cholesterol

Starting material for synthesis of bile salts, steroid hormones and other components

Question 11

Lipid digestion mainly occurs where?

Answer 11

Small intestine

Question 12

In what 3 ways are fats digested in the stomach?

Answer 12

· Pancreatic enzymes (lipates)
· Emulsification (dispersion) by bile salts
Peristalsis (mixing)

Question 13

How are FAs packaged and released?

Answer 13

Packaged into chylomicrons

Released by exocytosis

Question 14

How are chylomicrons broken down?

Answer 14

In tissues, TAG in chylomicrons is hydrolysed to FA and glycerol by lipoprotein lipase. Chylomicrons depleted of TAG are called chylomicron remnants which go to the liver

Question 15

After chylomicrons are degraded, what happens to the FAs?

Answer 15

The FAs are used for energy or re-esterified to TAG for storage.

Question 16

In what complex are free FAs transported around the body?

Answer 16

In a complex with serum albumin

90% of FAs are esterified (not free)

Question 17

Define essential fatty acid

Answer 17

Polyunsaturated fatty acids that we must get from the diet because they’re needed for health but we cannot synthesise these in the body.

Question 18

Where do FAs come from?

Answer 18

Diet

Stored lipid/tryglyceride (released from adipose tissue)

Synthesised in body through Citrate Shuffle (via palmitate from Acetyl CoA)

Question 19

What 3 places does free FA synthesis occur in the body?

Answer 19

Liver

Lactating mammary gland

Adipose tissue

Question 20

What does the Citrate Shuffle do?

Answer 20

Synthesises FAs

Question 21

Where does the Citrate Shuffle take place? Where does modification occur?

Answer 21

Mitochondria and cytosol

Further modification in mitochondria and ER

Question 22

Which of the following can be used in the Citrate Shuffle to make FAs: Fat, protein, carbohydrate

Answer 22

All

Question 23

What does b oxidation involve?

Answer 23

It involves taking a long FA chain and nibbling bits off to produce FADH, ATP, NADH and Acetyl CoA

Question 24

Name the 3 steps of b oxidation

Answer 24

1) Oxidation of FAs

2) Carnitine shuttle to transport into mitochondrial matrix

3) Degradation with 4 main enzyme reactions

Question 25

What type of chemical reactions are the steps of b oxidation?

Answer 25

Dehydrogenation
Hydration
Dehydrogenation
Thiolysis

Question 26

Describe the function of ketone bodies

Answer 26

Provide energy when fasting, as there’s no glucose to use. If there’s no insulin it impairs use and leads to diabetic ketoacidosis

Question 27

Where are ketone bodies produced?

Answer 27

Liver

Question 28

How are ketone bodies produced and what happens to the product?

Answer 28

β-oxidation of fatty acids => Acetyl CoA

Acetyl CoA + Pyruvate enter Citric Acid Cycle to form ATP

Question 29

In what part of cells are KBs metabolised? What do they yield? What are they reconverted into?

Answer 29

KB can be oxidised in the mitochondria to yield 2 GTP and 22 ATP

They’re transported to tissues and reconverted to Acetyl CoA

Question 30

In b oxidation, what transports oxidised fatty acids into the mitochondrial matrix?

Answer 30

Carnitine shuttle