Session 2 Lecture 2

Question 1

Are lipids soluble or insoluble?

Answer 1

Insoluble in water (hydrophobic) but are soluble in organic solvents

Question 2

How many classes of lipids are there?

Answer 2

3

Question 3

What are the different classes of lipids?

Answer 3

• Fatty acid derivatives
• Hydroxyproline-methyl glutaric acid derivatives
• Vitamines

Question 4

Give some examples of fatty acid derivatives

Answer 4

Fatty acids
Triacylglycerides
Phospholipids
Eicosanoids

Question 5

What are fatty acids?

Answer 5

Fuel molecules

Question 6

What are triacylglyerols?

Answer 6

Fuel storage and insulation

Question 7

What are phospholipid function?

Answer 7

Component of membrane and plasma lipoproteins

Question 8

What is eicosanoids function?

Answer 8

Local mediators

Question 9

Give some examples of hydroxyl-methyl acid derivatives

Answer 9

Ketone bodies
Cholesterol
Cholesterol esters
Bile acids and salts

Question 10

What are ketone bodies?

Answer 10

Water soluble fuel molecules

Question 11

What is function of cholesterol?

Answer 11

Membrane and steroid hormone synthesis

Question 12

What is the function of cholesterol esters?

Answer 12

Cholesterol storage

Question 13

What is the function of bile acids and salts?

Answer 13

Lipid digestion

Question 14

What is the major dietary and storage lipid in the body?

Answer 14

Triacylglycerols

Question 15

What is the structure of a triacylglycerol?

Answer 15

3 fatty acids esterified to glycerol

Question 16

Describe some features of triacylglycerols?

Answer 16

Triacylglycerols are hydrophobic therefore stored in an anhydrous form.

Question 17

How are TAGs stored?

Answer 17

Adipose tissue

Question 18

When are TAGs used?

Answer 18

Utilised in prolonged exercise, starvation and during pregnancy

Question 19

What sort of control is the storage of TAGs under?

Answer 19

Hormonal control

Question 20

What is the storage of TAGs promoted by?

Answer 20

Insulin

Question 21

What is storage of TAGs reduced by?

Answer 21

Glucagon, adrenaline, cortisol, growth hormone and thyroxine.

Question 22

What happens when you ingest lipids?

Answer 22

The lipid is hydrolysed by pancreatic lipase in the small intestine to glycerol and fatty acids

Question 23

What does the hydrolysation of lipids require?

Answer 23

Bile salts and a protein factor called colipase

Question 24

What happens to the glycerol from the lipid breakdown?

Answer 24

Glycerol enters the blood stream and is transported to the liver where it is metabolised

Question 25

Describe some features of fatty acids?

Answer 25

They are hydrophobic and highly reduced molecules, properties that make them ideal for energy storage

Question 26

Are saturated fatty acids non essential components of the diet?

Answer 26

Yes because they can be synthesised from carbohydrates and certain amino acids

Question 27

Why are certain polyunsaturated fatty acids essential components of the diet?

Answer 27

They can't be synthesised in the body

Question 28

Give a n example of an important polyunsaturated fatty acid?

Answer 28

Arachidonic acid - it is a starting point for the synthesis of the eicosanoids

Question 29

What are the eicosanoids?

Answer 29

They are a family of signalling molecules in the body, including prostaglandins

Question 30

What happens to some of the fatty acids and glycerol in the small intestine?

Answer 30

Some is recombined and transported as TAG by chylomicrons and stored as adipose tissue

Question 31

What activated fat metabolism?

Answer 31

Stressful situations - aerobic exercise, starvation, lactation. Adrenaline, glucagon, GH, cortisol and thyroxine

Question 32

What inhibits fat metabolism?

Answer 32

Insulin

Question 33

What is the first stage in fat metabolism?

Answer 33

Adipose tissue TAG are hydrolysed by the enzyme hormone-sensitive lipase to release fatty acids and glycerol

Question 34

What is the first stage of fat metabolism called?

Answer 34

Lipolysis

Question 35

How are fatty acids carried to tissues?

Answer 35

This is done via the blood stream bound non-cavelently to albumin

Question 36

What are albumin bound fatty acids known as?

Answer 36

Non-esterified fatty acids (NEFA) or free fatty acids (FFA)

Question 37

What happens to glycerol in the liver?

Answer 37

It may be oxidised, converted to glucose or used in the synthesis of TAGs

Question 38

What is Beta-oxidation?

Answer 38

The process by which fatty acids are oxidised to release energy

Question 39

Where does beta-oxidation occur?

Answer 39

Mitochondria

Question 40

Why does beta-oxidation not occur in cells of the central nervous system?

Answer 40

Fatty acids do not readily cross the blood-brain barrier

Question 41

What needs to happen before fatty acids oxidised?

Answer 41

They have to be activated

Question 42

How are fatty acids activated?

Answer 42

Link the fatty acids to coenzyme

Question 43

What is required for the activation of fatty acid?

Answer 43

ATP and is catalysed by fatty acyl coA synthase

Question 44

Where does the activation of fatty acids occur?

Answer 44

Outside of the mitochondrion

Question 45

How does the activated fatty acid cross the inner mitochondrial membrane?

Answer 45

Carnitine shuttle

Question 46

What inhibits the transport of activated fatty acids?

Answer 46

Malonyl coA - an intermediate in the synthesis of fatty acids

Question 47

What happens if someone suffers from a defective micotchondiral fatty acid transport system?

Answer 47

They suffer from poor exercise tolerance and have usually large amounts of TAGs in their muscle cells therefore get lipid droplets in muscle

Question 48

What happens overall in beta-oxidation of fatty acids?

Answer 48

Oxidised the fatty acid and removes a C2 unit. The shortening fatty acid is cycled through the reaction sequence repeatedly removing a C2 unit each turn until only 2 carbon atoms remain

Question 49

What does the reaction sequence for beta-oxidation require?

Answer 49

Mitochondrial NAD+ and FAD and can;t occur in the absence of oxygen.

Question 50

Is ATP synthesised in b-oxidation

Answer 50

No direct synthesis

Question 51

What is special about all the intermediates in the pathway?

Answer 51

They are linked to coA and the C atoms of the fatty acid are converted to acetyl coA

Question 52

Which process derives more energy - FA oxidation or glucose oxidation?

Answer 52

Fatty acid oxidation

Question 53

What is the main convergence point for catabolic pathways?

Answer 53

Acetyl coA

Question 54

How many different ketone bodies are produced in the body?

Answer 54

3

Question 55

What are the different ketone bodies produced in the body?

Answer 55

Acetoacetate, acetone and b-hydroxybutyrate

Question 56

Where is acetoacetate synthesise?

Answer 56

Liver from acetyl coA

Question 57

Where is b-hydroxybutyrate synthesised and where from?

Answer 57

Liver from acely coA

Question 58

How is acetone synthesised?

Answer 58

Arises from spontaneous (non-enzymatic)

Question 59

When can the concentration of ketone bodies increase?

Answer 59

Increases in starvation and untreated type 1 diabetes

Question 60

Where are ketone bodies synthesised?

Answer 60

Liver mitochondria

Question 61

What enzymes are responsible for synthesis of ketone bodies in the liver?

Answer 61

Lyase and reductase enzymes

Question 62

What controls the lyase and reductase enzymes?

Answer 62

Controlled by the insulin/glucagon ration

Question 63

What happens when the insulin/glucagon ration falls?

Answer 63

Lyase is activated and reductive is inhibited and ketone body formation is activated

Question 64

What happens when the insulin/glucagon ratio increases?

Answer 64

The lyase is inhibited and the reductive is activated and cholesterol synthesis occurs

Question 65

What does the synthesis of ketone bodies require?

Answer 65

Fatty acids to be available for oxidation in the liver following excessive lipolysis in adipose tissue. The plasma insulin/glucagon ratio to be low, usually due to a fall in plasma insulin

Question 66

Ketone body function?

Answer 66

Important fuel molecules that can be used by all tissues containing mitochondria including the CNS

Question 67

What happens if acetoacetate and b-hydroxybutyrate are present in high concentrations?

Answer 67

They may cause acidosis (ketoacidosis)

Question 68

Why do you get the characteristic smell of acetone on someone's breath if they have untreated type 1 diabetes?

Answer 68

Acetone is a volatile substance that may be excreted via the lungs