Lipids

Question 1

Describe the general map of fat metabolism in fed vs. fasting state

Answer 1

Fed: through your diet, you obtain nutrients that are absorbed in your body and transported - they then make triglycerides for future use (resulting in adipose tissue)

Fasting: when hungry lipolysis of fats occurs producing fatty acids. These fatty acids are used in beta oxidation for energy, as well as ketogenesis in the liver to make ketones used for energy

Question 2

What is MCAD deficinecy?

Answer 2

MCAD = medium chain acyl CoA dehydrogenase deficiency

MCAD is involved in mitochondrial fatty acid beta oxidation - it fuels hepatic ketogenesis: major source of energy once hepatic glycogen stores become depleted during prolonged fasting and periods of higher energy demands

MCAD deficiency presents as intolerance to prolonged fasting, hypoglycaemia, impaired ketogenesis

Question 3

What is the main function of lipids in the body?

Answer 3

it is the major source of energy, structural component of cells and organelles, and it is involved in cellular signalling events (steroids, prostaglandins, and leucotrienes)

Question 4

Describe the structrue of a fatty acid

Answer 4

a hydrophobic hydrocarbon chain with a terminal carboxyl group

Question 5

What does omega 3 or omega 6 nomenclature refer to with regards to lipids?

Answer 5

The ‘omega 6 fatty acid’ refers to a fatty acid with a double bond present 6 carbons away from the omega carbon

Question 6

What is a saturated fatty acid?

Answer 6

a fatty acid that contains no double bonds - highly flexible due to free rotation around single bonds

Question 7

If I describe a fatty acid as a 16:1(9) what the hell does that mean?

Answer 7

number before colon = number of carbons in chain

number after colon = numbers and positions of double bonds relative to carboxyl carbon

number in parenthesis = where the double bonds are located

so this is a 16 carbon fatty acid with one double bond situated between the 9th and 10th carbon

Question 8

What are two fatty acids that we cannot synthesize on our own? (essential fatty acids)

Answer 8

linoleic acid (omega 6 fatty acid)

and alpha linolenic acid (omega 3 fatty acid)

Question 9

What are leucotrienes? What are their functions?

Answer 9

Leucotrienes = synthesized from arachidonic acid and used in inflammatory responses and neutrophil adhesion

Question 10

What are TAGs? What are the used for in the body?

Answer 10

TAG= triacylglycerols or triglycerides - made up of 3 fatty acids and glycerol

They are the principal storage form of energy in the body - stored in adipose tissue

Question 11

What is a DAG? What is it used for?

Answer 11

diacylglyerol = it is a triacylglycerol minus one acyl group.

This is used as a potent intracellular signaller - and as the mobilizer of calcium

Question 12

What lipid structure is the major compoenent of cell membranes?

Answer 12

phospholipids (phosphoglycerides)

Question 13

What sort of structure is indicated with four rings?

Answer 13

steroid

Question 14

What is Cholesterol?

Answer 14

cholesterol is an essential biomolecule that functions as a metabolic precursor of Vitamin D, Bile acids, and steroid hormones - it plays a key role in the structure of membranes - we need a constant supply of cholesterol

Question 16

What are lipoproteins - what are they used for?

Answer 16

They are particles that are part lipid and part protein - they are found in plasma and help transport lipids throughout the body (including steroids and cholesterol)