T3 L5: Introduction to lipids

Question 1

What are 3 examples of labile energy stores?

Answer 1

ATP (in the phosphate groups), Redox agents (NADH, FADH2) and ionic transmembrane gradients

Question 2

What is creatine phophate?

Answer 2

An energy store in muscles

Question 3

Give 2 examples of large and stable energy stores

Answer 3

Carbohydraes and fats

Question 4

What is the importance of acetyl-CoA in energy production?

Answer 4

Its an energy mediator used to begin the Krebs cycle by oxidising citric acid

Question 5

What molecule is cholesterol produced from?

Answer 5

Acetyl-CoA

Question 6

What organ absorbs glycogen?

Answer 6

The liver

Question 7

What are ketone bodies and what is their function?

Answer 7

They are produced by the liver from fatty acids during a low-carbohydrate diet, fasting or too much alcohol. They are alternatives to ATP

Question 8

During ketosis, where will high levels of ketones be present?

Answer 8

In the urine and blood but not enough to cause acidosis

Question 9

Why does the brain need a constant supply of ketone bodies and glucose from plasma?

Answer 9

There is no glycogen in the brain

Question 10

What does fatty acid synthesis lead to?

Answer 10

A fatty acid with an even number of carbons. The process requires ATP

Question 11

What is the structure of a fatty acid?

Answer 11

A straight carbon chain with a COOH group

Question 12

What are essential fatty acids?

Answer 12

Those that must be in the diet because they can’t be produced

Question 13

What is an ester bond?

Answer 13

A glycocidic bond but in fatty acid

Question 14

What 4 types of molecules is cholesterol a precursor for?

Answer 14

Bile acids, steroids, hormones and vitamin D

Question 15

What are the sources of cholesterol?

Answer 15

From the diet or can be made by the liver

Question 16

When is cholesterol amphipathic?

Answer 16

When it’s free

Question 17

When is cholesterol hydrophobic?

Answer 17

When its esterified (because there is nothing to interact with water as the OH is gone)

Question 18

When are ketone bodies produced by the body?

Answer 18

During fasting (after all fat and glucagon is used up)

Question 19

What are ketone bodies produced from?

Answer 19

Acetyl-coA

Question 20

Give 3 examples of ketone bodies

Answer 20

Acetoacetate, beta-hydroxybutyrate and acetone (the waste product)

Question 21

Why do unsaturated fatty acids have a lower melting point?

Answer 21

They have an irregular structure compared to saturated fatty acids so their intermolecular forces are weaker

Question 22

What type of optical isomerism do most unsaturated fatty acids have? Cis or Trans?

Answer 22

Cis

Question 23

Why are trans unsaturated fats bad?

Answer 23

They increase levels of LDL

Question 24

What are the 4 pathways of lipid transport?

Answer 24

1. Exogenous pathways - Gut to liver and periphery (muscle and adipose tissue)
2. Endogenous pathway - Liver to periphery
3. Recycled pathway - Periphery to liver
4. In the form of bile acid - Liver to digestive tract

Question 25

Describe the exogenous pathway (from gut to liver and periphery) of lipid transport

Answer 25

Lipids from diet are packaged by the small intestine into chylomicrons which are taken up by the liver and periphery

Question 26

What is meant by exogenous?

Answer 26

From the outside

Question 27

Describe the endogenous pathway (from liver to periphery) of lipid transport

Answer 27

Lipids from the liver are packaged into VLDL and then stored in the periphery

Question 28

What is meant by endogenous?

Answer 28

Made by the body

Question 29

Describe the recycling pathways (from periphery to liver) of lipid transport

Answer 29

It occurs when the lipid supplies in the liver are being exhausted during starvation or exercise. HDL transports the lipids back to the liver so they can be converted back into energy

Question 30

What are chylomicrins?

Answer 30

Molecules that transport triglycerides

Question 31

Describe the bile production pathway of lipid transport

Answer 31

Cholesterol is converted into bile acids and released into the cystic duct. Most of the bile acids are reabsorbed by the gut and returned to liver and recycled

Question 32

What is the function of lipoprotein lipase?

Answer 32

It metabolises triglycerides into fatty acids and glycerol to remove the triglycerides from VLDL and then moves them across the capillary membrane. This happens because triglycerides cannot go through cell membranes

Question 33

What are apolipoproteins?

Answer 33

Proteins in lipoprotein molecules that can hold lipids . They're amphipathic so it can bind to the protein and to the lipid at the same time

Question 34

How dense is cholesterol compared to tryglycerides and proteins?

Answer 34

Between triglycerides and proteins

Question 35

Why are bigger lipoproteins lower in density?

Answer 35

Because they are carrying more proteins

Question 36

Why are LDL dangerous?

Answer 36

Because they are incorperated into atheromas. In the blood, it's storage for cholesterol that can't be stored anywhere else. It's what is left over once the periphery has absorbed endogenous triglycerides from VLDL from the liver

Question 37

Why is HDL better than LDL?

Answer 37

Because HDL lowers cardiovascular risk. It carries lipids from fat cells to the liver when cholesterol is being used up

Question 38

Which type of lipid signifies a risk of atheroma?

Answer 38

VLDL

Question 39

What is VLDL used for?

Answer 39

Used to transport endogenous cholesterol and triglycerides from the liver to the periphery

Question 40

What is IDL?

Answer 40

Intermediate density lipoprotein. It's the intermediate molecule before VLDL becomes LDL

Question 41

What do the beta cells of the pancreas produce?

Answer 41

Insulin

Question 42

What do the alpha cells of the pancreas produce?

Answer 42

Glucagon

Question 43

What does hypercholesterolaemia increase the risk of?

Answer 43

Arteriosclerosis

Question 44

What is the function of statins?

Answer 44

They block endogenous cholesterol synthesis by blocking HMG-CoA Reductase

Question 45

What is simvastatin prescribed for?

Answer 45

For cardiovascular disease prophylaxis especially for men over 50

Question 46

What is metabolic syndrome?

Answer 46

Its a group of risk factors that increase the risk of cardiovascular disease, stroke and type 2 diabetes