Lipids

Question 1

What are the essential FA?

Answer 1

linoleic and alpha-linolenic - form prostaglandins and omega 3 & arachidonic acid

Arachidonic acid essential IF linoleic acid deficient to lin. acid can’t form arach. - form eicosanoids

Question 2

What does omega 3 do?

Answer 2

Lowers plasma cholesterol and lowers high blood pressure

Deficiency - depression and ADHD

Question 3

What are the dietary lipids?

Answer 3

TAG!! phospholipid, cholesterol, cholesterol ester and free FA

Question 4

Outline digestion of TAG

Answer 4

1. Broken down by pancreatic lipase - FA cleaved
2. Bile emulsifies fat and products formed mixed MICELLES with bile salts
3. Go to microvilli and lipid products released and move through diffusion

Short and medium chain FA do not require micelles

Question 5

How are lipids transported after be digested?

Answer 5

1. Intestinal cells resynthesize TAG and then apoB-48 packages them in chylomicrons
2. Released by exocytosis to lymph then blood

Question 6

What happens when chylomicrons reach tissue?

Answer 6

1. TAG hydrolysed to FA and glycerol by lipoprotein lipase
2. FA used for energy or resynthesises to TAG for storage
   Glycerol can be taken liver to produce glycerol-3-phosphate for glycolysis and gluconeogenesis

Question 7

How is FA released from TAG in tissue?

Answer 7

Hormone sensitive lipase (HSL) - HSL activated by epinephrine (flight or flight adrenaline)

Question 8

List the different lipoproteins

Answer 8

• Chylomicrons: TAG - intestine to tissue
• VLDL - TAG: liver to tissue
• LDL - chol: liver to tissue -BAD
• HDL - chol: tissue to liver -GOOD

Can also be transported by serum albumin

Question 9

What is beta-oxidation of FA, where does it occur and what does it produce?

Answer 9

• Catabolism of FA
• Mitochondrial matrix
• Acetyl CoA, FADH2 AND NADH

Question 10

In simple terms, what are the 3 steps in beta oxidation?

Answer 10

1. Activation in the cytosol (needs ATP) - fatty acyl CoA
2. Transport to the mito. matrix
3. Degradation to 2 Acetyl CoA to be used for energy

Question 11

What is the carnitine shuttle?

Answer 11

Transports FA INTO mito. matrix - transports RC=O and once inside matrix, breaks down as RC=O resynthesised to fatty acyl CoA and carnatine goes back to cytosol

ONLY REQUIRED FOR LONG FA CHAIN - SHORT AND MEDIUM ARE CAT INDEPENDENT

Question 12

What prevents FA synthesis and beta oxidation from occurring simultaneously?

Answer 12

Malonyl CoA - inhibits carnitine palmitoyl transferase

Deficiency - no B-oxidation, so glucose stores used - hypoglycaemia
Treat - give medium chain that does not need CAT-1 for transport

Question 13

What are ketone bodies and what is their role?

Answer 13

Made from excess Acetyl CoA in mito. matrix in liver cells and used as fuel for cardiac and skeletal muscle

Question 14

Problem of excess ketone bodies

Answer 14

Uncontrolled diatbetes or starvation leads to high levels as FA broken down to replace - causes KETONEMIA (blood), KETONURIA (urine) and ACADEMIA - breath has fruity odour due to acetone

Question 15

What are FA derived from what does in require?

Answer 15

Acetyl CoA and needs ATP and NADPH

Occurs in cytosol

Question 16

What is the citrate shuttle?

Answer 16

Transport Acetyl CoA from matrix to cytosol

1. Citrate synthase binds to oxaloacetate and acetyl CoA to form citrate
2. Citrate lyase breaks it up in cytosol

Question 17

Outline of steps in FA

Answer 17

Acetyl CoA –> Malonyl CoA –> Palmitic Acid

First steps uses Acetyl CoA Carboxylase

Question 18

What is role of cholesterol?

Answer 18

In cell membrane and precursor for sterol hormones, Vit D and bile salts

Question 19

Role of statin

Answer 19

Lowers LDL level

Question 20

Role of eicosanoids

Answer 20

Precursor for prostaglandins, thromboxanes and leukotrienes

Inflammatory response - pain and fever, blood pressure, blood clotting etc

Question 21

What are COX inhibitors

Answer 21

Non-steroidal anti-inflammatory drugs (NSAIDs)

Inhibit COX synthesis of inflammatory prostaglandins