L10- Lipid metabolism

Question 1

lipids are

Answer 1

insoluble- hydrophobic

Question 2

lipids most commonly contain

Answer 2

C, H and O

-

Question 3

phospholipids also contain

Answer 3

P and N

Question 4

lipids are more …. than carbohydrates

Answer 4

reduced

Question 5

what does it mean if lipids are more reduced than CHOs

Answer 5

release more energy when oxidised (requires more oxygen too)

Question 6

classes of lipids

Answer 6

1. Fatty acid derivatives
2. Hydroxy-methyl-glutaric acid derivative (C6 compounds)
3. Vitamins

Question 7

Fatty acid derivatives

Answer 7

• Fatty acids- fuel molecules
• Triglycerides (TAG)- fuel storage and insulation
• Phospholipids- membranes
• Eicosanoids

Question 8

Hydroxy-methyl-glutaric acid derivative (C6 compounds)

Answer 8

• Ketone bodies- water soluble fuel molecules
• Cholesterol- membrane and steroid hormones
• Cholesterol esters
• Bile acids and salts

Question 9

vitamins

Answer 9

A, D, E, K

Question 10

Triglycerides (TAG) structure

Answer 10

• Glycerol backbone
• Fatty acid side chain
• Hydrophobic
• Amphiphatic
• Formed via esterification

Question 11

TAG stored in

Answer 11

anhydrous form in adipose tissue

Question 12

when is TAG utilised

Answer 12

prolonged exercise, starvation and during pregnancy

Question 13

TAG gets hydrolysed to

Answer 13

glycerol and fatty acids

Question 14

fatty acids produce how much of the energy of TAG

Answer 14

95% (B-oxidation)

Question 15

glycerol produces how much of the energy of TAG

Answer 15

5% ( glycolysis)

Question 16

TAG cannot be used by

Answer 16

cells without mitochondria

e.g. RBC and the brain (FA cannot pass BBB)

Question 17

outline how triglycerides (TAG) is metabolised

Answer 17

1. Triglycerides (TAG/ dietary lipids) eaten
2. In the GI tract (small intestine) TAG is hydrolysed by pancreatic lipases
3. TAG  Glycerol + fatty acids
   o Glycerol
4. Glycerol is absorbed into the blood from the small intestine
5. Glycerol in the blood is transported to the liver
6. Where it is used as a precursor to synthesise glucose
   o Fatty acids
7. FAs absorbed into the blood from the small intestine after TAG is broken down
8. In the GI tract fatty acids are converted back to TAG
9. In the blood TAG is then transported to the adipose tissue by lipoprotein particles called Chylomicrons
10. Stored as TAG in adipose tissue
11. Released as fatty acids when needed and carried to consumer tissues as albumin-fatty acid complex
12. FA oxidation leads to release of ATP (energy)

Question 18

structure of fatty acid

Answer 18

CH3(CH2)nCOOH

• sat or unsatisfyingly

Question 19

unsat

Answer 19

at least one double carbon bond)

Question 20

name a FA is an essential requirement for the diet

Answer 20

linolenic acid

Question 21

FA metabolism simple: consumer tissue vs adipose tissue

Answer 21

• Consumer tissue = FA oxidation –>energy
• Adipose tissue (Stored as TAG) –> Fat mobilisation-hormone sensitive lipase
  o Increase- glucagon/adrenaline
  o Decrease- Insulin

Question 22

when is TAG mobilised from adipose tissue

Answer 22

glucagon or adrenaline

Question 23

fatty acid metabolism summary

Answer 23

Where? The mitochondria

1. FA is activated by linking Coenzyme A outside the mitochondrion
2. FA is transported across the inner mitochondrion using a carnitine shuttle
3. FA cycles through sequence of oxidative reactions, with 2 Carbons removed each cycle- B-oxidation

Question 24

we want to oxides the fatty acid to

Answer 24

extract as many electrons as possible so that they can be transferred to electron carrying molecules like NAD+ and FAD+, so that NADH and FADH2 can be used to produce ATP on the electron transport chain.

Question 25

fatty acid activation

Answer 25

Fatty acyl CoA synthase links Coenzyme A to fatty acid

Question 26

activated fatty acids (Acyl-CoA)

Answer 26

do not readily cross the inner mitochondrial membrane

Question 27

what is coenzyme A derived from

Answer 27

vitamin B5

Question 28

outline the carnitine shuttle of fatty acyl-CoA

Answer 28

- Fatty acyl-CoA (activated fatty acid) binds to carnitine to produce Acyl Carnitine (losing CoA) - Acyl carnitine is then transported across the mitochondrial membrane via the Carnitine shuttle transporter - Once within the Acyl Carnitine loses carnitine and recombines with CoA to form Acyl-CoA

Question 29

what inhibits carnitine shuttle

Answer 29

malonyl-CopA

Question 30

B-oxidation of Acyl-CoA

Answer 30

Where activated fatty acid chain get oxidised within B-oxidation cycle, which breaks the off 2 carbon chains per round- H+ and e- transferred to NADH and FADH2 (oxidation in ETC)

Question 31

2 carbon chains produced via B-oxidation are caleld

Answer 31

Acetyl Co-A

Question 32

Acetyl CoA prodded from B-oxidation

Answer 32

enter Kreb cycle and then the ETC to produce ATP

Question 33

glycerol is transported in the blood to the

Answer 33

liver where it is metabolised

Question 34

in the liver what starts the metabolism of glycerol

Answer 34

glycerol kinase Converts glycerol to glycerol phosphatw

Question 35

glycerol phsophate

Answer 35

1) Can be converted to DHAP and used in glycolysis to produce some ATP and reducing power (NADH/FADH2) 2) Or be used in the synthesis of triglycerides

Question 36

acetyl coA is the main

Answer 36

convergence point for catabolic pathways

Question 37

Acetyl CoA function

Answer 37

act as an important intermediate in both catabolic and anabolic pathways

Question 38

ketones are

Answer 38

water soluble molecules, which are alternative substrates to glucose and fatty acids

Question 39

three types of ketone body synthesised in there liver mitochondria (from fatty acids)

Answer 39

1. Acetoacetate (liver) 2. Acetone o Spontaneous decarboxylation of acetoacetate 3. B-hydroxybutyrate (liver)

Question 40

normal plasma ketone conc

Answer 40

<2mM

Question 41

starvation plasma ketone body (physiological ketosis)

Answer 41

2-10mM

Question 42

untreated type 1 diabetes (pathological ketosis)

Answer 42

>10mM

Question 43

stains inhibit the enzyme

Answer 43

HMG-CoA

Question 44

HMG-CoA reductase catalyses

Answer 44

production of cholesterol from acetyl coA

Question 45

Ketoacidosis

Answer 45

- characteristic smell of acetone on breath when acetone excreted via the lungs - Acetoacetate and B-hydroxybutyrate are strong organic acids.

Question 46

ketones above renal threshold

Answer 46

excreted in the urine (Ketonuria)

Question 47

Regulation of ketone body synthesis by insulin/glucagon (fed/starved) ratio - Ketone bodies and early starvation:

Answer 47

Ketones spare glucose in early starvation/diabetes - release of glucagon in reaction to starvation (increase ketone bodies production) 1. Triglycerides go through lipolysis to produce fatty acids which are released from adipose tissue 2. These circulate to the liver where the fatty acids undergo ketogenesis where ketone bodies are produced 3. Ketone bodies are broken down to acetyl CoA where they are used to produce ATP via the TCA and ETC

Question 48

Regulation of ketone body synthesis by insulin/glucagon (fed/starved) ratio - ketone bodies in well fed state

Answer 48

release of insulin's stimulates production of cholesterol from acetyl CoA

Question 49

in late starvation

Answer 49

1. Protein from muscles are hydrolysed to amino acids 2. Amino acids circulate to the liver where they are converted to pyruvate 3. Pyruvate goes through gluconeogenesis to produce glucose 4. Glycogen in the liver is hydrolysed to produce more glucose 5. Circulating glucose used to power the brain