Lipid Metabolism

Question 1

describe the various classes of lipids

Answer 1

1. Fatty acid derivatives

• Fatty acids – fuel molecules.
• Triacylglycerols (triglycerides) – fuel storage and insulation
• Phospholipids – components of membranes and plasma lipoprotein

2. Hydroxy-methyl-glutaric acid derivatives

• Cholesterol – membranes and steroid hormone synthesis
• Cholesterol esters – cholesterol storage
• Bile acids and salts – lipid digestion

3. Vitamins

AKED

Question 2

what r the fat soluble vitamins?

Answer 2

AKED

Question 3

what r ketone bodies?

Answer 3

water soluble fuel molecules produced by liver from fatty acids during periods of low food intake (fasting) or starvation.

Ketone bodies are important fuel molecules that can be used by all tissues containing mitochondria including the central nervous system.

Question 4

why should there also be dietry restriction if u r giving advice for an obese person

Answer 4

Fatty deposits r high energy stores, theyre very difficult to lose

Question 5

where does fatty oxidation take place?

Answer 5

in mitochondria

Question 6

when triglycerides break down, and yield glycerol that goes to liver, what does this glycerol do? where do what about the fatty acids?

Answer 6

in non fasting>>goes to make TAG

fasting>> goes through glycolysis to make pyruvate

FFA= goes to liver via albumin and enters FA B-oxidation.

Question 7

effects of glucagon and insulin in fat mobilisation

Answer 7

glucagon= stimulates Insulin=inhibits

Question 8

explain how, when and why ketone bodies are formed

Answer 8

they spare glucose in early starvation/diabetes.

r produced from acetyl-CoA in the mitochondrial matrix of hepatocytes when carbs r so scarce that energy must be obtained from breaking down FFA. (which will become acetyl coa> HMGca> Acetoacetate and so on))

The kidney can also produce ketone bodies under extreme conditions but at a much lower level than liver.

Question 9

describe the central role of acetyl~CoA in metabolism

Answer 9

important intermediate in lipid biosynthesis.

main convergence point in catabolic pathways.

Question 10

how is fatty acid transported into the mitochondria for b-oxidation

Answer 10

carnatine shuttle

Question 11

what r the 3 ketone bodies produced in the body?

Answer 11

acetoacetate, acetone, B-hydroxybutyrate

Question 12

describe how fatty acids r activated, where does this occur?

Answer 12

by linking to COENZYME A, in cytoplasm

Question 13

**LOW EXTRACELLULAR GLUCOSE RESULTS IN FATTY ACID RELEASE AS AN ALTERNATIVE FUEL

Answer 13

yas

Question 14

r lipids more reduced or more oxidised than carbs? what does this mean?

Answer 14

more REDUCED, meaning they have a higher energy content, they therefore release more energy when oxidised.

Question 15

what is the typical daily energy requirement of a 70kg man?

Answer 15

11.000 kilojoules

Question 16

stage 1 of metabolism of triacylglycerol

(hint: in SI)

Answer 16

hydrolised by pancreatic lipase in SI, a complex that requires bile salts & protein factor called Colipase

Question 17

in fatty acid catabolism, which enzyme facilitates the activation of FA by linking coenzyme-A

Explain the process of fatty acid catabolism starting its release from adipose tissue into the liver.

Coenzyme A is derived from vitamin ____

Answer 17

fatty acyl CoA synthase

1) its gunna be activated by linking w/ co-enzyme A outside the mitochondria
2) Transported across the inner mitochondrial membrane using a carnitine shuttle
3) cycles through sequence of oxidative reactions, with C2 removed each cycle

B5!

Question 18

what would inhibit the carnation shuttle?

Answer 18

Malonyl-CoA

Question 19

during B-oxidation of FA, how many carbons r removed per cycle?

Answer 19

2 carbons

Question 20

explain the pathway which glycerol can re-enter glycolysis

Answer 20

after phophorylation into glycerol phosphate &conversion to DHAP,

glycerol can now enter glycolysis

Question 21

which enzyme converts glycerol to glycerol phosphate?

Answer 21

Glycerol kinase

Question 22

in which organ r ketone bodies synthesised?

Answer 22

liver

Question 23

products of b-oxidation

Answer 23

• acetyl coA–> enters kreb cycle
• NADH & FADH2–>goes to ETC

Question 24

a patient was given Disulfiram and drank alcohol that day, he turned up with ‘hangover symptoms” what is disulfuram and how does it work & why did it cause a hangover?

Answer 24

treatment of chronic alcohol

inhibits enzyme aldehyde dehydrogenease

Acetate is NOT made when patient drank alchohol, aceytlaldehyde accumalated in blood causing hangover

Question 25

How r lipids stored and where

Answer 25

TAG in adipose tossue

TAGs are hydrophobic and therefore stored in an anhydrous form in specialised tissue – adipose tissue

Question 26

****Increased acetyl-CoA from alcohol oxidation would lead to an increase in__________

Answer 26

in the synthesis of fatty acids and ketone bodies.

Question 27

Which reactive oxygen species is produced when molecular oxygen (O2) gains an electron?

Answer 27

Superoxide is produced by adding an electron to molecular oxygen.

Superoxide is also an important source of other reactive oxygen species such as hydrogen peroxide and hydroxyl radicals

Question 28

Reactive oxygen species (ROS) damage to proteins can result in protein glycosylation. (TRUE or FASE?)

Answer 28

Glycosylation is a normal post-translational modification to some proteins not a consequence of oxidative damage.

Oxidative damage to proteins by free radicals includes hydroxylated adducts, di-tyrosine dimers, inappropriate disulphide bond formation and the formation of ring open species.

Question 29

Name two sources of free radicals (oxidants) inside cells (i.e. endogenous sources)?

Answer 29

• The ETC is a major source of free radicals since electrons can occasionally accidently escape the chain and react with dissolved O2 to form superoxide.
• peroxidase enzymes, nitric oxide synthase (nitric oxide is a free radical) lipooxygenases, NADPH oxidase enzyme (used in “respiratory burst”), Xanthine oxidase and Monoamine oxidase.

Question 30

Which enzyme is involved in protecting cells from oxidative damage by converting superoxide to H₂O₂ and O₂

Answer 30

Superoxide dismutase (SOD).

Question 31

Which enzyme protects cells from oxidative damage by converting H₂O₂ into H₂O and O₂

Answer 31

Catalase

Question 32

why is paternal utilisation of glucose is reduced during the second half of pregnancy?

‘Decreased maternal utilisation of glucose’

Answer 32

paternal utilisation of glucose is reduced during the second half of pregnancy by switching tissues to the use of FFA.

This conserves glucose for the maternal brain and for supply the the fetus for growth.

Question 33

Which class of hormone does adrenaline fall under?

Answer 33

amine

Question 34

Which hormonal change would occur during the course of a marathon run?

Answer 34

rise in GLUCAGON would stimulates gluconeogenesis by activating PEPCK and fructose 1,6 bisphosphatase

Question 35

What would the presence of Howell-Jolly bodies in circulating red blood cells be a sign of?

Answer 35

damaged spleen

Question 36

just a recap Glyerol metabolism

Question 37

Functions of Acetyl Coa

Answer 37

Question 38

______________is an important polyunsatrutaed fatty acid as it is the starting point for the synthesis of eicosanids, which r a family of signalling molecules like Prostaglandins!

Answer 38

Arachadoinic acid

Question 39

which hormone stimulates/ inhibits lipolysis?

Answer 39

adreniline, glucagon, GH, cortisol, thyroxine,

Insulin inhibits!

Question 40

the process by which fatty acids are released as energy is called __________

Answer 40

B- oxidation!

Question 41

which cells in our body cannot undergo B-oxidation & why?

Answer 41

RBC’s> cuz they dont have mitchondria

cell of CNS> bc they FFA cannot cross blood brain barrier!

Question 43

Explain how tissues obtain the lipids they need from lipoproteins.

Answer 43

TAG’s are obtained from chylomicrons and VLDLs by the lipoprotein lipase present in the capillary bed of the tissue. This hydrolyses TAG to fatty acids and glycerol. The fatty acids are taken up by tissues and re-esterified to TAG using glycerol phosphate derived from glucose metabolism.

Cholesterol is obtained from LDLs by receptor mediated endocytosis. The LDL particles bind to LDL receptors on the surface of target cells. The receptor with its bound LDL is taken into the cell by endocytosis. The endosome is attacked by lysosomal enzymes releasing free cholesterol in the cell and destroying the receptor protein. The cholesterol is converted to cholesterol esters for storage. When the cell has enough cholesterol, cholesterol inhibits the synthesis of new LDL receptors and the uptake of cholesterol is reduced