Lipid metabolism

Question 1

Fatty acid metabolism and acetyl CoA

Answer 1

fatty acid metabolism leads to acetyl CoA production in mitochondria of cells

Question 2

Describe bile salts

Answer 2

generated by liver and stored in gall bladder
pass from bile duct to intestine - emulsify fats aiding digestion amd absorbtion of fats and fat soluble vitamins (A, D, K, E)
lack of bile salts = steatorrhea - fatty stool

Question 3

describe fatty acid metabolism

Answer 3

caloric yield from fatty acid x2 carbs 
>1/2 energy comes from fatty acids 
B oxidation 
mt 
generation of acetyl CoA

Question 4

The reaction to convert fatty acids into acyl CoA `

Answer 4

Fatty acid + ATP + HS-CoA
enzyme: acyl CoA synthetase
acyl CoA + AMP (2 high energy bonds are used) + PPi

Question 5

Describe the carnitine shuttle

Answer 5

generation of acyl CoA is in outer mt membrane
transport into matrix
carnitine and acyl carnitine are moved to and from matric by a translocase

Question 6

describe the B-oxidation cycle

Answer 6

Acyl CoA undergo oxidation, hydration, oxidation and thiolysis reactions
makes 1 acetyl CoA and an acyl CoA
continue to remove 2C from acyl CoA until make 2 acetyl CoA
in each cycle have 1 FADH2 and 1 NADH

Question 7

describe fatty acid biosynthesis

Answer 7

enzymes: Acetyl CoA carboxylase, fatty acid synthase (FAS) - polypeptide with 7 enzymatic activities
decarboxylative condensation reactions involving acetyl CoA and malonyl CoA
elongation then reduction and dehydration by ketoreductase, dehydratase and enol reductase
the growing fatty acyl group is linked to an acyl carrier protein (acp)

Question 8

Structural organisation of fatty acid biosynthesis domains

Answer 8

FAS polypeptide

ACP provides swinging arm to move fattu acid chain from 1 domain to another

Question 9

Describe lipogenesis

Answer 9

acetyl CoA – Malonyl CoA [acetyl CoA carboxylase]
malonyl CoA – malonyl-ACP (acyl carrier protein) [malonyl CoA ACP transferase]
acetyl Coa – Acetyl-ACP [acetyl CoA ACP transferase]
condensation of acetyl-ACP and malonyl-ACP – 4C fatty acid [B-ketoacyl ACP synthase]
Reduction of Acetoacetyl-ACP – D-3-hydroxylacyl-ACP [B-ketoacyl ACP reductase]
dehydration too crotonyl ACP [3-hydroxyacyl-ACP dehydrase]
reduction to butyryl-ACP [Enol-ACP reductase]
cycles 6 times from step 4-7 to yield the 16C species palmitoyl-ACP - hydrolysed - palmitate and ACP

Question 10

Difference between fatty acid synthesis and B-oxidation

Answer 10

syth: ACP, NADPH, cytoplasm
B: CoA, NAD+/FAD, mt matrix

Question 11

Summary of lipogenesis

Answer 11

Acetyl CoA + 7 Malonyl CoA + 14 NADPH + 14H+
Palmitate + 7CO2 + 6H2O + 8CoA-SH + 14NADP+
elongation in ER and mt
desaturation of fatty acid need fatty acyl-CoA desaturase
stearate – oleic acid + palmitoleic acid [change-9 desaturase - double bond 9 c from terminal carboxyl gp]

Question 12

acyl-CoA-dehydrogenases

Answer 12

family of acyl-CoA-dehydrogenases catalyse initial step in B oxidation - each dehydrogenase bind fatty acid of diferent length 
short chain acyl-CoA dehydrogenase <6C
medium 6-12
long 13-21
V. long >22

Question 13

Describe MCADD

Answer 13

medium chain acyl-CoA dehydrogenase deficiency
autosomal recessive
can’t fast

Question 14

Primary carnitine deficiency

Answer 14

Autosomal recessive
symptoms in infancy/early childhood - encephalopathies
gene mutation - reduced ability to take up carnitine