6 Lipid Metabolism Flashcards
(34 cards)
Q: What’s the general structure for a fatty acid?
A: hydrophilic carboxylic head and hydrophobic hydrocarbon tail
Q: What’s a saturated fatty acid? (3)
A: completed saturated with H
No double bonds
Completely straight
Q: What’s does an unsaturated fatty acid contain? Shape?
A: double bond
Db inhibits rotation around the bond = kink in chain
Q: What form are fatty acids stored in?
A: triacylglycerols (triglycerides)
Q: Which cells in mammals are specialised for fat storage?
A: adipocytes
Q: Which is solid and which is liquid?
Saturated fatty acids
Unsaturated
A: solids, liquids
Q: What are the 3 main sources of fats?
A: diet, de novo biosynthesis in liver, adipocytes storage (hydrolysed to give fatty acids and glycerol)
Q: What is the role of bile salts? Generated? Stored? Release?
A: emulsify fats and aid absorption-> Interacts with solute and triacylglycerides due to hydrophobic and hydrophilic ends
Get them into soluble form
Generated in liver
Stored in gal bladder
Secreted into small intestine during digestion
Q: What’s a mixed micelle? (8)
A: mixture of triacyl, diacyl, monoacylglycerols and free fatty acids WITH bile salts, cholesterol, lysophosphatidic acid, fat soluble vitamins
Q: What occurs to mixed micelles after formation? (4)
A: absorbed by enterocytes and triacylglycerols TAGs are resynthesised
TAGs are packed into chylomicrons which enter lymphatic system and join circulatory system
Q: How does the caloric yield of fatty acids differ to that of carbohydrates?
A: FA is double that of carbs
Q: What’s the process of fat metabolism and where does it occur? What does it result in?
A: beta oxidation, mitochondria (outer membrane), acetyl CoA
Q: Summarise the process of beta oxidation using a general equation. Enzyme? What does the reaction use? (2)
A: FA + ATP + HS-CoA -> acyl-CoA + AMP + PPi
E: acyl CoA synthetase
ATP -> AMP
2 high energy bonds used
2 phosphoanhydride bonds used
Q: What is the general formula for acyl CoA?
A: O
II
R— C — S —CoA
Q: How do you move acyl CoA into the mitochondria? Draw a diagram.
A: carnitine shuttle
3 components
- CPTI
- CPTII
- translocase
Q: What occurs in the beta oxidation cycle? Draw a diagram.
A: “Fatty acids are firstly converted within the mitrochondrial matrix into an acyl CoA species via the enzyme Acyl CoA synthetase which requires ATP hydrolysis”
1 fatty acyl CoA is oxidised and FAD reduced to FADH2
2 molecule produced is hydrolysed
E: 3 hydroxyacyl CoA hydrolase
3 product is oxidised and NAD is reduced to form NADH
E: L-3-hydroxyacyl CoA dehydrogenase
4 molecule of acetyl CoA is kicked off by bringing in molecule of CoA
E: beta ketothiolase
Fatty acyl CoA as a result has been shortened by 2 carbons and cycle repeats
Q: What first occurs during the beta oxidation of palmitic acid? What’s the overall equation? Final cycle?
A: first E: acyl CoA synthetase converts into 16 C palmitoyl CoA
Palmitoyl CoA + 7FAD + 7 NAD+ + 7H2O + 7CoA -> 8 acetyl CoA + 7FADH2 +7NADH
On the final cycle (4C fatty acyl CoA intermediate enters cycle) 2 acetyl CoA molecules are produced
Q: What is palmitic acid?
A: saturated fatty acid
Q: How does acetyl CoA enter aerobic respiration and under what circumstances? Why?
A: TCA cycle but only if beta oxidation and carbohydrate metabolism are balanced, oxaloacetate is needed for acetyl CoA entry into the TCA cycle
Q: What occurs if fat breakdown predominates carbohydrate metabolism?
A: acetyl CoA forms
Q: Name 3 ketone bodies?
A: Acetoacetate
D-3-hydroxybutyrate
Acetone
Q: What is the net ATP production of palmitate beta oxidation compared to aerobic respiration?
A: Palmitoyl CoA + 7FAD + 7 NAD+ + 7H2O + 7CoA -> 8 acetyl CoA + 7FADH2 +7NADH
7 cycles of beta oxidation = 35
8 a CoA = 96
NADH FAD —> 131
-2 ATP used in beginning = 129
Compared to 38
Much more ATP from fatty acid metabolism that glucose metabolism.
Q: What is fatty acid synthesis called?
Describe the process? Involves? (2) Sequential action of? (3) Link?
A: liposynthesis
Decarboxylative condensation reactions involving the molecules Acetyl-CoA and Malonyl-CoA
After each round of elongation, the fatty acid undergoes reduction and dehydration by the sequential action of:
Ketoreducatase (KR)
Dehydratase (DH)
Enol Reductase (ER)
The growing fatty acyl group is linked to an acyl carrier protein (ACP).
Q: What are the differences between fatty acid synthesis and fatty acid degradation? Type of reaction? Carriers? Reducing power?
A:
FAS= synthesis, FAD= beta oxidation
carriers: FAS= ACP, FAD= CoA
Reducing power: FAS= NADPH, FAD= FAD/NAD
