Biochemistry Final Exam: UNE CHEM 1005 (Weeks 9-
15) – Q’s And A’s
Control of Fatty Acid Synthesis vs. Oxidation Correct Ans - When
Insulin is HIGH --> fatty acid synthesis occurs
When Glucagon is HIGH --> lipolysis, fatty acid B-oxidation, ketogenesis
occur
**These never happen at the same time!
Lipolysis Correct Ans - Process of releasing free fatty acids from
triacylglycerols stored in the adipose IN THE FASTED STATE
Steps of lipolysis Correct Ans - 1) Hormone Sensitive Lipase:
activated by glucagon and epinephrine
TAGs are hydrolyzed into FFAs and glycerol (inhibited by insulin)
2) Long chain FFAs travel bound to albumin to peripheral tissues to be used
as energy source
3) Glycerol travels to liver to be used as gluconeogenesis substrate
4) Acyl-CoA Synthetase: can reconvert FFAs to acyl-CoA to be used for re-
esterification in the adipose (continuous cycle of lipolysis & re-
esterification)
Beta Oxidation Correct Ans - Process of generating acetyl-CoA,
NADH, and FADH2 from the oxidation of FFAs taken up by peripheral
tissues (mostly liver & skel. muscle tissue).
Happens in mitochondria. Long chain FFAs cannot cross the mito
membrane, so a transport system is in place.
Ketogenesis Correct Ans - Process of generating ketones from
excess acteyl-CoA produced from Beta-Oxidation
Mitochondrial pathway
Ketones can be used as fuel by other tissues but cannot be oxidized by...
Correct Ans - The liver.
, Skeletal muscle can oxidize ketones.
The brain will oxidize ketones when starving.
Ketogenesis is regulated by... Correct Ans - 1) Activity of lipolysis
2) Cytosolic levels of malonyl-CoA (which inhibit CPTI)
3) Flux through the TCA depending on NADH levels & concentration of
intermediates (especially OAA)
Ketoacidosis can occur from prolonged ketogenesis, such as... Correct
Ans - During starvation and uncontrolled diabetes
Important connections between Beta-Oxidation and other pathways
Correct Ans - 1) It supplies high levels of ATP in the fasted state
2) ATP is required for both process of glucose synthesis via
gluconeogenesis & nitrogen disposal via the urea cycle
3) deficiencies in beta-oxidation can result in hypoglycemia due to inability
to support glucose synthesis (such as CPTI deficiency, or medium chain
acyl-dehydrogenase deficiency)
Fatty Acid Synthesis: Activators & Inhibitors Correct Ans -
Activated by insulin
Inhibited by glucagon
Fatty acid synthesis takes place in the... Correct Ans - Cytosol
Fatty acid synthesis: what occurs in the mitochondria? Correct Ans -
Substrates need to be shuttled out of the mitochondria
In the mito:
-Acetyl-CoA and OAA in the mito --> citrate
-Tricarboxylate transporter --> removes excess citrate from the mito
Fatty acid elongation Correct Ans - Requires malonyl-CoA, fatty
acyl-CoA and NADPH.
This pathway determines the chain length for fatty acids (medium, long,
etc.)
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