Biochemistry Final Exam UNE CHEM 1005 Questions with Correct Solutions, A+

Control of Fatty Acid Synthesis vs. Oxidation - 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 - Process of releasing free fatty acids from triacylglycerols stored in the adipose IN THE FASTED STATE Steps of lipolysis - 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 - 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 - 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... - The liver. Skeletal muscle can oxidize ketones. The brain will oxidize ketones when starving. Ketogenesis is regulated by... - 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... - During starvation and uncontrolled diabetes Important connections between Beta-Oxidation and other pathways - 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 - Activated by insulin Inhibited by glucagon Fatty acid synthesis takes place in the... - Cytosol Fatty acid synthesis: what occurs in the mitochondria? - 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 - Requires malonyl-CoA, fatty acyl-CoA and NADPH. This pathway determines the chain length for fatty acids (medium, long, etc.) Fatty acid synthesis connection to the PPP - PPP provides glycerol (for TAG synthesis) and NADPH (for fatty acid synthesis) Fate of newly synthesized fatty acids - -Fatty acids are NOT stored in the liver -instead, they're packaged into VLDL particles as TAGs (along with cholesterol) and are transported to adipose for storage HDL: Origin, Primary Apo Protein, Composition, Primary Role - Origin: Liver Primary Apo Protein: ApoA Composition: Cholesterol and Cholesteryl Ester Triacylglycerol (C and CE TG) Primary Role: reverse cholesterol transport *HDL is the most dense LDL: Origin, Primary Apo Protein, Composition, Primary Role - Origin: Maturation of VLDL Primary Apo Protein: ApoB100 Composition: Cholesterol and Cholesteryl Ester Triacylglycerol (C and CE TG) Primary role: cholesterol transport from the liver VLDL: Origin, Primary Apo Protein, Composition, Primary Role - Origin: Liver Primary Apo Protein: ApoB100 Composition: Triacylglycerol Cholesterol and Cholesteryl Ester (TG C and CE) Primary role: carries newly synthesized TAG from the liver to the adipose