48 Questions
What is the result of the complete hydrolysis of triglycerides?
Glycerol and three fatty acids
How are free fatty acids transported through the cell membrane?
By binding with albumin
Where does fatty acid degradation occur?
Mitochondria
What is the result of the activation of fatty acids?
Fatty acyl CoA
Where does fatty acid synthesis occur?
Cytoplasm
How is excess acetyl CoA utilized when the liver's oxidative capacity is exceeded?
Converted into ketone bodies
What is the fate of glycerol produced from triglyceride hydrolysis?
Converted into glycerol phosphate or used in gluconeogenesis
What is the energy yield for each cleavage of a saturated carbon-carbon bond in fatty acid degradation?
5 ATP
What is the role of hormone sensitive lipase in triglyceride metabolism?
Hydrolyzes all three ester bonds in triglycerides
What is the fate of fatty acids with an odd number of carbon atoms in β-oxidation?
Produce propionyl CoA
What is the product of the complete oxidation of fatty acids?
CO2 and H2O
What is the key component of the fatty acid synthase complex that allows for the elongation of fatty acid chains?
Acyl carrier protein
What is the primary carrier for transporting free fatty acids in the blood?
Albumin
What regulates the transcriptional control of fatty acid synthesis through the phosphorylation of Acetyl CoA carboxylase?
All of the above
Which molecule is required for the net reaction of palmitate synthesis?
ATP
Which process involves the conversion of palmitate to stearic acid and further to monounsaturated fatty acids?
Fatty acid synthesis
What is the major control point in cholesterol metabolism?
Reduction of HMG-CoA to mevalonic acid
What is primarily involved in cholesterol catabolism?
Elimination of intact steroid nucleus in the form of bile acids and bile salts
What are the major metabolites of cholesterol?
Bile acids/salts
How is bile metabolism regulated?
By 7-α-hydroxylase
What serves as a precursor for the synthesis of steroid hormones and vitamin D?
Cholesterol
What are the key components of the fatty acid synthase complex?
Acyl carrier protein and condensing enzyme
What is the net reaction for palmitate synthesis?
Formation of Malonyl CoA
What is the limitation of human cells in synthesizing certain highly unsaturated fatty acids?
Lack of specific enzymes
What are the precursors for the biosynthesis of triacylglycerol (TAG) and phospholipids (PL)?
Glycerol-3-PO4 and fatty acyl CoA
Which hormone triggers the mobilization and degradation of TAG in adipocytes?
Glucagon
What happens to fatty acids and glycerol when TAG is degraded for energy?
Fatty acids enter the blood and glycerol is used for TAG synthesis or becomes glucose
What is the fate of most cells' continuously degraded membrane phospholipids (PL)?
They are replaced
What are the precursors for the biosynthesis of triacylglycerol (TAG) and phospholipids (PL)?
Glycerol-3-PO4 and fatty acyl CoA
What triggers the mobilization and degradation of triacylglycerol (TAG) in adipocytes?
Hormone sensitive lipase
What happens to fatty acids after the degradation of TAG?
Taken up by skeletal muscles, kidney, and liver for various purposes
What is the fate of glycerol after the degradation of TAG?
It can be used for TAG synthesis, converted into glucose, or used in glycolysis
Which molecule inhibits the pyruvate dehydrogenase complex?
ATP
What is the function of dihydrolipoyl dehydrogenase in the pyruvate dehydrogenase complex?
Transfer H to NAD+
What activates the pyruvate dehydrogenase complex?
ADP
What is the result of phosphorylation of E1 in the pyruvate dehydrogenase complex?
Inactivation of E1
Which pathway is important for producing NADPH and Ribose-5-PO4?
Pentose Phosphate Pathway
Where does the Electron Transport System (ETS) primarily take place?
Inner mitochondrial membrane
Which of the following is an ATP synthesis inhibitor in the Electron Transport Chain?
Oligomycin
What is the purpose of the Hexose Mono Phosphate (HMP) Pathway?
Produce NADPH and Ribose-5-PO4
Which situation requires the cell to adjust its biochemical pathways to produce only NADPH?
High energy demand
Which molecule is reduced to produce NADPH in the Pentose Phosphate Pathway?
Glucose-6-phosphate
Which complex in the Electron Transport System is responsible for ATP synthesis?
Complex V
What is the primary purpose of the HMP-shunt?
Produce NADPH
Which compound is used as an uncoupler of electron transport and ATP synthesis?
2,4-dinitrophenol
What is the end product of the non-oxidative part of the pentose phosphate pathway?
Ribose-5-PO4
Which organ is particularly important for the Hexose Mono Phosphate (HMP) Pathway?
Liver
Which molecule is used in the reduction of hydrogen peroxide in cells?
NADPH
Study Notes
Biochemical Pathways: Fatty Acid Synthesis, Cholesterol Metabolism, and Regulation
- Fatty acid synthesis involves carboxylation of Acetyl CoA to Malonyl CoA, with regulation by reversible phosphorylation and allosteric activation by citrate.
- The key components of the fatty acid synthase complex are the acyl carrier protein and condensing enzyme, which allow for the elongation of fatty acid chains through a series of enzyme steps.
- The net reaction for palmitate synthesis involves the formation of Malonyl CoA and requires multiple acetyl-CoA, CO2, ATP, and NADPH molecules.
- Transcriptional control of fatty acid synthesis occurs through the phosphorylation of Acetyl CoA carboxylase, which is regulated by insulin, glucagon, and AMPK.
- The synthesis of unsaturated fatty acids involves the conversion of palmitate to stearic acid and further to monounsaturated fatty acids, as well as the limitations of human cells in synthesizing certain highly unsaturated fatty acids.
- Cholesterol metabolism includes the biosynthesis of cholesterol in various tissues, with the major control point at the reduction of HMG-CoA to mevalonic acid by HMG-CoA reductase.
- The remaining steps in cholesterol biosynthesis involve the formation of activated isoprene units, condensation to form squalene, and cyclization into the steroid nucleus.
- Cholesterol catabolism primarily involves the elimination of intact steroid nucleus in the form of bile acids and bile salts, which are excreted in feces.
- Major metabolites of cholesterol include bile acids/salts, steroid hormones, and vitamin D, with bile acids aiding in the digestion of lipids.
- Bile metabolism occurs through enterohepatic circulation, where the majority of bile secreted is absorbed and taken back to the liver, regulated by the rate-limiting enzyme 7-α-hydroxylase.
- Synthesis of steroid hormones and vitamin D from cholesterol are essential processes in the body, with cholesterol serving as a precursor for these important molecules.
- The biochemical pathways of fatty acid synthesis and cholesterol metabolism are highly regulated processes involving multiple enzymes, substrates, and regulatory factors, essential for the production of lipids and sterols in the body.
Test your knowledge of biochemical pathways with a focus on fatty acid synthesis, cholesterol metabolism, and regulation. Explore key components, regulatory mechanisms, and the synthesis of important molecules such as bile acids, steroid hormones, and vitamin D.
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