95 Questions
What is the primary difference between the polar head group of phospholipids and glycolipids?
The type of linkage between the head group and the backbone
What is the parent compound of glycerophospholipids?
Phosphatidic acid
What is the characteristic of the acyl chains in glycerophospholipids?
Non-polar
What determines the surface properties of membranes in glycerophospholipids?
The properties of the head group
What is the characteristic of the head group in glycerophospholipids?
Polar
What is the unique feature of cardiolipin among glycerophospholipids?
It has two phosphatidic acids sharing a single glycerol
What is the primary function of bile acids in the intestine?
To emulsify dietary fats and make them more accessible to lipases
What is the role of cholesterol in the plasma membrane of eukaryotic cells?
To thicken the plasma membrane and reduce its fluidity
What is the primary source of cholesterol for mammals?
Food and de novo synthesis in the liver
What is the role of eicosanoids in the body?
To act as signaling molecules between nearby cells
What is the effect of nonsteroidal anti-inflammatory drugs (NSAIDs) on the production of prostaglandins and thromboxanes?
They inhibit the production of prostaglandins and thromboxanes
What is the function of prostaglandins, thromboxanes, and leukotrienes in the body?
To mediate inflammation, vasoconstriction, and platelet aggregation
What is the primary location where fatty acids are converted to TAGs or enter gluconeogenesis?
Liver
What is the minimum number of carbon atoms required for fatty acids to be transported via the acyl-carnitine/carnitine transporter?
12
What is the total energy equivalent used in the conversion of a fatty acid to a fatty acyl-CoA?
2 ATP equivalents
What is the enzyme responsible for catalyzing the conversion of a fatty acid to a fatty acyl-CoA?
Fatty acyl-CoA synthetase
What is the purpose of the carnitine shuttle in fatty acid transport?
To transport fatty acids across the mitochondrial membrane
What is the byproduct of the conversion of a fatty acid to a fatty acyl-CoA, in addition to FA-CoA and AMP?
PPi
What is the total number of acetyl-CoA molecules formed after passing through the pathway?
Eight
Which enzyme is responsible for catalyzing the dehydrogenation of alkane to alkene?
Acyl-CoA Dehydrogenase
What is the result of the dehydrogenation reaction catalyzed by Acyl-CoA Dehydrogenase?
Formation of a trans double bond
What is the purpose of the Electron-Transferring Flavoprotein (ETF) in the electron transport chain?
To transfer electrons from FAD to the electron transport chain
What is the genetic defect that leads to Medium-Chain Acyl-CoA Dehydrogenase (MCAD) deficiency?
Recessive mutation in Medium-Chain Acyl-CoA Dehydrogenase
What is the consequence of MCAD deficiency in terms of energy metabolism?
Cells rely on glucose for energy
Which enzyme is responsible for transferring electrons from acyl-CoA dehydrogenase to ubiquinone?
ETF: ubiquinone oxidoreductase
What is the result of the reaction catalyzed by enoyl-CoA hydratase?
Addition of water across the double bond
Which coenzyme is used as the hydride acceptor in the reaction catalyzed by β-hydroxyacyl-CoA dehydrogenase?
NAD+
What is the net result of the thiolase reaction in the β oxidation process?
Thiolysis of a carbon-carbon bond
How many molecules of acetyl-CoA are produced from the complete β oxidation of one molecule of palmitoyl-CoA?
8
What is the role of the enzyme acyl-CoA acetyltransferase (thiolase) in the β oxidation process?
To catalyze the thiolysis of a carbon-carbon bond
Which of the following fatty acids is a C18 mono-unsaturated fatty acid with a double bond at the 9th carbon?
Oleic acid
What is the designation of the carbon at the end of the fatty acid chain in the alternative convention for naming polyunsaturated fatty acids?
ω
Which of the following fatty acids can be synthesized from Alpha Linolenic Acid (ALA)?
Both Eicosa Pentanoic Acid (EPA) and Docosa Hexanoic Acid (DHA)
What is the number of carbon atoms in Palmitoleic acid, a C16 mono-unsaturated fatty acid?
16
Which of the following is NOT an omega-3 fatty acid?
Oleic acid
What is the notation for Palmitic acid, a C16 saturated fatty acid, in the standard convention for naming fatty acids?
16:0
What is the result of the photochemical reactions that occur when a rhodopsin molecule is excited by visible light?
Conversion of 11-cis-retinal to all-trans-retinal
What is the primary function of vitamin E in the body?
Removal of free radicals
What is the role of ubiquinone in the body?
Part of the electron transport chain
What is the function of dolichols in animals?
Unknown function
Where do the digestion and absorption of dietary lipids occur?
Small intestine
What is the result of the conversion of 11-cis-retinal to all-trans-retinal in rhodopsin?
Change in the shape of the entire rhodopsin molecule
What is the net energy cost of fatty acid synthesis in eukaryotes?
3 ATPs per 2-carbon unit
What is the role of citrate in fatty acid synthesis?
It activates acetyl-CoA carboxylase
What is the product of the condensation reaction in fatty acid synthesis?
Palmitate
What is the feedback inhibitor of acetyl-CoA carboxylase?
Palmitoyl-CoA
What is the purpose of the first step in fatty acid synthesis, where acetyl-CoA is converted to malonyl-CoA?
To commit acetyl-CoA to the fatty acid synthesis pathway
What is the energy equivalent of the reduced electron carriers generated in fatty acid synthesis?
14 NADPH
What is the cost of malonyl-CoA formation in terms of ATP molecules?
3 ATPs per 2-carbons unit
What is the role of biotin in the Acetyl-CoA Carboxylase (ACC) reaction?
To transport CO2 to the active site
What is the intermediate formed in the Acetyl-CoA Carboxylase (ACC) reaction?
Carboxyphosphate
What is the function of the transcarboxylase region in the Acetyl-CoA Carboxylase (ACC) enzyme?
To transfer activated CO2 to acetyl-CoA
How many functional regions does the Acetyl-CoA Carboxylase (ACC) enzyme have?
3
What is the net result of the reaction catalyzed by Acetyl-CoA Carboxylase (ACC)?
Formation of malonyl-CoA
What is the mechanism by which free ammonia competes with K+ in astrocyte cells?
Through Na+-K+-2Cl- cotransporter 1 (NKCC1)
What is the source of the first amino group of urea in the urea cycle?
Free ammonia
What is the effect of elevated extracellular [K+] on neuronal response to the neurotransmitter GABA?
Altered response
What is the enzyme responsible for the first nitrogen-acquiring reaction of the urea cycle?
Carbamoyl phosphate synthase I
What is the fate of NH4+ liberated from the side chain of glutamine in the liver mitochondria?
Incorporated into urea
What is the ATP requirement for the first nitrogen-acquiring reaction of the urea cycle?
2 ATPs
What is the consequence of a deficiency in vitamin B12?
Both megaloblastic anemia and homocysteinemia and homocysteinuria
What is the role of N5,N10-methylene THF in DNA synthesis?
It is a necessary cofactor for the thymidylate synthase reaction
What is the result of the accumulation of homocysteine in the blood and urine?
Heart disease, hypertension, and stroke
Why is vitamin B12 necessary for the formation of methionine?
It is necessary for the methionine synthase reaction
What is the consequence of a deficiency in THF?
Megaloblastic anemia
What is the role of folates in the treatment of megaloblastic anemia?
It can partially treat the anemia
What is the oxidation state of the cofactor N5,N10-methylene H4folate?
Intermediate state
What is the primary source of one-carbon units for H4folate?
Conversion of serine to glycine
What is the limitation of H4folate in biosynthetic reactions?
Insufficient for transferring methyl groups
What is the role of S-adenosylmethionine in biosynthetic reactions?
To transfer methyl groups
What is the product of the conversion of serine to glycine in the folate cycle?
N5,N10-methylene H4folate
What is the primary function of S-adenosylmethionine in biological reactions?
Methyl transfer, with a methyl group 1000 times more reactive than THF methyl
What is the consequence of a folate deficiency in the body?
Folates are trapped in the N5-MTHF form
What is the role of methionine synthase in the folate cycle?
To regenerate THF from N5-MTHF
What is the source of carbon in the formation of tetrahydrofolate?
Serine
What is the intermediate formed in the conversion of formic acid to N5,N10-methenyl-H4folate?
N10-formyl H4folate
What is the role of biotin in the folate cycle?
Transferring CO2
What is the consequence of folate deficiency in DNA synthesis?
Abnormal uracil incorporation into DNA
What is the target of fluorouracil, a chemotherapeutic agent?
Thymidylate synthase
What is the role of serine hydroxymethyltransferase in the folate cycle?
Synthesis of N5,N10-methylene THF
What is the primary function of reciprocal control in the synthesis of adenine and guanine nucleotides?
To balance the synthesis of AMP and GMP
What is the outcome of the reaction catalyzed by thymidylate synthase?
dUMP is converted to dTMP
What is the consequence of dihydrofolate reductase inhibition?
Reduced synthesis of dTMP
What is the committed step in the de novo synthesis of pyrimidine nucleotides?
The reaction between Asp and carbamoylphosphate, catalyzed by aspartate transcarbamoylase
What is the role of glutamine analogs, such as azaserine and acivicin, in chemotherapy?
Inhibition of glutamine amidotransferase
What is the committed step in purine synthesis?
Formation of 5-phosphoribosylamine
What is the role of ADP and GDP in the regulation of PRPP synthesis?
They inhibit the synthesis of PRPP
What is the precursor of the pyrimidine ring in de novo pyrimidine synthesis?
Carbamoylphosphate
What is the starting material for the synthesis of aspartate in humans?
Oxaloacetate
What is the enzyme responsible for the synthesis of carbamoylphosphate in pyrimidine synthesis?
Carbamoylphosphate synthase II
What is the effect of the excretion of large concentrations of homogentisate on urine?
It turns urine black
What is the role of glutamine in the synthesis of purines?
It donates a nitrogen atom
What is the fate of PRPP in mammals, apart from its use in pyrimidine synthesis?
It is used in the salvage pathway
What is the immediate precursor of inosine monophosphate (IMP) in purine synthesis?
5-Phosphoribosylamine
What is the net result of the synthesis of asparagine from aspartate in humans?
It releases one NH4+ molecule
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