Homework Answers

The main enzyme (though not the only one) of fatty acid biosynthesis under control is: (select one) 

a. β-hydroxy-β-methyl-glutaryl-CoA synthase 

b. private acid synthase 

c. citrate lyase 

d. acetyl-CoA carboxylase 

e. β-hydroxy-β-methyl-glutaryl-CoA lyase 

Which of the properties of an RNA indicate that it is a ribozyme? 

a. contains amino acids 

b. degraded by proteases 

c. shows substrate specificity 

d. exhibits catalytic action 

e. degraded by nucleases 

Phosphoenolpyruvate carboxykinase is important for metabolism for the following reasons: 

a. use cellular GTP 

b. forms oxaloacetate from phosphoenolpyruvate 

c. overcomes the irreversibility and pyruvate the kinase reaction 

d. stimulates the activity of pyruvate carboxylase 

e. synthesizes alanine in the liver 

Which of the following statements is NOT valid for RNA biosynthesis? (select one) 

a. RNA synthesis is performed by nucleophilic attack of the 3 'hydroxyl group of the growing chain on the α-hosphate group of the newly introduced nucleotide 

b. RNA synthesis takes place in the 3 ' to 5' direction 

c. DNA synthesis requires a primer and RNA polymerase does not 

d. RNA polymerase includes uridine in the polynucleotide chain instead of thymidine 

e. promoters in RNA synthesis play a similar role as the onset of replication in DNA synthesis 

Transmission is a process in which (select one) 

a. the α-amino group is oxidized 

b. the α-amino group is removed 

c. the carboxyl group is removed from the amino acid 

d. amino acid interacts with α-oxo acid 

e. polymerize amino acids 

In the liver, glucagon activates (select one) 

a. Gluconeogenesis and glycogenolysis 

b. Gluconeogenesis and protein phosphatase 

c. Glycolysis and ketogenesis 

d. Glycolysis and glycogen synthesis 

e. Gluconeogenesis and glycogen synthesis 

Which of the following statements are incorrect? (select one or more) 

a. Non-competitive inhibitors usually bind to the enzyme irreversibly 

b. In competitive inhibition, the substrate competes with the enzyme upon binding to the inhibitor 

c. Competitive inhibitors are similar in structure to substrates 

d. Non-competitive inhibition is observed when the inhibition cannot be removed by adding large amounts of substrate 

e. In competitive inhibition, the substrate and the inhibitor compete for the active site of the enzyme 

Which of the following properties are common to NAD and NADPH? (select one) 

a. They are interchangeable as cofactors of dehydrogenases 

b. Both easily cross the mitochondrial membrane 

c. Both contain two ribose residues, a nicotinamide ring, the nitrogen base adenine and phosphoanhydrides 

d. They have the same redox potential 

e. Both have the same total charge at pH 7 

Which of the following statements best explains the hyperchromatism of DNA? (select one) 

a. the shift of UV absorption to longer wavelengths during denaturation 

b. increase in absorbance at 260 nm after complementary chain coupling and double chain formation 

c. the shift of UV absorption to longer wavelengths after complementary connection of the two chains 

d. the shift of UV absorption to shorter wavelengths during hydrolysis 

e. increase in absorbance at 260 nm after denaturation and chain separation