Biochem Final

Proinsulin is converted into insulin by:

Regulation of metabolism by activation of the gene encoding a particular enzyme is called

Usually the quickest method of influencing an enzymatic activity is by:

Which of the following statements is correct regarding isozymes? -they catalyze the same reaction but have vastly different structures -they are always monomeric proteins -their differences are based upon the type of tissue in which they are present -they often respond to different inhibitors and activators

All are characteristics of allosteric enzymes EXCEPT: -effectors may show stimulatory of inhibitory activity -they have multiple subunits -they obey Michaelis-Menten kinetics -the regulatory effect is by altering conformation and interaction of subunits -binding one subunit impacts binding of substrate to other subunits

Which of the following statements regarding enzyme regulation is true?

Characteristics of glycogen phosphorylase include all EXCEPT: -covalently linked pyridoxal phosphate -an active site at the center of each of two identical subunits -regulatory phosphorylation site on a Ser residue -allosteric effector sites for ATP and glucose-6-phosphate
-all are true

The G-alpha subunit of GTP-binding protein (G protein) has all of the following characteristics EXCEPT: -activates adenylyl cyclase -hormone-receptor complez promotes G alpha release from G beta-y -has a very active GTPase activity -binds GDP in the G alpha-beta-y complex -GTP hydrolysis leads to G-alpha-adenylyl cyclase dissociation

All are true for camp-dependent protein kinase EXCEPT:-also known as PKA -phosphorylase kinase is a substrate -consists of a pair of catalytic subinutes -two regulatory subunits block catalytic activity without camp binding -phosphorylates glycogen phosphorylase

Glycogen phosphorylase displays allosteric activation and inhibition by multiple modes. Which of the following is a correct correlation?

Adenyl cyclase catalyzes the synthesis of camp, and camp hydrolysis is catalyzed by a 5’-phosphodiesterase. If caffeine inhibits 5’-phosphodiesterases, drinking a caffeinated beverage would _____ camp levels and ____ glycogen phosphorylase activity.

The polypeptide of myoglobin serves all of the following functions EXCEPT: -protects the heme iron from oxidation -cradles the heme group -provides a pocket for O2 fit -keeps the heme iron in the ferric form -none of the above

We are protected to some extent against low level CO poisoning because:

All are true for the effect of proteins on binding of O2 by hemoglobin EXCEPT: -the saturation curve of Hb for O2 is displaced to the left (greater binding) as acidity increased -actively metabolizing tissues produce acid which is an antagonist of oxygen binding by Hb -as the pH decreases, dissociation of O2 from Hb is enhanced -the phenomenon is called the Bohr Effect -All are true

Fetal hemoglobin (Hb F) has an intrinsically greater affinity for O2 than adult hemoglobin (Hb A) because: