Quiz Flashcards
Which of the following statements is correct about competitive enzyme inhibition?
A.
The inhibitor binds reversibly at the active site of the enzyme.
B.
The inhibitor binds at several different sites on an enzyme.
C.
The inhibitor binds only to the enzyme-substrate (ES) complex.
D.
The inhibitor binds irreversibly to a region on the enzyme that is not the catalytic site.
E.
The inhibitor lowers the characteristic Vmax of the enzyme.
.
The inhibitor binds reversibly at the active site of the enzyme.
The liver is important in maintenance of blood sugar levels in the body. It synthesises one critical enzyme involved in gluconeogenesis that the muscle does not make. This enzyme is A. Hexokinase (aka Glucokinase) B. Glucose-6-phosphatase C. Pyruvate kinase D. Pyruvate carboxylase E. Fructose - 1,6 - bisphosphatase
Glucose-6-phosphatase
Which of the following is NOT involved in electron transport? A. Coenzyme A B. Cytochrome C C. Coenzyme Q10 (CoQ) D. NADH E. Iron-sulfur proteins
Coenzyme A
The pyruvate dehydrogenanse complex bridges the gap between glycolysis and the citric acid cycle. Its function is to
A.
Decarboxylate glucose and transfer electrons to NADP+
B.
Decarboxylate pyruvate and transfer electrons to NADP+
C.
Decarboxylate glucose and transfer the remaining acetate (2-carbon) groups to coenzyme A
D.
Decarboxylate pyruvate and transfer the remaining acetate (2-carbon) group to coenzyme A
E.
None of the above
.
Decarboxylate pyruvate and transfer the remaining acetate (2-carbon) group to coenzyme A
Why is the citric acid cycle referred to as oxidative if no oxygen is involved with any of its reactions?
A. Electrons are lost from the incoming acetyl-coA and transferred to electron carriers, NADH and FADH2 B. Electrons are transferred to the incoming acetyl-coA from water C. Electrons are lost from the incoming acetyl-coA and transferred to electron carriers coenzyme Q10 and cytochrome C D. Electrons are transferred to the incoming acetyl-coA from NADPH E. Oxygen is not in its elemental form (O2), but rather utilised as carbon dioxide (CO2)
A
As electrons are transferred from NADH or FADH2 to oxygen along the electron trasnport chain, _____________ are pumped from the mitochondrial matrix into the intermembrane space.
A. phosphate ions B. negatively charged molecules C. electrons D. protons E. proteins
Protons
The first five (5) reactions of glycolysis are considered the “preparatory phase” because:
A.
ATP is consumed at two (2) consecutive steps to phosphorylate two (2) separate, three (3) carbon molecules.
B.
ATP is produced via two (2) separate dephosphorylation reactions.
C.
The six (6) carbon sugar is broken down into two (2), three (3) carbon, unphosphorylated molecules.
D.
ADP is produced via two (2) separate dephosphorylation reactions.
E.
ATP is consumed to phosphorylate a six (6) carbon sugar.
ATP is consumed to phosphorylate a six (6) carbon sugar.
GTP is produced from GDP in the citric acid cycle. This reaction is called A. Dephosphorylation B. Favourable phosphorylation C. Oxidative phosphorylation D. Substrate level phosphorylation E. Unfavourable phosphorylation
Substrate level phosphorylation
Which of the following is true of allosteric enzymes?
A.
Allosteric enzymes are regulated primarily by cleavage of the inactive zymogen.
B.
Allosteric enzymes usually show strict Michaelis-Menten kinetics.
C.
Allosteric enzymes are regulated by compounds binding at a site other than the catalytic (active) site.
D.
Allosteric enzyme are never multi-meric (ie having more than one polypeptide chain in the final functional enzyme).
E.
Allosteric enzymes usually catalyse several different reactions within a metabolic pathway.
Allosteric enzymes are regulated by compounds binding at a site other than the catalytic (active) site.
Entropy is a measure of randomness. A favourable reaction will lead to an increase in entropy of the compounds involved.
True
False
T
What is the role of an enzyme in an enzyme-catalysed reaction?
A.
To increase the rate at which a substrate is converted into a product.
B.
To ensure that the reaction product is not re-converted back to substrate.
C.
To ensure that all the substrate is converted to product.
D.
To make the free-energy change for the reaction more favourable.
E.
To ensure that the product of the reaction is more stable than the substrate.
.
To increase the rate at which a substrate is converted into a product.
How many CO2 and ATP molecules are formed during one complete turn of the citric acid (tricarboxylic acid, Krebs’) cycle? A. 1CO2 and 5ATP B. 2CO2 and 2ATP C. 2CO2 and 12ATP D. 2CO2 and 16ATP E. 2CO2 and 1ATP
E.
2CO2 and 1ATP
In which cellular compartment are the enzymes of glycolysis located? A. the mitochondria B. the lysosomes C. the nucleus D. the cytoplasm / cytosol E. the interstitial fluid
D.
the cytoplasm / cytoso
Enzymes are potent catalysts because they…
A.
drive reactions to completion while other catalysts drive reactions to equilibrium.
B.
are very specific and can prevent the conversion of products back to substrates.
C.
increase the equilibrium constants for the reactions they catalyse.
D.
lower the activation energy for the reactions they catalyse.
E.
are consumed in the reactions they catalyse.
D
The negative feedback control of un-competitive or mixed inhibitors can be reversed by addition of excess substrate.
True
False
F
