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66 Cards in this Set

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T/F receptor proteins, enzymes and carrier proteins are all proteins which can bind to certain mcs and then perform some fx
T
A certain enzyme exhibits a definite 3-D tertiary structure which can accomodate a specific substrate. This can be explained by the
A. allosteric site theory
B. lock and key theory
C. induced fit theory
D. none of these
B
T/F The active site of an enzyme can consist of binding sites for the substrate and coenzymes as well as a catalytic site.
T
An enzyme increases the rates of rxn by:
A. inc'ing the value of the equilibrium constant
B. lowering the heat of rxn lowering the energy of activation
C. inc'ing the energy of the transition state
D. all of these
B
Which of the following is NOT a possible component of a holoenzyme:
A. an apoprotein
B. a coenzyme
C. light metal ions
D. heavy metal ions
D
T/F an enzyme which catalyzes some oxidation-reduct rxns is called a dehydrogenase
T
T/F The active site of an enzyme can bind and "react" any mc which has the same shape and size as the substrate mc.
F
T/F the rate of rxn of an enzymatic rxn is directly proportional to the concentration of the enzyme
T
T/F the rate of a chemical rxn depends on the activation energy for the rxn
T
As catalysts, enzymes are
A. significantly less effective than non-enzymatic catalysts
B. slightly less effective than non-enzymatic catalysts
C. significantly more effective than non-enzymatic catalysts
D. slightly more effective than non-enzymatic catalysts
C
The transition state of a rxn is:
A. the final stage of a reaction when products are just appearing
B. The unstable arrangement of atoms between the reactants and products
C. a relatively stable molecule or ion between the reactants and products
D. none of the above
B
An enzyme inc's the rate of reaction by:
A. inc'ing the value of the equilibrium constant
B. lowering energy of activation
C. inc'ing the energy of the transition state
D. all of the above
B
In contrast to inorganic catalysts, enzymes have intricately shaped surfaces called:
A. substrates
B. cofactors
C. active sites
D. holoenzymes
C
in the induced fit model:
A. the substrate changes its conformation to fit the active site
B. the active site changes its conformation to fit the substrate
C. there is a conformational change in the enzyme when substrate binds
D. none of the above
C
T/F the rate of an enzymatic rxn is directly proportional to the substrate concentration
F
In the rxn catalyzed by chymotripsin, a monomeric enzyme, a plot of rate vs. substrate concentration:
A. is sigmoidal
B. shows cooperative kinetics
C. shows that the rxn is zero order
D. is hyperbolic
D
T/F chymotrypsin is an allosteric enzyme
F
Which is a coenzyme?
A. Zn++
B. H2O
C. NADPH
D. insulin
E. cholesterol
c
Alcohol dehydrogenase w/o NAD+ is called a (an)
A. apoenzyme
B. holoenzyme
C. substrate
D. cofactor
a
Which of the following enzymes is an oxidoreductase?
A. aminotransferase
B. glucokinase
C. peptidase
D. alcohol dehydrogenase
D
T/F peptidases catalyze the phosphorylation of other proteins
F
A plot of the reaction rate vs substrate concentration for a normal enzyme is a
A. bellshaped curve
B. a hyperbolic curve
C. a sigmoid curve
D. none of the above
B
T/F A plot of the activity of a receptor protein vs substrate concentration levels out to a constant at high substrate concentrations.
T
A plot of enzyme activity vs temp is
A. bell shaped curve
B. hyperbolic curve
C. sigmoid curve
D. none of the above
A
A protein whose quaternary structure consists of several subunits which behave in a cooperative manner is called a :
A. induced protein
B. an allosteric protein
C. an isotonic protein
D. none
B
A plot of the activity of such a protein vs substrate concentration is a :
A. bell shaped curve
B. hyperbolic curve
C. sigmoid curve
D. none
c
T/F competitive inhibition of a protein is the competition between the substrate and the inhibitor for the same active site
T
T/F competitive inhibition is an example of irreversible inhibition
F
T/F an enzyme which undergoes competitive inhibition has the same Vmax and Km as the uninhibited enzyme
F
An enzyme which undergoes non-competitive reversible inhibition, in comparison to the uninhibited enzyme,:
A. has a separate inhibitor site
B. has a lower Vmax
C. has the same Km
D. all of these
D
Irreversible inhibition of an enzyme is characterized by:
A. covalent bonding of the substrate to the active site
B. covalent bonding of the inhibitor to the coenzyme
C. covalent bonding of the inhibitor to the active site
D. none
c
T/F allosteric enzyme kinetics are characterized by a sigmoid plot of activity vs substrate concentration
T
The sturcture of allosteric enzymes is characterized by:
A. a quaternary structure
B. one or more effector sites
C. cooperativity between subunits
D. all of these
D
In metabolism, often one enzyme in a rxn sequence has the following characteristics- it's a v. large quaternary enzyme which has several sites for both homotropic and heterotropic effectors and controls the metabolisms by a neg feed-back mechanism. this enzyme is called a :
A. induced enzyme
B. ribozyme
C. regulatory enzyme
D. isozyme
C
The activity of enzymatic rxns can be controlled by:
A. allosteric modification
B. covalent modification
C. induction
D. all of these
D
In the process of facilitated or mediated diffusion
A. energy is required
B. a substance is moved against its conc gradient
C. binding to a protein is involved
D. all of these
C
in a ligand-gated sodium channel:
A. sodium ion moves against its gradient
B. sodium ion moves with its gradient
C. the ligand moves w its gradient
D none
B
in the functioning of the Na/K pump,
A. na ion is moved against its gradient out of the cell
B. a positive charge develops at the outer leaf of the membrane
C. it undergoes a conformational change at the expense of ATP
D all of these
D
The Na/K pump is an example of:
A. passive transport
B. primary active transport
C. secondary active transport
D. a symport
B
in the transport of glucose into a cell in a secondary transport system
A. glucose moves w/ its gradient
B. sodium ion leads glucose thru the membrane down its conc gradient
C. ATP is used to maintain the Na ion gradient
D. all of these
D
Endocytosis of LDL follows Michaelis-Menton kinetics b/c
A. LDL is an enzyme
B. LDL binds via active transport
C. LDL binds to a receptor protein
D. none
C
membrane lipids in a lipid bilayer are held together by
A. hydrophobic interactions
B. hydrophilic interactions
C. hydrogen bonds
D. covalent bonds
A
The structure of a membrane is
A. unsymmetrical with respect to lipid composition
B. symetrical with respect to lip comp
C. determined by the presence of cholesterol
D. random
A
In the fluid-mosaic model of membranes
A. the proteins are specifically bonded to the lipids
B. the proteins "float" in the lipid bilayer
C. the proteins are sandwiched in the lipid bilayer
D. the lipids are sandwiched between proteins
B
The degree of membrane fluidity depends on
a. the percent of choline lipids
b. the percent of triglycerides
c. the percent of glycolipids
d. the percent of unsaturated F.A. lipids
d
In the Lineweaver-Burk double reciprocal plot, the y-intercept is equal to
A. 1/[S]
B. 1/V
C. 1/Vmax
D. -1/Km
E. Km/Vmax
C
In the Lineweaver-Burk double reciprocal plot, the x-intercept is equal to
A. 1/[S]
B. 1/V
C. 1/Vmax
D. -1/Km
E. Km/Vmax
d
In competetive inhibition, inc'ing the conc of substrate
A. dec's the overall rate of rxn
B. inc's the overall rate of rxn
C. has no effect
B
Steroid hormones transduct their signal to the cell by
A. endocytosis
B. passive diffusion
C. facilitated diffusion
D. active transport
b
G-proteins cannot
A. bind GDP
B. bind GTP
C. undergo conformational changes
D. phosphorylate GDP to GTP
D
Which is not true about G-proteins?
A. they bind GDP in their inactive state
B. they bind GTP in their active state
C. they can stimulate kinases directly or thru secondary messengers
D. none
D
Which of the following is NOT true of secondary messengers?
A. they are all produced at or near the inner leaf of the membrane
B. they all function in the cytoplasm
C. they are all small mc's or ions
D. they cause a cascade of rxns leading to biological activity
b
T/F G proteins have a quaternary structure in which one of the subunits is a GTP-ase
T
T/F the activation of the G-protein involves the replacement of GDP by GTP and dissociation and migration of the active gamma subunit laterally into the membrane
F
The inactivation of the G-protein subunit first involves
A. replacement of GTP to GDP
B. hydrolysis of GTP to GDP
C. reassembling of the holo G protein
D. none of these
B
Which compound is the membrane bound secondary messenger formed by G-protein stimulation?
A. NAD+
B. CoA
C. DAG
D. IP3
C
Which is the polar secondary messenger derived from phosphatidylinositol (PI)?
A. NAD+
B. IP3
C. PIP2
D. DAG
B
which molecule, under the action of phospholipase, produces diacyl glycerol and inositol triphosphate?
A. PIP2
B. PI
C. FADH2
D. cAMP
A
Which compound is formed from ATP thru the activation of a membrane enzyme by an active G-protein?
A. ADP
B. IP3
C. cAMP
D. PI
C
Which compound is the reduced form of the coenzyme used in catabolic oxidation-reduction rxns?
A. FADH2
B. NADH
C. CoA
D. NAD+
B
Which compound is involved in the conversion (reduction) of a double bond to a single bond?
A. FADH2
B. NADH
C. CoA
D. ATP
A
Which compound is the coenzyme used in the reduction of compound in anabolism (synthesis)?
A. FADH2
B. NADH
C. NAD+
D. ATP
C
What are the coenzymes that transfer a phosphate in a.a. metabolism?
A. kinases
B. dehydrogenases
C. phosphatases
D. transaminases
D
Which of the following exists in the body?
A. pyridoxal phosphate
B. pyridoxine
C. pyridoxamine
D. pyridoxal
A
Which molecule accepts an amine group from pyridoxamine phosphate to form an aldehyde?
A. cAMP
B. pyridoxal
C. pyridoxamine
D. pyridoxal phosphate
D
T/F CoA combines with a fatty acid to form acetyl CoA.
T