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84 Cards in this Set

  • Front
  • Back
T/F
Receptor proteins, enzymes and carrier proteins are all proteins which can bind to certain molecules and then perform some function.
T
A certain enzyme exhibits a definite three dimentional teriary 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 rate of reaction by...
a. increasing the value of the equilibrium constant
b. lowering the heat of reactio, lowering the energy of activation
c. increaing 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 apoenzyme
b. a coenzyme
c. "light" metal ions
d. "heavy" metal ions
D
T/F
An enzyme which catalyzes some oxidation/reductio reaction is called a dehydrogenase
T
T/F
The active site of an enzyme can bind and react any molecule which has the same size and shape as the substrate molecule.
F
T/F
The rate of reaction of an enzymatic reaction is directly proportional to the concentration of enzyme.
T
A polt of reation rate v. substrate concentration for normal enzymes is a:
a. bellshaped curve
b. hyperbolic curve
c. aigmoid curve
d. none of these
B
T/F
A plot of the activity of a receptor protein v. substrate concentration levels out to a constant at high substrate concentration.
T
A plot of enzyme activity v. temperature is a:
a. bellshaped curve
b. hyperbolic curve
c. sigmoid curve
d. none of these
A
A protein whose quaternary structure consists of several subunits which behave in a cooperative manner is called a:
a. induced protein
b. allosteric protein
c. isotonic protein
d. none of these
B
A plot of the activity of such a protein, as an allosteric protein, vs substrate concentration is a:
a. bellshaped curve
b. hyperbolic curve
c. sigmoid curve
d. none of these
C
T/F
Competitive inhibition of a protein is the competition b/w the substrate and the inhibitor fot the same active site.
T
T/F
Competitive inhibition is an example of an 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 inhibtion, 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 tot he active site
d. none of these
C
T/F
Allosteric enzyme kinetics are characterized by a sigmoid plot of activity v. substrate concentration.
T
The structure of allosteric enzymes is characterized by:
a. a quaternary structure
b. one or more effector sites
c. cooperativity b/w subunits
d. all of these
D
In metabolism, often one enzyme in a reaction sequence has the following characteristics. It is very large quaternary enzyme which has several sites for both homotrophic and heterotrophic effectors and controls the metabolisms by a negative feedback mechanism. This enzyme is called a :
a. induced enzyme
b. ribozyme
c. regulatory enzyme
d. isozyme
C
The activity of anzymatic reactions 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 moves against its concentration gradient
c. binding to a protein is involved
d. all of these
C
In a ligand-gated sodium ion channel:
a. sodium ion moves against its gradient
b. sodium ion moves with its gradient
c. the ligand moves with its gradient
d. none of these
B
In the functioning of the Na/K+ pump
a. sodium ion is moved against its gradient out of the cell
b. a positive charge develops at the outer leaf of the mb
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 with its gradient
b. sodium ion "leads" glucose through the mb down its gradient
c. ATP is used to maintain the sodium ion gradient
d. all of these
D
Endocytosis of LDL follows Michaelis-Menton kinetics. This is b/c:
a. LDL is an enzyme
b. LDL moves via active transport
c. LDL binds to a mb receptor protein
d. none of these
C
Steroid hormones transduction their signal to the cell by:
a. endocytosis
b. passive diffusion
c. facilitated diffusion
d. active transprt
B
G-protein 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 through secondary messengers
d. none of these
D
Which of the following is not true about secondary messengers?
a. they are all produce at or near the inner leaf of the mb
b. they all function in the cytoplasm
c. they are all small molecules of ions
d. they cause a cascade of reactions 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 in the mb.
F
The inactivation of the G-protein subunit first involves:
a. replacement of GTP by GDP
b. hydrolysis of GTP to GDP
c. reassembling of the holo-G-protein
d. none of these
B
Which compound is the mb bound secondary messenger formed by G-Protein stimulation?
a. NADPH
b. DAG
c. FAD
d. PIP2
B
A 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
T/F
The rate of a chemical reaction depends on the activation energy for the reaction.
T
The transition state of a reaction is
a. the final stage of a reactio when the products are just appearing
b. the instable arrangement of atoms b/w the reactants and products
c. a realatively stable molecule or ion b/w the reactants and products
d. none of the above
B
An enzyme increases the rate of a reaction by:
a. increasing the value of the equilibrium constant
b. lowering the energy of activation
c. increasing the energy of the transition state
d. all of the above
B
In contrast to inorganic catalysts, enzymes have intricately shaped surfaces which are called:
a. substrates
s. cofactors
c. active sites
d. holoenzymes
C
In the induced-fit model of an enzyme:
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 the substrate binds
d. none of the above
C
T/F
The rate of an enzymatic reaction is directly proportional to the substrate concentration
F
In the reaction catalyzed by chymotrypsin, a monomeric enzyme, a plot of rate v. substrate concentration:
a. is sigmoidal
b. shows cooperative kinetics
c. shows that the reaction is zero order
d. is hyperbolic
D
T/F
Chymotrypsin is an allosteric enzyme.
F
Which of the following is a coenzyme?
a. Zn++
b. HOH
c. NADPH
d. insulin
e. cholesterol
C
Alcohol dehydrogenase w/o NAD+ is called a(n)____.
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
Peptidase catalyzes the phosphorylation of other proteins.
F
A certain protein is a tetramer each of which subunits binds to a substrate molecule. Its kinetics do not follow the normal Menton-Michaelis model. Which of the following statements about this enzyme is true?
a. a plot of rate v [substrate] is sigmoid
b. it is an allosteric enzyme
c. it involves a homotropic effect
d. all of the above
D
T/F
An enzyme which undergoes competitive inhibition has the same Vmax and Km as the uninhibited enzyme.
F
An enzyme undergoing non-competitive inhibtion, in comparison to the uninhibited enzyme:
a. has the same Vmax
b. has the same Km
c. has the smae site for substrate and inhibitor
d. none of these
B
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 competive inhibition, increasing the concentration of substrate:
a. decreases the overall rate of reaction
b. increases the overall rate of reaction
c. has no effect
d. competitive inhibitors have no affect no rate
B
The activity of enzymatic reactions can be controlled by:
a. allosteric modification
b. covalent modification
c. induction
d. all of the above
D
Membrane lipids in a lipid bilayer are held together by:
a. hydrophillic interactions
b. hydrophobic interactions
c. hydrogen bonds
d. covalent bonds
B
The degree of membrane fluidity depends on:
a. the percent of choline lipids
b. percent of glycolipids
c. the percent of triglycerides
d. the percentage of unsaturated fatty acid lipids
D
Membrane proteins can be:
a. integral (intrinsic)
b. peripheral (extrinsic)
c. proteins with hydrophobic domains
d. all of the above
D
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 b/w the lipid bilayers
d. the lipids are sandwiched b/w proteins
B
In the simple diffusion a solute:
a. is driven by random molecular motion
b. moves against its concentration gradient
c. moves through the membrane with an expenditure of energy
d. all of the above
A
Facillitated diffusion requires:
a. a free open protein channel with no binding to the transported molecule
b. a carrier protein which binds to the transported molecule
c. an extrinsic receptor molecule
d. the expenditure of energy
B
T/F
In mediated or facillitated diffusion the transported molecule is moving against its concentration gradient.
F
Active transport:
a. takes place down the concentration gradient
b. requires an expenditure of energy
c. a thermodynamically favored event
d. none of the above
B
In the Na/K pump:
a. Na+ goes out and K+ goes into the cell, both against their concentration gradient
b. K+ goes out and Na+ goes into the cell, both against their concentration gradient
c. Na+ goes out and K+ goes into the cell, both down their concentration gradient
d. both Na+ and K+ are transported out of the cell against their concentration gradients
A
In the operation of the Na/K pump:
a. membrane protein cannot undergo conformational changes
b. the involved ions bind to the lipid portions of the membrane
c. a membrane protein is phosphorylated by ATP
d. a membrane protein is phosphorylated by ADP
C
T/F
The Na/K pump is an example of a symport.
F
The function of glucose/Na+ transporter, glucose permease, is an example of:
a. primary active transport
b. secondary active transport
c. passive diffusion
d. facilitated diffusion
B
In the transport of glucose by via the glucose permease:
a. glucose moves against its concentration gradient
b. sodium ion move with its gradient
c. ATP is used to maintain the sodium gradient
d. all of the above
D
In a ligand-gated sodium ion channel:
a. Na ions moves against its gradient
b. Na ions move with its gradient
c. the ligand moves with its gradient
d. none of the above
B
Voltage-gated channels are open:
a. when a molecule binds to its receptor site
b. at all times
c. when membranes are depolarized
d. when membranes are polarized
C
Uptake of LDL by a cell follows Michaelis-Menton kinetics. This is b/c:
a. LDL is an enzyme
b. LDL moves via active transport
c. LDL binds to a membrane receptor protein
d. LDL moves via a passive diffusion process
C
T/F
The release of Ach from a nerve cell by a process of budding of presynaptic vesicles is an example of endocytosis.
F
Steroid hormones transduct their signal to the interior of 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--> GTP
D
Which of the following is not true about G-Proteins?
a. they bind GDP in their inactive state
b. they bind GTP in their active state
c. they stimulate kinases either directly or through secondary messengers
d. they exchange GDP fot GTP
D
Which of the following is not true about secondary messengers?
a. they are all produced at or near the inner membrane leaf
b. they all function in the cytoplasm
c. they are all small molecules or ions
d. they stimulate kinases either directly or indirectly
B
T/F
The activation of a G-Protein involves the replacement of a GTP by a GDP, dissociation and migration of the alpha subunit laterally in the inner membrane leaf.
F
The inactivation of a G-Protein signal involves:
a. replacement of GTP by GDP
b. hydrolysis of GTP to GDP
c. dissociation of the holo-G-Protein
d. stimulation by a receptor protein
B
T/F
NADPH is the coenzyme involved in catabolic oxidations
F
FAD is either a prosthetic group or co-substrate associated with:
a. aminotransferases
b. kinases
c. dehydrogenases
d. isomerases
C
The polar secondary messenger derived from the phosphatidylinositol is:
a. Ca++
b. cAMP
c. DAG
d. IP3
D
Which compound is the carrier and the activator of fatty acids in catabolism?
a. carnitine
b. CoASH
c. CoASAc
d. PIP2
B
Which coenzyme is used to form double bonds in catabolism?
a. NAD+
b. NADP+
c. FAD
d. FADH2
C