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77 Cards in this Set

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Receptor proteins, enzymes and carrier proteins are all proteins that can bind to certain molecules and then perform some function. T/F
True
What is the lock and key theory
Certain enyzme exhibits a definite 3-D tertiary structure which can accomodate a specific substrate
What is induced fit theory?
Enzyme changes shape slightly as substrate binds
The active site of an enzyme consists of
Binding sites for substrate and co enzymes and a catalytic site
An enyzme increases the rate of reaction by
Lowering the heat of reaction by lowering the energy of activation
What do holoenzymes consist of?
Coenzyme, apoprotein and light metal ions
Type of enzyme that catalyzes some oxidation-reduction reactions
Dehydrogenase
T/F: the active site of an enzyme can bind and react any molecule which ahs the same shape and size of the substrate molecule
False
T/f: The rate of reaction of an enzymatic reaction is directly proportional to the concentration of an enzyme
True---1st order
A plot of reaction rate versus substrate concentration for normal enzymes is
Hyperbolic curve (it levels off once all the enzyme is saturated)
T/F: A plot of the activity of a receptor protein versus substrate concentration levels out to a constant at high substrate concentrations
True
A plot of enzyme activity vs temperature is a
bell shaped curve
What is an allosteric protein?
A protein whose quaternary structure consists of several subunits which behave in a cooperative manner; binding of something at one site may cause drastic changes in properties at a distant site
The plot of cooperative binding looks like
sigmoid curve....the binding of the first molecule facilitates binding of the second...etc
T/F: Competitive inhibition of a protein is the competition between the substrate and the inhibitor for the same active site
True
Competitive and noncompetitive are examples of what type of inhibition
Reversible
What is a reversible inhibition
When the enzyme binds it can be released and leaves enzyme in it's original shape
What is irreversible inhibition
Once the inhibitor binds, the enzyme cannot go back to it's original condition; covalent bonding of the inhibitor to the active site
Effect of kinetics of competitive inhibition
The Vm does not change but the Km increases..more substrate is needed to get to a rate in the presence of an inhibitor...X intercept and slope changes
Effect of kinetics of noncompetitive inhibition
Y intercept and slope change; Vm decreases and Km remains the same
The structure of allosteric enzymes is charecterized by
Quaternary structure, cooperative binding, and one or more effector sites
What is the charecteristics of a regulatory enzyme
Involved in controlling metabolism by using negative feedback inhibition also is a quaternary enzyme with homotropic and heterotropic effectors
The activity of enzymatic reactions can be controlled by
Allosteric modifications, covalent modifications and induction
Two types of passive transport
Diffusion and facilitated diffusion
Charecteristics of facilitated diffusion
No energy, binds to a protein and goes w/ the concentration gradient
In a ligand gated sodium ion channel
The Na moves with it's concentration gradient and is therefore passive
Three things for the funcitoning of a sodium/potassium pump
Conformation change at expense of ATP, sodium goes against it's concentration gradient, positive charge builds up outside of membrane
The Na/K pump is an example of
Primary active transport
The Na/K pump with glucose symport is an example of
Secondary active transport
Three charecteristics of transport of glucose into a cell in a secondary transport system
Goes w/ it's gradient, uses ATP to maintain Na ion gradient, Na ion leads glucose through the membrane down gradient
Why does endocytosis of LDL follow Michaelis menton kinetics?
Because LDL binds to a membrane receptor protein
Sterior hormones transduce their signal to the cell by
passive diffusion
G-proteins
Bind GDP, bind GTP and undergo conformational changes
Three things that are true about G-proteins
Bind GDP in the inactive state, bind GTP in their active state and stimulate kinases directly ot through secondary messengers
T/F: All secondary messengers are functioning in cytoplasm
False...DAG does not
T/F: All secondary messengers are produced near the inner leaf of membrane
True
T/F: All secondary messengers are small molecules or ions
True
T/F: Secondary messengers cause a cascade of reactions leading to biological activity
True
The quaternary structure of G-proteins has GTP-ase as one of it's subunits
True
two things involved in the activation of the G-protein
Replacement of GDP by GTP and the dissociation and migration of the active alpha subunit laterally in the membrane
The inactivation of the G-protein subunit first involves
Hydrolysis of GTP to GDP
Which compound is the membrane bound secondary messenger formed by G-protein stimulation?
DAG
Which is the polar secondary messenger derived from phosphatidylinositol
IP3
Which molecule under the action of a phospholipase produces diacyl glycerol and inositol triphosphate
PIP2
which compound is phosphatidylinositol
PI
Function of DAG?
DAG causes the release of PKC
(protein kinase C)
Function of IP3
Causes calcium release from SER which then allows DAG to stimulate release of PKC
Which compound is derived from ATP through the activation of a membrane enzyme by an active G-protein
cAMP
Function of cAMP
activates protein kinases and regulates passage of calcium through channels
Which compound is the reduced form of the coenzyme used in the catabolic oxidation-reduction reactions
NADH
Which compound is involved in the conversion of a double bond to a single bond?
FADH2
Function of NAD+
Coenzyme used in catabolizing oxidation-reduction reactions
What is FAD?
coenzyme, precursor to FADH2
Which compound is the coenzyme used in the reduction of compounds in anabolism
NADP
Which compound is the carrier and activator of fatty acids?
NADP
What is NADPH
Enzyme oxidase complex
What is co-enzyme A?
synthesis and oxidization of fatty acids, and the oxidation of pyruvate in the citric acid cycle
T/F: The rate of a chemical reaction depends on the activation energy for the reaction
True
What is the transition state of a reaction?
When the unstable arrangements of the atoms between the reactants and products
In a reaction catalyzed by chymotrypsin, a monomeric enzyme, a plot of rate vs. substrate concentration
is hyperbolic
Is NADPH a coenzyme?
yes
Alcohol dehydrogenase without NAD+ is called
apoenzyme
What is an enzyme that is oxidoreductase?
Alcohol dehydrogenase
T/F: Peptidases catalyze the phosphorylation of other proteins?
False
In the lineweaver burke double reciprocal plot the y-intercept is equal to
1/Vmax
In the lineweaver-burk double recipricol plot the x-intercept is equal to
1/Km
In competitive inhibition, increasing the concentration of substrate
Increases the overall rate of a reaction
The degree of membrane fluidity depends on
the percent of unsaturated fatty acid lipids
In the fluid mosaic model of membranes
the proteins float in the lipid bilayer
In the sodium potassium pump
Sodium is pumped out and potassium in...both against concentration gradients
In operation of the sodium potassium...the membrane protein is phosphorylated by
ATP
In a ligand gated sodium ion channel sodium ion moves
with it's gradient
Voltage gated channels are open
When membranes are depolarized
Which coenzyme is involved in anabolic oxidations
NADPH
FAD is either a prostehtic group or a co-substrate associated with
dehydrogenases
Which compound is the carrier and activator of fatty acids in catabolism
CoASH
Which co-enzyme is used to form double bonds in catabolism
FAD