Enzymes Flashcards
Enzymes are proteins that ___ the rates of biochemical reactions; ___
increase, biological catalysts
Enzymes make up ____ ____ such as those that synthesize new molecules and generate __ ____
metabolic pathways, cellular energy
Three distinct features of enzymes
- Catalytic power
- Specificity
- Regulation
Increases the rates of biochemical reactions as much as 10^16
Catalytic power
Selectively act upon a substrate to carry out a particular reaction
Specificity
Enzyme activity is regulated by a variety of mechanisms
Regulation
____ ____ increase the rates of biochemical reactions as much as __
catalytic power, 10^16
_____ selectively act upon a ____ to carry out a ____ reaction
specificity, substrate, particular
____ enzyme activity is regulated by a ___ of mechanisms
regulation, variety
How many fundamental categories can enzymes be classified in?
6 fundamental categories
Fundamental Enzyme Category:
Oxidoreductases
Transfer electrons from one molecule to another
Fundamental Enzyme Category:
Transferases
Transfer chemical groups
Fundamental Enzyme Category:
Hydrolases
Break covalent bonds by hydrolysis
Fundamental Enzyme Category:
Lyases
Cleave various bonds, or add groups to double bonds
Fundamental Enzyme Category:
Isomerases
Produce isomers
Fundamental Enzyme Category:
Ligases
Join large molecules by forming covalent bonds
Oxidoreductases ____ ____ from one molecule to another
transfer electrons
Transferases transfer ___ ___
chemical groups
Hydrolases break ____ ____ by hydrolysis
covalent bonds
Lyases ____ various bonds, or ___ groups to ___ ____
cleave, add double bonds
Isomerases _____ isomers
produce
Ligases join ____ ____ by forming ___ ____
large molecules, covalent bonds
Cofactors are ___ ___ or ___ ____ that bond to enzymes and are required for ___ ____
metal ions, organic molecules, enzyme activity
Coenzymes are ___ ___ (B-vitamin derivatives) that act as ___ ____
organic molecules, enzyme cofactors
Prosthetic groups are tightly bound ___ or ____
cofactors or coenzymes
Holoenzyme are _____ ___ complex of ___ and _____
catalytically active, protein and coenzyme
Apoenzyme are ___ without the ___ ___
proteins, prosthetic group
Holoenzyme are made of ___ and ____
protein and coenzyme
Coenzymes are ___ ___
organic molecules
Cofactors are ___ or ____
metal ions or organic molecules
Prosthetic groups are ____ or ____
cofactors or coenzymes
Apoenzymes are ____
proteins
Understanding the rates and processes of chemical reactions is ____
chemical kinetics
velocity (v) or the ____ ___ ____, is the amount of ___ formed or the amount of __ consumed per unit of time
rate of the reaction, P, A
The velocity (or rate) is ______ to the concentration of __
proportional, A
What is the proportionality constant or rate constant?
k
v=k[A] is the equation for what?
first order reaction
The Michaelis-Menten Equations is a
kinetics of enzyme-catalyzed reaction
v=k[A][B] is the equation for what?
second order reaction
In a __ ___ ___, there is a directly proportionate relationship between substrate concentration and the amount of produce produced per unit time
first order reaction
The Michaelis-Menton equation __ is no longer dependent on __ and the equation is obeying __ __ __
v, [S], zero-order kinetics
The Michaelis-Menton equation is __ ___ ____
zero order reaction
What equation is used for the kinetics of enzyme catalyzed reactions?
Michaelis-Menton equation
The M/M equation gives the rate of an enzyme reaction (v) in terms of what?
substrate concentration
What are the two constants in the M/M equation?
Vmax, Km
When substrate concentration is high, v=_____
v=Vmax
When substrate concentration is high, v is no longer dependent on what?
substrate concentration
When substrate concentration is high, the reaction is following what order kinetics?
zero
When substrate concentration is low, the reaction is following what order kinetics?
first
What variables are fixed in the M/M equation?
temp, pH, and ionic strength
v=(vmax/Km)*[S] is the equation for when the substrate concentration is __
low (first order)
The M/M equation for an enzyme-catalyzed reaction describes a ___ ___
hyperbolic curve
What is the shape of the curve of the M/M equation?
hyperbolic curve
A __ __ is a curve that approaches but never reaches the max value
hyperbolic curve
v=
product produced/unit time
Km is the ___ ___ at which the rate of the reaction, v, is ___ ____ since v=1/2Vmax when [S]=Km
substrate concentration, half maximal
At Vmax/2, what is equal to what?
substrate, enzyme
Km is a measure of what?
amount of substrate/unit volume
Kcat is the value for what?
catalytic constant/turnover number
Kcat measures the __ amount of product produced per second when the enzyme is ___ with the substrate
maximum, saturated
Kcat ___ greatly for different enzymes
varies
What is the pH that most enzymes have peak activity?
7.4
Kcat must be determined and compared under what type of conditions?
the same
Kcat is similar to what other value?
Vmax of the M/M equation
Kcat is determined under ___, standard conditions
fixed
The activity most enzymes have a peak at around __
40 degrees C
Kcat values are high/low because of what two things?
- efficiency of the enzyme
- nature of substrate (large, complex vs small, simple)
Staphylococcal nuclease has a __ Kcat
low (95)
Carbonic anhydrase has a __ Kcat
high (1,000,000)
[S] large =
zero order kinetics
[s] very small =
first order kinetics
What does enzyme staphylococcal nuclease do?
attack DNA, RNA, and other molecules
Why does carbonic anhydrase have such a high kcat?
CO2 and H2O are simple and small molcules
There’s no activity at too low or too high of pH because of the interaction of what part of the amino acid?
positively or negatively charged side chains
___ is an enzyme that breaks down food in the stomach, and is therefore at peak activity at a ___ pH of ___
pepsin, low, 1.5
___ is an enzyme that breaks down food in the intestines and has peak activity at pH 7.7
trypsin, 7.7
What in the stomach makes it acidic?
HCl
At low temps, enzyme activity is ___ due to lack of energy
slowed
At high temps, enzyme activity might undergo irreversible ____
denaturing (unfolding)
denaturing of enzymes causes lack of ___
activity
What are the two reversible enzyme inhibitors?
- Competitive Inhibitors
- Noncompetitive inhibitors
Competitive inhibitors are _____ _____ ____
reversible enzyme inhibitors
Noncompetitive inhibitors are ___ ____ ___
reversible enzyme inhibitors
the ____ and _____ bind to the same site (the active site) on the enzyme in a ____ ____
substrate (S) and inhibitor (I), competitive inhibitor
the inhibitor binds to a site different from the active site and brings about a _____ ____ that _____ enzyme activity in a _______ _____
conformational change, reduces, noncompetitive inhibitor
What are the two types of noncompetitive inhibitors?
Mixed & pure
Mixed inhibitors ____ kcat and ___ substrate binding (Km)
decrease, change
Pure inhibitors are _____
uncommon
Pure inhibitors _____ kcat, but ____ affect substrate binding (Km)
decrease, don’t
A competitive inhibitor is similar in ___ and __ to the normal substrate.
size, shape
A competitive inhibitor cannot undergo a ___ ____
chemical reaction
The inhibitor and substrate compete for a binding site to the active site of the enzyme in ___ ___
competitive inhibition
The inhibitor and substrate bind to different sites in __ ____
noncompetitive inhibition
Binding of the inhibitor ____ the activity of the enzyme and therefore decreases Kcat and Vmax in noncompetitive inhibition
decreases
Inhibitors might make it so the substrate is ___ bound to the enzyme.
loosely
Inhibitors decrease the ____ of the subsrate/reaction
Vmax
Inhibitos increase ____ of the substrate/reaction
Km
Irreversible inhibitors binds ____ to the enzyme, usually by ___ ___
irreversibly, covalent bonds
____ substrates generate a reactive group that forms a covalent bond during binding the active site.
suicide
Penicillin is an example of ___ substrate
suicide
Penicillin forms a covalent bond with an enzyme involved in the synthesis of what?
bacterial cell walls.
