Enzyme Activity Flashcards
moles of
substrate converted to product per
unit time.
Enzyme Activity
The _____ of appearance of product or the rate of disappearance of
substrate
rate
Factors affecting enzyme activity
❖ Concentration of substrate
❖ Concentration of enzyme
❖ Temperature
❖ PH
❖ Activators
❖ Inhibitors
For Non-enzymic reactions:
The increase in velocity is proportional to the ______________________
Substrate Concentration
For Enzymic Reaction:
Faster reaction but it reaches the ________________ when all the enzyme molecules are ____________
saturation point ; occupied
What equipment is used to test the absorbance?
Spectrophotometer
For Enzymic Reaction:
If you alter the concentration enzyme the Vmax will ______________
change too
The rate of reaction increases as ___________________________________________________________________
substrate concentration increases (at constant enzyme concentration)
Maximum activity occurs when the enzyme is
saturated
The relationship between reaction rate and substrate concentration is
exponential, and asymptotes (levels off) when the enzyme is saturated
The initial rate of an enzymecatalyzed reaction is ________________________
always
proportionate to the concentration of enzyme.
This property of enzyme is made use in determining the serum enzyme for the diagnosis of diseases.
[S]»[E] V∝[E]
The rate of reaction increases as ______________________
enzyme concentration increases (at
constant substrate concentration)
At ___________________________, more enzymes are available to catalyze the reaction (more reactions at once)
higher enzyme concentrations
There is a linear relationship betweenn ____________________ (at constant substrate concentration)
reaction rate and enzyme concentration
Enzymes are most active at an _______________________________
optimum temperature
Lose activity at high temperatures as _____________ occurs
denaturation
Enzymes shows little activity at ________________
low temperatures
Effect of Temperature
Speed of reaction increases until an __________________________
Optimum temperature is reached
Optimum temperature is the
temperature at ________________________
which the enzyme works best
After this point the rate of reaction decreases until there is _____________
no reaction
At this point enzyme is said to be
DENATURED which means?
active site destroyed
Effect of temperature
A reaction rate will generally increase with increasing Temperature due to __________________________________________________________________________________________________________
increased kinetic energy in the system until a maximal velocity is reached.
Above this maximum, the kinetic
energy of the system exceeds the energy
barrier for breaking weak H-bonds and
hydrophobic interactions, thus__________________________________________________________________________________________________________________________
leading to unfolding and denaturation of the enzyme and a decrease in reaction rate
denature protein = ______________ = ______________________
unfold ; lose shape
lower temperature, molecules move _________
slower
Enzyme-controlled reactions follow
this rule as they are ___________________
chemical reactions
The optimum temperature for an
enzyme-controlled reaction will be a
balance between the ______________________
Q10 and denaturation.
For most enzymes (outside the
human body) the optimum
temperature is about _________
30°C
Many are a lot lower, cold-water
fish will die at 30°C because _________________________
their enzymes denature
A few bacteria have enzymes that
can withstand very high
__________________
temperatures up to 100°C
Most enzymes however are fully
_____________________
denatured at 70°C
Each enzyme has an ________________________
optimal pH or pH range
Effect of pH
Variations in pH can affect a particular
enzyme in many ways, especially if ionizable
amino acid side chains are involved in
______________________________________
binding of the substrate and/or catalysis.
Extremes of pH can also lead to denaturation
of an enzyme if the ionization state of ___________________________________________________________
amino acid(s) critical to correct folding are altered.
changes in pH changes __________________
protein shape
most human enzymes’ pH ranges ___________
6 to 8
trypsin (small intestine) pH
8
pepsin (stomach) pH
3
Enzymes are most active at
______________________
optimum pH
Amino acids with acidic or basic side-chains have the ________________________
proper charges when the pH is optimum
Activity is lost at low or high pH as
_______________________________
tertiary structure is disrupted
Most enzymes of the body have an
optimum pH of about ____________ However, in
certain organs, enzymes operate at
_______________________________________
7,4 ; lower and higher optimum pH values
Enzyme activators are
molecules that bind to enzymes and increase their activity
Enzyme Activators
Give Inorganic Ions (Metal Ions and Anions)
Metal Ions: Na+ , K+ , Mg2+ , Ca2+ , Cu2+ , Zn2+ , Fe2+
Anions: Cl- , Br-, I-, CN-
Enzyme Activators
Give Organic Enzyme Activators
Cys , GSH
any molecule which acts directly on an enzyme to lower its catalytic rate is called
an inhibitor
Some enzyme inhibitors are
normal body matabolites
are regulated by molecules
called effectors (modifiers) that binds
nonconvalently at a site other than the
active site.
Allosteric enzymes
most frequently by the
addition or removal of phosphate group
to serine, threonine or tyrosine residue
of the enzyme by kinases. (enzyme)
Covalent Modification
Cells can also regulate the
amount of enzymes present by altering
the rate of enzyme synthesis
Induction and repression of enzyme
synthesis
Some enzyme are
synthesized as inactive precursor,
called zymogens, that are activated by
proteolysis (e.g., digestive enzyme,
pepsinogen is Inactive and cleaved to
pepsin which is active chymotrypsin)
Zymogen Cleavage
Many enzymes are localized in specific
organelles within the cell. This,
compartmentation helps in the
regulation of the metabolic pathway.
Location within the cell
are chemicals that reduce
the rate of enzymic reactions
Inhibitors
