Enzymes (part one) Flashcards
Protein catalysis of biologic origin which enhances the rates of biochemical reactions at a rate as to be compatible with life
Definition of enzymes
Five general properties of enzymes
- Not altered or consumed during the reaction
- Only small amounts of enzyme are required
- Accelerate the speed at which a chemical reaction reaches equilibrium, but do not alter the equilibrium constant
- Each enzyme is highly specific for a given reaction
- Enzymes act by lowing the activation energy
Occurs when the 3-D structure starts to uncoil. Caused by
Denaturation
High or low cause denaturation of enzymes
Effect of temperature and pH
Non-protein compounds required by some enzymes to make them active
Cofactor
Inorganic cofactor is known as…?
Activator
Organic cofactor is known as…?
Coenzyme
Complete cofactor: enzyme complex
Holoenyme
Bound cofactor
prosthetic group
Protein portion of the enzyme
apoenzyme
A unique sequence and orientation of amino acids to form a pocket or groove that provides for the enzyme’s specificity for only a unique substrate
Active site
A region other than the active site where a separate compound reacts, altering the shape of the active site, altering its fit with the substrate; is used to regulate enzyme activity
Allosteric site
Different physical forms of an enzyme that all catalyze the same reaction. These differences allow isoenzymes to be separated, identified, and qualified
Isoenzymes
The quantity of enzyme that will catalyze the reaction of one micromole of substrate per minute under defined conditions
International unit
Amount of enzyme that catalyzes with a reaction rate of one mole/ second
Katal
The rate of enzymatic activity increases as the concentration of substrate increased until the maximum velocity of the reaction is achieved. This max is called the _______?
Vmax
one half of the vmax ***
Km
List examples of activators (inorganic cofactors) and coenzymes (organic cofactors)
Inorganic: Zn2+, Fe2+, Cu2+, Mg2+, Mn2+
Organic: NAD+, NADH, NADP+, NADPH, Pyrixodal-5-phosphate
Why is enzyme activity, rather than enzyme concentration, is measured in the laboratory
The amount of the enzyme is so small that it is difficult to devise assays that are sensitive enough. Instead, the rate of product formed or amount of substrate consumed during reaction is measured.
More enzyme that is present, the faster the reaction proceeds.
Initial period when enzyme and substrate are first mixed, but no product is formed yet, so there is no detectable change in absorbance
Phases of an enzymatic reactions:
- lag phase
Rate of product formed is linear with time, so reaction follows Beer’s Law
Phases of an enzymatic reactions:
log phase
No change in absorbance b/c there is no substrate left to be converted to product. Rate of reaction is dependent on substrate concentration not enzyme concentration.
Phases of an enzymatic reactions:
- depletion phases
Why should enzyme measurements should be made during the log phase
It corresponds to zero order kinetics! It follows Beers Law so it is an accurate measurement
For a typical enzyme measurement curve, how are the axis labeled?
Y axis: Change in Absorbance
X axis: Time (seconds)
Enzyme Curve Zero order kinetics
- Define
- Where on graph
- The rate of the reaction is independent of reactant (substrate)
- Corresponds to Log (linear) phase on the graph
Enzyme curve First order kinetics
- Define
- Where on graph
- rate of reaction is proportional to reactant (substrate)
- corresponds with the substrate depletion phase of the curve
Reaction rate methods:
Kinetic
?
Reaction rate methods:
Multipoint
?
Reaction rate methods:
Continuous monitoring
?
Michaelis-Menten curve:
- Zero Order kinetics
- Where on curve
At the end of the curve when it starts to flatten out
Michaelis-Menten curve:
- First Order kinetics
- Where on curve
At the beginning of the curve were it is increasing
Michaelis-Menten curve:
How are the axis labeled?
Y-axis: V, initial reaction rate (mol L-1 s-1)
X-axis: [S], concentration of substrate (mol L-1)
Michaelis-Menten curve:
Vmax and Km on the curve
Vmax: Highest point curve goes
Km: half way up the Vmax
Six factors that which influence enzymatic activity
- Enzyme concentration
- Substrate concentration
- Temperature
- pH
- Presence of cofactors
- Presence of inhibitors
ESSAY
Plasma-specific enzymes
-Definition
Are expected to be in higher concentration in blood because they function there (ex: coagulation factors)
ESSAY
Non-plasma-specific enzymes
-Definition
Have no known function in plasma; have functions in tissue (cellular metabolism, etc) (ex: LD or CK)
ESSAY
Plasma-specific enzymes
-expected relative plasma and tissue concentrations
?
ESSAY
Non-plasma-specific enzymes
-expected relative plasma and tissue concentrations
?
ESSAY
Two GENERAL mechanisms for increased (enzyme)
- Increased in the rate of enzyme release into the bloodstream
- Increase in the rate of production of an enzyme
ESSAY
Seven specific causes of cell damage or death
- Hypoxia
- Chemicals and Drugs
- Physical Agents
- Microbiological Agents
- Immune mechanisms
- Genetic Defects
- Nutritional Disorders
- ESSAY*
- Two SPECIFIC causes of increased enzyme production
- Enzyme induction (via drugs, alcohol, or other agents)
2. Proliferation of cells that produce that enzyme (cancer)
List five physiological factors which affect enzyme reference ranges
- sampling time
- Age
- Sex
- Race
- Exercise (lack or and excessive)
