Clinical Chemistry Exam 1 Lecture 6

True or False:
Enzymes are found in All body tissues
True
Many enzymes are present in ___ from normal cellular turnover
Plasma
Enzymes are ____ ____ and _____, not altered or consumed during the reaction
Biologic proteins
Catalysts
_____ amounts of Enzyme are released following cellular damage
Increased
Basic Enzyme Reaction
E + S <--> ES <--> E + P
Substrate Concentration is what order kinetics?
First
First Order Kinetics is directly proportional to what?
Substrate concentration
In First Order Kinetics, what is provided in excess?
Enzyme
At some point in First Order Kinetics, substrate will be consumed and ____ ____ is reached
Maximum Velocity
Michaelis-Menton Constant (Km)
Mathematical expression of the relationship between velocity and substrate
M-Mm Constant (Km) =
Substrate concentration at which the enzyme yields half the possible maximum velocity
Which two types of plots provide visualization of first order kinetics?
M-M and Lineweaver-Burk
Enzyme Concentration is what order Kinetics?
Zero
What is in excess during Zero Order Kinetics?
Substrate
True or False:
With Zero Order Kinetics, the Reaction rate depends on enzyme concentration
True
With Zero Order Kinetics what is supplied by the patient?
Enzyme
With Zero Order Kinetics what is supplied by manufactured reagent?
Substrate
Why is it called Zero Order Kinetics?
When the rate of velocity no longer increase, velocity rates level off, signalling “zero” amount of increase in rate
pH
Extremes will denature or change ionic state of enzymes
Most enzymes function at what pH?
7-8
pH is controlled in labs by what?
Buffer solutions
Increasing the temperature increases the ____ ____ to a point
Reaction Rate
For every ___ degree rise, the rate doubles until the enzyme is denatured
10
At what temperature will the enzyme usually denature?
>40 degrees Celsius
Most assays are run at what temperatures?
25, 30, 37 degrees Celsius
True or False:
Avoid repeated freeze-thaw
True
If testing is delayed what should you do with the sample to preserve the enzyme levels?
Freeze or Refrigerate
True or False:
It takes a few minutes for ALL enzymes to combine with substrate
True
The reaction time is what phase of the reaction?
Linear
About ______ or more minutes into testing, the reaction rate begins to diminish
6
Measurements should be taken during what phase of the reaction?
Linear
Cofactors
Nonprotein molecules that may be necessary for proper enzyme function
Cofactor Activators
Inorganic molecules
Name 3 Cofactor Activators
Calcium
Magnesium
Other Metallic ions
Cofactor Coenzymes
Organic Molecules
Often provided in the testing reagent
Name 2 Cofactor Coenzymes
NAD
Vitamin B family
What is the following an example of?
Creatine + ATP –(CK / Mg)–> Creatine Phosphate + ADP
Activators
What is the following an example of?
Pyruvate + NADH –(LD)–> Lactate + NAD
Coenzymes
What are 7 Factors that influence Enzyme Reactions?
Substrate Concentration
Enzyme Concentration
pH
Temperature
Reaction Time
Cofactors
Inhibitors
Competitive Inhibitors
Bind to the active site of an enzyme
What do you add to overcome Competitive Inhibitors?
Substrate
Is Competitive Inhibitors possible to anticipate?
No
Noncompetitive Inhibitors
Bind to enzyme at a place other than the active site
Causes structural changes to the enzyme
True or False:
Adding more substrate may not help with noncompetitive inhibitors
True
True or False:
The results of Noncompetitive inhibitors may be irreversible
True
Assays measure enzyme _____ which is a reflection of concentration
activity
What can be used to measure enzyme activity?
Increase in product
Decrease in substrate
Decrease in coenzyme
Increase of an altered coenzyme
In what Order are Measurements of Enzyme Activity always performed?
Zero
What must be in excess when measuring enzyme activity?
Coenzyme
Fixed-Time Method (End Point)
The reaction proceeds for a designated time and is then stopped
The velocity of a Fixed-Time Method is assumed to be what?
Linear and proportional to enzyme concentration
Continuous-Monitoring Method (Kinetic Analysis)
Multiple measurements of absorbance are made every 30-60 seconds OR continuously
True or False:
Continuous-Monitoring Method – Linearity may be more adequately verified
True
A sudden _____ in the reaction rate can be readily observed in the Continuous-Monitoring Method
Decrease
If a change in Absorption is not constant, then an ____ _____ is present
Unknown Variable
If the change in Absorption is not constant it may result from what?
high levels of patient enzymes rapidly depleting the substrate
What should you do if the change is absorption is not constant?
Dilute patient sample and re-run
International Unit (U or IU)
The amount of enzyme that will catalyze the reaction of 1 micromole of substrate per minute under specified conditions of temperature, pH, substrates, and activators
The International Unit is in what concentration?
Units per Liter (U/L or IU/L)
If an enzyme assay is 150 IU/L at 25C, what will be the product concentration if the assay is run at 35C?
300 IU/L