Lecture 3 and 4 Flashcards
To measure analyte levels, laboratory assays most commonly use ____
serum
___:the watery acellular portion of blood separated by centrifugation of whole blood in the presence of anticoagulant
Plasma
True or False: plasma is a non-physiologic solution while serum is a physiological solution
False
plasma = physiological
serum = non-physiological
What is a major advantage of serum?
There are NO additives required to prevent clotting
True or False: plasma contains plasminogen while serum does not
True
True or False: Most diagnostically important enzymes have intracellular functions and do not normally function in blood
True
What are two reasons that a healthy person may have enzymes in their blood?
- Active secretion (i.e., coagulation precursors such as prothrombin)
- Release from cells at LOW LEVELS during normal cell turnover.
Elevated blood enzyme concentrations result when
____are damaged and intracellular enzymes are released into the blood
cell membranes
Detection of elevated enzyme levels can help to:
1)
2)
3)
- Make or confirm a diagnosis.
- Develop a prognosis.
- Monitor response to a drug therapy
Two clinical reasons for elevated enzymes?
1) Normal cell turnover
2) Pathologies
-Cellular damage, disrupts cell membranes (hepatitis, MI)
-Enzyme induction (response to metabolism of drugs)
-Physical obstructions (i.e., tumors, stones)
-Cell proliferation
Creatine kinase (CK or CPK) is found in the ___ and ___
Lactate dehydrogenase (LDH or LD) is found in ____, ___, ___, and ___
muscle and brain
liver hepatocytes, muscle, RBCs, brain
True or False: Both ALT/AST are found in liver hepatocytes. However, AST is also found in muscle.
True
ALK or ALP is found in the ___ and bone
Gamma glutamyltransferase GGT or GGTP is found in ___ and ___
Liver (hepatobiliary) and bone
Liver (biliary tree), pancreas
Which of these enzymes is the most specific test?
Which of these enzymes is the least specific test?
Most specific = ALT
Least specific = LDH
How might you improve diagnostic specificity?
Panels/profiles; isoforms
What is found in BMP?
hint: SPOON CCCG
sodium
potassium
CO2
BUN
creatine
chloride
calcium
glucose
Which panel is best for identifying acute problems involving kidney, diabetic shock, respiratory
distress and congestive heart failure?
A. CMP
B. BMP
C. LDH
B. BMP
Which panel is also known as Chem 7? Which panels is also known as Chem 12?
BMP (Chem 7); CMP (Chem 12)
Which panel is common for
during physical exam or to monitor chronic conditions such as HTN, DM, or monitor response to a drug regimen
that may have kidney- or liver-related adverse reactions
CMP
In addition to the tests in the BMP, CMP’s look at what other 6 substances?
-Albumin
-ALK/ALP
-AST
-ALT
-Total Bilirubin
-Total Protein
Renal profile (4) ?
Blood urea nitrogen (BUN)
Creatinine
BUN/Creatinine ratio
Uric Acid
Liver profile?
Muscle profile?
- AST
- LDH
- CK
The Comprehensive Metabolic Panel includes the
Basic Metabolic Panel tests and also assesses which
of the following organs?
A. Heart
B. Pancreas
C. Liver
D. Brain
C. Liver
Which blood-derived substance does not require the addition of an anticoagulant?
A. Plasma
B. Serum
B. Serum
___: urea is a waste product of protein digestion; indicates kidney dysfunction
____:waste product of muscle contraction cleared by
kidneys; indicates kidney dysfunction.
BUN; Creatine
_____: >10:1 to 20:1 indicates poor blood flow to kidneys (i.e., congestive heart failure)
BUN: Creatinine
____: waste product of purine breakdown cleared by the kidneys; indicates hyperuricemia/gout and kidney disease
Uric Acid
In the liver profile, what three tests assess hepatocellular damage?
ALT:
AST:
LDH*
*=non specific
Which liver profile test is used to assess chronic (decreased value) vs. acute (normal) liver damage?
Albumin
In the liver profile, ___, ___, and ___ are used to assess biliary tract damage - cholestasis
ALP/ALK; GGT; 5 NT
What tests are used to identify heme degradation product diagnostic for liver function, hemolytic anemias?
T, D, and I BIL
___ is expressed in sk. and cardiac muscle and liver
AST
____ is non-specific test for muscle and heart damage
LDH
____is required for muscle cell function; after heart attack, strenuous exercise, muscle injury
CK
What is a good screening test for prostate cancer?
Prostate-specific antigen (PSA)
What 4 tests evaluate pancreatic function?
-Amylase
-Lipase
-Lipase:Amylase ratio (possible differentiation of alcoholic vs. non-alcoholic acute pancreatitis)
-Trypsinogen/Trypsin
Which elevated serum test result paired with elevated
AST levels would be the most specific diagnostic for
liver disease?
A. LDH
B. ALT
C. ALK
D. BUN
B. ALT
Which analyte is most likely to be elevated in a
patient’s serum following a heart attack?
A. CK
B. BUN
C. Creatinine
D. Amylase
A. CK
Elevated CK following a heart attack will most likely
accompany elevated…
A. Albumin
B. BUN
C. AST
D. Lipase
C. AST
____: the ability of test to actually measure what it claims to measure
___: the ability to reproducibly obtain the same result on the same patient sample.
Accuracy
Precision
The reference range is the range of values within __ SD of the mean,
which covers __% of healthy
individuals
2; 95%
:D
All isozymes of an enzyme catalyze the same reaction but differ slightly in what three ways?
1) Amino acid composition (often different related gene products)
2) Cell- and tissue-type in which they function
3) Timing of expression
Which isozyme is a tetramer composed of various combinations of H-subunits (Heart) and M-subunits (muscle)?
LDH Isoenzymes
If LDH-1:LDH-2 >1, what does this indicate?
If LDH-5:LDH-4 > 1, what does this indicate?
HEART damage
LIVER damage
Where is LDH-1 predominately found? Where is LDH-5 predominately found?
LDH-1: Heart
LDH-5: Liver
Which isoezyme is dimer composed of 2 B-monomers (Brain), 2 M-monomers (muscle) OR one of each?
CK
CK-1, found in the brain, can help diagnose ____
CNS damage
Found in the myocardium, CK-2 can help diagnose ___
an acute MI
Located predominately in the skeletal muscle, CK-3 can help diagnose ____
skeletal muscle damage
Combination of ___and LDH-1 isozymes, along with ____ and ____ are diagnostic for AMI (acute MI)
CK-MB ; Troponins ; Myoglobin
True or False: There is a Troponin I, T, and C
True
While TnI, TnT, and CK-MB become elevated within 3 to 12 hours, TnI and TnT take ~5-14 days to return to normal range while CK-MB takes ___ days
2-3 days
Which LDH isozyme is the most specific diagnostic test for liver damage?
A. LDH-1
B. LDH-2
C. LDH-3
D. LDH-4
E. LDH-5
E. LDH-5
Which specific diagnostic test for AMI would be least sensitive for
diagnosis after 2 days post-MI?
A. LDH-1
B. CK-MB
C. Troponins
B. CK-MB
____forms upon binding of substrate to the enzyme and leads to a conformation change
Enzyme-substrate (ES) complex
True or False: Enzymes have catalytic efficiency and specificity
True
____: non-protein molecules that enhance
enzyme activity
Co-factors/co-enzymes
Zinc is an example of a ___ while NAD is an example of a ___
Co-factor, Co-enzyme
____: an active enzyme associated with its non-protein component
____: inactive enzyme without its non-protein component
Holoenzyme; Apoenzyme
True or False: enzymes provide a more energetically favorable path from reactants to products by lowering the activation energy barrier
True
The higher the energy barrier, the ____ the reaction
slower
Another name for the activation energy barrier is ____
free energy of activation
___: energy difference between reactants and transition state
Free energy of activation
_____: high-energy intermediate formed
prior to product formation
Transition state (T*)
True or False: Enzymes ↓ free energy of activation required to reach T*
True
A reaction occurs if molecules contain enough energy to overcome the energy
barrier to achieve __
T*
_____ is determined by # of molecules that have sufficient
energy to overcome the barrier
Reaction rate or velocity
True or False: If free energy of activation is low: more molecules have sufficient energy to reach T* AND reaction proceeds more rapidly
True
The active site contains ____ groups, which contain
amino acid residues
that _____ protons
catalytic
donates/accepts
True or False: hydrogen bonding promotes T state formation
True
Factors influencing enzymatic reaction velocity?
-**substrate concentration [S]
-Temperature
-pH
With constant [E], reaction rate increases with ↑[S] until reaching ___
Vmax (maximum
velocity)
True or False: nce Vmax reached, reaction rate does increase with addition
of more substrate
False - NOT
What type of curve do allosteric enzymes show?
Sigmoidal
There is a ____ curve for most
enzymatic reactions
Hyperbolic
MM assumptions?
- [S]»_space; [E]
- rate of ES formation = rate of ES breakdown
Km = ___ at ½ Vmax
[S]
Small Km means ___ [S] needed to reach Vmax
Low
What type of inhibitor covalent binds to enzyme, prevents enzyme from interacting with substrate, and leads to “loss” of enzyme activity (i.e., lead poisoning)?
Irreversible inhibitor
____: noncovalent binding with enzyme
Reversible Inhibitor
True or False: There are competitive and non-competitive irreversible inhibitors
False
What type of inhibitors compete with S to bind enzyme’s active site?
Competitive (reversible) Inhibitors
What effect does a competitive inhibitor have on Vmax and Km?
Statin (Pravastin) drugs inhibit rate-limiting step
in cholesterol biosynthesis and are an example of what type of inhibitor?
Competitive Inhibitor
What drug competes with substrate HMG-CoA for
binding to HMG CoA-reductase?
Pravastin (competitive inhibitor)
____: bind to different site than the substrate and prevent reaction from occurring –
does NOT compete with S for binding.
Non-competitive Inhibitors
What two places can non-competitive inhibitors bind to?
Can bind to either:
1. free enzyme
2. ES complex
Penicillin, Amoxicillin inhibit bacterial cell wall synthesis and are irreversible/reversible?
Irreversible
True or False: ACE inhibitors are reversible competitive inhibitors
True
True or False: COX inhibitors are competitive inhibitors
Tru
Aspirin is a ____inhibitor while Advil/Motron are ___, ___ inhibitor
irreversible ; reversible competitive
What type of enzymes frequently catalyze the committed, rate-limiting step in a pathway?
Allosteric Enzymes
What type of molecules regulate allosteric enzymes?
Effector molecules (bind non-cov at site other than active)
____ effector: reduce or inhibit enzyme activity
____ effector: stimulates or increase enzyme activity
Negative
Positive
True or False: Effectors can modify Vmax only
False - Vmax, K 0.5 or both
Homotropic effectors are usually ___ effectors
positive
Binding of substrate at allosteric site enhances activity at substrate-
binding site = ____
cooperativity
Why do allosteric effectors show sigmoidal curve?
Sigmoidal curve because higher [S] initially
needed for reaction to proceed
True or False: For a homotropic effector, the substrate = effector, but this is not the case with heterotropic effectors.
True
An example of covalent modifications is phosphorylation of specific ___, ___, or __residues:
Ser, Thr, Tyr
True or False: Phosphorylation may activate or inhibit its target enzyme
True
True or False: allosteric and covalent modifications are more rapid (seconds to minutes)
True
In the case of enzyme inhibition by a competitive
inhibitor, the Km will…?
A. Increase
B. Decrease
C. Not change
A. Increase
In the case of enzyme inhibition by a non-competitive
inhibitor, the Vmax will…?
A. Increase
B. Decrease
C. Not change
B. Decrease
Which of the following is most likely to decrease the
velocity of an enzymatic reaction?
A. Moderate rise in temperature
B. Increase in [S]
C. Binding of a positive homotropic effector
D. Extremely high or low pH
D. Extremely high or low pH
Which of the following directly interferes with binding
of a substrate to an enzyme’s active site?
A. A non-competitive inhibitor
B. Binding of a heterotropic allosteric effector
C. A competitive inhibitor
C. A competitive inhibitor
Which of the following is defined by the x-intercept in
a Lineweaver-Burke plot for an enzyme?
A. 1/Vmax
B. vo
C. -1/Km
D. [S]
C. -1/Km
