Enzymology

Question 1

Enzymes are specific proteins that _______biochemical reaction without altering the _______ point of the reaction, or being _______ or ______ in composition

Answer 1

Enzymes are specific proteins that catalyze biochemical reaction without altering the equilibrium point of the reaction, or being consumed or changed in composition

Question 2

what is the spot where a substrate interacts with the enzyme?

Answer 2

the active site

Question 3

Ideal enzymes have three properties. What are they?

Answer 3

1. easily measure
2. high degree of precision and accuracy
3. tissue/organ specific

Question 4

What is a holoenzyme, apoenzyme, and coenzyme?

Answer 4

Holoenzyme: the complete, active enzyme complex, including the apoenzyme with the coenzyme

apoenzyme: the protein portion of the enzyme

coenzyme: organic cofactors needed for enzyme activity

Question 5

What is a metalloenzyme and isoenzyme?

Answer 5

metalloenzyme: trace element associated with an enzyme as an essential component or cofactor

Isoenzyme: the forms of a particular enzyme that differ genetically

Question 6

What is a cofactor, catalyst, and substrate?

Answer 6

cofactor: a nonprotein molecule that may be necessary for enzyme activity

catalyst: a substance that increases the rate of a chemical reaction without itself undergoing any permanent chemical change

substrate: a molecule that an enzyme interacts with

Question 7

What are six classes of enzymes?

Answer 7

Oxidoreductases, transferases, hydrolases, lyases, isomerases, and ligases

Question 8

What do oxidoreductases do, and give an example

Answer 8

they catalyze an oxidation-reduction reaction between two substances

eg: lactate dehydrogenase or G6PD

Question 9

What do transferases do, and give an example

Answer 9

they catalyze the transfer of a group other than hydrogen from one substrate to another

eg: creatine kinase

Question 10

What do hydrolases do, and give an example

Answer 10

catalyze hydrolysis of various bonds

eg: ALP and ACP

Question 11

What do lyases do, and give an example

Answer 11

catalyze the removal of groups from substances without hydrolysis; the product contains double bonds

eg: aldolase

Question 12

what do isomerases do?

Answer 12

catalyze the interconversion of geometric, optical, or positional isomers

Question 13

what do ligases do?

Answer 13

catalyze the joining of two substrate molecules, couples with breaking of the pyrophosphate bound in ATP or a similar compound

Question 14

How do enzymes help chemical/biological reactions? What is the equation for enzyme kinetics?

Answer 14

the lower the activation energy level that the reactants (substrates) require to form the transitional state

E + S –> ES –> E + P

Question 15

what are the four different specificities of enzymes?

Answer 15

absolutely specific: bind to only one substrate

group specific: combine with all substances containing a particular functional group

bond specific: bind to specific chemical bonds

stereoisomeric specific: combine with only one optimal isomer of a specific compound

Question 16

What are the basic steps of enzyme and substrate interaction?

Answer 16

1. enzymes bind to substrate
2. bonds are rearranged forming product
3. product released from enzyme
4. enzyme comes out unchanged

Question 17

Substrate readily binds to enzyme at ___ substrate concentration. The rate of rxn increases as ____ substrate is added

Answer 17

low; more

Question 18

What is first and zero order kinetics in enzyme kinetics?

Answer 18

1st order: rate is directly proportional to substrate concentration

Zero order: the rate only depends on enzyme concentration

(zero order happens after substrate concentration is high enough to saturate all binding sites and velocity is at max)

Question 19

What is the Michalis-Menten equation, and what does each part of the equation represent?

Answer 19

v = (Vmax x S)/(Km +S)

where v = velocity of rxn

Vmax = max velocity with max substrate concentrations

S = substrate concentration

and Km = Michaelis constantat when reaction velocity is 1/2 the Vmax

Question 20

What are four factors that influence enzyme kinetic reactions?

Answer 20

1. enzyme concentration
2. temperature
   - enzymes have optimal temps
3. pH: changes affect ionization state
4. ionic strength

Question 21

Low temps will do what to enzyme kinetics? High? What about low/high pH? What is used to keep pH in optimal ranges?

Answer 21

low temps = decrease enzyme function activity

high temp = denaturation

pH: too high or low = denaturation

use a buffer to keep pH in optimal range

Question 22

what three things does ionic strength do to enzyme kinetics?

Answer 22

changes polarity of the medium, changes shape of the enzyme, and decreases the rate of reaction

Question 23

What can act as a coenzyme that absorbs light on the UV spectrum at 340 nm?

Answer 23

NADH

Question 24

enzymes can be used as reagents to measure _______ constituents in serum. What are three things that can be tested by using enzymes as reagents?

Answer 24

measuring nonenzymatic constituents in serum such as
1. glucose
2. cholesterol
3. uric acid

Question 25

in order to use enzymes as reagents, they require the enzyme to be _______, which means the enzyme is coupled to

Answer 25

immobilized agarose/cellulose or antigen/antibody for immunoassay testing

Question 26

what is the function of Creatine Kinase, and where are the three sites that it's widely distributed in?

Answer 26

it regenerates ATP in muscle cells. Widely made in skeletal, heart, and brain tissue

Question 27

what are the three CK isoenzymes, and where are they found?

Answer 27

CK-MM: heart and skeletal muscle (bone and muscle marker) CK-MB: mostly heart, and some skeletal muscle CK-BB: brain, bladder, lung - CK-BB: is CNS problem-related

Question 28

what does it mean if all CK markers are increased? What about if there's macro-CK?

Answer 28

myocardial infarction, Duchenne muscular dystrophy, or intense exercise Macro-CK: advanced malignancies

Question 29

what is the role of lactose dehydrogenase? What are the five LDHs and where are each of their sources? (which isoenzyme is the most abundant?)

Answer 29

They catalyze the interconversion of lactic and pyruvic acids LD1: Heart and RBCs LD2: Heart and RBCs - most abundant of the LDs LD3: lungs, lymphs, spleen, pancreas LD4: liver and muscle (mostly liver) LD5: muscle and liver (mostly muscle) - injury indicator

Question 30

what do increased LD markers mean? What is something that greatly affects LD measurements?

Answer 30

cardiac disease (LD1 and 2), hepatic disorders (LD4), skeletal and renal disease, pernicious anemia, hemolytic disorders hemolysis greatly affects levels

Question 31

Aspartate aminotransferase (AST) is found in what tissues, what are the two isoenzyme forms, and what are the two main disorders it's increased in?

Answer 31

found in heart, liver, and skeletal muscle 2 isoenzymes: - cytoplasmic (plasma) - mitochondrial (cellular necrosis) increased in hepatocellular disorders and skeletal muscle disorders

Question 32

what does AST look like for viral hepatitis and cirrhosis?

Answer 32

super high for viral hepatitis, but only moderately high for cirrhosis

Question 33

Alanine Aminotransferase (ALT) is found in what one place? What condition is it increased in?

Answer 33

found in liver tissue increased in hepatocellular disorders

Question 34

In acute (inflammatory) liver conditions (like hepatitis), which is increased more, ALT or AST? What about in chronic liver conditions (such as cirrhosis or biliary obstruction)

Answer 34

Acute: ALT more than AST (or AST/ALT ratio less than 1) Chronic: AST more than ALT (or AST/ALT ratio greater than 1)

Question 35

What five sites can alkaline phosphatase be found in? What is it a marker for? What isoenzyme is used to distinguish malignant tissue?

Answer 35

liver, bone, spleen, placenta, kidney marker for biliary obstruction Regan isoenzyme used for finding malignancy

Question 36

increased ALP is found in what two disorders and what one disease?

Answer 36

hepatobiliary obstructive disorders and bone disorders Paget's disease (a bone disorder)

Question 37

Acid Phosphatase (ACP) found in what tissues, and uses _________ inhibition to distinguish between tissues? What diseases is it increased in?

Answer 37

found in prostate tissues (and also RBCs) uses tartare inhibition found increased in bone diseases and also prostate cancer

Question 38

What is gamma glutamyl transferase (GGT) used to differentiate, and what are the results of this differentiation? What else is it a good marker for?

Answer 38

Used to differentiate increased ALP bone or liver disorders if bone disease, only ALP increase if liver disease, ALP and GGT both increase also good marker for chronic alcohol consumption

Question 39

5'nucleotidase is widely distributed in the body, but it's usually used in the diagnosis of _____ disorders. It's increased in what two situations?

Answer 39

diagnosis of hepatobiliary disorders increased in biliary obstruction and a slight increase in the third trimester of pregnancy

Question 40

what is amylase, what one main condition is it increased in, and what is the onset and fall times for this condition?

Answer 40

it's breakdown of starch and glycogen (salivary amylase is inactivated by gastrin, and then pancreatic amylase takes over) increased in acute pancreatitis - rise 5 - 8 hrs after onset - falls after 3 - 5 days

Question 41

what is macroamylasemia, and why does it need to be ruled out?

Answer 41

it's amylase + immunoglobulins that are too large to clear. Need to be ruled out because macroamylasemia will increase serum amylase levels and decrease urine amylase levels

Question 42

What is lipase, and what does an increase of it mean, and why do we prefer it more than amylase?

Answer 42

it makes alcohols and fatty acids (and triglycerides in the intestine) increased in acute pancreatitis prefer its measurement over amylase due to it being more specific to pancreatitis, and it lasts longer as a measurement (8 - 14 days)

Question 43

what organs does G6PD deficiency affect? How to acquire G6PD deficiency?

Answer 43

(G6PD found in RBCs and is needed to reduce harmful oxidative substances) affects adrenal cortex, spleen, thymus, lymph nodes, lactating mammary glands, and erythrocytes X-linked recessive or drug-induced hemolytic anemia

Question 44

What is the role of (pseudo)cholinesterase? What does its increase and decrease signify?

Answer 44

nerves use this to send signals (so succinylcholine is used for anesthesia) increased: breathing issues, myocardial infarction, organophosphate poisoning decreased: muscle paralysis

Question 45

what are five cardiac markers, which is the first to increase (and why we don’t we use it), which marker distinguished between muscle and heart, and which marker do we prefer to use for myocardial infarction?

Answer 45

1. CK-MB - distinguished between muscle and heart 2. Myoglobin - first to increase but also quickly drops off 3. LDH (1 and 2) 4. AST 5. Troponin (T more than I used)

Question 46

slow-moving LDH5 is likely what disease?

Answer 46

It's the muscle disease LDH, so Duchenne Muscular Dystrophy