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Chemistry! > Enzymology > Flashcards

Enzymology Flashcards

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1
Q

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

A

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

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2
Q

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

A

the active site

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3
Q

Ideal enzymes have three properties. What are they?

A
  1. easily measure
  2. high degree of precision and accuracy
  3. tissue/organ specific
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4
Q

What is a holoenzyme, apoenzyme, and coenzyme?

A

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

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5
Q

What is a metalloenzyme and isoenzyme?

A

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

Isoenzyme: the forms of a particular enzyme that differ genetically

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6
Q

What is a cofactor, catalyst, and substrate?

A

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

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7
Q

What are six classes of enzymes?

A

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

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8
Q

What do oxidoreductases do, and give an example

A

they catalyze an oxidation-reduction reaction between two substances

eg: lactate dehydrogenase or G6PD

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9
Q

What do transferases do, and give an example

A

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

eg: creatine kinase

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10
Q

What do hydrolases do, and give an example

A

catalyze hydrolysis of various bonds

eg: ALP and ACP

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11
Q

What do lyases do, and give an example

A

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

eg: aldolase

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12
Q

what do isomerases do?

A

catalyze the interconversion of geometric, optical, or positional isomers

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13
Q

what do ligases do?

A

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

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14
Q

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

A

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

E + S –> ES –> E + P

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15
Q

what are the four different specificities of enzymes?

A

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

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16
Q

What are the basic steps of enzyme and substrate interaction?

A
  1. enzymes bind to substrate
  2. bonds are rearranged forming product
  3. product released from enzyme
  4. enzyme comes out unchanged
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17
Q

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

A

low; more

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18
Q

What is first and zero order kinetics in enzyme kinetics?

A

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)

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19
Q

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

A

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

20
Q

What are four factors that influence enzyme kinetic reactions?

A
  1. enzyme concentration
  2. temperature
    - enzymes have optimal temps
  3. pH: changes affect ionization state
  4. ionic strength
21
Q

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

A

low temps = decrease enzyme function activity

high temp = denaturation

pH: too high or low = denaturation

use a buffer to keep pH in optimal range

22
Q

what three things does ionic strength do to enzyme kinetics?

A

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

23
Q

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

A

NADH

24
Q

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

A

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

25
Q

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

A

immobilized

agarose/cellulose

or antigen/antibody for immunoassay testing

26
Q

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

A

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

27
Q

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

A

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

28
Q

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

A

myocardial infarction, Duchenne muscular dystrophy, or intense exercise

Macro-CK: advanced malignancies

29
Q

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?)

A

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

30
Q

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

A

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

hemolysis greatly affects levels

31
Q

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?

A

found in heart, liver, and skeletal muscle

2 isoenzymes:
- cytoplasmic (plasma)
- mitochondrial (cellular necrosis)

increased in hepatocellular disorders and skeletal muscle disorders

32
Q

what does AST look like for viral hepatitis and cirrhosis?

A

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

33
Q

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

A

found in liver tissue

increased in hepatocellular disorders

34
Q

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)

A

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

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

35
Q

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

A

liver, bone, spleen, placenta, kidney

marker for biliary obstruction

Regan isoenzyme used for finding malignancy

36
Q

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

A

hepatobiliary obstructive disorders and bone disorders

Paget’s disease (a bone disorder)

37
Q

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

A

found in prostate tissues (and also RBCs)

uses tartare inhibition

found increased in bone diseases and also prostate cancer

38
Q

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?

A

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

39
Q

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?

A

diagnosis of hepatobiliary disorders

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

40
Q

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

A

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

41
Q

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

A

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

42
Q

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

A

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)

43
Q

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

A

(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

44
Q

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

A

nerves use this to send signals (so succinylcholine is used for anesthesia)

increased: breathing issues, myocardial infarction, organophosphate poisoning

decreased: muscle paralysis

45
Q

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?

A
  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)
46
Q

slow-moving LDH5 is likely what disease?

A

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

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