Biochemistry Ch 2. Enzymes

Question 1

Enzymes

Answer 1

Biological catalyst that are unchanged by the reactions they catalyze and are reusable, lower activation energy necessary for biological reactions, do not alter deltaG or deltaH values that accompany the reaction of the final equilibrium positions, they charge the rate at which equilibrium is achieved, act by stabilizing the transition state

Question 2

Oxidoreductases

Answer 2

Catalyze oxidation-reduction reactions that involve the transfer of electrons

Question 3

Transferases

Answer 3

Move a functional group from one molecule to another molecule

Question 4

Hydrolases

Answer 4

Catalyze cleavage with the addition of water

Question 5

Lysases

Answer 5

Catalyze cleavage without the addition of water and without the transfer of electrons, the reverse reaction (synthesis) is often more important biologically

Question 6

Isomerases

Answer 6

Catalyze the interconversion of isomers, including both constitutional isomers and stereoisomers

Question 7

Ligases

Answer 7

Responsible for joining two large biomolecules, often of the same type

Question 8

Exergonic reactions

Answer 8

Release energy, deltaG negative

Question 9

Active site

Answer 9

Part on the enzyme that is the site of catalysis, binding explain by lock and key theory or induced fit model

Question 10

Lock and key theory

Answer 10

Hypothesizes that the enzyme and substate are exactly complementary

Question 11

Induced fit model

Answer 11

Hypothesizes that the enzyme and substrate undergo conformational changes to interact fully

Question 12

Cofactors

Answer 12

Nonprotein molecules (usually inorganic motels or metal ions ingested as dietary minerals) that bind to active site of enzyme and participate in catalysis, usually by carrying charge through ionization, protonation, or deprotonation

Question 13

Coenzymes

Answer 13

Small organic groups (many vitamins or derivatives of vitamins), bind to the activate site of an enzyme and participate in catalysis usually by carrying charge through ionization, protonation, or deprotonation

Question 14

Saturation kinetics

Answer 14

What enzymes experience –> as substrate concentration increases, the reaction rate does as well until a maximum value is reached (at constant enzyme concentration)

Question 15

Michaelis Menten plot

Answer 15

Plot that represents the relationship between substrate concentration and reaction rate hyperbolically

Question 16

Lineweaver-Burk

Answer 16

Plot that represents the relationship between substrate concentration and reaction rate linearly

Question 17

Cooperative enzymes

Answer 17

Display a sigmoidal curve because they change in activity with substrate binding

Question 18

In vivo conditional effects on enzyme activity

Answer 18

Changes in temperature and pH can result in denaturing of the enzyme and loss of activity due to loss of secondary, tertiary, or quaternary structure

Question 19

In vitro conditional effects on enzyme activity

Answer 19

Salinity, temperature, and pH can impact the action of enzymes

Question 20

Feedback inhibition

Answer 20

Regulatory mechanism whereby the catalytic activity of an enzyme is inhibited by the presence of high levels of a product later in the same pathway

Question 21

Reversible inhibition

Answer 21

Characterized by the ability to replace the inhibitor with a compound of greater affinity or to remove it using mild laboratory treatment

Question 22

Competitive inhibition

Answer 22

Results when the inhibitor is similar to the substrate and binds at the active site, can be overcome by adding more substrate, vmax unchanged, km increases

Question 23

Noncompetetive inhibition

Answer 23

Results when the inhibitor bonds with equal affinity to the enzyme and the enzyme substrate complex, vmax decreased, km unchanged

Question 24

Mixed inhibition

Answer 24

Results when the inhibitor binds with unique affinity to the enzyme and the enzyme substrate complex, vmax decreased, km increased or decreased depending on if the inhibitor has higher affinity for the enzyme or enzyme substrate complex

Question 25

Uncompetitive inhibition

Answer 25

Results with the inhibitor binds only with the enzyme-substrate complex, Km and Vmax both decrease

Question 26

Irreversible inhibition

Answer 26

Alters the enzyme in such a way that the active site is unavailable for a prolonged duration or permanently, new enzyme molecules must be synthesized for the reaction to occur again

Question 27

Allosteric sites

Answer 27

Can be occupied by activators, which increase either affinity or enzymatic turnover, or inhibitors

Question 28

Enzyme activation

Answer 28

Regulatory enzymes can experience activation as well as inhibition through allosteric sites, phosphorylation or glycosylation, and zymogens

Question 29

Enzyme phosphorylation or glycosylation

Answer 29

Covalent modification with either phosphate or carbohydrate that can alter the activity or selectivity of enzymes

Question 30

Zymogens

Answer 30

Secreted in an inactive form and are activated by cleavage

Question 31

Activators

Answer 31

Increase either affinity or enzymatic turnover, can bind to allosteric site

Question 32

Michaelis Menton Equation

Answer 32

v = vmax[S]/(K_m+[S])

Question 33

k_cat equation

Answer 33

k_cat = v_max/[E]

Question 34

Catalytic efficiency equation

Answer 34

eta_cat = k_cat/K_m

Question 35

v_max

Answer 35

Enzyme max velocity

Question 36

K_m

Answer 36

Michaelis constant - substrate concentration at which half of the enzymes active sites are full

Question 37

K_cat

Answer 37

Measures the number of substrate molecules “turned over” or converted to product per enzyme molecule per second