Exam 2: Chp 13

Question 1

What are enzymes?

Answer 1

Proteins specialized to catalyze metabolic reactions by changing kinetics

Question 2

What is catalytic power?

Answer 2

The ratio of enzyme-catalyze rate to uncatalyzed rate

Question 3

What is specificity of a molecule?

Answer 3

it is selective for substrate, product, or type of reaction

Question 4

What is regulation of enzymes?

Answer 4

the rate controlled to meet cellular requirements

Question 5

On what two levels is regulation performed?

Answer 5

production/genetic level and binding interaction by inhibitors or activators

Question 6

What type of reactions do oxidoreductase enzymes catalyze?

Answer 6

redox reactions

Question 7

What type of reactions do transferase enzymes catalyze?

Answer 7

transfer functional groups

Question 8

What type of reactions do hydrolase enzymes catalyze?

Answer 8

hydrolysis

Question 9

What type of reactions do lyase enzymes catalyze?

Answer 9

bond cleavage not via redox or hydrolysis

Question 10

What type of reactions do isomerase enzymes catalyze?

Answer 10

isomerization

Question 11

What type of reactions do ligase enzymes catalyze?

Answer 11

bond formation with the help of ATP

Question 12

What type of reactions do translocate enzymes catalyze?

Answer 12

molecule or ion movement across a membrane

Question 13

What is an enzyme cofactor? Examples?

Answer 13

An inorganic component that allows chemistry AAs cannot perform alone; metal ions, Na+, Ca+

Question 14

What is a coenzyme/prosthetic group?

Answer 14

A small organic fragment covalently or non-covalently associated with an enzyme

Question 15

What is an holoenzyme?

Answer 15

A complex of protein and cofactor or coenzyme

Question 16

What is an apoenzyme?

Answer 16

A protein without its specific cofactor or coenzyme; typically inactice

Question 17

How does temperature affect reaction rate?

Answer 17

Reaction rate increases as temperature does

Question 18

How do catalysts affect reaction rate?

Answer 18

Stabilizes the transition state which lowers activation energy, speeding up the reaction

Question 19

What is the lock and key model?

Answer 19

The substrate molecular structure is complementary to the enzyme structure which create specificity

Question 20

What is the induced fit model?

Answer 20

As the substrate binds the active site and substrate change confirmation and become complimentary

Question 21

Why is the induced fit model beneficial?

Answer 21

Explains catalytic activity and specificity

Question 22

Where does the energy for confirmation changes during substrate and enzyme binding come from?

Answer 22

Formation of stabilizing non-covalent interactions between enzyme and substrate

Question 23

What is Vmax?

Answer 23

The maximum reaction rate of an enzyme-substrate complex

Question 24

When does Vmax occur?

Answer 24

when all enzyme is occupied by substrate

Question 25

What is steady state assumption kinetics?

Answer 25

Assume ES is constant in E+ S → ES → E + P is nonreversible

Question 26

What is Km and what does is measure?

Answer 26

It is 1/2 of Vmax and is a measure of binding affinity between substrate and enzyme

Question 27

What is Kcat?

Answer 27

A measure of catalytic efficiency

Question 28

What does a low Km mean?

Answer 28

Strong binding affinity

Question 29

What does a high Kcat mean?

Answer 29

High catalytic efficiency

Question 30

What is the x-intercept of a Lineweaver-Burke plot equal to?

Answer 30

-1/km

Question 31

What is the slope of a Lineweaver-Burke plot equal to?

Answer 31

Km/Vmax

Question 32

What is the y-intercept of Lineweaver Burke plot equal to?

Answer 32

1/Vmax

Question 33

What are two factors that influence enzyme kinematics?

Answer 33

pH and temperature

Question 34

How does pH influence enzyme kinetics?

Answer 34

Enzymes have a standard distribution surrounding their optimal pH because pH influences their protonation, thus overall structure

Question 35

How does temperature influence enzyme kinetics?

Answer 35

Most enzyme activity increases rate up to 50-60°C then denature

Question 36

What are enzyme inhibitors?

Answer 36

Small molecules that bind to the enzyme and either slow or completely inhibit the catalytic process

Question 37

What are the two general kinds of inhibitors?

Answer 37

Reversible and Irreversible

Question 38

Why are reversible inhibitors able to be removed?

Answer 38

They bind via non-covalent interactions

Question 39

What are the four kinds of reversible inhibitors?

Answer 39

Competitive, Noncompetitive uncompetitive, and mixed

Question 40

How does a competitive inhibitor interact with the enzyme and substrate?

Answer 40

Competes with substrate to bind to active site

Question 41

How does concentration affect competitve inhibition?

Answer 41

Binding favors that in higher concentration

Question 42

How does a **competitive inhibitor** affect the **y-intercept** of a Lineweaver-Burke plot of an enzyme?

Answer 42

Vmax stays the same because it assumes high substrate concentration → **y-intercept does not change**

Question 43

How does a **competitive inhibitor** affect the **x-intercept** of a Lineweaver-Burke plot of an enzyme?

Answer 43

Km increases because more substrate is needed to reach Vmax → **x-intercept decrease**

Question 44

How does a noncompetitive inhibitor interact with an enzyme and its substrate?

Answer 44

The inhibitor binds to a site distinct from the active site and does not affect substrate binding, but prevents catalytic activity

Question 45

How does a **non-competitive inhibitor** affect the **y-intercept** of a Lineweaver-Burke plot of an enzyme?

Answer 45

Vmax decreases because no turnover → **y-intercept increases**

Question 46

How does a **non-competitive** inhibitor affect the **x-intercept** of a Lineweaver-Burke plot of an enzyme?

Answer 46

Km stays the same because substrate binding is unaffected→ **x-intercept remains unchanged**

Question 47

How does a uncompetitive inhibitor interact with an enzyme and its substrate?

Answer 47

Inhibitor binds to the enzyme-substrate complex and inhibits catalytic activity

Question 48

How does a **uncompetitive inhibitor** affect the **y-intercept** of a Lineweaver-Burke plot of an enzyme?

Answer 48

Vmax decreases because substrate cannot compete with inhibitor → **y-intercept increases**

Question 49

How does a **uncompetitive inhibitor** affect the **x-intercept** of a Lineweaver-Burke plot of an enzyme?

Answer 49

Km decreases because more inhibitor complex shifts the equilibrium → **x-intercept increases**

Question 50

How does a mixed inhibitor interact with an enzyme and its substrate?

Answer 50

inhibitor binding to the enzyme makes it harder for substrate to bind

Question 51

What are two kinds of mixed inhibition?

Answer 51

1) inhibitor favors binding E on its own 2) inhibitor favors binding to enzyme substrate complex

Question 52

In **mixed inhibition where lone enzyme is favored**, how is the **y-intercept** of a Lineweaver-Burke plot of an enzyme affected?

Answer 52

Vmax stays the same → **y-intercept stays the same**

Question 53

In **mixed inhibition where lone enzyme is favored**, how is the **x-intercept** of a Lineweaver-Burke plot of an enzyme affected?

Answer 53

Km increases because more substrate is needed to reach Vmax → **x-intercept decreased**

Question 54

In **mixed inhibition where enzyme-substrate complex is favored**, how is the **y-intercept** of a Lineweaver-Burke plot of an enzyme affected?

Answer 54

Vmax is decreased → **y-intercept increased**

Question 55

In **mixed inhibition where enzyme-substrate complex is favored**, how is the **x-intercept** of a Lineweaver-Burke plot of an enzyme affected?

Answer 55

Km is decreased → **x-intercept is increased**

Question 56

How does an irreversible inhibitor affect Vmax and Km?

Answer 56

Km remains the same and Vmax is decreased

Question 57

Why can irreversible inhibitors not be removed?

Answer 57

They follow the enzyme catalytic process but form covalent intermediate

Question 58

What is the chemical function of penicillin?

Answer 58

prevents crosslinking of peptidoglycan in bacterial cell walls by inhibiting transpeptidase

Question 59

How and why does penicillin inhibit transpeptidase?

Answer 59

Mimics D-Ala-D-Ala pattern of normal substrate that **irreversibly binds to serine**