Chapter 5 Bio Enzymes

Question 1

Other enzymes that don’t end in “ase”

Answer 1

Trypsin, chrmotrypsin, and pepsin.

Question 2

Isomerases

Answer 2

Transfer groups with in a given molecule
G6P -> F6P
phosphoglucoisomerase

Question 3

Oxidoreductase

Answer 3

Catalyze redox reaction; dehydrogenases and NADH or FADH2

Question 4

Hydrolases

Answer 4

Cuts bonds by using H20
Urease
Urea + H20 -> 2 NH3 + CO2

Question 5

Lyases

Answer 5

Cuts C-C C-S, and some C-N bonds

Question 6

Ligases

Answer 6

Catalyzes formation of bonds such as C-O, C-N, C-C, and C-S.

Question 7

Transferases/ Kinase

Answer 7

Catalyzes group transfer

Glucose + ATP - > G6P + ADP

Question 8

Enzyme Structure

Answer 8

Have active sites containing aa, ions, and groups that take part in substrate binding.

Question 9

Enzyme turnover #

Answer 9

Number of substrate molecules making product.

Turnover #= K_cat

Question 10

Enzymes work by

Answer 10

specificity of fit and charge

Question 11

Holoenzyme

Answer 11

The active enzyme including the nonprotein portion

Question 12

Apoenzyme

Answer 12

Inactive enzyme- does not contain the non protein portion

Question 13

Nonprotein portion is an ion called

Answer 13

Cofactor (Zn2+ or Fe2+)

Question 14

Non protein portion that is a small organic molecule

Answer 14

Coenzyme

Question 15

Prosthetic group enzyme

Answer 15

Coenzyme permanently bound to the enzyme and returned to its original form after a reaction is complete.
E.g. Heme found in myoglobin, hemoglobin, cytochromes, and chlorophyll.

Question 16

Enzymes do not change

Answer 16

Equilibrium, ΔG, ΔH, Keq constant, or product amount

Question 17

Enzyme optimum conditions and pH

Answer 17

Pepsin, stomach: pH =2
Pyrvuate carboxylase, liver: pH=5
Trypsin- small intestine: pH=8
Temp: 37 C
>40 C human enzymes begin to denature

Question 18

Adding H+ or OH- to enzymes

Answer 18

Interefers with binding and decreases reaction rate

Question 19

Michaelis Menten Kinetics

Answer 19

Enzymes can become saturated with substrate.

Reaction rate vs substrate concentration. Vmax, 1/2Vmax.

Question 20

Michaelis Menten Kinetics characteristics

Answer 20

At relatively low sub concentration, the graph is 1st order linear relationship between rate and sub conc.
At high concentrations of sub, it is mixed order kinetics. Rate still depends on substrate concentration but it is not linear.
Eventually the rate becomes constant. After the rate of reaction is independent of Sub conc. and depends on E concentration. Zero Order kinetics.

Question 21

Michaelis Menten Kinetics abbreviations

Answer 21

Km is the Michaelis constant and reflects the affinity of the enzyme for it’s substrate.
Small Km: high affinity of enzyme. Small substrate amount is need to half saturate the enzyme for 1/2Vmax.
Kcat = Turnover number

Question 22

Michaelis Menten Kinetics Catalytic Efficiency

Answer 22

Kcat/Km = efficiency

Big K Cat and small Km for optimal efficiency.

Question 23

Competitive Inhibitor

Answer 23

Reversible, inhibitors compete for the active site that the substrate normally binds. Vmax stays the same.
Increase the substrate to reverse the effect of the inhibitor.
E.g. statin drugs (which lower cholesterol) inhibit certain enzymes that makes cholesterol.

Question 24

If you drink methanol, you might go blind.

Answer 24

Alcohol dehydrogenases convert methanol into formaldehyde. If given ethanol, it will compete for the active sites and methanol can be excreted in urine harmlessly.

Question 25

How would a competitive inhibitor affect Km?

Answer 25

Increase the Km, more substrate is needed to achieve 1/2Vmax.

Question 26

Noncompetitive inhibitor

Answer 26

Binds to a site distant from the active site, altering the shape of the enzyme. Vmax decreases, Km is unchanged.

Question 27

Can Km be changed by increase substrate?

Answer 27

No

Question 28

Uncompetitive Inhibitor

Answer 28

Binds to the enzyme substrate complex, not at the active site. Cannot be reversed by increasing subtrate. Vmax is decreased.

Question 29

Zymogen

Answer 29

Inactive form of an enzyme.
E.g Chymotripsinogen - > Chymotrypsin
Pepsinogen -> Pepsin
Inactive -> Active

Question 30

Proteolytic cleavage

Answer 30

Can cause zymogen activation. Cleavages can cause conformational changes that expose the enzyme active site.

Question 31

Enzyme Denaturation

Answer 31

Lose 2,3,4, structure.

Temperature, radiation, mechanial agitation, pH, slalts of heavy metals, organic solvents, and oxi-reduc agents.

Question 32

Enzyme denaturation mechanical agitation

Answer 32

Violent mixing will cause polypeptide chains to unfold.

Question 33

Enzyme denaturation salts of heavy metals

Answer 33

Pb++, Hg++, Ag+ react with SH(sulfhydryl) groups and prevent formation.

Question 34

Oxidizing and reducing agents enzyme denaturation

Answer 34

Form S-S bridges or destroy them by reduction

Question 35

Isozymes

Answer 35

Enzymes that catalyze the same reactions but differ in subunit composition. Isozyme composition in various tissues is determined by genetics, may have slightly different Vmax, Km.

Question 36

Allosteric enzyme

Answer 36

Undergoes a conformational change and functional change when binding to specific molecules called activators or inhibitors.
Do not follow Michaelis-Menton graph. Sigmoidal curve.

Question 37

Allosteric regulation

Answer 37

We control the enzyme by binding an effector molecule at a site other than the active site.