CHE 334 Biochemistry Unit 3 Quiz

Enzymes…

lower activation energy, lower transition state

Enzymes help _____ bonds making them easier to rearragne

weaken

Activation energy

energy needed for the reaction to begin

Gibbs Free energy

how spontaneous a rxn is

oxidoreductase

the transfer of electrons, can catalyze both foward and reverse rxn

Å + B ← → Bº + A

transferase

transfer of a chemical group to create a new substance

AX+ B ← → BX + A

Hydrolase

addition of water to cleave a molecule into two

A + H2O → B + C

Lyase

Breaking a molecule down into two W/O H2O, No ATP used

Generates either a double bond or a ring in order to work

A → B + C

Isomerase

molecule being converted to one of its isomers by rearranging atoms w/in the molecule

A → B

Ligase

A and B are being catalyzed to combine the two

A + B -→ AB

Cofactors

small inorganic chemicals

tightly binds to enzymes

added to enzyme to help with activation

Coenzymes

organic

binds loosely to enzymes

added to enzyme to help with activation

Competitive inhibition

similar structure yet not the exact same shape

Blocks enzyme from working

Binds directly to the active site, competing with the substrate

Non Competitive Inhibition

Binds to the allosteric site

changes enzyme shape to not bind to its specific substrate, does not work

What is the Michaelis-Menten Equation

How do you calculate kCat?

How to calculate specificity constant?

Which of these produces the most product per unit time (Kcat)?

1) 9.7 x 10 ⁴

2) 1.4 × 10 ³

3) 3.8 × 10 ³

4) 4.0 × 10 ⁵

4) 4.0 × 10 ⁵

Which enzyme likely binds most tightly to its substrate (Km)?

1) 1.5 × 10 ^-4

2) 2.6 × 10 ^-1

3) 9.5 × 10 ^-3

4) 2.5 × 10 ^-2

1

Which enzyme is the most catalytically efficient (specificity constant)?

1) 9.3 million

2) 1.5 million

3) 10 million

4) 152k

3

How do you know if an enzyme is catalytically efficient?

If it has a high product per unit per time and a loose binding to a substrate

High Kcat and low Km

Where does chymotrypsin cleave and where?

Cleaves on carboxyl

Specific for aromatic acids: Tyr, Phe, Trp

Where does trypsin cleave and where?

Cleave on carboxyl

Specific for amino acids with positive side chains: Lys, Arg

Where does elastase cleave and where?

Cleaves on carboxyl

Specific for Gly, Val, Ala, Leu, & Ile small hydrophobic amino acids

Covalent catalysis

involves transient covalent bonds btw enzyme and substrate

Acid-base catalysis

reaction is accelerated by addition of acid or base that will not be consumed by the rnx

Metal-ion catalysis

metal atom binds to active site, metal atom interacts with H2O, and deprotonates H2O to make it a nucleophile

Cysteine protease

cleaves at carbonyl group

specific for cysteine

role: immunity and apoptosis

Aspartyl Protease

Cleaves at carbonyl group

specific for aspartic acid

aids in digestion, protein degradation

Metalloprotease

cleaves at carbonyl group

specific for metal atoms

cell proliferation, angiogenesis, apoptosis