Specific Enzyme stuff maybe

What is the definition of catalytic power?

Ratio of catalyzed rate to uncatalyzed rate

Do enzymes change ΔG of a reaction?

No

What do enzymes lower to speed reactions?

activation energy (ΔG‡)

What must enzymes stabilize more than the substrate?

Transition state (EX‡)

Why are transition-state analogs potent inhibitors?

They mimic the transition state and bind tightly

What is the induced fit model?

Enzyme changes shape upon substrate binding

What is the lock-and-key model?

Substrate fits rigid active site

What type of bond interactions stabilize ES complex?

Noncovalent interactions

What is the term for inactive enzyme without cofactor?

apoenzyme

What is the active enzyme with cofactor called?

Holoenzyme

What are metal ions considered in enzyme function?

Cofactors

What are organic cofactors called?

Coenzymes

What is a prosthetic group?

Tightly bound cofactor

What is a cosubstrate?

Loosely bound coenzyme

What is Km?

Substrate concentration at ½ Vmax

What does a low Km indicate?

High affinity

What does a high Km indicate?

Low affinity

Does Km depend on enzyme concentration?

No

What does Vmax represent?

Maximum velocity at saturation

What determines Vmax?

Enzyme concentration

at low substrate concentration, reaction order is?

First-order

at high substrate concentration, reaction order is?

Zero-order

What is the steady-state assumption?

[ES] remains constant

What is kcat?

Turnover number

What does kcat/Km represent?

Catalytic efficiency

What does Lineweaver-Burk plot graph?

1/v vs 1/[S]

What is the slope of LB plot?

Km/Vmax

What is the y-intercept?

1/Vmax

What is the x-intercept?

-1/Km

Why use Lineweaver-Burk?

Determine Km and Vmax

Which inhibitor increases Km only?

Competitive

Which inhibitor decreases Vmax only?

Noncompetitive

Which inhibitor decreases Km and Vmax?

Uncompetitive

Which inhibitor binds ES complex only?

Uncompetitive

Which inhibitor binds active site?

Competitive

Which inhibitor binds allosteric site?

Noncompetitive

Which inhibition can be overcome by substrate?

Competitive

Which inhibition produces parallel LB lines?

Uncompetitive

What type of inhibition forms covalent bonds?

Irreversible

Can irreversible inhibition be reversed by dialysis?

No

What type of catalysis involves proton transfer?

acid-base catalysis

Which amino acid is most important in acid-base catalysis?

Histidine

What type of catalysis forms temporary covalent bond?

Covalent catalysis

Which amino acid acts as nucleophile in serine proteases?

Serine

What type of catalysis uses metal ions?

Metal ion catalysis

What do metal ions stabilize?

Charged intermediates

What is a nucleophile?

Electron donor

What is an electrophile?

Electron acceptor

What intermediate forms in serine proteases?

Tetrahedral intermediate

What type of enzyme is chymotrypsin?

Serine protease

What residues form catalytic triad?

Serine, Histidine, aspartate

What does serine do in mechanism?

Nucleophilic attack

What does histidine do?

acts as base/acid

What does aspartate do?

Stabilizes histidine

What type of residues does chymotrypsin cleave?

aromatic/hydrophobic

What is the first step of chymotrypsin catalysis?

Serine attacks carbonyl

What intermediate forms?

Tetrahedral intermediate

What is an allosteric enzyme curve shape?

Sigmoidal

What does cooperative binding mean?

Binding affects affinity of other sites

What shifts curve left?

activators

What shifts curve right?

Inhibitors

What type of modification is phosphorylation?

Covalent

Which amino acids are phosphorylated?

Ser, Thr, Tyr

What is a zymogen?

Inactive enzyme precursor

How are zymogens activated?

Proteolytic cleavage

Is zymogen activation reversible?

No

Example of zymogen pair?

Pepsinogen → Pepsin

What happens when 2,3-BPG binds hemoglobin?

Decreases O₂ affinity

Which state of hemoglobin does BPG stabilize?

T-state

What does low pH do to hemoglobin affinity?

Decreases it

What is the Bohr effect?

H⁺ and CO₂ decrease O₂ affinity

Which hemoglobin has higher O₂ affinity?

Fetal hemoglobin

Why does fetal Hb bind O₂ better?

Binds BPG less tightly

What is the difference between ΔG and ΔG‡?

ΔG is free energy change; ΔG‡ is activation energy

Do enzymes affect ΔG or ΔG‡?

ΔG‡ only

Why do enzymes not change equilibrium?

Lower forward and reverse activation energies equally

What determines reaction spontaneity?

ΔG

What determines reaction rate?

ΔG‡

What happens if enzyme stabilizes ES too much?

Increases ΔG‡ and slows reaction

What is transition state (X‡)?

High-energy intermediate

What are transition-state analogs?

Mimic transition state

What interactions stabilize ES?

Hydrogen bonds, ionic, van der Waals, hydrophobic

What happens during desolvation?

Water removed from substrate

Does desolvation raise or lower ES energy?

Raises energy

Why is desolvation beneficial?

Makes substrate more reactive

What is proximity effect?

Brings substrates together

What is orientation effect?

aligns substrates

What do oxidoreductases catalyze?

Redox reactions

What do transferases do?

Transfer functional groups

What do hydrolases do?

Cleave bonds with water

What do lyases do?

Form/break double bonds without water

What do isomerases do?

Rearrange atoms

What do ligases do?

Form bonds using

What do translocases do?

Move molecules across membranes

What is initial velocity (v₀)?

Rate at beginning of reaction

Why measure v₀?

avoid reverse reactions

What happens to ES in steady state?

Remains constant

What is diffusion limit?

Maximum enzyme rate (~10⁸–10⁹ M⁻¹s⁻¹)

What happens to slope in competitive inhibition?

Increases

What happens to y-intercept in competitive inhibition?

No change