biochem random

An enzyme converts substrate to product rapidly at low [S], but at high [S] velocity plateaus. What property does this illustrate?

Vmax saturation

Which statement explains why enzymes decrease activation energy?

They stabilize the transition state

Which kinetic scenario indicates competitive inhibition?

Km ↑, Vmax unchanged

In a Lineweaver–Burk plot, a noncompetitive inhibitor causes what change?

Y-intercept ↑

Hexokinase binds glucose tighter than fructose. Why?

Lower Km = higher affinity

Common phosphorylation amino acids?

Serine, Threonine, Tyrosine

A zymogen becomes active after proteolytic cleavage. What is this?

Irreversible covalent activation

Enzyme very inactive at lowest pH. Why?

Denaturation of catalytic residues

Increasing enzyme concentration (constant [S]) has what effect?

Increases Vmax

Enzyme displays sigmoidal curve. What type?

Allosteric enzyme

Mutation lowers affinity but Vmax unchanged. What changes?

Km ↑

Lactate → pyruvate belongs to which class?

Oxidoreductase

Serine → Pyruvate + NH3 belongs to which class?

Lyase

Enzyme forming peptide bonds using ATP?

Ligase

Covalent inhibitors differ from reversible inhibitors how?

Permanent bond with active site

Heterotropic inhibitor binding does what?

Alters conformation → lowers activity

Amino acid most used in acid–base catalysis?

Histidine

Plot with slope = Km/Vmax is what?

Lineweaver–Burk

Condition that makes reaction appear irreversible?

Product far more stable than substrate

ATP → ADP energy used by which class?

Ligases

Which interaction is NOT part of ES binding?

Peptide bonds

Effect of positive allosteric activator?

Decreases Km

Competitive inhibitor structural property?

Resembles substrate

Noncompetitive inhibitor binds where?

Allosteric site

Irreversible inhibitor effect on LB plot?

Vmax ↓ only

Removing catalytic serine from serine protease causes what?

Loss of catalytic power

Apoenzyme + cofactor = ?

Holoenzyme

Coenzyme from Vitamin B3?

NAD+

Coenzyme in decarboxylation?

TPP (Thiamine pyrophosphate)

Parallel LB lines indicate what?

Uncompetitive inhibitor

High temperature effect on enzymes?

Denaturation → activity loss

Step with highest energy?

Transition state

Glucose-6-phosphate → fructose-6-phosphate class?

Isomerase

Metal ions assist catalysis how?

Stabilize negative charges

Pepsin optimal pH?

pH 2

Enzyme forming double bonds by group removal?

Lyase

Kcat measures what?

Turnover number

Velocity increases with [S] indicates?

Substrate-level control

Allosteric inhibitor effect on curve?

Shift right

Which is a zymogen?

Trypsinogen

Phosphorylation typically changes what?

Conformation

Which bond stabilizes tertiary structure?

Disulfide bond

Strongest protein bond?

Disulfide bond

Which enzyme has catalytic triad?

Serine protease

Noncompetitive inhibitor impact on rate?

Lower Vmax at all [S]

Transition state analog type?

Strong competitive inhibitor

Rate-limiting factor at low [S]?

Substrate availability

Rate-limiting factor at high [S]?

Enzyme concentration

Michaelis–Menten curve shape?

Hyperbolic

Cooperative kinetics shape?

Sigmoidal

Enzyme using PLP?

Aminotransferase

Removing cofactor gives what?

Apoenzyme

Inhibitor binding ES only?

Uncompetitive inhibitor

Class using FAD?

Oxidoreductase

Enzyme specificity depends on what?

Active-site 3D structure

Amino acid NOT phosphorylated?

Alanine

Metal-dependent enzyme example?

Carbonic anhydrase

If rate unaffected by [S] increase?

Enzyme saturated

Increased slope on LB plot means?

Inhibition

Fastest regulation type?

Allosteric modulation

Slowest regulation type?

Gene expression

Substrate binding increasing other sites’ affinity?

Positive cooperativity

Zn²⁺ in alcohol dehydrogenase acts as?

Cofactor

25→37°C effect on enzymes?

Rate increases until denaturation

Optimal temperature for human enzymes?

37°C

Active site formed by what?

Tertiary structure folding

Amino acid forming salt bridge with Asp?

Arginine

Bond broken by hydrolase?

Ester/peptide bond

Class removing groups without hydrolysis?

Lyase

Drop in Vmax only indicates?

Noncompetitive inhibition

Enzyme catalyzing glucose + ATP → G6P?

Kinase (Transferase)

Km = 2 mM; at [S]=2 mM, V₀?

½ Vmax

Parameter changing with enzyme concentration?

Vmax

Parameter unchanged by enzyme concentration?

Km

Enzymes accelerate reactions by decreasing?

Activation energy (ΔG‡)

Functional group difference between aldose/ketose?

Carbonyl position

Glucose vs galactose differ at C4. They are?

Epimers

D-glucose vs L-glucose are?

Enantiomers

D-glucose vs D-mannose differ at C2. They are?

Epimers

Non-reducing disaccharide?

Sucrose

General monosaccharide formula?

CnH2nOn

Cyclic glucose structure is?

Haworth form

α vs β glucose differ at what carbon?

Anomeric carbon

Cyclization creates what new center?

Anomeric carbon

Benedict test detects?

Reducing sugars

Disaccharide with β(1→4)?

Lactose

Disaccharide with α(1→2)β?

Sucrose

Highly branched polysaccharide?

Glycogen

Sugar with ketone group?

Fructose

Carbon determining D/L?

Highest-numbered chiral carbon

Cellulose linkage?

β(1→4)

Aldose oxidation produces?

Aldonic acid

Primary alcohol oxidation yields?

Uronic acid

Carbonyl reduction yields?

Sugar alcohol

Glucose reduced → ?

Sorbitol

RNA sugar?

Ribose

DNA sugar?

Deoxyribose

Fructose forms what ring?

Furanose

Glucose forms what ring?

Pyranose

GAG charge?

Highly negative (sulfate)