What is the Michaelis–Menten equation?
[V_0 = \frac{V_{\text{max}} [S]}{K_m + [S]}] It describes how reaction velocity changes with substrate concentration.
What is Km?
The Michaelis constant — the substrate concentration at which the reaction rate is ½ Vmax.
- Small Km → high affinity
- Large Km → low affinity
What is Vmax?
The maximum reaction velocity when all enzyme active sites are saturated.
What is initial velocity (V₀)?
The reaction rate immediately after mixing E + S, before significant product accumulates.
What is the Lineweaver–Burk plot?
A double-reciprocal plot of 1/V₀ vs 1/[S] used to estimate Km and Vmax and identify inhibitor type.
Hexokinase vs glucokinase: Km and affinity
- Hexokinase: low Km → high affinity
- Glucokinase: high Km → low affinity
Hexokinase vs glucokinase: Vmax and function
- Hexokinase: low Vmax → active in most tissues for consistent glucose use
- Glucokinase: high Vmax → allows liver to uptake glucose only when plentiful
Hexokinase vs glucokinase: physiological role
- Hexokinase: provides cells with glucose at all blood glucose levels
- Glucokinase: regulates blood sugar by trapping excess glucose in the liver
What are competitive inhibitors?
Molecules that bind the active site and compete with substrate; inhibition reversible with ↑ substrate.
Effects of competitive inhibition on Km and Vmax
- Km ↑ (lower affinity)
- Vmax unchanged
What are noncompetitive inhibitors?
Inhibitors that bind to a site other than the active site; cannot be overcome by ↑ substrate.
Effects of noncompetitive inhibition on Km and Vmax
- Km unchanged
- Vmax ↓
What are uncompetitive inhibitors?
Inhibitors that bind only to the ES complex (mentioned as a subclass in your slides).
Effects of uncompetitive inhibition on Km and Vmax
- Km ↓
- Vmax ↓
(Parallel shift in Lineweaver–Burk)
What is irreversible inhibition?
Inhibitors bind the enzyme through covalent bonds → permanently inactivating it (e.g., aspirin).
What is allosteric regulation?
Regulation by effectors binding noncovalently at a site other than the active site.
Can be:
- Positive (increase activity)
- Negative (decrease activity)
What is homotropic allosteric regulation?
Substrate itself acts as the allosteric effector (usually positive cooperativity).
What is heterotropic allosteric regulation?
A different molecule (not substrate) acts as effector, e.g., feedback inhibition.
What is methanol?
A toxic alcohol used in fuels, solvents, and industrial products.
What molecules cause methanol toxicity?
Formaldehyde and formic acid, produced by metabolism via alcohol dehydrogenase.
Symptoms of methanol poisoning?
- Visual disturbances (“snowfield vision”)
- Headache
- Nausea/vomiting
- Metabolic acidosis
- Blindness
- CNS depression
What is the treatment principle for methanol poisoning?
Inhibit alcohol dehydrogenase to stop toxic metabolite formation.
Main treatments:
- Fomepizole (1st line)
- Ethanol (competitively inhibits metabolism)
- Bicarbonate for acidosis
- Hemodialysis if severe
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Week 1- Water, Buffers43
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Amino Acids45
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Fibrous Proteins38
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Quick Ones For Fibrous Proteins23
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Quickies For Protein Structure28
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Quickies For Week 429
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Quickies For Enzymes32
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