10 Questions
What is the primary function of oxidoreductase enzymes?
To catalyze oxidation and reduction reactions
Which vitamin is required for the synthesis of FAD and FMN?
Vitamin Riboflavin
What is the primary role of cofactors in enzyme activity?
To serve as a metal ion required for enzyme activity
What is the consequence of mutations in the SOD enzyme?
Development of amyotrophic lateral sclerosis
What is the primary mechanism of the induced fit model of enzyme activity?
Binding of the substrate to the enzyme causes a conformational change in the enzyme
At what pH does salivary amylase catalyze best?
pH 7
What happens to the activity of an enzyme if the temperature is very high?
The activity of the enzyme decreases due to denaturation
What is the significance of a low Km value for an enzyme?
It indicates a strong affinity of the enzyme towards the substrate
What is the effect of a competitive inhibitor on the Km and Vmax of an enzyme?
Km increases, Vmax remains the same
What is the purpose of acetaldehyde dehydrogenase enzyme?
To detoxify acetaldehyde produced from breakdown of alcohol
Study Notes
Cofactors and Coenzymes
- TPP (Thiamine Pyrophosphate) is synthesized from Vitamin Thiamine
- FAD (Flavin Adenine Dinucleotide) and FMN (Flavin Mononucleotide) are synthesized from Vitamin Riboflavin
- Examples of coenzymes include FAD, FMN, TPP, and others
Types of Enzymes
Oxidoreductases
- Enzymes involved in oxidation-reduction reactions
- Example: Superoxide Dismutase (SOD), mutations of which lead to Amyotrophic Lateral Sclerosis
Hydrolases
- Enzymes that cleave molecules using water
- Example: Tissue Plasminogen Activator, which cleaves Plasminogen to Plasmin to dissolve clots
Ligases
- Enzymes that catalyze synthetic reactions, forming covalent bonds at the expense of high-energy phosphate bonds (usually ATP)
- Example: Pyruvate Carboxylase
Enzyme Activity
- The Induced Fit model is the most accepted model, stating that binding of substrate to enzyme induces a conformational change in the enzyme, directing appropriate amino acids to the active site
- Factors affecting enzyme activity: availability of enzyme, optimum pH, optimum temperature, coenzymes, and cofactors
Optimum pH and Temperature
- Enzymes work best at optimum pH and temperature
- Examples: Salivary Amylase catalyzes best at pH 7, Pepsin catalyzes best at pH 2, and high temperatures can cause denaturation of enzymes
Km and Vmax
- Km is the substrate concentration at which ½ Vmax is reached
- Low Km value indicates strong affinity of enzyme towards substrate, while high Km reflects weak affinity
- Vmax is the maximum rate of enzyme activity, where all enzymes are saturated with substrate and are in the ES (Enzyme-Substrate) complex
Hexokinase and Glucokinase
- Both catalyze phosphorylation of glucose
- Hexokinase: present in all cells except hepatocytes and β-cells of pancreas, has low Km (high affinity) for glucose, and works even at low glucose concentrations
- Glucokinase: present in hepatocytes and β-cells of pancreas, has high Km (low affinity) for glucose, and removes glucose from circulation only after a meal
Acetaldehyde Dehydrogenase
- Required to detoxify acetaldehyde from breakdown of alcohol
- Two types: low Km form and high Km form, with the low Km form breaking down acetaldehyde more efficiently
Competitive Inhibition
- A type of reversible inhibition where the inhibitor is a structural analog of the substrate and binds to the active site of the enzyme
- Examples: Sulfonamides, Trimethoprim, Dicoumarol, Captopril, and Allopurinol
Test your knowledge of enzymes, cofactors, and coenzymes, including their functions, synthesis, and examples. Learn about oxidoreductases, hydrolases, lyases, and ligases, and how they relate to various biological processes.
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