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Questions and Answers

What happens to the rate of enzyme action when enzyme concentration increases?

It decreases when substrate is in low concentration.

It is proportional to enzyme concentration under constant conditions. (correct)

It remains constant regardless of substrate concentration.

It always reaches Vmax immediately.

What is the significance of Vmax in enzyme kinetics?

It indicates the maximum concentration of substrate.

It means that all enzyme sites are vacant.

It is the substrate concentration at which all enzymes are inactive.

It represents the maximum rate of reaction achievable. (correct)

Which enzyme has a high affinity for its substrate based on its Km value?

Neither has a significant affinity.

Glucokinase

Both have the same affinity.

Hexokinase (correct)

What does a higher Km value indicate about an enzyme?

It has a low affinity for its substrate. Signup and view all the answers

Which factor does NOT affect the rate of enzyme action?

Product concentration Signup and view all the answers

What happens to the reaction rate if substrate concentration increases beyond Vmax?

The reaction rate will plateau and remain constant. Signup and view all the answers

Which enzyme is characterized by functioning effectively at high substrate concentrations?

Glucokinase Signup and view all the answers

What role do coenzymes play in enzyme activity?

They are necessary for the activity of some enzymes. Signup and view all the answers

What happens to the rate of enzyme reaction as temperature increases until it reaches the optimum temperature?

It increases gradually Signup and view all the answers

What is the optimum temperature range for enzyme activity as mentioned?

37-40°C Signup and view all the answers

What effect does the concentration of coenzymes have on the rate of reaction?

It increases the reaction rate Signup and view all the answers

What is the optimum pH range for pepsin activity?

1.5-2.0 Signup and view all the answers

What is one of the reasons that a change in pH affects the rate of enzyme action?

It affects the ionization state of the enzyme and substrate Signup and view all the answers

What type of enzyme inhibitor decreases enzyme activity by competing with the substrate for the active site?

Competitive inhibitors Signup and view all the answers

Which ion activates the enzyme salivary amylase, facilitating carbohydrate digestion?

Chloride ion Signup and view all the answers

What consequence does prolonged reaction time have on enzyme activity?

Reduces the substrate concentration Signup and view all the answers

What characterizes an enzyme with a low Km value?

Reaches maximal velocity at low substrate concentration Signup and view all the answers

Which factor does NOT influence the enzyme reaction rate according to enzyme kinetics?

Enzyme purity Signup and view all the answers

At what point does adding more substrate concentration have no effect on the enzyme reaction rate?

As soon as Vmax is achieved Signup and view all the answers

Which enzyme is likely to function effectively at low glucose concentrations?

Hexokinase Signup and view all the answers

What is the relationship between substrate concentration and reaction rate up to Vmax?

Reaction rate increases as substrate concentration rises, then plateaus Signup and view all the answers

Which statement about the effect of temperature on enzyme activity is true?

Enzyme activity peaks at an optimum temperature, then declines Signup and view all the answers

What defines the Michaelis constant (Km) in enzyme kinetics?

Substrate concentration at half maximal velocity Signup and view all the answers

What effect do inhibitors have on enzyme activity?

They can prevent the enzyme from binding to the substrate Signup and view all the answers

How does temperature affect enzyme activity beyond the optimum range?

Enzyme denaturation occurs, leading to decreased activity. Signup and view all the answers

What is the primary reason a change in pH impacts enzyme activity?

It affects the ionization state of both enzyme and substrate. Signup and view all the answers

What defines the effect of time on enzyme activity?

Substrate concentration decreases over time impacting reaction rates. Signup and view all the answers

Which ion is known to activate thrombokinase enzyme?

Calcium ion Signup and view all the answers

What is the impact of a competitive inhibitor on enzyme function?

It increases the km value for the substrate. Signup and view all the answers

What is the optimal pH for pancreatic lipase activity?

7.5-8 Signup and view all the answers

What happens to the rate of reaction as enzyme concentration increases?

It increases initially until all substrate is saturated. Signup and view all the answers

How does the presence of non-competitive inhibitors affect enzyme function?

They alter enzyme conformation without affecting substrate binding. Signup and view all the answers

Study Notes

Enzyme Action Factors

Enzyme concentration is directly proportional to reaction rate, if substrate is present.
Substrate concentration increases reaction rate to a maximum (Vmax). Further substrate increase doesn't affect the rate.
Coenzymes' concentration increase reaction rate.
Metal ion activators increase reaction rate.
Time affects reaction rate by decreasing substrate concentration and accumulating products.

Temperature

Reaction rate increases with temperature to a maximum, then decreases due to denaturation.
Optimum temperature for enzymes is ~37-40°C.
Reactions decrease in rate above 60-65°C.
Temperature affects reaction rate by increasing kinetic energy of the substrate or collision frequency.

pH

Each enzyme has an optimal pH, at which maximal activity occurs.
Pepsin (acidic environment, pH 1.5-2)
Pancreatic lipase (alkaline environment, pH 7.5-8)
Salivary amylase (slightly acidic environment, pH 6.8)
pH change affects enzyme or substrate ionization, and significant changes lead to denaturation.

Michaelis Constant (Km)

Substrate concentration yielding half of the maximum velocity (Vmax).
Low Km signifies high affinity to the substrate.
High Km signifies low affinity to the substrate.
Hexokinase (low Km/high affinity for substrate)
Glucokinase (high Km/low affinity for substrate)

Enzyme Inhibitors

Inhibitors decrease or stop enzyme activity.
Competitive inhibitors compete with the substrate for the active site.
Non-competitive inhibitors bind to the enzyme at a site other than the active site, changing the enzyme's shape.

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