Biochemistry: Enzyme Action & Theories

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Questions and Answers

What happens to enzyme action when substrate concentration increases?

Enzyme action increases (correct)

Enzyme action remains unchanged

Enzyme action decreases

Enzyme action stops completely

What is the optimum temperature for enzyme activity in the human body?

50°C

37°C (correct)

25°C

45°C

Which of the following statement about pH levels and enzymes is correct?

Enzymes have a specific optimum pH for maximum activity (correct)

Basic environments always enhance enzyme activity

Enzymes are unaffected by changes in pH

All enzymes work best at a neutral pH of 7

What is a common effect of low temperatures on enzyme action?

Enzyme activity slows down Signup and view all the answers

Which of the following is considered an inhibitor of enzyme activity?

Streptomycin Signup and view all the answers

What effect do accelerators have on enzymes?

They activate the enzyme Signup and view all the answers

Which environmental hazard is associated with cigarette smoke?

Cadmium Signup and view all the answers

Which enzyme is commonly used as an index for the pathology of pancreatitis?

Lipase Signup and view all the answers

What is a primary use of enzymes in clinical enzymology?

As analytical tools for measuring biological constituents Signup and view all the answers

What is the result of each 10°C increase in temperature on enzyme reaction rate?

Doubles or triples the reaction rate Signup and view all the answers

What forms when a substrate contacts the active site of an enzyme?

Enzyme-substrate complex Signup and view all the answers

What is the role of activation energy in enzymatic reactions?

It is required to initiate a chemical transformation. Signup and view all the answers

Which statement best describes Fischer's Lock and Key Theory?

The substrate and enzyme fit together without modification. Signup and view all the answers

In Koshland's Induced Fit Theory, what happens upon the initial binding of the substrate?

Secondary binding strengthens the enzyme-substrate interaction. Signup and view all the answers

How is the catalytic reaction initiated in Fischer's Lock and Key Theory?

Through the formation of the ES complex. Signup and view all the answers

Which of the following is NOT a factor affecting enzyme activity?

Vascular resistance Signup and view all the answers

What happens to the enzyme after it catalyzes a reaction?

It returns to its original state. Signup and view all the answers

Which of the following enzymes breaks down sucrose into glucose and fructose?

Sucrase Signup and view all the answers

What distinguishes Koshland's Induced Fit Theory from Fischer's Lock and Key Theory?

Induced Fit requires prior substrate binding for changes. Signup and view all the answers

Which term describes the transformation from substrate to product in enzymatic reactions?

Catalysis Signup and view all the answers

Study Notes

Mode of Enzyme Action

Enzyme activity begins when the substrate contacts the active site of the enzyme.
An enzyme-substrate complex forms as a temporary intermediate.
The substrate is converted into products within the complex.
Products are released, and the enzyme remains unchanged, ready for another reaction.
Activation energy is the minimum energy needed for molecules to undergo transformation.

Theories Explaining Enzyme Action

Fischer's Lock and Key Theory: Enzyme and substrate fit together precisely like a key in a lock.
- The active site's structure is complementary to that of the substrate.
- The general reaction involves the formation and breakdown of the enzyme-substrate complex.
Koshland's Induced Fit Theory: Suggests that binding alters the shape of the enzyme or substrate.
- Initial binding of the substrate induces conformational changes for optimal fit and catalysis.

Factors Influencing Enzyme Action

Concentration of Substrate: Increasing substrate concentration enhances enzyme activity.
Concentration of Enzyme: Higher enzyme concentration leads to increased reaction rates.
Temperature:
- Optimum temperature for human enzymes is around 37°C.
- A 10°C increase can double or triple reaction rates.
- Excessive heat can inactivate enzymes, whereas low temperatures slow reactions without destroying enzymes.
pH Level: Each enzyme has a specific pH for maximum activity, with significant decreases in activity outside this range.
- Example: Pepsin (pH 1.5 to 2.2), Lactase (pH 5.7), Trypsin (pH 7.8).
Presence of Accelerators: Certain metallic ions (e.g., Mg, Mn, Co) can activate enzyme activity.
Presence of Inhibitors: Substances like antibiotics or antienzymes can inhibit enzyme activity through reversible or irreversible binding.
Environmental Hazards:
- Heavy metals such as Mercury (Hg), Cadmium (Cd), and Lead (Pb) from sources like cigarettes and gasoline can negatively affect enzyme function.

Clinical Enzymology

Enzymes serve as analytical tools for measuring substances in biological fluids, e.g., urease and alcohol dehydrogenase.
Enzymes are used as indicators for disease pathology.
- Elevated levels of certain enzymes, like amylase, lipase, and creatinine phosphokinase (CPK), can indicate various medical conditions (e.g., pancreatitis).

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Description

Explore the fascinating world of enzyme action in biochemistry. This quiz covers the mechanisms of enzyme function, including theories such as Fischer's Lock and Key and Koshland's Induced Fit. Test your knowledge on factors influencing enzyme activity and the role of activation energy.