Enzyme Activity and Factors Affecting It

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Questions and Answers

What happens to enzyme activity as product concentration increases?

Enzyme activity remains constant.
Enzyme activity increases proportionally.
Enzyme activity decreases. (correct)
Enzyme activity becomes unpredictable.

What is the impact of lowering the free energy of activation by an enzyme?

It eliminates the need for substrates in the reaction.
It increases the energy needed for the reaction.
It reduces the number of substrate molecules.
It allows more molecules to reach the transition state. (correct)

Which factor does NOT affect enzyme activity?

pH level of the medium
Color of the substrate (correct)
Competitive inhibitor presence
Product concentration

What is the primary role of an enzyme in a biochemical reaction?

To provide an alternative pathway with lower activation energy. (B) Signup and view all the answers

How does an allosteric enzyme differ from a regular enzyme?

It can be influenced by binding at sites other than the active site. (A) Signup and view all the answers

Which statement about transition states is correct?

Transition states are the points where reactants convert to products. (B) Signup and view all the answers

What is the effect of increased temperature on enzyme activity up to a certain point?

It generally increases enzyme activity. (C) Signup and view all the answers

Which scenario demonstrates enzyme inhibition?

Inhibitor molecules compete with the substrate for the active site. (C) Signup and view all the answers

Which type of plasma enzymes is involved in the blood coagulation cascade?

Functional plasma enzymes (B) Signup and view all the answers

What does an elevation in plasma levels of Alanine aminotransferase (ALT) typically indicate?

Hepatic tissue damage (B) Signup and view all the answers

What is the optimum temperature for most human enzymes to function effectively?

37°C (D) Signup and view all the answers

Which enzyme is used to treat myocardial infarctions by promoting thrombus degradation?

Alteplase (B) Signup and view all the answers

Which of the following statements about non-functional plasma enzymes is correct?

Their plasma levels remain constant in healthy individuals. (B) Signup and view all the answers

What effect does temperature have on enzyme activity?

It increases reaction velocity until a peak is reached. (D) Signup and view all the answers

What limitation is observed with increases in plasma levels of enzymes with wide tissue distribution?

They complicate the identification of the injury site. (A) Signup and view all the answers

Which factor is NOT mentioned as affecting enzyme activity?

Enzyme concentration (D) Signup and view all the answers

What is the primary consequence of extreme temperatures on enzyme activity?

Decreased reaction velocity due to enzyme denaturation. (B) Signup and view all the answers

Which factor primarily influences the protonation state of enzyme active sites?

pH levels of the surrounding environment. (A) Signup and view all the answers

At what pH does pepsin exhibit maximal enzyme activity?

1-2 (A) Signup and view all the answers

What happens to enzyme activity as substrate concentration increases at a fixed enzyme concentration?

Activity increases until a maximum velocity is reached. (D) Signup and view all the answers

Which of the following statements regarding enzyme denaturation is correct?

Denaturation can occur due to extreme pH levels. (C) Signup and view all the answers

Why might hypothermia be a life-threatening condition affecting enzymes?

Complete inactivity of enzymes at zero degrees Celsius. (D) Signup and view all the answers

What is true regarding salivary amylase's functioning in acidic environments?

It is denatured and ceases to work effectively. (D) Signup and view all the answers

What occurs after reaching the maximal velocity in enzyme reactions when substrate concentration continues to increase?

The reaction rate plateaus and remains unchanged. (D) Signup and view all the answers

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Study Notes

Enzyme Activity and Factors Affecting It

Temperature: The optimal temperature for most human enzymes is 37°C. Enzyme activity increases with temperature until reaching a peak, then decreases due to denaturation. This explains why fever and hypothermia can be life-threatening.
pH: The pH at which optimal enzyme activity occurs is called the "Optimum pH." This varies for different enzymes, often reflecting the pH of the environment where they function (e.g., pepsin in the stomach is most active at pH 1-2). Extremes of pH can denature enzymes.
Substrate Concentration: Increasing substrate concentration increases enzyme activity until reaching a maximum "maximal velocity." Further increases in substrate concentration have no effect on reaction rate.
Enzyme Concentration: Increasing enzyme concentration directly increases the rate of reaction.
Product Concentration: Product accumulation can decrease enzyme activity due to:
- Changes in the pH of the medium
- Competition with substrate for the active site
- Product binding to the enzyme at the allosteric site

Enzyme Action: Mechanism and Clinical Impact

Enzymes accelerate reactions by lowering the activation energy (Ea). This is the energy required for molecules to reach the transition state, where bonds are most likely to break or form, leading to product formation.
Enzymes provide an alternative pathway with a lower activation energy, increasing the number of molecules that can reach the transition state and thus speeding up the reaction.
The lower the activation energy, the faster the rate of reaction.
This concept explains why certain reactions in the body, like digestion or muscle contraction, require enzymatic catalysis to occur at a rate that is physiologically usable.
Enzymes are categorized based on their actions on different chemical bonds.
Pharmacological activation or inhibition of enzyme activity can have significant clinical implications.

Classes of Plasma Enzymes

Functional Plasma Enzymes: These are secreted by specific organs into the plasma, where they perform specific functions (e.g., liver enzymes involved in blood coagulation).
Non-functional Plasma Enzymes: These are released from cells during normal cell turnover and have no physiological function in the plasma. Their levels are normally stable, representing a balance between release and removal.

Clinical Significance of Plasma Enzymes

Elevated levels of non-functional plasma enzymes can indicate tissue damage.
Measuring specific enzyme levels can help diagnose and monitor diseases:
- Elevated alanine aminotransferase (ALT) in the plasma suggests possible liver damage.
- Increased alkaline phosphatase in bone indicates conditions like osteoporosis, rickets, or bone tumors.
Enzymes are used therapeutically for conditions such as maldigestion and myocardial infarction (e.g., alteplase is used to activate enzymes that break down thrombus).