Chapter 20, Problem 20.101CQ

Interpretation Introduction

20.101 Interpretation:

It is given that Cd is a poisonous metal. Cd²⁺ ions are inhibitors of hexokinase. Increasing the concentration of glucose or ATP, the substrates of hexokinase or Mg²⁺, the cofactor of hexokinase, does not change the rate of the Cd inhibited reaction. So based on this information is Cd a competitive or non-competitive inhibitor.

Concept Introduction:

An enzyme inhibitor is a molecule that binds to an enzyme and decreases its activity. Since blocking an enzyme's activity can kill a pathogen or correct a metabolic imbalance, many drug molecules are enzyme inhibitors. Inhibition can be reversible or irreversible.

Reversible inhibition is a type of inhibition in which a molecule (inhibitor) reacts with the enzyme and once removed lets the enzyme it was inhibiting to work again normally. It does not result in any permanent effects on the enzyme. In other words, reversible inhibitors of an enzyme bind non-covalently to it. Reversible inhibition is of three different types namely: Competitive, Non-competitive, and uncompetitive.

Competitive reversible inhibition: In this kind of inhibition, the inhibitor molecule has some structural similarity to the normal substrate. Hence the inhibitor binds to the active site and prevents the normal substrate binding to the enzyme.

In the case of competitive reversible inhibition, the activity of the enzyme does not increase by increasing the concentration of the substrate because the inhibitor is not competing at the active site and secondly the active site is also deformed. The only way the enzymatic activity can be increased is by reducing the concentration of inhibitor.

Non-competitive reversible inhibition: In this kind of inhibition, the inhibitor molecule binds to a different site that is not the active site of the enzyme and changes the structure of the enzyme; therefore, it blocks the enzyme from binding to substrate, which stops enzyme activity.

In the case of non-competitive reversible inhibition, the activity of the enzyme depends on the concentration of substrate and the inhibitor. If the substrate concentration is increased it displaces the inhibitor molecule and the enzyme activity increases.

To determine: If Cadmium is a competitive or non-competitive inhibitor

Interpretation Introduction

20.102 Interpretation:

Beano contains an enzyme that breaks down polysaccharides into smaller, more digestible sugars, which diminishes the intestinal gas formation. Beano contains alpha- galactosidase. It is to be determined what kind of enzyme is alpha- galactosidase. Secondly what is the substrate for this enzyme? Lastly why Beano should not be heated or cooked.

Concept Introduction:

Enzymes are classified based on the type of reaction they catalyze:

(1) Oxidoreductases

(2) Transferases

(3) Hydrolases

(4) Lyases

(5) Isomerases

(6) Ligases

To determine: It is to be determined what kind of enzyme is alpha- galactosidase. Secondly what is the substrate for this enzyme? Lastly why Beano should not be heated or cooked.