Factors Affecting Rate Of Enzyme Reaction - pH, Temperature, Substrate Concentration, Enzyme Concentration

Factors affecting rate of enzyme reaction are pH, temperature, substrate concentration and enzyme concentration.

Effect of pH on enzyme reaction

Enzymes are active within narrow range of pH. At optimum pH, the rate of enzyme reaction reaches its maximum. Pepsin works best in acidic environment, amylase works best in neutral environment and trypsin works best in alkaline environment.

Effect of temperature on enzyme reaction

At low temperature, the rate of enzyme reaction is low because enzymes are inactive. As temperature increases, the rate of enzyme reaction increases. At optimum temperature of 370C, the rate of enzyme reaction reaches its maximum. At high temperature, the rate of enzyme reaction decreases. At temperature above 600C, enzymes are denatured.

Effect of substrate concentration on enzyme reaction

As substrate concentration increases, the rate of enzyme reaction increases to a certain level, whereby the enzyme concentration becomes the limiting factor.

Effect of enzyme concentration on enzyme reaction

As enzyme concentration increases, the rate of enzyme reaction increases to a certain level, whereby the substrate concentration becomes the limiting factor.

Read More

Four Structural Levels Of Proteins - Primary, Secondary, Tertiary, Quaternary Structures

The four structural levels of proteins are primary structure, secondary structure, tertiary structure and quaternary structure.

Primary structure

Primary structure is the number and sequence of amino acids or peptides. An example of primary structure is a polypeptide.

Secondary structure

Secondary structure involves coiling of a polypeptide chain in a helical or parallel structure which is stabilised by hydrogen bonds. An example of secondary structure is a fibrous protein.

Tertiary structure

Tertiary structure involves folding of polypeptide into a more compact, globular structure which is stabilised by disulphide, ionic and hydrogen bonds. An example of tertiary structure is a globular protein.

Quaternary structure

Quaternary structure involves combining two or more polypeptide chains to form a larger, more complex molecule which is stabilised by disulphide, ionic and hydrogen bonds. Non protein molecules are usually integrated onto this complex, forming a conjugated protein. An example of quaternary structure is haemoglobin.

Read More

Lock-And-Key Hypothesis And Induced-Fit Hypothesis

All enzymes are proteins, required in small quantities, reusable and denatured at high temperature. Enzyme reaction is reversible and specific. Two hypotheses about enzyme actions are lock-and-key hypothesis and induced-fit hypothesis.

Lock-and-key hypothesis

In lock-and-key hypothesis, enzyme acts as the lock and substrate acts as the key. Substrate binds to enzyme at active site, forming enzyme-substrate complex which lowers the activation energy. Products are formed and enzyme remains unchanged and reusable.

Induced-fit hypothesis

In induced-fit hypothesis, substrate binds to enzyme at active site, enzyme adjusts its shape to fit substrate, forming enzyme-substrate complex which lowers the activation energy. Products are formed and enzyme remains unchanged and reusable.

Read More