🤚🏻 Factors Affecting

Factors Affecting, Inhibtors, Types of Plants

An increase in the concentration of the substrate firstly increases the rate of the reaction but when all the active sites of the enzyme surface are occupied by the substrate molecule, the increase is stopped. And there is no effect of the further increase in substrate conc. on the rate of reaction.
This is because of the limiting effects of the enzyme concentration.

Fig: Relationship between the substrate conc. and the rate of reaction.

Firstly there is an increase in the rate of reaction with the increase in enzyme concentration but the rate of reaction stops at a point and becomes constant when substrate conc. becomes the limiting factor of reaction

The enzymic reaction rate increases twice (i.e. doubles) for every rise of 10°C within the certain limit. i.e. Q₁₀ = 2. At 0°C enzymatically active reaction rate becomes zero and at higher temperature i.e. 55°-60°C, the Denaturation of enzyme takes place (i.e. the loss of natural properties). However, the optimum temp. is 30 °C. They also get temporarily inactive at lower temperature.

Enzymes are very sensitive to pH and works in narrow range of pH. The pH between 7 - 7.5 is ideal for the normal enzymic activity but there are certain enzymes like pepsin requires very low pH i.e. 1.5 - 3.0 whereas enzymes like Trypsin are active even at high pH.

In the seeds, the amount of water is too less so no enzymic activity is observed. With the increase in the amount of water, enzymes become active and seed starts to germinate.

Enzymic reactions are reversible in nature and acts on the ‘Mass action’ principle.
Therefore the accumulation of the end products results in an increase in the rate of the, reverse reaction.

👉🏻 Enzyme inhibitors are of two types:

Such inhibitors are structurally similar to the substrate molecule e.g. Succinic dehydrogenase is inhibited by its competitor Malonate. Malonate is known as substrate analogue of Succinate. This effect is overcome by increasing the concentration of succinic acid.
Similarly, sulpha drugs are substrate analogue of p-amino benzoic acid (PABA) used in folic acid synthesis in bacterial cells. Hence these drugs are used to kill bacterial cells.

In this type of inhibition, inhibitor substance can bind simultaneously to an enzyme, other than it’s active site and destroy the sulfhydryl (S-H) group of enzyme. Ex. Toxic metals, CO, CN.
Examples: CN (Cyanide) poisoning of cytochrome oxidase. Such inhibition are irreversible inhibition.

When inhibitor binds at allosteric site reversibly.
When product of biochemical reaction inhibits the enzyme action. It is known as product inhibition or retro inhibition or feedback inhibition.
Example: Inhibition of hetrokinase by glucose 6P.
The product may binds at allosteric site of allosteric enzyme then it is non-competitive, reversible, allosteric inhibition
In the allosteric modulation, chemical or products fits in allosteric sites & bring a change in shape of active site of enzyme.
Chemicals which binds at allosteric site of allosteric enzymes are known as allosteric modulators.
If allosteric modulator positively change the configuration of active site, then called positive allosteric modulation and if negatively change then called negative allosteric modulation respectively by positively modulator (activators) and negative modulators (inhibitors).
Ex. Phosphofructokinase inhibited by ATP (negative modulation), activated by AMP, ADP (positive modulation).
All allosteric modulation are not feed-back inhibition.

Types of Plants