Chemistry MCQs for NEET — Practice Questions with Answers

The NCERT text mentions: 'However, enzymes isolated from organisms who normally live under extremely high temperatures (e.g., hot vents and sulphur springs), are stable and retain their catalytic power even at high temperatures (upto 80°-90°C). Thermal stability is thus an important quality of such enzymes isolated from thermophilic organisms.'

The NCERT text states: 'During the state where substrate is bound to the enzyme active site, a new structure of the substrate called transition state structure is formed.'

According to the NCERT text: 'Transferases: Enzymes catalyzing a transfer of a group, G (other than hydrogen) between a pair of substrate S and S’ e.g., S - G + S’ → S + S’ - G'.

The NCERT text clarifies: 'Low temperature preserves the enzyme in a temporarily inactive state whereas high temperature destroys enzymatic activity because proteins are denatured by heat.'

The NCERT text explains: 'Enzymes eventually bring down this energy barrier making the transition of ‘S’ to ‘P’ more easy.' The 'energy barrier' refers to the activation energy.

The NCERT text states: 'The essential chemical components of many coenzymes are vitamins, e.g., coenzyme nicotinamide adenine dinucleotide (NAD) and NADP contain the vitamin niacin.'

The NCERT text clearly states: 'Catalytic activity is lost when the co-factor is removed from the enzyme which testifies that they play a crucial role in the catalytic activity of the enzyme.'

The NCERT text explains: 'The reaction ultimately reaches a maximum velocity ($V_{ ext{max}}$) which is not exceeded by any further rise in concentration of the substrate. This is because the enzyme molecules are fewer than the substrate molecules and after saturation of these molecules, there are no free enzyme molecules to bind with the additional substrate molecules.'

According to the NCERT text: 'One such pocket is the ‘active site’. An active site of an enzyme is a crevice or pocket into which the substrate fits. Thus enzymes, through their active site, catalyse reactions at a high rate.'

The NCERT text states: 'Rates of physical and chemical processes are influenced by temperature among other factors. A general rule of thumb is that rate doubles or decreases by half for every 10°C change in either direction.'