Q.1 What is metabolism?
Ans : Metabolism is a highly coordinated cellular activity in which many multienzyme systems (metabolic pathways) cooperate to (1) obtain chemical energy by capturing solar energy or degrading energy-rich nutrients from the environment; (2) convert nutrient molecules into the cell’s own characteristic molecules, including precursors of macromolecules; (3) polymerize monomeric precursors into macromolecules: proteins, nucleic acids, and polysaccharides; and
(4) Synthesize and degrade biomolecules required for specialized cellular functions, such as membrane lipids, intracellular messengers, and pigments. Metabolism is the totality of an organism’s chemical reactions.
Q.2 Define Catabolism and Anabolism.
Ans: Catabolism: Catabolic pathways release energy by breaking down complex molecules into simpler compounds.
Anabolism: Anabolic pathways consume energy to build complex molecules from simpler ones.
Q.3 Define exergonic and endergonic process/reaction. Show using diagram change of free energy in these processes.
Ans: exergonic process : An exergonic reaction proceeds with a net release of free energy and is spontaneous.
endergonic process : An endergonic reaction absorbs free energy from its surroundings and is nonspontaneous.
Q.4 Explain ATP involves in mechanical, transport and chemical.
Ans: ATP drives endergonic reactions by phosphorylation, transferring a phosphate group to some other molecule, such as a reactant. The recipient molecule is now phosphorylated.
• The three types of cellular work (mechanical, transport, and chemical) are powered by the hydrolysis of ATP.
Q.5 Define Substrate.
Ans: The reactant that an enzyme acts on is called the enzyme’s substrate. The enzyme binds to its substrate, forming an enzyme-substrate(ES) complex.
Q.6 Define active site.
Ans: The active site is the region on the enzyme where the substrate binds. Induced fit of a substrate brings chemical groups of the active site into positions that enhance their ability to catalyze the reaction.
Q.7 What are the factors through which active site can lower an activation energy (EA) barrier in an enzyme-catalyzed reaction.
Ans: The active site can lower an EA barrier by
– Orienting substrates correctly.
– Straining substrate bonds.
– Providing a favorable microenvironment.
– Covalently bonding to the substrate.
Q.8 Define co-factor of an Enzyme with example.
Ans: A cofactor is a non-protein chemical compound that is bound to a protein and is required for the protein's biological activity. These proteins are commonly enzymes, and cofactors can be considered "helper molecules" that assist in biochemical transformations.
Some enzymes or enzyme complexes require several cofactors. For example, the multienzyme complex pyruvate dehydrogenase at the junction of glycolysis and the citric acid cycle requires five organic cofactors and one metal ion: loosely bound thiamine pyrophosphate (TPP), covalently bound lipoamide and flavin adenine dinucleotide (FAD), and the cosubstrates nicotinamide adenine dinucleotide (NAD+) and coenzyme A (CoA), and a metal ion (Mg2+).
Organic cofactors are often vitamins or are made from vitamins. Many contain the nucleotide adenosine monophosphate (AMP) as part of their structures, such as ATP, coenzyme A, FAD, and NAD+. This common structure may reflect a common evolutionary origin as part of ribozymes in an ancient RNA world. It has been suggested that the AMP part of the molecule can be considered a kind of "handle" by which the enzyme can "grasp" the coenzyme to switch it between different catalytic centers.
Q.9 Write short note on competitive and noncompetitive inhibition with figure.
Ans: competitive inhibition: Competitive inhibitors bind to the active site of an enzyme, competing with the substrate. This process is called competitive inhibition.
Noncompetitive inhibition: Noncompetitive inhibitors bind to another part of an enzyme, causing the enzyme to change shape and making the active site less effective.
Q.10 Explain with diagram- allosteric activation and inhibition of enzyme.
Ans: Allosteric regulation is the term used to describe cases where a protein’s function at one site is affected by binding of a regulatory molecule at another site. Allosteric regulation may either inhibit or stimulate an enzyme’s activity.
• Most allosterically regulated enzymes are made from polypeptide subunits.
• Each enzyme has active and inactive forms.
• The binding of an activator stabilizes the active form of the enzyme.
• The binding of an inhibitor stabilizes the inactive form of the enzyme.
Q.11 What is cooperativity, explain with figure?
Ans: Cooperativity is a form of allosteric regulation that can amplify enzyme activity. In cooperativity, binding by a substrate to one active site stabilizes favorable conformational changes at all other subunits
Q.12 What is feedback inhibition? Why it is necessary in metabolic pathway or in biological reactions?
Ans: Feedback inhibition: In a metabolic pathway when the end product of metabolic pathway shuts down the pathway, then the process is called feedback inhibition.
Importance of feedback inhibition:
• Feedback inhibition prevents a cell from wasting chemical resources by synthesizing more product than is needed.
