Question

1- describe three means by which enzymes can facilitate chemical reaction and state how the energy barrier of the reaction might be affected.

2- contrast the way in which metal ions, coenzymes, and prosthetic groups facilitate enzymes reactions.

3- explain why allosteric regulators often act on non-catalytic subunits and how those actions influence catalysis.

4- describe the feedback inhibition in the metabolic pathways and how could this provide an adaptive advantage to the organism.

Answer 1

1. Enzymes are the biomolecules which facilitate enzymatic reaction by increasing the rate of reaction . At every point of life from enery synthesis by photosynthesis to energy utilization by glycolysis and further breakdown steps ,enzymes are required .

◆enzyme facilitate reaction by increasing rate of reaction but equilibrium remain unchanged .

◆enzyme provides the binding energy to substrate which help in overcoming the high activation energy. The activation energy is major barrier which is helpfull also for life otherwise every biomolecule can be degraded spontaneously . Due to this activation energy a specific enzyme with high specificity will only recognise and catalyze reaction.

2.metal ion ,co enzymes and prosthetic group provides the stability to enzyme and brings the enzyme in active confirmation ,which is important for binding to substrate and catalyze reaction .They also stabilize the substrate binding in active site by binding with substrate.

If these groups are absent in enzymes ,enzyme become non functional.

3. Allosteric regulator usually binds to the enzyme at site other then main substrate binding site because enzymes have diffrent sites for allosteric regulator . These regulator generally bind to these allosteric sites and regulates the enzyme's active site confirmation . Allosteric regulator can be inhibitor or activator .

The allosteric inhibitor after binding to allosteric site disruptes the active site confirmation of enzyme and it will no longer bind to substrate and thus inhibites enzymatic reaction

The allosteric activator after binding to enzyme facilitates substrate binding thus enhance enzymatic reaction.

4.Feedback inhibition pathway works in a way like glycolysis multisteps pathway . If the end product of the pathway accumulates then that accumulated product will in turn inhibit the initial step enzyme's activity .,so that a multy step pathway keeps on surveillance by there own products.

◆Advantage of this system is that by this every pathway kept on regulation by it's products. Cell have setup this system to reduce the waste of energy for example glycolysis ,TCA and electron transport chain (ETC) are interconnected pathways .Whenever ATP increases in cell which is formed by ETC ,ATP by feedback inhibition inhibites the earlier steps of Glycolysis .So that now energy will not be consumed in ATP synthesis but glucose is converted to some other storage forms like glycogen.

So this is the advantage of feedback inhibition pathway.