Question

1.Discuss the use of ATP as the energy currency of the cell (include in your discussion the types of work performed by the cell)

2. Discuss ATP synthesis and ATP hydrolysis; How do cells obtain the energy to synthesize ATP? Why do cells hydrolyze ATP? What do cells do with released energy obtained from the hydrolysis of ATP?

3. Discuss oxidation & reduction and the role of electron transfer in ATP synthesis • discuss the role of NAD+ and FAD in electron transfer and discuss how the oxidation of NADH at the electron transport chain results in ATP synthesis

4. Discuss standard reduction potential and its relationship to electron donor, electron acceptor, and exergonic reactions

5. Describe the role of enzymes in the catalysis of biological reactions (include in the discussion substrate, product, active site, lock and key model, activation energy, enzyme-substrate complex, and transition state complex, and steps of enzyme action)

6. Discuss the factors that influence enzyme action?

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Answer 1

ANS 6- FACTORS THAT INFLUENCE ENZYME ACTION-

Enzymes are the bio-catalyst that works to accelerate the rate of reaction in a particular reaction.

• The activity of an enzymes are influenced by serveral factors such as Temperature,water, specific pH value, substrate concentration, enzyme concentration,presence of inhibitors,activators effect, light and radiations effect.

(1) Specific (pH) vaule --> enzymes active on a specific pH,and every enzyme is having its optimum pH value where the velocity of a reaction is maximum. change in ph value will results in enzyme inactivation.

examples-

• Pepsin (digestive enzyme)show highest acitivity at the acidic pH.
• Trypsin (digestive enzyme)shows highest activity in an alkaline medium.
• Diastase shows its optimum activity in neutral medium.

(2) Temperature-->specific(normal) temperature(30 degree- 45 degree) is required for the optimum activity of an enzyme, if the temperature gets very low around 10- 20 degree, it will leads to the decrease in activity of an enzyme and if the temperature goes very high around 60-70 degree it will leads to the denaturation of an enzyme, so it is neccessary to maintaine the normal temperature value.

(3) Enzyme concentration-->Small amount of enzyme is sufficient for the large amount of substrate,this is because of the extraordinary catalytic power of an enzymes.As the concentration of an enzymes will increase it will also causes the increase in a rate of reaction because higher concentration of enzymes reduces the effect of inhibitors and apart of that increased number of enzyme molecules consist of more active sites.

(4) Presence of Inhibitors--> Inhibitors are the proteins that causes the reduction in the  activity of an enzymes,inhibitors are less affective when concentration of an ezymes is higher. Different types of inhibitors are present such as-

1. Non-competitive inhibitors->those inhibitors that binds the enzymes somwehere other than active site and modifies the conformation of an enzyme in order to prevent the catalyzation of reaction.
2. Uncompetitive inhibitors-->In this inhibitors only bind to enzyme-substrate complex in order to stop enzyme from reacting with substrate to form product.
3. competitive inhibitors-->In this inhibitors compete with substrate for the single binding site of an enzyme.

(5) Effect of Activators-->Some additional molecules are required by some enzymes for their optimum activity these molecules known as prosthetic group or co-factors ,prosthetic groups are inorganic metal ions(Mg2+,Cu2+,Na+) or complex organic vitamin dervatives(NAD,FAD), these molecules regulate the overall enzymatic activity.

(6) Light and radiations effect--> Presence of light is very important for the optimum activity of some enzymes, example:In Photoreaction DNA repair system photolyase enzyme is envolved which required presence of light for its optimum enzymatic activity.

• Sometimes,enzymes activity is reduced due to effect of radiations such as X rays , $\beta$ and $\gamma$ rays.

(7) Substrate concentration--> Higher the substrate concentration results in higher the activity of an enzyme until all the active sites of an enzyme molecule are saturated with the substrate.

• Higher concentration of a substrate will also leads to nullification of competitive inhibitors effects in a medium.