BIO303 Final Term Current Paper Spring 2021 by Amaan Khan

BIO 303 Current Final Term Spring 2021

Q1. Define pH and write its equation and what is the pH of water at 25°C? 2 Marks

The pH of a solution is defined as the logarithm to the base 10 of the reciprocal of the [H+], i. e, the negative logarithm of the [H+]

• pH = log 1/[H+]
• = -log[H+]

The pH of water at 25°C, in which H+ and OH– ions are present in equal numbers, is 7.0

• pH = -log[1 x 10-7]= 7

Q2. Competitive Inhibition? 2 Marks

that site.

Q3. 5 types of chemical reactions in biological system. 3 Marks

The reactions going on in biological systems can be categorized into 5 types:

1. Reactions that make-or-break carbon-carbon bonds
2. Internal rearrangements, isomerizations, and eliminations
3. Free-radical reactions
4. Group transfer
5. Oxidation-reduction reactions

Q4. Difference between Oxidation and Reduction? 2 Marks

Oxidation

• Addition of oxygen
• loss of electrons
• Loss of hydrogen

Reduction

• Removal of oxygen
• Gain of electrons
• Gain of hydrogen

Q5. Enone. 2 Marks

An enone, also called an α, β-unsaturated carbonyl, is a type of organic compound consisting of an alkene conjugated to a ketone. The simplest enone is methyl vinyl ketone or CH₂=CHCOCH₃.

Q6. Competitive Inhibition and Noncompetitive Inhibition. 3 Marks

Competitive Inhibition

that site. Reversible inhibitors bind to enzymes through non covalent bonds.

Noncompetitive Inhibition

Inhibitors bind enzymes at sites distinct from the substrate binding site and generally bear little or no structural resemblance to the substrate. Noncompetitive inhibition cannot be overcome by increasing the concentration of substrate.

Q7. What is Equilibrium constant (K)? 3 Marks

The composition of a reacting system tends to continue changing until equilibrium is reached. At the equilibrium concentration of reactants and products, the rates of the forward and reverse reactions are exactly equal and no further net change occurs in the system.

Q8. Why pure water passes electric current? 2 Marks

Pure water carries electrical current as H3O+ migrates toward the cathode and OHtoward the anode.

Q9. What is competitive inhibitor Effect of Competitive Inhibition on Vmax? 5 Marks

enzyme.

1. Effect on Vmax

• The effect of a competitive inhibitor is reversed by increasing [S].
• At a sufficiently high substrate concentration, the reaction velocity reaches the Vmax as observed in the absence of inhibitor.
• When [S] far exceeds [I], the probability that an inhibitor molecule will bind to the enzyme is minimized and the reaction exhibits a normal Vmax.
• Therefore, a competitive inhibitor does not decrease Vmax

Q10. What is entropy? 2 Marks

Entropy is a quantitative expression for the randomness or disorder in a system. When the products of a reaction are less complex and more disordered than the reactants, the reaction is