Question

22. pH = and is an indicator of ; the the pH, the higher the concentration of protons in a solution.

A) [A–]/[AH], density; higher

B) –log [H+], acidity; lower

C) –log [OH–], alkalinity; lower

D) pKa, alkalinity, higher

E) None of the above

23. What is the proportion of H2N–CH2–COO– / + H3N–CH2–COO– at pKa2 (9.6)?

A) 100%/0%

B) 75%/25%

C) 50%/50%

D) 25%/75%

E) 0%/100%

24. Are all enzymes proteins?

A) Yes, of course! What kind of question is that?

B) No. Actually, the coenzymes and cofactors are the molecules that catalyze biological reactions.

C) No. Ribozymes depend on RNA for their catalytic activity.

D) No. DNA can repair itself due to intrinsic catalytic activity.

E) None of the above.

25. Find the incorrect statement regarding the dalton (Da) unit:

A) 1 u (unified atomic mass unit) = 1 dalton (Da)

B) 1 Da = 1.66 X 10–24 g

C) 1 Da = 1/12 the mass of 12C

D) A molecule of human insulin has a mass of 5,808 Da. This can be represented as 5.8 kilodaltons (kDa).

E) None of the above

26. Briefly describe what is an ultracentrifuge. Compare and contrast an ultracentrifuge with a clinical centrifuge in terms of capabilities and applications.

27. Why do polar substances such as NaCl dissolve so readily in water?

A) NaCl is a very dry powder, and the water is able to soak into the salt.

B) The sodium ions repel the negative end of the water molecule.

C) Spheres of hydration form between the water and the ions.

D) The charged ends of the water molecules are able to surround the oppositely charged salt ion.

E) both C and D

28. When bound to certain atoms, hydrogen can form a special type of bond. The following is correct regarding hydrogen bonds:

A) In order to form a hydrogen bond, H must be bound to a more electronegative element such as O or N.

B) Hydrogen bonds are non-covalent.

C) Hydrogen bonds are weaker but numerous so they contribute to stabilize the structure of molecules such as proteins.

D) All of the above.

E) None of the above.

Answer 1

22) B. -log[H+] , Acidity, Lower

pH=-log[H+] is the indicator of acidity. Lower is the pH , higher the concentration of protons in the solution.

Explanation: The pH is used to denoted the concentration of the protons in a solution or mixture. As it is a negative logarithmic of H+ concentration, the higher the H+ concentration is, lower is the value of pH.

It is important to note that the pH is not an absolute value. It can change with temperature and other physical and environmental conditions of the experiment and calculation.