Biochemistry Makeup CAT (Past Paper, Set 1)

15 clinical MCQs in Biochemistry. If two electrons (i) and (ii) in an atom are described by the quantum numbers shown below;. Kenya, Africa and global r...

Questions, Answers & Explanations

1. Q1. If two electrons (i) and (ii) in an atom are described by the quantum numbers shown below; n l ml ms --- --- ---- ---- (i) 4 1 1 +½ (ii) 3 1 1 -½ Select one:

   • They have the same magnetic spin
   • They are located in different p-orbitals
   • They have same energy levels
   • All the above are true
   • They are located in different d orbitals

   Answer: They have the same magnetic spin

2. Q2. In the molecule H-S-D the proton (H) is; Select one:

   • easily lost when S and D are equal in electronegativity
   • None of the other choices is true
   • easily lost when D is much more electronegative than S
   • Remains unchanged when D is replaced by a more electronegative element
   • easily lost when D is a Methyl group

   Answer: easily lost when S and D are equal in electronegativity

3. Q3. Chiral, or optical, isomers have the same chemical formula but differ in their three dimensional molecular structure and their Select one:

   • interaction with polarized light
   • number of carbon bonds
   • configuration around carbon-carbon double bond
   • interaction with carbon
   • interaction with a catalyst

   Answer: interaction with polarized light

4. Q4. If chemical analysis of a sample of DNA shows that 20% of the bases present are Guanine, what percentage would be Thymine? Select one:

   • 20%
   • 30%
   • 40%
   • 80%
   • 10%

   Answer: 20%

5. Q5. Salt dissolves well in water because water molecules

   • form hydrogen bonds with the positively and negatively charged ions
   • are larger than the salt molecules
   • share electrons with the ions to make polar covalent bonds
   • surround the ions because of their charge but do not form hydrogen bonds
   • make nonpolar covalent bonds with the positively charged ions only

   Answer: form hydrogen bonds with the positively and negatively charged ions

6. Q6. Expansion of octet

   • None of the other choices is true
   • is quite common in Period 2 elements
   • accounts for the existence of Boron trifluoride (BF₃)
   • account for SF₄
   • account for PCl₃

   Answer: None of the other choices is true

7. Q7. The normal pH of normal human urine ranges from 4.6 to 8.0, what is the hydrogen ion concentration range for normal human urine?

   • 2.5 x 10-5 to 1 x 10-8
   • 2.5 x 10-2 to 1 x 10-6
   • 2.5 x 10-6 to 1 x 10-9
   • 2.5 x 10-3 to 1 x 10-7
   • 2.5 x 10-4 to 1 x 10-8

   Answer: 2.5 x 10-5 to 1 x 10-8

8. Q8. The following elements are paramagnetic, except;

   • are always hydrocarbons.
   • are all constitutional isomers.
   • may also be classified as tautomers
   • each differ from its nearest neighbors by 14 amu.
   • may have identical physical and chemical properties.

   Answer: are always hydrocarbons.

9. Q9. The major dietary carbohydrates includes

   • Sucrose, lactose, starch and cellulose.
   • Sucrose, lactose, galactose and glycogen.
   • Glucose, fructose, galactose and ribose.
   • Glucose, fructose, mannose and deoxyribose.
   • Glycogen, starch, cellulose, glucose

   Answer: Sucrose, lactose, starch and cellulose.

10. Q10. Which of the following pairs would be the best buffer at pH 10.0?

    • H2CO3 and NaHCO3 (pKas are 3.77 and 10.4)
    • Acetic acid and sodium acetate (pKa = 4.76)
    • Sodium succinate and succinic acid (pKa = 4.21)
    • Lactic acid and sodium lactate (pKa = 3.86)
    • NaH2PO4 and Na2HPO4 (pKas are 2.1, 7.2, 12.4)

    Answer: H2CO3 and NaHCO3 (pKas are 3.77 and 10.4)

11. Q11. The solubility of alcohols in water

    • Increases as the carbon chain length increases.
    • Is due to H- bonding between alcohol and water molecules
    • Increases with increasing molecular mass.
    • Increases there alcohol proof
    • Decreases as the number of --OH groups present increases.

    Answer: Increases as the carbon chain length increases.

12. Q12. Rank the following bonds in order of increasing bond strength.

    • van der Waals, hydrogen bond, ionic, covalent single bond
    • Ionic, covalent single bond, van-der Waals, hydrogen bond
    • Covalent single bond, van der Waals, ionic, hydrogen bond
    • van der Waals, ionic, hydrogen bond, covalent single bond
    • Ionic, hydrogen bond, van der Waals, covalent single bond

    Answer: van der Waals, hydrogen bond, ionic, covalent single bond

13. Q13. Magnetic quantum number Select one:

    • takes the value of plus or minus ½ only
    • determines the orbitals
    • none of the other choices is true
    • determines the shape of orbital
    • is independent of angular momentum quantum number

    Answer: takes the value of plus or minus ½ only

14. Q14. Which one is true? Select one:

    • II is the least acidic
    • V is more acidic than IV
    • I is the most acidic
    • III is less acidic than I
    • IV is more acidic than II

    Answer: II is the least acidic

15. Q15. Repulsions between electron pairs on a central atom is Select one:

    • lowest between lone pairs
    • greatest between lone pairs
    • greatest between lone pair-bonding pairs
    • lowest between bonding and lone pairs
    • greatest between bonding pairs

    Answer: lowest between lone pairs