MCAT Physical Biological Sciences Practice Test 5

Question – 1

1. What is the correct IUPAC name for the following compound?

  • A. 2-Methyl-2-bromobutanone

  • B. (S)-2-Bromo-2-ethylcyclobutanone

  • C. (R)-2-Bromo-1-ethyl-2-cyclobutanone

  • D. (S)-1-Bromo-1-ethyl-2-cyclobutanone

  • E. (R)-1-Bromo-1-ethyl-2-cyclobutanone

  • Answer:B

  • Answer Explanation:For naming the compound, keto group gets higher priority than other carbon atoms. For naming (R, S) notation of chiral carbon, bromine atom gets higher priority than keto group, because of its atom mass. Since, the highest priority group is on below the plane. So, it gets S-configuration and it is named as (S)-2-Bromo-2-ethylcyclobutanone.

Question – 2

2. Which of the following nitrogen base replaces thymine in an RNA molecule?

  • A. Guanine

  • B. Uracil

  • C. Adenine

  • D. Cytosine

  • E. All of the above

  • Answer:B

  • Answer Explanation:In an RNA molecule, thymine is replaced by uracil. Uracil is a pyrimidine derivative that binds to adenine via two hydrogen bonds. Adenine, Guanine, Cytosine and Uracil are the nitrogen bases present in an RNA molecule.

Question – 3

3. The visible physical characteristics of an organism are termed as

  • A. Allelelomorph

  • B. Somite

  • C. Genotype

  • D. Phenotype

  • E. None of the above

  • Answer:D

  • Answer Explanation:The observable physical characteristics such as morphology, biochemical properties etc., which are developed from the gene expression and environmental influence, are called phenotype. The genetic makeup of an individual is called genotype.

Question – 4

4. Predict the major product of the following reaction.

  • A. Propanaldehyde

  • B. Propanoic acid

  • C. Acetaldehyde

  • D. Acetic acid

  • E. Pyruvic acid

  • Answer:D

  • Answer Explanation:The first step of the reaction is the addition of water to alkynes in presence of an acid catalyst. Terminal alkynes are less reactive than the internal alkynes. So, mercury ion is added to the acidic solution to increase the rate of addition of water to alkyne. The product of the reaction is an enol, which tautomerize to a carbonyl compound. The second step of the reaction is an oxidation process. The aldehyde formed is oxidized to carboxylic acid by potassium dichromate-sulphuric acid mixture. The reaction as follows.

Question – 5

5. Which of the following is a secondary consumer?

  • A. Cow

  • B. Rabbit

  • C. Grass hopper

  • D. Lizard

  • E. None of the above

  • Answer:D

  • Answer Explanation:Secondary consumers are the animals that feed on smaller plant eating animals in the food chain. Lizard is an example for secondary consumer. Cow, rabbit and grass hopper are examples for primary consumers as they feed on producers.

Question – 6

6. Which of the following figures represents rotational motion?

  • A. A

  • B. B

  • C. C

  • D. Both A and B

  • E. Both B and C

  • Answer:B

  • Answer Explanation:A body is said to be in rotational motion if it is rotating with some angular velocity in rad/s. The figure A is moving in forward direction with linear velocity of 10 m/s. Hence, a is incorrect. Body in the figure B is rotating with angular velocity 2 rad/s and so, b is the correct option. Again in figure C, body is moving in forward direction with linear velocity of 10 m/s. Hence, c is incorrect.

Question – 7

7. Which of the following is an RNA virus?

  • A. TMV

  • B. Poliovirus

  • C. Adenovirus

  • D. SV-40

  • E. Both a and b

  • Answer:E

  • Answer Explanation:Both tobacco mosaic virus and poliovirus are RNA viruses i.e. their genome is made of ribonucleic acid. Adenovirus and SV-40 have double stranded DNA as their genetic material.

Question – 8

8. Which of the following has the more acidic character?

  • A. Phenol

  • B. 4-Nitro phenol

  • C. 4-Methyl phenol

  • D. 4-Hydroxy benzonitrile

  • E. 4-Hydroxy benzaldehyde

  • Answer:B

  • Answer Explanation:The acid strength of phenols depends on the nature of the substituent attached with it. Electron withdrawing groups increases the acid strength. Electron releasing groups decreases the acid strength. Here, the phenol attached with three different withdrawinggroups, in that nitro group has the more withdrawing nature than the other substituent. Therefore, 4- nitro phenol will be more acidic than the rest of the molecules.

Question – 9

9. Which of the following genes codes for a repressor molecule?

  • A. Regulator gene

  • B. Operator gene

  • C. Structural gene

  • D. Both b and c

  • E. a, b and c

  • Answer:A

  • Answer Explanation:The regulator gene codes for the repressor molecule.A repressor is a DNA-binding protein that turns off the expression of one or more genes. The repressor binds to the operator and blocks the attachment of RNA polymerase to the promoter and thus prevents transcription of genes. The operator gene serves as a starting point for reading the genetic code and controls the activity of structural genes through interaction with a repressor. Structural gene describes the amino acid sequence of polypeptide chain.

Question – 10

10. An object having moment of inertia I spins with angular momentum L. What will be its kinetic energy?.

  • A.

  • B.

  • C.

  • D.

  • E.

  • Answer:D

  • Answer Explanation:We have been given moment of inertia and angular momentum. Angular momentum is given asL = I??WhereL is the angular momentum;I is the moment of inertia;?? is the angular velocity;Since, angular momentum = L and moment of inertia = I, angular velocity becomes?? =
    LI———-(1)Kinetic energy for rotational motion is given asKE =


    ??2—————(2)Putting the value of from 1 in 2 we get

    12I(LI )2Or, KE =

    L 22IHence, d is the correct answer option.

Question – 11

11. A group of organisms that occupy the same position in food chain or ecological pyramid with similar feeding mode is called

  • A. Food web

  • B. Food chain

  • C. Trophic level

  • D. Primary consumers

  • E. Producers

  • Answer:C

  • Answer Explanation:A trophic level is made up of organisms that occupy the same position in food chain or ecological pyramid with similar feeding mode. For example: all green plants form the first trophic level as they produce their own food. Herbivores and carnivores are not included in this trophic level as they depend on green plants and herbivores respectively.

Question – 12

12. Choose the correct order of aromaticity.

  • A. I > II > III

  • B. II > III > I

  • C. III > I > II

  • D. III > II > I

  • E. I = II = III

  • Answer:C

  • Answer Explanation:Aromaticity order of these compounds depends on the eletronegativity value of oxygen, nitrogen and sulfur. Among the three, oxygen is more electronegative than nitrogen and sulfur. Because of this thiophene has more resonance energy than pyrrole than furan.

Question – 13

13. Which of the following enzymes is involved to separate the double strands of DNA?

  • A. Topoisomerase

  • B. Helicase

  • C. Primase

  • D. DNA polymerase

  • E. None of the above

  • Answer:B

  • Answer Explanation:Helicase is an enzyme that separates the double strands DNA. Helicase are involved in many cellular processes such DNA replication, recombination, DNA repair etc.

Question – 14

14. Which of the following has the highest electron affinity?

  • A. Chlorine

  • B. Iodine

  • C. Oxygen

  • D. Fluorine

  • E. Bromine

  • Answer:A

  • Answer Explanation:In periodic table halogens have high electron affinity than the rest of the groups. In halogens, the electron affinity of chlorine, bromine and iodine decreases as the size of the element increases. However, the electron affinity of fluorine is lower than that of chlorine due to the small size.As a result, inter electronic forces increase in the 2p orbital which prevents the income of a new electron into orbital.

Question – 15

15. Which of the following metals is responsible for Itai-itai disease?

  • A. Arsenic

  • B. Cadmium

  • C. Lead

  • D. Mercury

  • E. Uranium

  • Answer:B

  • Answer Explanation:Itai-itai is a disease caused by cadmium poisoning. The symptoms of the disease include weak and brittle bones. The disease is initially characterized by spinal and leg bone pain. It also includes complications like kidney failure.

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