Sindh Mdcat Exclusive Course Chemistry Biochemistry — Solved MCQs

Question 1

Which of the following bond is responsible for joining the amino acids in proteins?

Accepted Answer

A. Peptide Bond — Option A is correct, as within a protein chain, each amino acid is linked to each other by a peptide bond which is a covalent bond.Options B and D describe those bonds that hold proteins in their complex three dimensional structures, but the question asks for the bond that holds individual amino acids within proteins.Option C describes a metallic bond which is only found in metals, and not in proteins as it is molecular in nature.

Question 2

Enzymes that are functioning within the cell are called:

Accepted Answer

A. Endoenzymes — Enzymes that function within the cell are called endoenzymes, out of the cell are called exoenzymes. Holoenzyme is the biochemically active part of an enzyme.

Question 3

Monosaccharides contain _ carbon atoms.

Accepted Answer

B. 3-10 — Monosaccharides can contain carbon atoms ranging from 3-10.

Question 4

Which of the following is correct about Ascorbic acid?

Accepted Answer

E. All of these answers — All the options are correct.

Question 5

The normal pH of blood is:

Accepted Answer

C. 7.35 — Our blood has a normal pH range of 7.35 to 7.45. This means that blood is naturally slightly alkaline or basic.

Question 6

Amylopectin has _ linkage.

Accepted Answer

C. α 1-4 and 1 - 6 glycosidic — Amylopectin has both α 1-4 and 1 - 6 glycosidic bond linkages.

Question 7

Which one is not a monosaccharide?

Accepted Answer

D. Lactose — Lactose is not a monosaccharide but a disaccharide,as shown below:

Question 8

Based on the physico-chemical properties, proteins may be classified into the following types:

Accepted Answer

D. All of the above — Proteins can be classified as: (a) Simple proteins. (b) Conjugated proteins. (c) Derived proteins.

Question 9

L - Asparaginase enzyme has been used for the treatment of:

Accepted Answer

B. Blood cancer — L-asparaginase is an enzyme that has been used in the treatment of certain types of cancer, particularly acute lymphoblastic leukemia. L-asparaginase works by depleting levels of the amino acid asparagine in the blood. Cancer cells, unlike normal cells, are unable to synthesize their own asparagine and rely on external sources. By depleting asparagine, L-asparaginase interferes with the growth and survival of cancer cells, ultimately leading to their death.

Question 10

Sucrose is a non reducing sugar because?

Accepted Answer

E. Both a and b — A sugar that serves as a reducing agent due to its free aldehyde or ketone functional groups in its molecular structure. Sucrose is a non-reducing sugar because the two monosaccharide units are held together by a glycosidic linkage between C1 of α-glucose and C2 of β-fructose. Sucrose has no aldehyde or ketone group to reduce Fehling's solution , so both options A and B are true. Hence the correct option is E

Question 11

A dipolar charged but overall electrically neutral ion is called:

Accepted Answer

A. Zwitterion — A zwitterion is an ion that contains two functional groups. In simple terms, it is an ion possessing both positive and negative electrical charges. Therefore, zwitterions are mostly electrically neutral (the net formal charge is usually zero). So option A is the correct answer.

Question 12

Alanine, lysine and tryptophan are:

Accepted Answer

D. Amino acids — All the three named compounds(lysine, alanine and Tryptophan) are amino acids in nature. However, Alanine is neutral Alpha-amino acid. Lysine is a basic amino acid. Tryptophan is also a neutral amino acid.

Question 13

The energy produced by 1g of carbohydrate is:

Accepted Answer

B. 4.2 kcal — Carbohydrates, proteins and fats in the foods provide energy for the body functions and physical activities. They, however, do not have same energy content. The following is the energy-content by respective nutrients:1 gram of carbohydrates- 4kcal1 gram of protein- 4 kcal1 gram of fats- 9 kcalSo, the correct answer is '4.2 kcal'

Question 14

Ferritin deposits iron in spleen. It is an example of:

Accepted Answer

C. Storage protein — Ferritin are actually the stores of iron that are utilized when the serum iron depletes.

Question 15

Starch is a polymer of:

Accepted Answer

B. d-D- Glucose (d=alpha) — Starch is constituted by α-D-glucose units, which can be organized to form two distinct molecules, amylose and amylopectin. Use the image below to help recall:

Question 16

Which of the following is NOT a fatty acid?

Accepted Answer

A. Phenyl acetic acid — Fatty acids are a group of heterogeneous compounds that consist of a long aliphatic alkyl chain which may be saturated or unsaturated and a terminal carboxylic acid functional group.Phenyl acetic acid consists of an aromatic benzene ring bonded with the carboxylic acid group. Therefore, it does not qualify to be categorised as a fatty acid. Hence option A is correct.Option B,C and D are all examples of fatty acids and their structures conform to the definition of fatty acids as shown:

Question 17

According to Watson and Crick’s model of DNA, the DNA molecule consists of a double helix. What type of forces are responsible to keep two strands of DNA together?

Accepted Answer

C. Hydrogen bonding — The bases in each complementary base pair have hydrogen bonds between them, which keeps the two strands together and stable. 'A' and 'T' have 2 hydrogen bonds between them, while 'G' and 'C' have three hydrogen bonds between them. The answer is C, as the other options do not mention hydrogen bonding.

Question 18

Fats are a type of lipid called glycerides. They are esters of long chain carboxylic acids:

Accepted Answer

B. Propane-1, 2, 3-triol — The correct term for the compound is "Propane-1, 2, 3-triol."Fats, also known as triglycerides, are esters formed from glycerol (propane-1,2,3-triol) and three fatty acid molecules. Glycerol is a triol, meaning it has three hydroxyl (OH) groups. When esterified with fatty acids, these hydroxyl groups react with the carboxyl groups (-COOH) of the fatty acids, forming ester bonds. Therefore, the compound "Propane-1, 2, 3-triol" is the correct chemical name for glycerol, which is a component of fats.

Question 19

Which one of the following bases is NOT present in RNA?

Accepted Answer

C. Thyamine — The base "Thymine" (T) is not present in RNA. Instead, RNA contains the base "Uracil" (U). Thyamine is a nucleotide base found in DNA but not in RNA. In DNA, thymine pairs with adenine through two hydrogen bonds, forming a T-A base pair.

Question 20

The amino acids which largely exist in dipolar ionic form are:

Accepted Answer

D. Alpha amino acids — α-amino acids exist as dipolar ions or zwitter ions.

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