All Free Biology MCQs with Answers

4261. Antibodies are actually:

• A. Globular proteins
• B. Glycoproteins
• C. Fibrous proteins
• D. Both Options A and B are correct

Explanation: An antibody, also known as an immunoglobulin, is a large Y-shaped globular protein produced mainly by plasma cells and is used by the immune system to neutralize pathogens such as pathogenic bacteria and viruses.

4262. In an amino acid, in which the R-group is H, its name will be:

• A. Alanine
• B. Glycine
• C. Leucine
• D. Valine

Explanation: R-group in amino acid may be a hydrogen atom as in glycine, or CH3, as in alanine, or any other group. So amino acids mainly differ due to the type and nature of R group.

4263. Fatty acids are the organic compounds containing hydrogen, oxygen and one of the following are:

• A. -COOH
• B. -NH
• C. Acyl
• D. Sucrose

Explanation: Generally, a fatty acid consists of a straight chain of an even number of carbon atoms with hydrogen atoms along the length of the chain and at one end of the chain and a carboxyl group at the other end. It is that carboxyl group that makes it an acid (carboxylic acid).

4264. The combination of a pentose sugar with a base result in a compound known as:

• A. Nucleotide
• B. Nucleoside
• C. Nucleic Acid
• D. Polynucleotide

Explanation: The compound formed by a combination of a base and a pentose sugar is called nucleoside,A nucleoside and a phosphoric acid combine to form a nucleotide. Nucleotides join to form polynucleotides. Nucleic acid is made up of polynucleotide.

4265. Which of the following bases is absent in DNA?

• A. Uracil
• B. Thymine
• C. Cytosine
• D. Adenine

Explanation: Adenine, guanine, and cytosine are the N2 containing bases present in both DNA and RNA. Uracil is present in RNA and absent in DNA while thymine is present in DNA, and absent in RNA.

4266. Carbohydrates are organic molecules and contain three elements:

• A. Carbon, water and oxygen
• B. Carbon, Sulphur and hydrogen
• C. Carbon, calcium and hydrogen
• D. Carbon, hydrogen and oxygen

Explanation: The word carbohydrate literally means hydrated carbons. They are composed of carbon, hydrogen, and oxygen and the ratio of hydrogen and oxygen is the same as in water.

4267. Which of the following substances are intermediates in respiration and photosynthesis both?

• A. Ribose and Heptulose
• B. Phosphoglyceraldehyde and Dihydroxyacetone phosphate
• C. Glucose and Galactose
• D. Fructose and Ribulose

Explanation: Phosphoglyceraldehyde and Dihydroxyacetone phosphate are isomers. They are formed during glycolysis in photosynthesis when Fructose 1,6 bisphosphate breaks down into interconvertible molecules Phosphoglyceraldehyde and Dihydroxyacetone phosphate. Also, Phosphoglyceraldehyde (Glyceraldehyde-3-Phosphate) is an intermediate in the Calvin cycle of photosynthesis

4268. Which of the following components is found in the cell wall of fungi?

• A. Cellulose
• B. Chitin
• C. Proteins
• D. Glycerol

Explanation: Chitin is a structural polysaccharide found in cell walls of fungi and made up of N-acetyl glucosamine subunits, while cell walls of plants are made up of cellulose.

4269. Which of the following is an unsaturated fatty acid?

• A. Acetic Acid
• B. Butyric acid
• C. Oleic acid
• D. Palmitic acid

Explanation: Fatty acid may contain no double bond (saturated fatty acids) or up to 6 double bonds (unsaturated fatty acids). Oleic acid is an example of unsaturated fatty acid and has one double bond between C9 and C16.

4270. Which of the following combinations of base pair is absent in DNA?

• A. A-T
• B. C-G
• C. A-U
• D. T-A

Explanation: In RNA, nitrogenous bases form the usual complementary pairing, via cytosine (C) with guanine (G) and uracil (U) with adenine (A). In DNA, adenine (A) pairs up with a thymine (T) nitrogenous base instead of uracil (U).