All Free Biology MCQs with Answers

4231. Which of the following sugar is mainly present in human blood?

• A. Glucose
• B. Sucrose
• C. Fructose
• D. Mannose

Explanation: Glucose is required for essential processes such as respiration, hence it is the main sugar present in blood. In non-diabetic individuals, the concentration of glucose in the blood is about 0.08%

4232. Which of the following is an amino acid and part of phospholipids?

• A. Serine
• B. Choline
• C. Ethanolamine
• D. Aspartic acid

Explanation: Serine and aspartic acids are examples of amino acids, while choline and ethanolamine are Nz-containing bases. Serine can be a constituent of phospholipids and can act as a nitrogenous base.

4233. What is the myelin sheath of a neuron composed of?

• A. Sphingolipids
• B. Choline
• C. Ethanolamine
• D. Waxes

Explanation: The myelin sheath of neurons is composed of sphingolipids. Ethanolamine and choline are nitrogenous bases found in phospholipids while axes are abundantly found in protective covering of fruits and leaves.

4234. How many double bonds are present in the R group of oleic acid?

• A. 4
• B. 6
• C. 2
• D. 1

Explanation: Oleic acid is an example of a mono-unsaturated fatty acid having a single double bond between C9 and C10.

4235. Which of the following fatty acids is least likely to be found in waxes?

• A. Stearic acid
• B. Acetic acid
• C. Oleic acid
• D. Palmitic acid

Explanation: Chemically, waxes are mixtures of long chain alkanes (with an odd number of carbon atoms ranging from 25 to 35), alcohols, ketones and esters

4236. Which of the following does not form a biopolymer?

• A. Amino acid
• B. Fatty acid
• C. Nucleotides
• D. Monosaccharides

Explanation: Amino acids join to form proteins. Nucleotides join to form nucleic acid, while monosaccharides join to form polysaccharides.

4237. How many oxygen atoms can Haemoglobin carry?

• A. 4
• B. 8
• C. 2
• D. 1

Explanation: Hemoglobin consists of 4 polypeptide chains and there is one haem group in each chain which can hold one oxygen molecule (two atoms), thus one hemoglobin molecule can carry eight oxygen atoms.

4238. How many kinds of amino acids are present in the cell?

• A. 170
• B. 20
• C. 25
• D. 3000

Explanation: Around 170 amino acids are found to be present in living cells and tissues. Out of these amino acids, only 20 are the components of proteins.

4239. Which of the following amino acids is next to glycine with respect to molecular structure?

• A. Alanine
• B. Serine
• C. Ethanolamine
• D. Aspartic acid

Explanation: The simplest amino acid is glycine in which R is a 'H' atom. Alanine is next to glycine which contains -CH3 as its R-group.

4240. A globular protein consisting of more than one polypeptide chains belongs to:

• A. Primary structure
• B. Secondary structure
• C. Tertiary structure
• D. Quaternary structure

Explanation: In many complex proteins, polypeptide tertiary chains are aggregated and held together by hydrophobic interactions, hydrogen and ionic bonds. This specific arrangement is the quaternary structure. Quaternary structure refers to when 2 or more polypeptide chains are joined together in a protein.