All Free Biology MCQs with Answers

4511. Proteins are;

• A. Homopolymer
• B. Heteropolymer
• C. Homogenous mixture of amino acids
• D. Heterogeneous mixture of amino acids

Explanation: Proteins are considered heteropolymers. A heteropolymer refers to a polymer composed of different types of monomers. In the case of proteins, they are made up of a wide variety of amino acids. There are 20 different types of amino acids commonly found in proteins, each with its own unique chemical properties. These amino acids can be arranged in different sequences within the protein chain, giving rise to the diverse structures and functions of proteins. Therefore, proteins are heteropolymers due to the presence of multiple types of amino acids.

4512. The given structure of protein is maintained by which of the following bonds?

• A. Hydrogen bonds only
• B. Hydrogen bonds and ionic bonds only
• C. Hydrogen bonds , ionic bonds and hydrophobic interactions
• D. Hydrogen bonds, ionic bonds and disulphide bonds

Explanation: In addition to hydrogen bonds and ionic bonds, disulfide bonds are another important type of bond involved in maintaining the tertiary structure of proteins. Disulfide bonds form between two cysteine residues through oxidation of their sulfhydryl (-SH) groups. These covalent bonds provide stability and structural integrity to the protein, particularly in extracellular proteins exposed to an oxidizing environment. Disulfide bonds can significantly affect the folding and functional properties of proteins.

4513. Haemoglobin is a protein present in blood and helps in transportation of oxygen. It is made up of four chains, two alpha and two beta chains. Myoglobin is another protein similar to haemoglobin. It is present in muscle cells and helps in storage of oxygen. Identify the correct structures of haemoglobin and myoglobin respectively:

• A. Quaternary, Quaternary
• B. Quaternary, Tertiary
• C. Tertiary, Secondary
• D. Secondary, Quaternary

Explanation: Haemoglobin has a quaternary structure because it is composed of four protein chains (two alpha chains and two beta chains) that interact and assemble to form the functional haemoglobin molecule. The arrangement and interactions of these subunits are essential for haemoglobin's oxygen-carrying function. Myoglobin, on the other hand, has a tertiary structure. The tertiary structure refers to the folding of a single polypeptide chain into a three-dimensional structure. Myoglobin consists of a single polypeptide chain that folds upon itself, forming a compact structure that allows it to bind and store oxygen in muscles.

4514. Given nucleotide is most energetic at point:

• A. A
• B. B
• C. C
• D. D

Explanation: The nucleotide is most energetic at point D because it is in the form of ATP, which contains three phosphate groups. The bonds between these phosphate groups store significant energy, which is released during hydrolysis. Option A is incorrect as a nucleoside has no phosphate groups and thus lacks stored energy. Option B is incorrect because AMP, with one phosphate group, is less energetic than ATP. Option C is incorrect as ADP, with two phosphate groups, has less stored energy compared to ATP.

4515. If a DNA has a total of 50 nucleotides with 15 adenines. How many sets of triple bonds are present?

• A. 15
• B. 10
• C. 30
• D. 20

Explanation: In DNA, the base pairing between adenine (A) and thymine (T) is established by two hydrogen bonds, while the base pairing between cytosine (C) and guanine (G) is established by three hydrogen bonds. Given that there are 15 adenines in the DNA, it means that there are also 15 thymines since A always pairs with T, which sums up to a total of 30 nucleotides.From the remaining 20 (50-30) nucleotides, the number of guanine and cytosine should be equal, which is 10-10.Each one forms one set of three hydrogen bonds with the other which means there will be 10 sets of three hydrogen bonds between guanine and cytosine. This is a tough question and has been added to help you fully prepare you for the AKU test.

4516. Most polysaccharides are composed of chains of condensed

• A. Cellulose units
• B. Hexose units
• C. Pentose units
• D. Sucrose units

Explanation: The correct answer is hexose units. Most polysaccharides are comprised of hexose units like glucose, which is a six-carbon sugar. These hexose sugars link together to form complex carbohydrates such as starch, cellulose, and glycogen. Option A is incorrect because cellulose is itself a polysaccharide and not a basic subunit. Option C is incorrect because pentose units are typically found in nucleic acids rather than polysaccharides. Option D is incorrect because sucrose is a disaccharide, composed of glucose and fructose, and is not a building block of polysaccharides.

4517. Despite gaining complete glucose, plants store fructose in ripening fruits because, in comparison to glucose, fructose is:

• A. More sweet
• B. Release more energy at the time of oxidation
• C. More stable for oxidation
• D. Occupy less space

Explanation: Fructose is indeed sweeter than glucose, so storing it in ripening fruits enhances their sweetness, making them more attractive to animals for seed dispersal.The correct answer is A (More Sweet). Storing fructose in ripening fruits enhances their sweetness, making them more appealing to animals for seed dispersal.

4518. Which of the following chemical characteristics is not common to all living beings?

• A. Similar triplet code for amino acids
• B. Energy is stored by high phosphate bonds
• C. Type of protein present in the body
• D. Ribosomes are the sites of protein synthesis

Explanation: This is the correct answer. The type of proteins present in the body can vary among different organisms. While the basic structure of proteins is conserved, specific proteins can differ across species. The correct answer is C (Type of Protein Present in the Body). The specific proteins present in the body can vary among different living beings, reflecting their unique genetic makeup and functional adaptations.

4519. Pick the incorrect statement.

• A. Sucrose is a disaccharide
• B. Uracil is a pyrimidine
• C. Glycine is a sulphur-containing amino acid
• D. Cellulose is a polysaccharide

Explanation: This statement is incorrect. Glycine is the simplest amino acid and does not contain sulphur in its structure.So, the incorrect statement is option C: "Glycine is a sulphur-containing amino acid."

4520. How many fatty acid molecules are normally present in a fat or oil molecule?

• A. 1
• B. 2
• C. 3
• D. 4

Explanation: The correct answer is 3. A typical fat or oil molecule is known as a triglyceride, which is composed of a glycerol backbone attached to three fatty acid molecules. Option A (1) and Option B (2) are incorrect because they do not reflect the structure of triglycerides. Option D (4) is incorrect as it exceeds the standard three fatty acids found in triglycerides.