All Free Biology MCQs with Answers

2231. Peptide bond is_____________?

• A. C-N link
• B. C- O lind
• C. N-H link
• D. C-H link

Explanation: A peptide bond is the covalent C-N bond formed between the carbonyl carbon of one amino acid and the nitrogen of another during condensation. Students may choose the N-H link because an amino group contains N-H bonds, but those bonds are not the linkage joining two amino acids in a peptide chain.

2232. The one which is not a globular protein__________?

• A. Anti Rh-antibody
• B. Enzyme
• C. Myosin
• D. Haemoglobin

Explanation: Myosin is a long, filamentous structural and motor protein, so it is classified as a fibrous protein rather than a globular protein. Students may choose an enzyme, but enzymes generally fold into compact globular shapes, as do antibodies and haemoglobin.

2233. Primary structure of proteins determines__________?

• A. Number of polypeptide chains involved
• B. Bending of polypeptide chains
• C. Amino acid sequence
• D. Coiling of polypeptide chains

Explanation: The primary structure of a protein is the exact linear sequence of its amino acids, joined by peptide bonds. Coiling and bending describe higher levels of structure, so students may incorrectly choose coiling of polypeptide chains.

2234. Variety among amino acids is produced due to_____________?

• A. NH2 group
• B. COOH group
• C. R group
• D. All of these

Explanation: All standard amino acids have an amino group and a carboxyl group, but their variable R groups differ and produce their chemical variety. The likely alternative is “all of these,” which confuses groups shared by amino acids with the group responsible for their differences.

2235. _________ is a condition characterized by an abnormal inability to see in dim light or at night.

• A. Nyctalopia
• B. Myopia
• C. Hyperopia
• D. All of the above

Explanation: Nyctalopia, or night blindness, is difficulty seeing in dim light and is commonly associated with inadequate vitamin A or impaired rod-cell function. Students may choose myopia or hyperopia because both affect vision, but they are focusing defects rather than inability to see at night.

2236. Circular disc shaped structure with a round hole is ___________ ?

• A. Iris
• B. Pupil
• C. Horoid coat
• D. Ciliary body

Explanation: The iris is a circular muscular diaphragm containing a central opening called the pupil, and it regulates the amount of light entering the eye. The pupil itself is only the opening, not the disc-shaped structure, so students may choose pupil after focusing on the phrase “round hole.”

2237. Sperms of liverworts, mosses, ferns move towards archegonia, in response to uncleic acid released by the ovum. This is an example of ____________?

• A. Chemotropic movement
• B. Chemotactic movement
• C. Chemosastic movement
• D. Haptonastic movement

Explanation: Chemotaxis is the directed movement of a cell in response to a chemical substance, as sperm move toward chemicals released by the ovum. Chemotropism refers to directional growth of a plant organ, so option a is a common mistake caused by confusing cell movement with growth movement.

2238. Receptors for hearing come under heading of___________?

• A. Chemical
• B. Mechanical
• C. Photo
• D. Nociceptors

Explanation: Hearing receptors respond to mechanical vibrations produced by sound waves, so they are mechanoreceptors. Students may choose chemical receptors because the receptor cells use chemical synapses, but the stimulus detected is mechanical movement, not a chemical substance.

2239. Any change in the environment of an organism is called___________?

• A. Stimulus
• B. Variation
• C. Response
• D. Reaction

Explanation: A stimulus is any detectable change in the internal or external environment, such as light, temperature, pressure, or a chemical change. Variation means a difference in characteristics, while response is the organism's reaction to the stimulus, so choosing either confuses the cause with the result.

2240. Which of the following are responsible for the detection of changes in environment?

• A. Receptors
• B. Neurons
• C. Effectors
• D. All of these

Explanation: Receptors detect changes in the environment and convert them into nerve impulses or other signals. Neurons transmit those signals and effectors carry out the response, so choosing either of them confuses detection with transmission or action.