All Free Biology MCQs with Answers

2171. prokaryotic and eukaryotic are two types of___________?

• A. cells
• B. tissues
• C. organs
• D. organisms

Explanation: Prokaryotic and eukaryotic are the two major types of cells, distinguished mainly by the presence or absence of a membrane-bound nucleus. Choosing organisms is less precise because organisms may be prokaryotic or eukaryotic, but the terms directly classify their cells.

2172. in which cell ribosome are of large size and present either on endoplasmic reticulum or free in cytoplasm?

• A. prokaryotic
• B. eukaryotic
• C. both
• D. all the above

Explanation: Eukaryotic cells have larger 80S ribosomes, either attached to rough endoplasmic reticulum or free in the cytoplasm. Prokaryotes have smaller 70S ribosomes and do not possess endoplasmic reticulum, so “both” is incorrect.

2173. Gram positive bacteria appear_______________?

• A. Purple
• B. Red
• C. Pink
• D. Blue

Explanation: Gram-positive bacteria retain the crystal violet-iodine complex because their thick peptidoglycan wall is not effectively decolorised, so they appear purple under the microscope. Students may choose red or pink by recalling the colour of Gram-negative bacteria after the counterstain instead.

2174. Cell wass of Archaeobacteria does not contain_____________________?

• A. Peptidoglycan
• B. Proteins
• C. Glycoproteins
• D. Polysaccharides

Explanation: Archaeobacterial cell walls lack peptidoglycan, the characteristic polymer of ordinary bacterial cell walls; they may instead contain proteins, glycoproteins or other polysaccharides. Students may choose proteins or glycoproteins because archaeal walls can contain these materials, but those are not universally absent.

2175. Cell wall is absent in___________?

• A. Cocci
• B. Bacilli
• C. Mycobacterium
• D. Mycoplasma

Explanation: Mycoplasma lacks a cell wall and is surrounded mainly by a plasma membrane containing sterols, making it naturally resistant to antibiotics that target peptidoglycan. Students may choose Mycobacterium because its wall is unusual and waxy, but it still possesses a cell wall.

2176. Which of the following structure primarily helps in attachment of bacteria on various surfaces____________?

• A. Flagella
• B. Pili
• C. Both of these
• D. None of these

Explanation: Pili, especially short fimbriae, help bacteria attach to host cells and other surfaces by means of specific surface-binding proteins. Students may choose flagella because they are prominent external structures, but flagella primarily provide motility rather than firm attachment.

2177. Flagella originate from_______________?

• A. Cell membrane
• B. Cell wall
• C. Capsule
• D. Basal body

Explanation: A bacterial flagellum is anchored in the envelope by a basal body, which connects the hook and filament to the cell and acts as part of the rotary motor. Students may choose the cell membrane because the basal body crosses it and receives energy from the membrane, but the flagellum originates structurally from the basal body.

2178. A bacterium with tuft of flagella at both poles is called_____________?

• A. Lophotrichus
• B. Monotrichous
• C. Peritrichous
• D. Amphitrichous

Explanation: A bacterium with tufts of flagella at both poles is amphitrichous, since “amphi” indicates both ends. Students may choose lophotrichous because that term also describes a tuft of flagella, but lophotrichous refers to a tuft at one pole rather than at both poles.

2179. Which of the following bacteria do not have flagella commonly__________?

• A. Cocci
• B. Bacilli
• C. Streptobacilli
• D. Vibrio

Explanation: Cocci are spherical bacteria and are commonly non-motile, so they usually lack flagella, although exceptions exist. Students may choose bacilli because rod-shaped bacteria can also be non-motile, but many bacilli and vibrios commonly possess flagella.

2180. Which of the following contains genes for drug and disease resistance in bacteria?

• A. Necleotide
• B. Plasmid
• C. Mesosome
• D. Ribosome

Explanation: Plasmids are small, usually circular DNA molecules that replicate independently of the bacterial chromosome and may carry genes for antibiotic resistance and other advantageous traits. Students may choose the nucleoid or “necleotide” because genetic material is associated with it, but resistance genes are often carried on plasmids.