All Free Biology MCQs with Answers

• A. Staphylococci
• B. Pseudomonas
• C. Diplococcus pneumoniae
• D. Mycoplasmas

Explanation: The correct option is D: Mycoplasmas. These bacteria are distinctive in lacking a cell wall, which makes them naturally resistant to…

• A. Aerotolerant anaerobe
• B. Facultative anaerobe
• C. Obligate aerobe
• D. Obligate anaerobe

Explanation: Obligate anaerobes are organisms that cannot survive in the presence of oxygen as they lack the necessary enzymes to process it, making…

• A. Bacteria contain plasma membranes that are made up of triglycerides
• B. Gram staining reveals that bacteria contain cell walls, but no cell membranes
• C. Bacteria do not contain a membrane-bound nucleus, but they contain an non membrane-bound region called the nucleoid
• D. All of these options are false

Explanation: Option A: All cells including bacteria contain cell membrane but it is not made up of triglycerides.Option B: Gram staining tells us about…

• A. Cilia
• B. Flagella
• C. Pili
• D. Pseudopodia

Explanation: The correct answer is Flagella. Flagella are the main organelles for motility in bacteria, allowing them to swim through liquid…

• A. Plasmid
• B. Nucleoid
• C. Mesosomes
• D. All of these

Explanation: Plasmids are small, circular, double-stranded DNA molecules that are separate from the bacterial chromosomal DNA, often harboring genes…

• A. Gram-positive bacteria
• B. Gram-negative bacteria
• C. Chemo-synthetic bacteria
• D. None of the above

Explanation: Pili are filamentous structures primarily found on gram-negative bacteria.

• A. Nuclear body
• B. Nuclear region
• C. Nucleoid
• D. All of the Above

Explanation: The correct term for the chromatin body in prokaryotes is 'nucleoid'. This is the specific region within the cytoplasm where the genetic…

• A. Gram-positive bacteria have more lipids in their cell wall
• B. Gram-negative bacteria have more lipids in their cell wall
• C. Lipids are absent in the cell wall of both gram-positive and gram-negative bacteria
• D. Both have equal amounts of lipids

Explanation: Gram-negative bacteria have a unique cell wall structure that includes an outer membrane rich in lipopolysaccharides (LPS), leading to a…

• A. Beta-proteobacteria
• B. Alpha-proteobacteria
• C. Gamma-proteobacteria
• D. Delta-proteobacteria

Explanation: The correct answer is Gamma-proteobacteria. This group includes sulfur bacteria that oxidize hydrogen sulfide (H2S) to obtain energy…

• A. Archaeobacteria
• B. Eubacteria
• C. Mycoplasma
• D. Cyanobacteria

Explanation: Mycoplasmas are unique among prokaryotes due to their lack of a cell wall, which gives them flexibility and resistance to certain…

• A. 0.5-1.5
• B. 2.0-4.0
• C. 1.1-1.5
• D. 2.0-6.0

Explanation: The correct diameter range for E. coli is 1.1-1.5 micrometers, as E. coli cells are typically around this size.

• A. Bacilli
• B. Staphylobacillus
• C. Bacillus
• D. Diplobacilli

Explanation: The correct answer is Bacillus. A single rod-shaped bacterium is known as a bacillus.

• A. Heterotrophic bacteria
• B. Chemosynthetic bacteria
• C. Saprophytic bacteria
• D. Parasitic bacteria

Explanation: Nitrifying bacteria are the examples of chemosynthetic bacteria. Nitrifying bacteria are a group of bacteria that plays a crucial role in…

• A. Chitin
• B. Cellulose
• C. Peptidoglycan
• D. Pectin

Explanation: A cell wall is defined as a rigid external layer that is specifically designed to provide structural support and rigidity.Diagram:

• A. A specific organism can always be found associated with a disease
• B. The organism cannot be isolated and grown in a pure culture in the laboratory
• C. The pure culture will produce the disease when innoculated into a suscepticle animal
• D. It is possible to recover the organisms in pure culture from an experimentally infected animal

Explanation: The germ theory of disease states that some diseases are caused by microorganisms.

• A. E.Coli
• B. Staphylococci and Streptococci
• C. Spirochetes
• D. Epulophiscuim fishelsoni

Explanation: Staphylococci and Streptococci are 0.75 - 1.25n in diameter. The average size of staphylococci and streptococci can vary slightly…

• A. Flagella
• B. Pilli
• C. Cilia
• D. Microtubules

Explanation: Flagella are long, whip-like structures that many microorganisms, including bacteria and some single-celled eukaryotes, use for…

• A. Bacteria
• B. Fungi Cell
• C. Algae
• D. Cortex cells

Explanation: The description of a cell wall containing polysaccharide chains linked with short chains of amino acids is characteristic of bacterial…

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

Explanation: Rod-shaped bacteria are known as bacilli. They are one of the two main shapes of bacteria, the other being cocci (spherical bacteria).

• A. Gram-positive
• B. Gram positive & Gram negative
• C. Gram-negative
• D. Capsule

Explanation: If lipopolysaccharides (LPS) did not appear in the wall of bacteria on staining, it would be known as Gram-positive bacteria.