Free Biodiversity and Variety of Life MCQs with Answers

2271. Bacterial cell wall made up of:

• A. Cellulose & pectin
• B. Cellulose & cutin
• C. Hemicellulose & chitin
• D. Amino acid & sugar

Explanation: Amino acids and sugar is correct.Cell-wall of bacteria is totally different from ordinary plant cell-wall. It is chemically complex and made up of amino acids, sugar and chitin but cellulose is totally missing. The cell-wall of most bacteria have unique macromolecule called peptidoglycan. It is composed of long glycan chains cross-linked with peptide fragments. In addition sugar molecules, teichoic acid, lipoprotein and lipopolysaccharides are also present.STB- Pg 102.

2272. Membranous infoldings in bacteria that initiate DNA replication is:

• A. Mesosomes
• B. Peroxisomes
• C. Glyoxysomes
• D. Nucleosomes

Explanation: Mesosomes are invaginations of the cell membrane into the cytoplasm. Mesosomes are in the form of vesicles, tubules, or lamellae. Their function is to help in DNA replication, cell division, respiration, and the export of enzymes.Hence, Option A is correct.STB Pg 102.

2273. Mesosomes are the invaginations of which bacterial cell structure?

• A. Cell Wall
• B. Cell Membrane
• C. Plasmid
• D. Cysts

Explanation: Mesosomes were once thought to be infoldings of the plasma membrane found in some bacteria, particularly Gram-positive species, and were believed to play roles in cell division, respiration, DNA replication, and nutrient absorption by increasing the surface area of the cell membrane. They were hypothesized to help anchor the cell division machinery, contain respiratory enzymes, and assist in organizing the bacterial chromosome during replication. However, subsequent research has demonstrated that mesosomes are artifacts resulting from chemical fixation techniques used during electron microscopy sample preparation. Therefore, they are not considered part of the natural structure of bacterial cells.

2274. Function of pilus in bacteria is to:

• A. Increase pathogenicity of bacteria
• B. Degrade host plasma membrane
• C. Degrade host enzymes
• D. Exchange of genetic material

Explanation: Pili (singular: pilus) arehair-like appendages found on the surface of some bacterial cells. One of the primary functions of pili is to facilitate the exchange of genetic material between bacterial cells, a process known as bacterial conjugation.Role of pili in bacterial conjugation- Pili act as a bridge between two bacterial cells, allowing for direct cell-to-cell contact.- The pilus of one bacterium attaches to a receptor on the surface of another bacterium.- The attached bacteria then form a conjugation bridge, allowing for the transfer of genetic material, such as plasmids.

2275. The number of layers of cell wall in Gram-positive bacteria is:

• A. 1
• B. 2
• C. 3
• D. 4

Explanation: In Gram-positive bacteria, there is only one major layer in the cell wall, while Gram-negative bacteria have two major layers in the cell wall.

2276. Bacterial cell have ability to maintain its shape through :

• A. Cell wall
• B. Capsule
• C. Cell wall & slime
• D. Slime

Explanation: The bacterial cell wall is a rigid structure that provides structural support and helps maintain the shape of the bacterial cell. It is responsible for giving bacteria their characteristic shapes, such as rod-shaped (bacilli), spherical (cocci), or spiral (spirilla), and it also plays a role in protecting the cell from osmotic pressure changes.The capsule (option B) and slime (option D) are not primarily responsible for maintaining the cell shape but may have other functions, such as protecting the cell or aiding in adhesion. Option C mentions both the cell wall and slime, but the cell wall is the primary component responsible for shape maintenance.

2277. Which of the following is an example of spiral-shaped bacteria?

• A. Diplococcus pneumoniae
• B. Hyphomicrobium
• C. Escherichia coil
• D. Pseudomonas

Explanation: Hyphomicrobium is a genus of bacteria that exhibits a spiral or helical shape. It is known for its spiral or curved rod morphology. The other options, Diplococcus pneumoniae (Option A), Escherichia coli (Option C), and Pseudomonas (Option D), do not typically exhibit a spiral shape; they have different bacterial morphologies.

2278. All the following are disinfectants to control bacterial growth except:

• A. Tincture of Iodine
• B. Potassium Permanganate
• C. Mercuric Chloride
• D. Hydrogen Peroxide

Explanation: **Tincture of iodine** (option A) is not typically used as a disinfectant to control bacterial growth. Tincture of iodine is more commonly used as an antiseptic for disinfecting skin or mucous membranes. It contains iodine dissolved in alcohol and is often used for wound care or as a preoperative skin disinfectant.The other options, **Mercuric Chloride** (Option C), **Potassium Permanganate** (Option B), and **Hydrogen Peroxide** (Option D), can be used as disinfectants to control bacterial growth in various settings. They are more commonly employed for this purpose.

2279. Number of major layer/layers of cell wall in gram positive bacteria is/are:

• A. 1
• B. 2
• C. 3
• D. 4

Explanation: In Gram-positive bacteria, there is only one major layer in the cell wall while hgram negative bacteria has two major layers.

2280. The capsule of a bacterial cell is a sticky gelatinous structure made up of protein and:

• A. Lipids
• B. Carbohydrates
• C. Nucleotide
• D. Alcohol

Explanation: Option B is correct.The capsule of a bacterial cell is a sticky gelatinous structure made up of carbohydrates. The capsule is a layer of polysaccharide material that surrounds the cell wall of some bacteria. It is composed of repeating units of sugar molecules. The capsule is a dynamic structure that can be produced or shed by the bacteria in response to environmental conditions. The capsule has a number of functions, including: Protecting the bacteria from dehydration Helping the bacteria to adhere to surfaces Evasion of the host immune system Some bacteria, such as Streptococcus pneumoniae, have a thick capsule that is essential for their virulence. The capsule protects the bacteria from phagocytosis, a process by which white blood cells engulf and destroy bacteria. The other options are not components of the bacterial capsule: Lipids are a type of organic molecule that is made up of fatty acids and glycerol. They are found in the cell membrane and other cellular structures. Nucleotides are the building blocks of DNA and RNA. Nucleotides are joined together by phosphodiester bonds to form DNA and RNA molecules. The order of the nucleotides in DNA and RNA determines the genetic code. Alcohols are a type of organic molecule that contains a hydroxyl group (OH). They are found in a variety of foods and beverages.