Free Biodiversity and Variety of Life MCQs with Answers

2141. Which type of bacteria has less amount of lipids in them:

• A. Positive bacteria
• B. Negative bacteria
• C. Gram-negative
• D. Gram-positive

Explanation: Gram-positive bacteria have a thick peptidoglycan layer and no outer lipid membrane which gives a positive result in the gram stain test appearing purple. Gram-negative bacteria have a thin peptidoglycan layer and an outer lipid membrane that appears pink.

2142. In nitrogen-fixing bacteria, the nitrogenase complex is sensitive to:

• A. O2
• B. CO2
• C. NO2
• D. NO3

Explanation: Nitrogen fixing bacteria contain an enzyme complex known as Nitrogenase which catalyses the conversion of nitrogen gas to ammonia. The nitrogenase complex is sensitive to oxygen. Oxygen will make the enzyme irreversibly inactive. So, the nitrogen-fixing bacteria needs to protect the nitrogenase enzyme from oxygen.

2143. Sulphur bacteria belongs to which group of bacteria called

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

Explanation: Sulfur bacteria belongs to gamma-proteo bacteria which take part in nitrogen and sulfur cycling processes

2144. In humans the disease symptoms develop during the:

• A. Log phase
• B. Lag phase
• C. Growth phase
• D. Decline phase

Explanation: Bacterial cells divide at exponential rate during log phase, hence disease symptoms become prominent during this phase.

2145. If one of the following components is missing , bacteria can not increase the number of its plasmid copies.

• A. Antibiotic resistance gene
• B. Origin of replication
• C. Cloning site
• D. Ligases enzymes

Explanation: An essential feature of bacterial plasmids is their ability to replicate as autonomous genetic elements in a controlled way within the host. Therefore, they can be used to explore the mechanisms involved in DNA replication and to analyze the different strategies that couple DNA replication to other critical events in the cell cycle therefore they can replicate to increase the number of plasmid.

2146. If in solution some bacteria infected by a certain phages had somehow developed the ability to make a particular amino acid that was not in their genes before. What would be the possible explanation to his new ability ?

• A. Induction
• B. Transformation
• C. Transduction
• D. Conjugation

Explanation: Transduction is the process by which a virus transfers genetic material from one bacterium to another. Viruses called bacteriophages are able to infect bacterial cells and use them as hosts to make more viruses with new genes.

2147. During the sterilization process, in order to control pathogens, we use dry heat that causes?

• A. Oxidation of bacterial compounds
• B. Coagulation of bacterial proteins
• C. Separate the bacteria from their media
• D. Decrease in bacterial growth

Explanation: Is correct as During the sterilization process, oxidation of bacterial compounds can occur due to the exposure of bacteria to various sterilizing agents or conditions In all sterilization methods, the oxidative damage to bacterial compounds occurs through the transfer of electrons, resulting in the formation of reactive oxygen species. These reactive species can react with essential biomolecules, causing structural changes, functional disruption, and ultimately leading to bacterial cell death.

2148. Photosythetic bacteria have the ablilty to release:

• A. Sulphur
• B. Oxygen
• C. Hydrogen
• D. Carbon dioxide

Explanation: The following are the chemical equations of photosynthesis in photosynthetic bacteria;

2149. For sterilization purposes, generally, X-rays are used which cause:

• A. Mutation in bacterial genome
• B. Denaturation of bacterial proteins
• C. Activation of bacteria
• D. Bacteria to become pathogen

Explanation: A is the most suitable option since X-rays do cause mutations in bacterial genomes and prevent them from dividing. Ionizing radiation such as X-rays and gamma rays can easily penetrate most tissues, and kill bacteria by causing irreparable DNA damage. Many Gram-negative bacteria such as E. coli, and Salmonella.

2150. The plasma membrane of eukaryotes differs from that of bacteria in having:

• A. Steroid
• B. Respiratory enzymes
• C. Cholesterol
• D. Phospholipids

Explanation: Cholesterol (or other higher sterols such as ergosterol and phytosterols) is universally present in large amounts (20-40 mol%) in eukaryotic plasma membranes, whereas it is universally absent in the membranes of prokaryotes.