Most Repeated MDCAT Biology: Kingdom Prokaryote MCQs

Explanation

E. coli (Escherichia coli) is a type of bacteria, which is a prokaryote. Prokaryotes are single-celled organisms that lack a true nucleus and other membrane-bound organelles. They have a simple cell structure and are typically small in size.

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.

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.

Explanation

This is the correct answer. Dry heat is a method of sterilization that involves exposing microorganisms, including bacteria, to high temperatures in a dry environment. This process causes the oxidation of the constituents of the bacterial cell wall, leading to cell death.Therefore, dry heat is the method that primarily causes the oxidation of the constituents of a bacterial cell wall.

Explanation

A bacterium with a single polar flagellum is classified as Monotrichous. This means that the flagellum is located at one end (pole) of the bacterial cell.

Explanation

The capsule is an additional covering that surrounds the cell wall of some bacteria, providing protection against:- Phagocytosis (engulfment by host cells)- Desiccation (drying out)- Antibiotics and other antimicrobial agentsThe capsule is composed of polysaccharides (complex sugars) and can be found in both Gram-positive and Gram-negative bacteria.

Explanation

The capsule is an additional covering that surrounds the cell wall of some bacteria, providing protection against:- Phagocytosis (engulfment by host cells)- Desiccation (drying out)- Antibiotics and other antimicrobial agentsThe capsule is composed of polysaccharides (complex sugars) and can be found in both Gram-positive and Gram-negative bacteria.

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.

Explanation

Numerous strategies exist in bacteria to cope with stressful conditions including the formation of endospores. An endospore is a dormant, tough, non-reproductive structure produced by a small number of bacteria from the Firmicute family. The primary function of most endospores is to ensure the survival of a bacterium through periods of environmental stress.

Explanation

The log phase, also known as the exponential phase, is the stage of bacterial growth where the cells divide at an exponential rate. During this phase, the bacterial population doubles at a constant rate, resulting in a rapid increase in cells number.