Bacteria and Disease

What is the composition of the bacterial cell wall?

• Only cellulose

• Peptidoglycan, a combined carbohydrate-protein

• Only protein

• Only lipid

Answer explanation

The bacterial cell wall is primarily composed of peptidoglycan, which is a complex structure made of carbohydrates and proteins. This distinguishes it from plant cell walls, which contain cellulose.

What is the main difference between bacteria and viruses in terms of genetic material?

• Bacteria have only RNA, viruses have only DNA

• Bacteria have both DNA and RNA, viruses have either DNA or RNA

• Bacteria have either DNA or RNA, viruses have both

• Both have only DNA

Answer explanation

Bacteria contain both DNA and RNA as part of their cellular structure, while viruses can have either DNA or RNA as their genetic material, but not both. Thus, the correct choice highlights this distinction.

What is the unit of measurement for the size of viruses?

• Micrometers (µm)

• Nanometers (nm)

• Millimeters (mm)

• Centimeters (cm)

Answer explanation

Viruses are typically measured in nanometers (nm), as they are much smaller than cells. Micrometers (µm) are too large for viruses, while millimeters (mm) and centimeters (cm) are even larger units not applicable to their size.

Which of the following is a correct pair of bacterial shape and description?

• Cocci - rod-shaped

• Bacilli - spherical

• Spirilla - twisted cells

• Vibrio - cluster forming

Answer explanation

The correct pair is 'Spirilla - twisted cells'. Spirilla are characterized by their spiral or twisted shape, while the other options incorrectly describe the shapes of cocci, bacilli, and vibrio.

Which of the following is NOT a way bacteria can be arranged?

• Singly

• In pairs

• In clusters

• In filaments

Answer explanation

Bacteria can be arranged singly, in pairs, or in clusters. However, they do not typically form filaments, making 'in filaments' the correct answer as it is NOT a common arrangement for bacteria.

Which of the following statements is true about viruses?

• Viruses are living things that can reproduce by themselves.

• Viruses are not living things and cannot reproduce by themselves.

• Viruses can reproduce without infecting a host cell.

• Viruses contain both DNA and RNA at the same time.

Answer explanation

Viruses are not considered living things because they cannot carry out metabolic processes independently. They require a host cell to reproduce, making the statement that they can reproduce by themselves false.

Which process allows new virus particles to leave the host cell?

• Budding from the host cell

• Integration with host DNA

• Binding to the receptor site

• Uncoating of viral RNA

Answer explanation

Budding from the host cell is the process by which new virus particles exit the host. This allows the virus to spread and infect other cells, while integration, binding, and uncoating are steps in the viral life cycle but do not facilitate exit.

Which of the following is NOT an example of a protective reflex?

• Sneezing

• Coughing

• Vomiting

• Sweating

Answer explanation

Sweating is a thermoregulatory response, not a protective reflex. In contrast, sneezing, coughing, and vomiting are reflex actions that help expel irritants or harmful substances from the body.

What is the role of heparin in the inflammatory response?

• Increases blood flow

• Prevents clotting

• Attracts phagocytes

• Stimulates pain receptors

Answer explanation

Heparin plays a crucial role in the inflammatory response by preventing clotting. This allows for increased blood flow and the movement of immune cells to the site of inflammation, facilitating the healing process.

What is the first step in the inflammatory response when the skin is broken?

• Attraction of phagocytes

• Activation of mast cells

• Release of pus

• Tissue repair by mitosis

Answer explanation

The first step in the inflammatory response is the activation of mast cells. They release histamine and other chemicals that increase blood flow and attract immune cells to the site of injury.