Question 1

Which bacterial structure may survive if temperatures applied during food preservation processes are too low?

Accepted Answer

Endospores are highly resistant structures that some bacteria can form as a protective mechanism in response to harsh environmental conditions, such as high temperatures or lack of nutrients. Endospores can survive extreme heat, cold, radiation, and chemicals, including many of the food preservation methods used by the food industry, such as boiling, baking, fermentation, salting, and drying. Therefore, if temperatures applied during food preservation processes are too low to kill vegetative cells, endospores may remain viable and can germinate into active cells once favorable conditions are restored. Flagella, plasma membranes, and ribosomes are essential structures for bacterial motility, metabolism, and protein synthesis, respectively, but they are usually more sensitive to external stressors and may be damaged or disrupted by low temperatures or other preservation methods.

Question 2

A new protein has been described that transports a growth factor across the plasma membrane.This protein is most likely a/an:

Accepted Answer

Integral membrane proteins are embedded within the lipid bilayer and can span the entire membrane, with parts facing both the extracellular and cytoplasmic sides. Since this protein transports a growth factor across the plasma membrane, it needs to be able to interact with molecules on both sides of the membrane, making it likely to be an integral membrane protein. Peripheral membrane proteins are typically located on the cytoplasmic side of the membrane and do not span the entire membrane, making it less likely that this protein is a peripheral membrane protein. Cytoplasmic proteins are located inside the cell and do not interact with the plasma membrane directly, ruling out option D.

Question 3

Endotoxic shock,resulting from the release of endotoxin by bacteria infecting a patient,is only caused by Gram-negative bacteria.

Accepted Answer

Endotoxin is a component of the cell wall of Gram-negative bacteria, which is released upon bacterial death or during infection. Endotoxic shock is a severe systemic reaction to endotoxin and is only caused by Gram-negative bacteria. Gram-positive bacteria do not have endotoxin in their cell walls.

Question 4

You have been studying the effect of a concentration gradient on the rate of transport of a nutrient into a bacterial cell.If a carrier protein is involved in the transport of this nutrient,which curve would you expect to see?

Accepted Answer

The answer of You have been studying the effect of...

Question 5

Which of the following contribute to the environmental resistance of bacterial endospores?

Accepted Answer

All of the choices contribute to the environmental resistance of bacterial endospores. The spore coat protects the endospore from harmful agents, the low water content prevents metabolic activity, the presence of calcium dipicolinate aids in heat and chemical resistance, and a lower pH can inhibit bacterial growth.

Question 6

The original differentiation of prokaryotes and eukaryotes was based on structures found in prokaryotes that are lacking in eukaryotes.

Accepted Answer

The original differentiation of prokaryotes and eukaryotes was based on structures found in eukaryotes that are lacking in prokaryotes, such as a nucleus, membrane-bound organelles, and cytoskeleton.

Question 7

Endospores are reproductive structures.

Accepted Answer

Endospores are not reproductive structures; they are dormant, tough, and non-reproductive structures formed by certain bacteria to survive in harsh conditions.

Question 8

Predict the change in surface area and volume of a spherical cell if the diameter of the cell doubles:

Accepted Answer

The formula for the surface area of a sphere is 4πr^2, where r is the radius of the sphere. When the diameter of the sphere doubles, its radius will also double. So, the new surface area will be:

4π(2r)^2 = 4π(4r^2) = 16πr^2

This is four times the original surface area, so the surface area will increase by a factor of 4.

The formula for the volume of a sphere is (4/3)πr^3. When the diameter of the sphere doubles, its radius will also double. So, the new volume will be:

(4/3)π(2r)^3 = (4/3)π(8r^3) = (32/3)πr^3

This is eight times the original volume, so the volume will increase by a factor of 8.

Therefore, the correct answer is A.

Quiz 3: Bacterial Cell Structure