prokaryotic cells, gram staining

Question 1

What are prokaryotic cells?

Answer 1

Prokaryotic cells are single-celled organisms that lack a nucleus and membrane-bound organelles. Examples include bacteria and archaea.

Question 2

What is the genetic material like in prokaryotic cells?

Answer 2

Prokaryotic cells contain a single, circular strand of DNA located in a region called the nucleoid, which is not enclosed by a membrane.

Question 3

What is a plasmid in prokaryotic cells?

Answer 3

A plasmid is a small, circular piece of DNA found in some prokaryotic cells, separate from the chromosomal DNA, and can replicate independently.

Question 4

Do prokaryotic cells have ribosomes?

Answer 4

Yes, prokaryotic cells have ribosomes, but they are smaller (70S) than eukaryotic ribosomes (80S), and they function in protein synthesis.

Question 5

What is the function of the prokaryotic cell wall?

Answer 5

The prokaryotic cell wall provides structural support and protection. In bacteria, it is primarily made of peptidoglycan.

Question 6

What are flagella in prokaryotes?

Answer 6

Flagella are long, whip-like structures that enable motility in some prokaryotic cells, allowing them to move towards nutrients or away from harmful substances.

Question 7

What are pili in prokaryotes?

Answer 7

Pili are hair-like structures on the surface of some prokaryotic cells that help in attachment to surfaces and in the exchange of genetic material during conjugation.

Question 8

How do prokaryotic cells reproduce?

Answer 8

Prokaryotic cells reproduce asexually through a process called binary fission, where the cell divides into two genetically identical cells.

Question 9

What is the difference between prokaryotic and eukaryotic cells?

Answer 9

Prokaryotic cells lack a nucleus and membrane-bound organelles, are generally smaller, and have circular DNA, while eukaryotic cells have a nucleus, organelles, and linear DNA.

Question 10

What is the role of the capsule in some prokaryotic cells?

Answer 10

The capsule is an outer layer found in some bacteria, providing extra protection against environmental stress and helping to evade immune responses.

Question 11

What is Gram staining?

Answer 11

Gram staining is a laboratory technique used to differentiate bacteria into Gram-positive and Gram-negative groups based on their cell wall structure.

Question 12

What color do Gram-positive bacteria appear after Gram staining?

Answer 12

Gram-positive bacteria appear purple or violet because their thick peptidoglycan layer retains the crystal violet stain.

Question 13

What color do Gram-negative bacteria appear after Gram staining?

Answer 13

Gram-negative bacteria appear pink or red after Gram staining because their thinner peptidoglycan layer does not retain the crystal violet stain, and instead, they take up the safranin counterstain.

Question 14

What is the key difference in the cell walls of Gram-positive and Gram-negative bacteria?

Answer 14

Gram-positive bacteria have a thick peptidoglycan layer and no outer membrane, while Gram-negative bacteria have a thin peptidoglycan layer and an outer membrane containing lipopolysaccharides.

Question 15

What are the four main steps in the Gram staining process?

Answer 15

1. Application of crystal violet (primary stain)
2. Application of iodine (mordant)
3. Alcohol or acetone wash (decolorization)
4. Application of safranin (counterstain).

Question 16

What role does iodine play in Gram staining?

Answer 16

Iodine acts as a mordant, forming a complex with the crystal violet, which helps the dye adhere more strongly to the peptidoglycan layer in Gram-positive bacteria.

Question 17

Why is the alcohol or acetone step important in Gram staining?

Answer 17

Alcohol or acetone is used to decolorize the cells. It dissolves the outer membrane of Gram-negative bacteria, allowing the crystal violet to be washed away, while Gram-positive bacteria retain the violet stain.

Question 18

What is the purpose of the counterstain (safranin) in Gram staining?

Answer 18

The counterstain, safranin, is used to color Gram-negative bacteria pink or red after decolorization, providing contrast to the violet-stained Gram-positive bacteria.

Question 19

Why are Gram-negative bacteria typically more resistant to antibiotics?

Answer 19

Gram-negative bacteria have an outer membrane that acts as a barrier to many antibiotics, making them more resistant compared to Gram-positive bacteria.

Question 20

What can Gram staining reveal about bacterial infections?

Answer 20

Gram staining helps identify the type of bacteria causing an infection, guiding the selection of appropriate antibiotics based on whether the bacteria are Gram-positive or Gram-negative.