16 Questions
What happens to crystal violet in Gram-negative bacteria during Gram staining?
It is easily rinsed away
What is the primary component of the peptidoglycan layer in Gram-negative bacteria?
Peptidoglycan
What is the function of the capsule in Gram-negative bacteria?
To protect against phagocytosis
What is a characteristic of the cell wall of Gram-negative bacteria?
Thin peptidoglycan layer
What is a component of the outer membrane of Gram-negative bacteria?
Porins
What traps crystal violet in Gram-positive bacteria?
Peptidoglycan
What is the main component of the cell wall in Gram-positive bacteria?
Peptidoglycan
What is the function of the capsule in bacteria?
To hinder phagocytosis
What is the purpose of Gram staining?
To determine the type of bacterial cell wall
What is the outermost layer of Gram-negative bacteria?
Outer membrane
What is the main component of the cell wall in Gram-positive bacteria?
Peptidoglycan
What is the function of the capsule in many prokaryotes?
To enable prokaryotes to adhere to their substrate or to other individuals in a colony
What is the typical size of the Gram-staining unit?
10 μm
What is the outermost layer of the Gram-negative bacterial cell wall?
Outer membrane
What is the main component of the Gram-negative bacterial cell wall?
Lipopolysaccharide
What is the primary function of the peptidoglycan layer in Gram-positive bacteria?
To provide structural support to the cell
Study Notes
Gram Staining
- Gram-positive bacteria: peptidoglycan traps crystal violet, resulting in a purple color.
- Gram-negative bacteria: crystal violet is easily rinsed away, revealing a red color.
Cell-Surface Structures of Bacteria
- Cell wall consists of peptidoglycan (also known as murein) layer.
- Outer membrane is present in Gram-negative bacteria.
- Cell wall is 10 μm in thickness.
- Capsule: a polysaccharide or protein layer that covers many prokaryotes, enabling them to adhere to their substrate or to other individuals in a colony.
Key Differences between Gram-Positive and Gram-Negative Bacteria
- Presence of outer membrane: Gram-negative bacteria have an outer membrane, while Gram-positive bacteria do not.
- Peptidoglycan layer: Gram-positive bacteria have a thick peptidoglycan layer, while Gram-negative bacteria have a thin peptidoglycan layer.
- Lipopolysaccharide: Gram-negative bacteria have a lipopolysaccharide layer in their outer membrane, which is not present in Gram-positive bacteria.
This quiz deals with the staining process of gram-negative bacteria, where crystal violet is easily rinsed away, revealing red dye. Understand the characteristics and identification of gram-negative bacteria.
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