Bacterial Cell Wall and Gram Stain Quiz

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5 Questions

Which type of bacteria can be identified in the lab by a differential stain known as the Gram stain?

Gram positive bacteria

What are the two glucose derivatives that make up peptidoglycan in bacterial cell walls?

N-acetylglucosamine and N-acetylmuramic acid

What is the color of Gram negative bacteria after the Gram stain procedure?


Which amino acid is part of the tetrapeptide that cross-links the NAG and NAM units in peptidoglycan?


What percentage of bacteria have a cell wall according to the text?


Study Notes

Cell Wall Characteristics

  • Not all bacteria have a cell wall, but approximately 90% do
  • There are two main types of cell walls: Gram positive and Gram negative
  • The Gram stain is a differential stain used to identify bacteria in a lab setting

Gram Stain Results

  • Gram Positive bacteria stain purple/blue
  • Gram Negative bacteria stain red

Peptidoglycan Composition

  • Peptidoglycan is a polysaccharide made up of two glucose derivatives: N-acetylglucosamine (NAG) and N-acetylmuramic acid (NAM)
  • NAM sugar units are cross-linked by a tetrapeptide
  • The tetrapeptide is composed of four amino acids: L-alanine, D-glutamine, L-lysine or meso-diaminopimelic acid (DPA), and D-alanine

Test your knowledge on bacterial cell walls and the Gram stain technique used to differentiate between Gram positive and Gram negative bacteria. Learn about the structure of peptidoglycan and the components that make up the cell wall.

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