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Questions and Answers
Gram-positive bacteria have a thick, peptidoglycan layer that retains a violet dye from the Gram stain procedure, causing the stained cells to appear ______ under a microscope.
Gram-positive bacteria have a thick, peptidoglycan layer that retains a violet dye from the Gram stain procedure, causing the stained cells to appear ______ under a microscope.
purple
In other groups of bacteria, the wall has thin peptidoglycan layer and does not retain the purple dye after Gram staining; such bacteria exhibit the background red dye and are characterized as ______.
In other groups of bacteria, the wall has thin peptidoglycan layer and does not retain the purple dye after Gram staining; such bacteria exhibit the background red dye and are characterized as ______.
Gram-negative
Their murein layer is covered on the outside with an additional outer membrane made up of ______ and Polysaccharides.
Their murein layer is covered on the outside with an additional outer membrane made up of ______ and Polysaccharides.
lipids
Gram Positive Cell Wall has (a) Thick ______
Gram Positive Cell Wall has (a) Thick ______
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Gram Positive Cell Wall has (b) ______ acid – composed of alcohol and phosphate.
Gram Positive Cell Wall has (b) ______ acid – composed of alcohol and phosphate.
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Gram Positive Cell Wall has (c) No outer ______
Gram Positive Cell Wall has (c) No outer ______
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Gram Negative Cell Wall has (a) Thin ______
Gram Negative Cell Wall has (a) Thin ______
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Gram Negative Cell Wall has (b) outer ______ (lipopolysaccaride-LPS, lipophospholipids and lipoproteins)
Gram Negative Cell Wall has (b) outer ______ (lipopolysaccaride-LPS, lipophospholipids and lipoproteins)
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Periplasm - Region between cytoplasmic membrane and the outer ______ (Gram negative cells)
Periplasm - Region between cytoplasmic membrane and the outer ______ (Gram negative cells)
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Peptidoglycan (murein) content in Gram-positive cell wall is ______ 50%
Peptidoglycan (murein) content in Gram-positive cell wall is ______ 50%
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The bacterial cell wall is composed of ______
The bacterial cell wall is composed of ______
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The disaccharide backbone is composed of N-acetyl glucosamine (NAG) and N-acetyl muramic acid (NAM), and the polypeptide chain consists of ______ amino acids
The disaccharide backbone is composed of N-acetyl glucosamine (NAG) and N-acetyl muramic acid (NAM), and the polypeptide chain consists of ______ amino acids
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Antibiotics interfere with the bond formation between the disaccharide and the polypeptide, making the cell wall ______
Antibiotics interfere with the bond formation between the disaccharide and the polypeptide, making the cell wall ______
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Peptidoglycan is a polysaccharide made of two glucose derivatives, N-acetylglucosamine (NAG) and N-acetylmuramic acid (NAM), alternated in ______ chains
Peptidoglycan is a polysaccharide made of two glucose derivatives, N-acetylglucosamine (NAG) and N-acetylmuramic acid (NAM), alternated in ______ chains
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The chains are cross-linked to one another by a ______ that extends off the NAM sugar unit
The chains are cross-linked to one another by a ______ that extends off the NAM sugar unit
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Gram staining procedure is used to detect differences in the cell walls of bacteria and was developed by Danish microbiologist ______
Gram staining procedure is used to detect differences in the cell walls of bacteria and was developed by Danish microbiologist ______
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Study Notes
Gram-Positive and Gram-Negative Bacteria
- Gram-positive bacteria have a thick peptidoglycan layer, allowing them to retain violet dye and appear purple under a microscope.
- Gram-negative bacteria possess a thin peptidoglycan layer and lose the purple dye, appearing red with counterstaining in the Gram stain procedure.
- The outer membrane of Gram-negative bacteria is composed of lipopolysaccharides and polysaccharides, adding an additional protective layer.
Structure of Gram Cell Walls
- Gram-positive cell walls feature a thick peptidoglycan layer, which provides structural support and rigidity.
- Gram-positive walls contain teichoic acid, made up of alcohol and phosphate, contributing to the cell wall's stability.
- Unique to Gram-positive bacteria, there is no outer membrane present, allowing the thick peptidoglycan layer to be the primary defense against external factors.
- In Gram-negative bacteria, the peptidoglycan layer is thin, contrasting with the robust structure of Gram-positive bacteria.
- The outer membrane in Gram-negative bacteria consists of lipopolysaccharides (LPS), lipophospholipids, and lipoproteins, providing an additional protective barrier.
Periplasm and Composition
- Periplasm refers to the space between the cytoplasmic membrane and the outer membrane in Gram-negative bacteria, containing enzymes and other proteins.
- Peptidoglycan constitutes more than 50% of the Gram-positive cell wall, indicating its critical role in bacterial structure.
- The bacterial cell wall is primarily composed of peptidoglycan, essential for maintaining cell integrity and shape.
Peptidoglycan Structure
- The disaccharide backbone of peptidoglycan consists of N-acetylglucosamine (NAG) and N-acetylmuramic acid (NAM).
- The polypeptide chain in peptidoglycan comprises amino acids that contribute to cross-linking between the disaccharide units.
- Antibiotics target bacterial cell walls by interfering with the bond formation between disaccharides and polypeptides, weakening the wall structure.
- Peptidoglycan is a polysaccharide structured in alternating chains of NAG and NAM, providing a flexible yet strong frame.
Gram Staining History
- The Gram staining technique, developed by Danish microbiologist Hans Christian Gram, is essential for differentiating bacterial cell wall types, aiding in identification and treatment decisions.
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Description
Explore the composition and structure of the bacterial cell wall, including the roles of peptidoglycan, disaccharide, and polypeptide. Learn about the impact of B-Lactam group antibiotics on cell wall formation and function.
