Questions and Answers
Which of the following is a characteristic of prokaryotic cells?
What is the primary function of the bacterial cell wall?
Maintain the shape of the cell and prevent rupturing.
Which type of bacteria has a thick peptidoglycan layer?
Gram Negative bacteria contain teichoic acid in their cell walls.
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What component contributes to the negative charge of the bacterial cell surface?
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The _______ is the outermost structure of a bacterial cell.
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What is the process of fixation in bacteriology?
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Study Notes
Prokaryotic vs. Eukaryotic Cells
- Prokaryotic cells lack a defined nucleus and membrane-bound organelles, whereas eukaryotic cells possess these features.
Bacterial Cell Structure
- Bacteria exhibit various shapes and components, important for identification and classification.
- The bacterial cell envelope comprises the glycoprotein glycocalyx, outer membrane (in gram-negative bacteria), cell wall, and plasma membrane.
Bacterial Cell Wall
- Peptidoglycan (murein) layer is crucial in maintaining cell shape and preventing lysis.
- Acts as an anchor for flagella and determines bacterial staining characteristics.
Types of Cell Walls
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Gram Positive Cell Wall
- Thick peptidoglycan layer composed of N-acetyl-D-glucosamine (NAG) and N-acetyl-D-muramic (NAM) acid.
- Contains negatively charged teichoic acid and lipoteichoic acid.
- Primary target for antimicrobial agents like penicillin that inhibit peptidoglycan synthesis.
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Gram Negative Cell Wall
- Thinner peptidoglycan layer but possesses porins that enhance permeability.
- Lacks teichoic acids, making it less susceptible to certain antibiotics.
Layers of Gram-Negative Cell Wall
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Outer Membrane
- Consists of proteins, phospholipids, and lipopolysaccharides (LPS), contributing to the cell's negative charge.
- Allows hydrophilic substances to penetrate via porins but acts as a barrier to harmful substances.
- Plays a role in evading host immune responses through its strong negative charge.
- LPS can function as an endotoxin, with exceptions like Listeria monocytogenes.
Fixation and Staining Techniques
- Fixation preserves or immobilizes bacteria, with heat fixation being the most effective.
- Crystal violet serves as the primary stain in Gram staining.
- Iodine functions as a mordant to stabilize dye in the bacterial cell wall.
- Acetone and ethanol mixture acts as a decolorizer, crucial for determining gram-positive or gram-negative bacteria classification.
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Description
This quiz covers the fundamental aspects of prokaryotic cells, including their structure, metabolism, and genetics. It aims to differentiate prokaryotic cells from eukaryotic ones, explore various bacterial shapes and classification methods, as well as the nutritional needs for bacterial growth.
