Questions and Answers
Which of the following structures is present in gram negative bacteria?
The cell wall of gram positive bacteria has a thicker peptidoglycan layer compared to gram negative bacteria.
True
What type of DNA molecule are plasmids?
Small circular double stranded DNA molecule
What is the function of ribosomes in prokaryotic cells?
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The ______________ is a component of the peptidoglycan layer in bacteria.
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Teichoic acids are present in gram negative bacteria.
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Match the following cellular structures with their descriptions:
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What is the primary role of the plasma membrane in prokaryotic cells?
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Which lipopolysaccharide (LPS) content is found in gram positive bacteria?
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What are fimbriae and pili?
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Study Notes
Bacterial Cell Components
- Prokaryotic cells consist of various structures that aid in functionality and protection.
- Cytoplasmic structures include the nucleoid, plasmids, ribosomes, and inclusions.
Cell Envelope Structure
- The cell envelope protects the cell interior and is crucial for maintaining cellular integrity.
- In Gram-negative bacteria, the cell envelope features periplasmic space and an outer membrane.
Plasma Membrane
- Composed of a phospholipid bilayer embedded with proteins, it encloses the cytoplasm and regulates substance entry.
Cell Wall
- Made primarily of peptidoglycan, it maintains cell shape and protects against osmotic pressure.
- Key components of peptidoglycan include:
- N-acetylglucosamine (NAG)
- N-acetylmuramic acid (NAM)
- Side chain amino acids
- Cross-bridge amino acids
Periplasmic Space
- Located between the inner and outer membranes in Gram-negative bacteria, it contains a gel-like matrix with nutrients and enzymes.
Outer Membrane
- Acts as an initial barrier against antibiotics and protects from phagocytosis.
- Composed of lipopolysaccharides (LPS), lipoproteins, and phospholipids, it is critical for bacterial defense.
- Contains porins that facilitate nutrient and solute passage.
Ribosomes
- Sites for protein synthesis, composed of ribosomal RNA and proteins.
Inclusions
- Storage structures, including:
- Metachromatic granules: reserves of polyphosphates important for ATP synthesis.
- Polysaccharide granules: consist of glycogen and starch, serving as energy reserves.
Spores
- Highly durable, dehydrated cells with thick walls that resist extreme environmental conditions including heat and disinfectants.
Flagella Characteristics
- Peritrichous flagella: distributed over the entire cell, exemplified by Escherichia coli.
Comparative Cell Envelope Characteristics
-
Gram-positive bacteria:
- Thick peptidoglycan layer (multilayered)
- Teichoic acids present
- No periplasmic space or outer membrane
- Virtually no LPS content
- High lipid/lipoprotein content
-
Gram-negative bacteria:
- Thin (single layered) peptidoglycan layer
- Lacks teichoic acids
- Present periplasmic space and outer membrane
- High LPS content
- Low lipid/lipoprotein content due to the outer membrane
Fimbriae and Pili
- Hairlike appendages that aid in attachment to surfaces and other cells, enhancing bacterial virulence.
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Description
This quiz covers key topics from Week 2 of Bacterial Physiology, focusing on aspects like metabolism, genetics, and growth. It includes details on prokaryotic cell structures such as the plasma membrane and cell envelope in gram-negative bacteria.
