40 Questions
What is the function of mesosomes in bacterial cells?
Invagination of plasma membrane towards cytoplasm
What is the shape of Spirilla bacteria?
Spiral-shaped and tightly coiled
What is the function of plasmids in bacterial cells?
Storage of genetic material
What is the characteristic of Mycoplasma bacteria?
Pleomorphic shape
What is the function of the cytoplasmic membrane in bacterial cells?
Electron transport and energy generation
What is the characteristic of Actinomyces bacteria?
Filamentous shape
What is the function of transposons in bacterial cells?
Mobile genetic elements that can jump from one location to another
What is the composition of the bacterial cell wall?
Peptidoglycan and lipopolysaccharides
What is the approximate percentage of the cell wall made up of peptidoglycan in Gram positive bacteria?
50-90%
What is the function of lipoteichoic acid in Gram positive bacteria?
It acts as a receptor molecule for Gram positive bacteriophages
What is the main difference between the cell wall of Gram positive and Gram negative bacteria?
The thickness of the peptidoglycan layer
What is the function of penicillin-binding proteins (PBPs) in bacterial cell wall synthesis?
They are essential for cell wall synthesis
What is the term for bacteria that have lost their cell wall but can still multiply and divide?
L forms
What is the term for the outer layer of the Gram negative bacterial cell wall?
Outer membrane
What is the component of the Gram negative bacterial cell wall that is responsible for its toxicity?
Lipid A
What is the term for the thin, high molecular weight secretory substance present in many bacteria external to the cell wall?
Glycocalyx
What is the primary function of a capsule in bacteria?
To protect bacteria from environmental factors
What is the characteristic of slime layer in bacteria?
It is a protein-linked and lipid-linked carbohydrate structure
What is the antigenic property of flagellin protein?
H antigen
What is the function of normal fimbria in bacteria?
To allow bacterial colonization on a surface via adhesion
What is the primary function of spores in bacteria?
To protect bacteria in non-ideal conditions
Why are biological molecules in microorganisms not visible under a microscope?
They do not absorb light
What is the primary purpose of Gram staining in microbiology?
To visualize bacteria under a microscope
What is the characteristic of the bacterial surface formation known as a biofilm layer?
It is a protein-linked and lipid-linked carbohydrate structure
What is the primary function of the cytoplasmic membrane?
To regulate the transport of molecules into the cell
What is the role of septal mesosomes in bacterial cell division?
To form the plasma membrane during bacterial cell division
What is the function of peptidoglycan in bacterial cell walls?
To maintain bacterial integrity
What is the composition of the glycan chain in peptidoglycan?
Alternating residues of N-acetylmuramic acid (NAM) and N-acetylglucosamine (NAG)
What is the function of lysozyme enzyme in animal secretions?
To protect against bacterial infections
What is the target of antibacterial drugs such as penicillin and cephalosporins?
The peptidoglycan layer
What is the function of lateral mesosomes in bacterial cells?
To regulate plasmid multiplication and spore formation
What is the main component of the cell wall that provides structural support to bacterial cells?
Peptidoglycan
What is the primary function of PHB granules in bacteria?
To serve as a source of energy for protein synthesis
What is the main difference between bacterial and eukaryotic ribosomes?
The size of the subunits
What is the primary function of plasmids in bacteria?
To provide a genetic advantage
What is the main difference between transposons and plasmids?
The ability to independently multiply
What is the composition of the cytoplasmic membrane in bacteria?
Phospholipids, proteins, and carbohydrates in small amounts
What is the function of the cytoplasmic membrane in prokaryotic cells?
To surround the cell cytoplasm
Why are most bacteria unable to synthesize sterol?
Because they are prokaryotic cells
What is the term for the appearance of the cytoplasmic membrane?
Mosaic
Study Notes
Bacterial Morphology
- Bacteria can be classified based on their shape:
- Bacilli: rod-shaped, 1-8 µm in length
- Cocci: round, spherical, 0.6-1.5 µm in size
- Spirilla: spiral-shaped, curved
- Filamentous: very long, thin, filament-shaped bacteria (e.g., Actinomyces)
- Pleomorphic: no characteristic shape (e.g., Mycoplasma)
- Bacilli: rod-shaped, 1-8 µm in length
Bacterial Cell Structure
- Nucleoid (nuclear material):
- No nuclear membrane
- 10% of cell content
- Circular, double-stranded DNA
- Bacterial chromosome length is 1 mm
- Cytoplasm and cytoplasmic structures:
- Transparent, colloidal system
- Contains water, ions, metabolites, proteins, nucleic acids, and granules
- Ribosomes (70s)
- Plasmids and transposons
- No mitochondria or chloroplasts; electron transport enzymes are in the cytoplasmic membrane
- Granules:
- Concentrated deposits of certain substances in the cytoplasm of certain bacteria
- Penicillin-binding proteins (PBPs):
- Found in the cell wall and essential for cell wall synthesis
- Bind to penicillin and other β-lactam antibiotics
- Inhibition of PBPs causes cell lysis
- Teichoic acid:
- Anionic glycopolymers found in the peptidoglycan layer
- Gives rigidity to the cell wall
- Made up of ribitol phosphate and glycerol phosphate
- Not found in Gram-negative bacteria
- Gram-positive and Gram-negative bacteria:
- Differences in cell wall structure and composition
- Gram-positive: thicker peptidoglycan layer, teichoic acid present
- Gram-negative: thinner peptidoglycan layer, no teichoic acid
Bacterial Surface Structures
- Capsule or slime layer:
- Glycocalyx: a thin, high molecular weight secretory substance
- Composed of polysaccharide, polypeptide, or both
- Functions: increases virulence, protects from phagocytosis, and protects from antibiotics and environmental factors
- Flagella:
- Locomotion organelle in bacteria
- Proteinaceous appendages protruding from the cell body
- Structure contains helical-shaped proteins called flagellin
- Antigenic properties
- Fimbria (Pili):
- Filamentous projections in Gram-negative bacteria
- Thinner, shorter than flagella, without folding
- Made up of simple protein units called pilin
- Divided into two types: normal and sex fimbria
- Spores (Endospores):
- Resistant to physical and chemical environmental factors
- Formed when environmental nutrients are scarce
- Function: protect bacteria in non-ideal conditions
Bacterial Staining Techniques
- Gram staining technique:
- Introduced by Hans Christian Gram in 1884
- Selective permeability and transport of various molecules into the cell
- Used to differentiate between Gram-positive and Gram-negative bacteria
Functions of Cytoplasmic Membrane
- Invaginations in the plasma membrane towards the cytoplasm
- Two types: septal mesosomes and lateral mesosomes
- Functions: formation of plasma membrane during bacterial cell division, plasmid multiplication, and spore formation
This quiz covers the basics of bacterial cellular morphology, including shapes and sizes of bacteria cells. It's designed for students of pharmaceutical microbiology.
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