17 Questions
What is the primary function of mesosomes in bacterial cells?
Cellular respiration and cell division
What is the characteristic of the genetic material in bacterial cells?
It is known as nucleoid
What type of ribosomes are found in bacterial cells?
70s ribosomes
What is the function of inclusion bodies in bacterial cells?
Storage of molecules
What is the approximate size of the E. coli chromosome?
10^7 bp
What is the primary factor that determines the shape of a bacterium?
Rigid cell wall and cytoskeleton
What is the primary function of the cell membrane in bacteria?
To regulate the movement of nutrients and waste
What is the size range of common bacteria like Escherichia coli?
1.1 to 1.5 µm in diameter
What is the term for the outermost layer of the bacterial cell that maintains the cell's shape and provides protection?
Cell wall
What is the term for the thick liquid inside the bacterium where organelles carry out cellular processes?
Cytoplasm
What is the composition of the bacterial cell wall?
Peptidoglycan, a mesh-like structure of sugars and amino acids
Which of the following bacteria is among the largest, with a length of up to half a millimeter?
Thiomargarita namibiensis
What is the term for the gel-like substance that surrounds the bacterial cell and protects it from the environment?
Capsule
What is the advantage of having a single circular DNA molecule in bacteria?
It allows for faster adaptation to environmental changes
What is the characteristic of prokaryotic cells that distinguishes them from eukaryotic cells?
Absence of a true nucleus
What is the function of plasmids in bacteria?
To provide antibiotic resistance
What is the reason why bacteria do not burst in a hypotonic medium?
The cell wall provides mechanical strength and rigidity
Study Notes
Genome and Chromosomes
- The length of a genome varies, but is generally at least a few million base pairs.
- Bacteria have one to several chromosomes, e.g., V. cholerae has two chromosomes, and E. coli has one chromosome of 106-107 bp in size.
Cellular Structures
- Mesosomes: inward foldings of the plasma membrane involved in cellular respiration and cell division.
- Ribosomes: structures responsible for protein synthesis, with bacterial cells containing '70s' ribosomes.
- Plasmids: additional small circular DNA molecules that carry accessory genes.
- Inclusion Bodies: insoluble cytoplasmic structures without a membrane, responsible for storage.
Cytoplasmic Inclusions
- Ribosomes
- Polyphosphates
- Poly-β-hydroxybutyrate
- Glycogen
- Gas Vacuoles
- Magnetosomes
- Sulfur Globules
- Carboxysomes
Morphology of Microbes
- Bacteria size: 0.5-5.0 μm in diameter, with the largest being Thiomargarita namibiensis (up to half a millimeter long) and Epulopiscium fishelsoni (0.75 mm long).
- Smallest bacteria: Mycoplasma gallicepticum, only 0.3 µm in diameter, as small as the largest viruses.
- Common bacteria like Escherichia coli range in size from 1.1 to 1.5 µm in diameter.
Shapes of Bacteria
- Shapes determined by the rigid cell wall and cytoskeleton.
- Bacteria classified by shape into three primary groups: cocci, bacilli, and spiral-shaped.
- Cocci: oval or spherical in shape, either remaining single or attached to one another.
Cell Wall and Cytoplasm
- Cell wall composed of peptidoglycan, a mesh-like structure of sugars and amino acids.
- Cell wall provides support, mechanical strength, and rigidity to the cell, and protects cells from bursting in a hypotonic medium.
- Cytoplasm: a thick liquid containing plasmid, nuclear materials, water, enzymes, nutrients, waste materials, and ribosomes.
- Cytoplasm is 80% water and 20% salts-proteins.
- Cytoplasm is responsible for cell growth, metabolism, elimination of waste, and replication (reproduction) of the cell.
Test your knowledge of the components and functions of bacterial cells, including the cell membrane, cytoplasm, and genetic material. Learn about the unique characteristics of prokaryotic cells and how they carry out essential cellular processes.
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