16 Questions
What is the basic unit of a living organism?
Smallest unit of life
Which category of cells do not contain membrane-bound organelles?
Prokaryotic cells
What is the average length range of most bacterial cells?
1-10 μm
What is the shape of bacterial cells that are usually round but can also be oval or elongated?
Cocci
Which type of cell arrangement results when bacterial cells remain in pairs after dividing?
Diplococci
Which type of cells have the genetic material contained within membrane-bound nuclei?
Eukaryotic cells
What is the characteristic arrangement of Streptococci?
Chains
Which bacteria are present as single cells and are rod-shaped?
Bacillus
What is the characteristic arrangement of Staphylococci?
Grape-like clusters
Which bacteria resemble both cocci as well as bacilli?
Coccobacilli
What is the characteristic shape of Vibrio bacteria?
Comma-shaped
Which bacteria have a helical shape and a flagellum but lack the endoflagella like spirochetes?
Spirilla
What is the function of the bacterial cell wall?
Support the weak cytoplasmic membrane against high internal osmotic pressure
What is responsible for the staining affinity of the organisms in Gram staining?
Cell wall composition
What is the characteristic arrangement of Tetrad bacteria?
Tetrad: Those cocci that divide into two planes and remain in groups of four.
What is the characteristic arrangement of Sarcina bacteria?
Sarcina: the bacterial cells form a group of eight cells.
Study Notes
Cellular Structure and Arrangement
- The basic unit of a living organism is the cell.
Types of Cells
- Prokaryotic cells do not contain membrane-bound organelles.
- Eukaryotic cells have genetic material contained within membrane-bound nuclei.
Characteristics of Bacterial Cells
- The average length range of most bacterial cells is 0.5-5.0 μm.
- Bacterial cells can be spherical (cocci), rod-shaped (bacilli), or spiral (spirilla).
- Cocci bacterial cells are usually round but can also be oval or elongated.
Cellular Arrangements
- Diplococci are formed when bacterial cells remain in pairs after dividing.
- Streptococci are characteristically arranged in chains.
- Staphylococci are characteristically arranged in clusters.
- Vibrio bacteria have a curved shape.
- Spiral bacteria, such as Spirilla, have a helical shape and a flagellum but lack the endoflagella like spirochetes.
Bacterial Cell Wall and Staining
- The bacterial cell wall provides structural support and maintains the cell's shape.
- The peptidoglycan layer in the bacterial cell wall is responsible for the staining affinity of the organisms in Gram staining.
Tetrad and Sarcina Bacteria
- Tetrad bacteria are characteristically arranged in tetrads (groups of four).
- Sarcina bacteria are characteristically arranged in cubes of eight cells.
Test your knowledge on bacterial cell morphology, size, and structure with this quiz. Topics include prokaryotic and eukaryotic cells, cell wall composition, and the basic unit of living organisms.
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