22 Questions
What is the main function of the bacterial cell wall?
To impart shape and rigidity to the cell
What is the key difference between the cell walls of gram-positive and gram-negative bacteria?
Gram-positive bacteria have a simpler chemical composition in their cell wall compared to gram-negative bacteria
What is the primary function of the bacterial cytoplasmic (plasma) membrane?
To act as a semipermeable barrier, controlling the flow of metabolites
Which of the following is not considered a cellular appendage in bacteria?
Cytoplasm
What is the main function of the bacterial cell interior, known as the cytoplasm?
To house the cell's genetic material (DNA)
Which of the following is a key function of the bacterial cell wall?
To provide a surface for the attachment of microbes
Which of the following is NOT a typical shape of bacteria?
Cuboidal
What is the arrangement of cocci bacteria called when they form square groups of four cells?
Tetrads
Which of the following describes the arrangement of bacilli bacteria when they split only across their short axes and form chains?
Streptobacilli
What is the term used for bacteria that lack a cell wall and do not possess a stable morphology?
Mycoplasma
Which of the following describes the arrangement of cocci bacteria when they form grape-like clusters?
Staphylococci
What is the term used to describe the arrangement of bacilli bacteria when they form a V-shaped or Chinese letter-like pattern?
Cuneiform
What is the primary function of the bacterial capsule?
Protect the cell from drying out and antimicrobial agents
Which of the following statements about fimbriae (pili) is incorrect?
They are present on both Gram-positive and Gram-negative cells
What is the primary function of flagella in bacteria?
Enable cell motility and locomotion
Which of the following is not a component of the bacterial flagellum?
Capsule
What is the primary function of ribosomes in bacterial cells?
Synthesize proteins by translating genetic code
Which type of RNA is specifically responsible for transferring genetic information from mRNA into functional proteins?
Transfer RNA (tRNA)
What is the primary function of mesosomes (chondroids) in bacterial cells?
Act as respiratory sites and aid in DNA segregation
What is the primary purpose of endospore formation in bacteria?
Cell preservation and survival in unfavorable conditions
What is the primary purpose of heat-fixing a bacterial smear during microscopy specimen preparation?
Both A and C
Which component of the bacterial cell is responsible for storing reserve materials like glycogen or starch?
Intracytoplasmic inclusions
Study Notes
Bacterial Cell Components
- Cell envelope consists of cell wall and plasma membrane, which provides shape and rigidity to the cell
- Cell wall is strong, relatively rigid, and porous, maintaining the characteristic shape of the bacterium
- Gram-positive bacterial cell walls have a simpler chemical nature, composed of thick layer of peptidoglycan and teichoic acids
- Gram-negative bacterial cell walls consist of peptidoglycan, lipoprotein, outer membrane, and lipopolysaccharide
Cytoplasmic (Plasma) Membrane Functions
- Semipermeable membrane controlling the inflow and outflow of metabolites
- Houses enzymes involved in outer membrane synthesis, cell wall synthesis, and assembly of extracytoplasmic and extracellular substances
- Generates chemical energy (i.e., ATP)
- Houses sensory and chemotaxis proteins
Morphology of Bacteria
- Bacteria are single-celled organisms that reproduce by simple division (binary fission)
- Shape of bacteria: Cocci (spherical or nearly spherical), Bacilli (relatively straight, rod-shaped), Vibrios (curves or comma-shaped rods), Spirilla (rigid spiral or helical forms), Spirochaetes (flexuous spiral forms), Mycoplasma (cell wall deficient, no stable morphology)
Arrangement of Bacterial Cells
- Cocci arrangement: Diplococci (paired), Long chains, Grape-like clusters, Tetrads, Cubical packets
- Bacilli arrangement: Shapes vary between species, ends of rods may be flat, rounded, cigar-shaped, or bifurcated
- Bacilli in clusters or chains (streptobacilli), resembling letters 'V' or Chinese letters
Capsule and Fimbriae
- Capsule: composed of complex polypeptides or polysaccharides, protects cell from drying and antibacterial agents
- Fimbriae (Pili): hair-like microfibrils, composed of protein (pillin), present on Gram-negative cells, involved in surface attachment
Flagella
- Long, slender, thin hair-like cytoplasmic appendages, responsible for motility
- Composed of protein (flagellin), has three parts: filament, hook, and basal body
- Types of flagella: Monotrichous (single polar flagellum), Lophotrichous (two or more flagella at one end), Amphitrichous (single polar flagella at both poles), Peritrichous (several flagella on the surface)
Cytoplasm
- Suspension of organic and inorganic solutes in a viscous water solution
- Contains ribosomes, proteins, and other water-soluble components and reserve material
- Extrachromosomal DNA (plasmid DNA) may be present
Ribosomes
- Found in all cells, center of protein synthesis
- Synthesizing proteins by translating genetic code transcribed in mRNA into an amino acid sequence
- Composed of different proteins associated with 3 types of RNA: mRNA, rRNA, and tRNA
- Sedimentation rate of 70S (S or Svedberg unit)
Test your knowledge on the anatomy of a bacterial cell, focusing on the cell envelope, cell wall, plasma membrane, cellular appendages, cytoplasm, and DNA. Learn about the functions of different bacterial cell components.
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