22 Questions
What is the process called by which a single endospore forms within some bacteria?
Endosporulation
What is the function of dipicolinic acid in endospore formation?
To stabilize the proteins and DNA in the endospore
What is the structure that surrounds the core of the endospore?
Inner membrane
What is the final stage of endospore formation?
Dehydration and maturation
What is the unique feature of the endospore that is not found in vegetative cells?
Exosporium, spore coat, cortex, and core wall
What is the purpose of the cortex in the endospore?
To protect the endospore from UV light and harsh chemicals
What is the approximate percentage of water in the cytoplasm of a prokaryotic cell?
80%
What is the primary function of the cytoplasm in a prokaryotic cell?
Site of most bacterial metabolism
What is the function of mesosomes in prokaryotic cells?
Increase plasma membrane surface area and enzymatic content
What is the characteristic of the chromosome in a prokaryotic cell?
Single circular chromosome of double-stranded DNA
What is the function of plasmids in prokaryotic cells?
Confer protective traits to the host
What is the role of some plasmids in antibiotic resistance?
They encode proteins that degrade antibiotics
What is the function of conjugative plasmids?
They allow the exchange of DNA between bacterial cells
What is the characteristic of the nucleoid in a prokaryotic cell?
It has no nuclear membrane or nucleoli
What is the primary function of ribosomes in all organisms?
To synthesize proteins
What is the purpose of plasmids in genetic engineering?
To insert specific genes
What is unique about the 70S ribosomes found in prokaryotes?
They are composed of a 50S subunit and a 30S subunit
What is the function of mRNA in protein synthesis?
To attach to the 30S subunit
What is the purpose of inclusion granules in bacteria?
To store reserve deposits
What is unique about endospores?
They are resistant to adverse conditions
What is the function of tRNA in protein synthesis?
To carry anti-codons and amino acids
What is the purpose of Bacillus stearothermophilus spores in quality control?
To test for heat sterilization equipment
Study Notes
Bacterial Internal Structures
- Cytoplasm: a gel-like matrix composed of 80% water, containing nucleic acids, enzymes, amino acids, carbohydrates, lipids, inorganic ions, and low molecular weight compounds, and is the site of most bacterial metabolism that leads to growth and replication.
- Mesosomes: plasma membrane infoldings that aid in:
- Cell wall formation
- DNA replication in prokaryotes
- Increasing plasma membrane surface area and enzymatic content
- Transferring chromosomes to daughter cells
- Nucleoid:
- A region with a single circular chromosome of double-stranded, supercoiled DNA
- No nuclear membrane or nucleoli
- Chromosome size varies from 580,000 base pairs in Mycoplasma gallinarum to 9,140,000 bp in Myxococcus xanthus
Plasmids
- Small, nonessential, extra-chromosomal DNA molecules that:
- Can confer protective traits such as drug resistance or toxin production
- Can be passed on during conjugation
- Replicate independently
- Can be gained or lost by bacteria
- Conjugative plasmids allow for the exchange of DNA between bacterial cells
- Plasmids are useful tools in genetic engineering/rDNA Technology
Ribosomes
- The most abundant component in the cytoplasm, with up to 15,000 ribosomes
- Site of protein synthesis in all organisms
- Prokaryotic ribosomes are 70S, composed of a 50S subunit and a 30S subunit
- Function as a workbench for protein synthesis, translating mRNA into proteins
Inclusion Granules
- Nonliving components that do not possess metabolic activity
- Not bounded by membranes
- Examples:
- Volutin granules (inorganic phosphate)
- Polysaccharide granules (glycogen or starch)
- Lipid inclusions (e.g., PHB granules)
- Sulfur and nitrogen granules
- Gas vacuoles (in some aquatic bacteria)
Endospores
- Dormant, resistant structures produced intracellularly upon starvation
- Resistant to:
- High temperatures
- Irradiation
- Cold
- Organic solvents
- Contain calcium dipicolinate
- Not a mechanism of reproduction
- Examples: Bacillus and Clostridium sp.
Endosporulation
- Process of forming an endospore, involving:
- DNA replication
- Formation of a spore septum
- Pinching off of the plasma membrane to form a double membrane around the DNA
- Incorporation of calcium dipicolinate
- Formation of a peptidoglycan cortex and spore coat
- Dehydration and maturation of the endospore
This quiz covers the internal structures of a prokaryotic cell, including the composition and functions of the cytoplasm, nucleic acids, and other components.
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