Prokaryotic Cell Structure

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Questions and Answers

What is the purpose of calcium dipicolinate in the formation of endospores?

To pinch off the plasma membrane

To break down the peptidoglycan cortex

To form the spore coat

To stabilize the proteins and DNA in the endospore (correct)

What is the final stage of endospore formation?

Formation of the spore coat

Pinching off of the plasma membrane

Replication of DNA

Dehydration and maturation of the endospore (correct)

What is the primary function of ribosomes in all organisms?

To store nutrients

To store genetic information

To synthesize proteins (correct)

To regulate metabolism

What is the function of the cortex in the endospore?

To protect the endospore from UV light and harsh chemicals Signup and view all the answers

What is the process by which a single endospore forms within some bacteria?

Endosporulation Signup and view all the answers

What is the composition of the 50S subunit of a 70S ribosome?

23S and 5S rRNA Signup and view all the answers

What is the purpose of plasmids in genetic engineering?

To transfer genes horizontally Signup and view all the answers

What is the structure that forms between the DNA and the rest of the cell during endosporulation?

Spore septum Signup and view all the answers

What is the characteristic of endospores that makes them resistant to adverse conditions?

They contain calcium dipicolinate Signup and view all the answers

What is the characteristic of the endospore that allows it to resist UV light and harsh chemicals?

The presence of an inner membrane surrounding the core Signup and view all the answers

What is the function of gas vacuoles in some aquatic bacterial inclusions?

To provide buoyancy and flotation Signup and view all the answers

What is the composition of ribosomes in eukaryotes?

80S Signup and view all the answers

What is the purpose of inclusion granules in bacteria?

To reserve energy and nutrients Signup and view all the answers

What is the purpose of Bacillus stearothermophilus spores?

For quality control of heat sterilization equipment Signup and view all the answers

What is the approximate water composition of the cytoplasm in a prokaryotic cell?

80 % Signup and view all the answers

What is the primary function of the cytoplasm in a prokaryotic cell?

Metabolic processes leading to growth and replication Signup and view all the answers

What is the function of mesosomes in prokaryotic cells?

All of the above Signup and view all the answers

What is the characteristic of the nucleoid in prokaryotic cells?

It is a single, circular chromosome of double-stranded, supercoiled DNA Signup and view all the answers

What is the primary function of plasmids in prokaryotic cells?

To confer protective traits to the cell Signup and view all the answers

What is the characteristic of conjugative plasmids?

They allow the exchange of DNA between bacterial cells Signup and view all the answers

What is an example of a virulence factor conferred by a plasmid?

Enterotoxin production Signup and view all the answers

What is the range of base pairs in prokaryotic chromosomes?

From 580,000 to 9,140,000 Signup and view all the answers

Study Notes

Bacterial Internal Structures

Cytoplasm: a gel-like matrix composed of 80% water, containing nucleic acids (DNA and RNA), enzymes, amino acids, carbohydrates, lipids, inorganic ions, and many low molecular weight compounds.
Functions of cytoplasm: site of most bacterial metabolism, leading to growth and replication.

Mesosomes

Mesosomes: plasma membrane infoldings.
Functions of mesosomes:
- Role in the formation of cell walls.
- Replication of DNA in prokaryotes.
- Increase plasma membrane surface area and enzymatic content.
- Aid in the transfer of chromosomes to daughter cells.
- Analogous to cristae in the mitochondria of eukaryotic cells.

Nucleoid

Nucleoid: also known as chromatin body, no nuclear membrane or nucleoli.
Characteristics of nucleoid:
- Single circular chromosome of double-stranded, supercoiled DNA.
- No nuclear membrane.
- No nucleolus.
- No mitotic spindle.
- No histones.
- Size: 580,000 base pairs in Mycoplasma gallinarum to 9,140,000 bp in Myxococcus xanthus.

Plasmids

Plasmids: small, nonessential, extra-chromosomal DNA, circular (linear in a few species).
Characteristics of plasmids:
- Present in cytoplasm, but may become incorporated into chromosomal DNA.
- Often confer protective traits such as drug resistance or the production of toxins and enzymes.
- Passed on in conjugation.
- Replicate independently.
- Examples: antibiotic resistance, virulence factors, and conjugative plasmids.

Ribosomes

Ribosomes: the most abundant in the cytoplasm, up to 15,000 ribosomes.
Characteristics of ribosomes:
- 70S ribosomes in prokaryotes, composed of 50S and 30S subunits.
- 50S subunit contains 23S and 5S rRNA, and 30S subunit contains 16S rRNA.
- Chemically composed of ribosomal RNA (rRNA) and protein.
- Function as a workbench for protein synthesis – translation of mRNA into proteins.

Inclusion Granules

Inclusion granules: nonliving components, not bounded by membranes, several kinds of reserve deposits.
Examples: volutin granules, polysaccharide granules, lipid inclusions, sulfur and nitrogen granules, and gas vacuoles.

Endospores

Endospores: dormant, resistant structures, produced intracellularly upon starvation.
Characteristics of endospores:
- Resistant to adverse conditions: high temperatures, irradiation, cold, and organic solvents.
- Contain calcium dipicolinate.
- Not a mechanism of reproduction.
- Examples: Bacillus and Clostridium species.
- Formation: through endosporulation, involving DNA replication, spore septum formation, peptidoglycan cortex, and spore coat formation.
- Structure: cortex, core, and inner membrane, leading to resistance against UV light and harsh chemicals.

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Description

This quiz covers the internal structures of a prokaryotic cell, including cytoplasm, protoplast, and mesosomes. It explains the composition and functions of each component.