Lecture 2: Structures and Characteristics of the Microbial World Flashcards
(68 cards)
two fundamental cell types that differ categorically in cellular organization
prokaryotic & eukaryotic
prokaryotic
Prokaryotic cell structure is found within two different groups of organisms we know as Bacteria and Archaea.
Prokaryotic cells have few internal structures, they lack a nucleus, and they typically lack organelles
eukaryotic
eukaryotic cell structure are found in a group of organisms called the Eukarya.
This group includes plants and animals as well as diverse microbial eukaryotes such as algae, protozoa, and fungi. Eukaryotic cells contain an assortment of membrane-enclosed cytoplasmic structures called organelles (F
Genome
The genome is the full set of genes in a cell. A gene is a segment of DNA that encodes a protein or an RNA molecule. The genome is the living blueprint of an organism; the characteristics, activities, and very survival of a cell are governed by its genome.
Cytoplasmic membrane
All cells have a permeability barrier that separates the inside of the cell, the cytoplasm, from the outside.
The cytoplasm
An aqueous mixture of macromolecules (e.g.proteins, lipids, nucleic acids, and polysaccharides), small organic molecules (mostly the precursors of macromolecules), various inorganic ions, and ribosomes.
Cell wall
The cell wall is a relatively permeable structure located outside the cytoplasmic membrane and is a much stronger layer than the membrane itself.
Cell walls are typically found in plant cells and most microorganisms but are not found in animal cells.
Eukaryotic cell
Are found in a group of organisms called the Eukarya.
plants
animals
diverse microbial eukaryotes
- Algae
- Protozoa
- Fungi
DNA in eukaryotic cells
DNA is present as several linear molecules
The genome locates within the membrane-enclosed nucleus
A human cell, for example, contains approximately 3 billion base pairs, which encode about 20,000–25,000 genes
DNA in prokaryotic cells
The genomes of Bacteria and Archaea are typically closed circular chromosomes (though some prokaryotic cells have linear chromosomes).
The chromosome aggregates within the prokaryotic cell to form the nucleoid, which is not enclosed by a membrane.
Most prokaryotic cells have only a single chromosome
Many also contain one or more small circles of DNA distinct from that of the chromosome, called plasmids
The genomes of Bacteria and Archaea are typically small and compact, and most contain between 500 and 10,000 genes encoded by 0.5 to 10 million base pairs
To be competitive in nature, a microorganism must
Metabolism
Cell division
Metabolism
Nutrients are acquired from the environment and transformed into new cellular materials and waste products.
Energy is used to support synthesis of new structures
Cell division
Production of these new structures culminates in the division of the cell to form two cells.
Microbial growth results from successive rounds of cell division.
Genes
Contain information that is used by the cell to perform the work of metabolism.
Proteins
Genes are decoded to form proteins that regulate cellular processes.
Enzymes
Those proteins that have catalytic activity, carry out reactions that supply energy and perform biosynthesis within the cell.
Gene expression
Enzymes and other proteins are synthesized during gene expression in the sequential processes of transcription and translation.
Transcription
The process by which the information encoded in DNA sequences is copied into an RNA molecule
Translation
The process whereby the information in an RNA molecule is used by a ribosome to synthesize a protein.
Gene expression and enzyme activity in a microbial cell are coordinated and highly regulated to ensure that the cell remains optimally tuned to its surroundings.
DNA replication
Microbial growth requires replication of the genome through the process of DNA replication, followed by cell division.
Responsiveness
Microorganisms have the ability to sense and respond to changes in their local environment.
Motility
Many microbial cells are capable of motility, typically by self-propulsion
Motility allows cells to relocate in response to environmental conditions.
Differentiation
Some microbial cells undergo differentiation, which may result in the formation of modified cells specialized for growth, dispersal, or survival.
Cell signaling
Cells respond to chemical signals in their environment, including those produced by other cells of either the same or different species, and these signals often trigger new cellular activities. Microbial cells thus exhibit intercellular communication; that is, they are “aware” of their neighbors and can respond accordingly.
