Bacterial Cell Structure (Internal) Flashcards
what are the contents of a cell collectively termed?
cytoplasm
cytoplasm
the collective contents of a cell
what is the liquid portion of the cytoplasm called?
cytosol
cytosol
the liquid portion of the cytoplasm, a gel-like substance, made mostly of water that contains dissolved and suspended substances such as ions, carbohydrates, proteins, lipids, wastes, etc.
what kind of substances are dissolved in cytosol?
ions, carbohydrates, proteins, lipids, wastes, etc.
plasmid DNA
a small DNA molecule that is physically separate from, and can replicate independently of, chromosomal DNA within a cell. Most commonly found as small circular, double-stranded DNA molecules. carry genes that may benefit survival of the organism (e.g. antibiotic resistance), and can frequently be transmitted from one bacterium to another (even of another species) via horizontal gene transfer. While the chromosomes are big and contain all the essential information for living (an adequate analogy is the hard-drive of a computer), plasmids usually are very small and contain additional information (in this analogy, plasmids are the USB flash drives).
types of genes carried by plasmids
replication genes (to copy the plasmid), also generally genes for one or more cellular traits that may confer an advantage to their host.
what is most commonly transferred by a sex pilus?
plasmids, chromosomal DNA is less common.
in what domains are plasmids found?
bacteria, archaea, eukaryotes.
ribosome
a large and complex molecular machine, found within all living cells, that serves as the primary site of biological protein synthesis (translation). Ribosomes link amino acids together in the order specified by messenger RNA (mRNA) molecules. Ribosomes consist of two major components — the small ribosomal subunit which reads the RNA, and the large subunit which joins amino acids to form a polypeptide chain. Each subunit is composed of one or more ribosomal RNA (rRNA) molecules and a variety of proteins. The ribosomes and associated molecules are also known as the translational apparatus.
in which are ribosomes smaller, bacteria or eukaryotes?
bacteria (70S vs 80S)
of what importance to humans is it that ribosomes differ between bacteria and eukaryotes?
it represents an attack vector (ex. antimicrobial chemicals can specifically target bacterial ribosomes).
why are the genes that encode ribosomes highly conserved?
because protein synthesis is crucial for life, so that mutations are not well tolerated
give examples of structures that appear within the cytoplasm?
storage granules, DNA, ribosomes, gas vesicles, endospores, (other answers acceptable)
where does bacterial genetic material reside in the cell?
cytosol, in a region termed the nucleoid
what encloses the nucleoid of a bacterial cell?
it has no membrane, resides in the cytosol
roughly how much of the volume of a bacterial cell does the nucleoid compose?
10%
nucleoid
the region in a bacterial cell that contains the genetic materal, NOT enclosed within a nuclear membrane
how many chromosomes do most bacteria possess? give examples of bacteria that defy this convention
one
Vibrio cholera and Agrobacterium tumefaciens possess two. Epulopiscium has hundreds or thousands of identical chromosomes.
how much of the DNA of bacteria is non-coding? how does this compare to eukaryotes?
almost none, unlike eukaryotes wherein the majority is non-coding
how does plasmid DNA replicate?
independently of the bacterial chromosome, all plasmids contain genes for self-replication
what would happen to bacteria if plasmid DNA were removed?
it would not die, but it MAY be less advantageous to remove it
how does plasmid DNA benefit biotechnology?
it allows for the easy manipulation and transfer of genes between species, such as for human insulin production by bacteria
what do ribosomes facilitate?
protein synthesis
give examples of three antimicrobial chemical types that specifically target bacterial ribosomes
tetracyclines, ahminoglycosides, macrolides
what are commonly used to determine or verify evolutionary relationships and why?
Highly conserved genes, such as those that create ribosomes. because mutations in rRNA genes are frequently lethal, the rate of mutation accumulation is low (they are conserved). perfect conservation of these long stretches of DNA is thought to imply evolutionary importance as these regions appear to have experienced strong negative selection.
negative selection
In natural selection, negative selection or purifying selection is the selective removal of alleles that are deleterious. This can result in stabilizing selection through the purging of deleterious variations that arise (see: highly conserved genes)
storage granules
reserve deposits of useful molecules (forms of lipids, starch, nitrogen, phosphorus, sulfur, etc.)
taken in when nutrients are abundant in the environment
and used when these nutrients are scarce. sometimes surrounded by a polypeptide “membrane”
what is often deposited in storage granules?
the polysaccharide glycogen or the lipid polyhydroxybutyrate (PHB)
gas vesicles
small, rigid, protein-bound compartments that provide buoyancy to the cell allowing an organism to maintain a favourable position in the water column.
Two notable endospore-forming genera are?
Clostridium and Bacillus
rRNA analysis indicates a close relationship between mitochondria and?
Rickettsia
