Bacterial Cell Structure (Internal)

Question 1

what are the contents of a cell collectively termed?

Answer 1

cytoplasm

Question 2

cytoplasm

Answer 2

the collective contents of a cell

Question 3

what is the liquid portion of the cytoplasm called?

Answer 3

cytosol

Question 4

cytosol

Answer 4

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.

Question 5

what kind of substances are dissolved in cytosol?

Answer 5

ions, carbohydrates, proteins, lipids, wastes, etc.

Question 6

plasmid DNA

Answer 6

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).

Question 7

types of genes carried by plasmids

Answer 7

replication genes (to copy the plasmid), also generally genes for one or more cellular traits that may confer an advantage to their host.

Question 8

what is most commonly transferred by a sex pilus?

Answer 8

plasmids, chromosomal DNA is less common.

Question 9

in what domains are plasmids found?

Answer 9

bacteria, archaea, eukaryotes.

Question 10

ribosome

Answer 10

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.

Question 11

in which are ribosomes smaller, bacteria or eukaryotes?

Answer 11

bacteria (70S vs 80S)

Question 12

of what importance to humans is it that ribosomes differ between bacteria and eukaryotes?

Answer 12

it represents an attack vector (ex. antimicrobial chemicals can specifically target bacterial ribosomes).

Question 13

why are the genes that encode ribosomes highly conserved?

Answer 13

because protein synthesis is crucial for life, so that mutations are not well tolerated

Question 14

give examples of structures that appear within the cytoplasm?

Answer 14

storage granules, DNA, ribosomes, gas vesicles, endospores, (other answers acceptable)

Question 15

where does bacterial genetic material reside in the cell?

Answer 15

cytosol, in a region termed the nucleoid

Question 16

what encloses the nucleoid of a bacterial cell?

Answer 16

it has no membrane, resides in the cytosol

Question 17

roughly how much of the volume of a bacterial cell does the nucleoid compose?

Answer 17

10%

Question 18

nucleoid

Answer 18

the region in a bacterial cell that contains the genetic materal, NOT enclosed within a nuclear membrane

Question 19

how many chromosomes do most bacteria possess? give examples of bacteria that defy this convention

Answer 19

one
Vibrio cholera and Agrobacterium tumefaciens possess two. Epulopiscium has hundreds or thousands of identical chromosomes.

Question 20

how much of the DNA of bacteria is non-coding? how does this compare to eukaryotes?

Answer 20

almost none, unlike eukaryotes wherein the majority is non-coding

Question 21

how does plasmid DNA replicate?

Answer 21

independently of the bacterial chromosome, all plasmids contain genes for self-replication

Question 22

what would happen to bacteria if plasmid DNA were removed?

Answer 22

it would not die, but it MAY be less advantageous to remove it

Question 23

how does plasmid DNA benefit biotechnology?

Answer 23

it allows for the easy manipulation and transfer of genes between species, such as for human insulin production by bacteria

Question 24

what do ribosomes facilitate?

Answer 24

protein synthesis

Question 25

give examples of three antimicrobial chemical types that specifically target bacterial ribosomes

Answer 25

tetracyclines, ahminoglycosides, macrolides

Question 26

what are commonly used to determine or verify evolutionary relationships and why?

Answer 26

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.

Question 27

negative selection

Answer 27

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)

Question 28

storage granules

Answer 28

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”

Question 29

what is often deposited in storage granules?

Answer 29

the polysaccharide glycogen or the lipid polyhydroxybutyrate (PHB)

Question 30

gas vesicles

Answer 30

small, rigid, protein-bound compartments that provide buoyancy to the cell allowing an organism to maintain a favourable position in the water column.

Question 31

Two notable endospore-forming genera are?

Answer 31

Clostridium and Bacillus

Question 32

rRNA analysis indicates a close relationship between mitochondria and?

Answer 32

Rickettsia