Chapter 27 terms/concepts Flashcards
Prokaryotes lack some parts found in eukaryotic cells, including which item ( or items)
A. Nuclear membrane
B. DNA
C: one or more chromosomes
D: a plasma membrane
E: All of the above
A
Peptidoglycan
A polymer composed of modified sugars that are cross-linked by short polypeptides that make up bacterial cell walls
Eukaryotic cell walls are made of cellulose or chitin
Also not found in Archaea cell walls either
What are the differences in cell wall composition between gram-postive and gram negative bacteria?
Gram-positive bacteria have relatively simple cell walls composed of a thick layer of peptidoglycan
Gram-negative bacteria, on the other hand, have a more complex cell wall with less peptidoglycan, with two membranes (the outer one contains lipopolysaccharides)
What is a capsule?
It is a polysaccharide or protein outer layer of bacteria that is considered a “hard” layer which allows the cell to stick to other substances and serves as a means of protection
“A slime layer” is a non-hard/thick layer of similar orientation
Endospores
Resistant cells that bacteria develop to withstand harsh conditions that allow them to remain viable while being metabolically inactive
Taxis
About half of all prokaryotes are capable of undergoing taxis, a form of motility exhibited by prokaryotes via flagella or cilia
How do the genetics of prokaryotes differ form eukaryotes?
They are simpler in both internal structure and physical arrangement of DNA
Prokaryotes have a singular circular chromosomes
They have a nucleoid instead of a nucleus, not enclosed by membrane
Prokaryotes also have plasmids, which are independently replicating DNA molecules only carrying a few genes
How do prokaryotes’ internal structure differ from eukaryotes?
Prokaryotic cells lack complex compartmentalization of membrane-enclosed organelles, cytoskeleton
How do prokaryotes reproduce?
Many prokaryotes reproduce by binary fission, reproducing asexually with short generation times
If bacterial cells do not sexually reproduce and have low mutation rates, how come they are still genetically diverse?
Since binary fission allows for them to reproduce at faster rates than sexually reproducing species, and thus rare mutations are more impactful given the short generation times they have
Genetic recombination
Another way (other than mutations) that prokaryotes can be genetically diverse: the combining of DNA from two sources.
Horizontal gene transfer
The movement of genes from one organism to another when the individuals are members of different species
Transformation
A type of genetic recombination where a prokaryotic cell’s genotype (and potentially phenotype) are altered due to the uptake of foreign DNA from surroundings
Replacing its allele with a foreign allele that was received (ie virulence or pathogenicity)
Transduction
a type of genetic recombination where bacteriophages carry prokaryotic genes from one host cell to another
Conjugation
a type of genetic recombination in which prokaryotic cells (usually of the same species) directly transfer DNA one-way between each other via a structure called a pilus
F factor/plasmid
The genetic information that allows for a bacterial organism to form a pili structure to undergo conjugation
Cells with F factor are DNA donors, and cells without it are acceptors
R plasmids
Genetic information that codes for the destruction / evasion of certain antibiotics, which causes antibiotic resistance in bacterial cells
They also can encode pili and enable DNA transfer between cells
Phototrophs
Organisms that obtain energy from light
Chemotrophs
Organisms that obtain energy from chemicals
Autotrophs
Organisms that only need CO2 or related compounds as a carbon source
Heterotrophs
Require at least one organic nutrient to make other organic compounds
Photoautotroph
An organism that harnesses light energy to drive the synthesis of organic compounds from CO2
Photoheterotroph
An organism that relies on light to create energy, but must obtain carbon through an organic source
Chemoheterotroph
Organism that relies on organic molecules for both energy and carbon
Chemoautotrophs
Organisms that rely on inorganic molecules for energy but need CO2 to derive a carbon source
Heterocyst
A specialized cell that engages in nitrogen fixation in some filamentous bacteria that helps exchange metabolic products during metabolic cooperation
Photosynthesis and nitrogen fixation cannot undergo processes at the same time with one cell, which is why prokaryotes form chains to undergo both processes at the same time
How do Archaea differ from both bacteria and eukaryotes?
Archaea do not have nuclear envelopes or membrane-enclosed organelles, have circular chromosomes similar to prokaryotes
Archaea do not have peptidoglycan in their cell walls, have introns in their genes, have several kinds of RNA polymerase, do not respond to antibiotics, have histones assoc. with DNA similar to eukaryotes
Some Archaea can grow at temperatures over 100 C, which is not present in either prokaryotes or eukaryotes
Extreme thermophiles
Archaea species that thrive in really hot environments
Extreme halophiles
Archaea species that thrive in highly saline environments
Methanogens
Archaea that live in swamps and marshes that produce methane - they are strict anaerobes that are poisoned by oxygen
Mutualism
A type of symbiosis where both organisms, the host and symbiont gain mutual benefit
Commensalism
The symbiont benefits and the host is neither harmed nor benefited
Parasitism / pathogens
The symbiont benefits and the host is harmed
Exotoxins
Chemicals secreted by pathogenic bacteria - can cause disease even if the producers of the chemical are not present
Endotoxins
Chemicals that are secreted by pathogenic bacteria when they die
