Viruses And Prokaryotes Flashcards
Viruses
Viruses - contain nuclear acid (DNA or RNA) in/is surrounded by a protein coat
1) some viruses enclosed by membrane
2) cannot carry out reproduction or metabolic processes on their own, require a host cell
3) essentially just packaged genes passed from one cell to the next
Variation in viruses
Affect a limited variety of host cells called host range of virus
Virus & host have to fit together like lock & key
Fit is of protein on surface virus & the receptor molecule on host cell
West Nile virus - broad host range, can affect the mosquito, birds & mammals
Measles virus - only infects humans
Some viruses are only cell type specific like aids - infect white blood cell lymphocyte
Cold viruses only infect cells of respiratory tract
Bacteria and archaea
Masters of adaptation
Halobacteria - use light to drive synthesis of ATP, extreme halophiles = salt tolerant, domain archaea
Deinococus Radiodurans - 3 million rads of radiation, domain archaea
Other prokaryotes - can live in acidic environments (even acid th/ melts metals)
Common prokaryote shapes
Small Unicellular Well organized even without membrane bound nucleus & organelles Spherical (cocci) - strep throat Rod (bacilli) - anthrax Spiral - syphillus
Cell wall comparison
Cell wall function Maintain shape Protection Maintain water balance Structure Bacteria - peptidoglycan made up if sugar polymers that are cross linked by polypeptides Archaea - polysaccharides & proteins
Cell wall: G+ vs. G-
Gram (+) - larger # of peptidoglycan in cell wall
Gram (-) - has lipopolysaccharides in outer membrane of cell wall
Is more complex - more resistant to antibiotics
Penicillin works by hindering the cross linking in the peptidoglycan - malfunction of cell wall & bacteria dies
Doesn’t hurt humans because our cells don’t have cell walls or peptidoglycan
Cell wall extensions
Some prokaryotes have a capsule on the outside of a cell wall
It is sticky and composed of polysaccharides or proteins
Allows prokaryotes to stick to substrates or each other (from colony)
Protects against dehydration
Offers protection from immune system of a host
Fimbriae - hair like projections
Allow prokaryote to stick to substrate, each other to a host
Sex pili - an appendage used to connect 2 prokaryotes prior to x-fer of DNA from one cell to the next
Motility
1/2 of all prokaryotes are capable of directional movement
Moves toward or away from a stimulus to food & nutrients
From predator, environmental damages
Primary structure of motility = flagella
May be arranged all over cell or [] at ends
Internal organization
How carry out cellular respiration without mitochondria?
Folds in cell membrane mimic the cristae of the mitochondria
How photosynthesis without chloroplast?
Thykaloid membrane used in photosynthesis
Genomic organization
- A single circular chromosome located in the region called nucleoid
2 small circular pieces of DNA called plasmids (have very few genes) - Like other DNA plasmids = self-replicating
Use to transfer DNA from one cell to another
Prokaryotes have less RNA, less protein& smaller ribosomes than eukaryotes
Smaller ribosome allow some antibodies to block protein synthesis - the prokaryote dies (erythromycin, tetracycline)
Reproduction
- Mitosis, nuclear division - identical daughter cells
- Plenty of resources
No predators- limited competition
Most bacteria 12-24 hours to reproduction
Some produce endosomes - are dehydrated& contain DNA
Unfavorable environment = dormant
Favorable = hydrate & full metabolic functions
Adaptability
Increase genetic variability from mutations
Can occur spontaneously
E. coli: mutation rate/gene = 1 in 10 million/ cell division
Rate - each day your intestine 2x10^10 ecoli cells are produced
2000 cells are mutated for one gene
Genome = 4300 genes – 9 million mutate Ecoli/day/person
Adaptability: genetic recombination
Transformation occurs hen prokaryote picks up DNA from the environment (from other prokaryotes)
Ex: prokaryote starts as non-pathogenic (non disease causing) — to pathogenic prokaryote (Dx)
Conjugation and recombination
Prokaryotes don’t use meiosis
Transformation: prokaryotes can take DNA that’s been left in the environment from other prokaryotes and use it in their gene sequence
Bacteriophages (phages) = viruses that infect bacteria
Occasionally phages transfer bacterial DNA from one host to the next
DNA is incorporated into the genome of the new host
Conjugation
Conjugation: genetic material is transferred between bacteria while they are temporarily joined
1. Transfer is one way
2. The ability to form mating bridge or sex pilus is due to the presence of an f-factor gene — located on a plasmid (f plasmid)
Plasmid is a circular piece of DNA that is found within a bacterium
F-plasmid creates a donor cell (f+ cell)
A copy of the f-plasmid is transferred to the recipient cell or bacterium (f- cell) - does not contain an f plasmid
Converts the f- cell to an f+ cell
The recipient cell is fertile, can produce a sex pilus too and transfer DNA
1. Chromosomal genes transferred if f-factor gene is located in bacterial DNA
