Prokaryotes Flashcards
What are prokaryotes?
- single celled organisms
- no nucleus or other membrane-bound organelles
(e.g. bacteria/arachae)
What are Eukaryotes?
single cell OR multi cell organism (mostly )
Contain nucleus and other membrane-bound organelles
e.g. fungi, plants, animals
What are the 3 common shapes of bacteria?
Cocci - spherical
Bacilli - Rod shape
Spiral
Name the 2 types of mouth bacteria.
Staphylococci
Streptococci
Explain staphylococci bacteria
- tend to be in bunches (like grapes)-round “cocci”
- cause skin infections
Explain Streptococci
- round “cocci “,tend to be in chains
- tend to be related to dental carries
- bacterial infections of oral cavity
which bacteria is commonly associated with mouth disease/caries
Streptococci
Do bacterial cells have cell walls?
Yes
Do human cells have cell walls?
No
Name the parts of the bacterium
A- cytoplasm
B- Ribosome
C - DNA (circular)
D- Plasma membrane
E - Cell wall
F - Flagellum
G - Capsule
H - Plasmid
I - Pilus
Explain plasmids.
- circular genetic material found outside of the main chromosome in prokaryote cells
- independent replication from the main chromosome and transfer independently
Explain ribosomes
- make proteins from mRNA
What does gram staining show?
Whether bacteria is gram positive or gram negative
G+ve stay purple
G-ve lose colour and look pink
How do G+ve and Gram -ve cells differ
G+ve. G+ve G-ve
Cell wall. single layer. Double layer
Peptidoglycans. Multi layers. Single layer
*Teichoic acid. Present. None
Outer membrane. No Yes
Morphology. Cocci. Rods
*Lipopolysaccharide No. Yes
Antibiotic resistance. More Less susceptible
Gram stain. stay purple. Pink
-
* in cell wall
Why are G+ve more susceptible to antibiotics than Gram -ve
Thick petidoglycans layers can absorb more of the antibiotic into them -so more concentrated in cell and fatal
No outer membrane wall as added barrier so
1. no lipopolysaccharides which do not let hydrophobic solutes ( e.g.antibiotics) in
2.No porin channels so unable to decrease number of channels/porins which then would decrease diffusion of the antibiotic into the cell
Why can G-ve be less susceptible to antibiotics than G+ve
Can alter their porins/so less number and decrease entry hydrophobic solutes ( antibiotics ) in
Less peptidoglycan in cell so absorb less antibiotic and outer membrane
Name 3 mechanisms antibiotics kill bacteria/fungi with example and how not harm human cells
1, INHIBITS CELL WALL SYNTHESIS - block peptidoglycan synthesis of bacteria - so cell fragile and bursts( eg penicillin)
2.INHIBIT PROTEIN SYNTHESIS- target 30S bacterial ribosome ( mRNA not translate into proteins)
eg tetracycline -
( humans not concentrate in large concentration to cause an affect or target different ribosome )
3. DISRUPTS MEMBRANE INTEGRITY- interacts with the lipopolysaccharide bacteria (lipid part ) or ergosterol in fungi production - so structure of membrane breaks down -leakage and death of the cell ( humans only have minimal ergosterol and no LPS in cell membrane so not harmed)
Why are viruses not affected by antibiotics
No peptidoglycan cell walls, no ribosomes, not replicate their own DNA
Need host cells to replicate not replicate by themselves
Why humans cells not harmed by antibiotics /antifungals
Human- minimal ergosterol and no LPS in cell membrane so not harmed by targeting or disrupting this process of cell membrane integrity which how some antibiotic /antifungal work
Human cells no peptidoglycans hence not susceptible to blocking of peptidoglycan synthesis
How do micro-organisms develop antibiotic resistance ( 4 ways)
- PRODUCE ENZYMES( ie Beta lactamases against penicillins beta lactase ring ) that hydrolyse the ring and makes it inactive-
- ALTER TARGET SITE- so ribosomes proteins develop less binding sites for the tetracycline so less effective
- REDUCE PERMEABILITY OF DRUG - alter or decrease membrane channels ie porins, altering the ability to uptake the drug
- increase EFFLUX PUMPS to pump it back out ion the cell membrane
THES GENE ALTERATIONS CAN OCCUR THRU MUTATION OR HORIZONTAL TRANSFER OR PASSED ON FROM PARENT TO DAUGHTER CELLS
What is horizontal gene transfer
A process where an organism transfers genetic material into another organism that is not its offspring ( this can spread antibiotic resistance)
3 mechanisms of horizontal gene transfer
TRANSFORMATION- bacteria takes up free DNA from environment
CONJUGATION- bacteria directly transfers gene into another bacteria (cell to cell )
TRANSDUCTION- bacteriophage transfers gene from 1 cell to another
What is transduction in horizontal gene transfer
A Bacteriophage incorporates a fragment of bacterial DNA into its genome ,then this piece of DNA transfers into a newley infected cell during the phage infection by the virus
Only short DNA segments can be transferred
What’s transformation in horizontal gene transfer
A type of horizontal gene transfer where DNA is released from bacteria by cell lysis and the “free DNA” is taken up by a competent bacteria cell that then t incorporates it into its genome
Multiple genes may transferred
What’s conjugation in horizontal gene transfer
Bacteria directly transfer genes into another bacteria due to cell to cell contact thru a sex pilus and phormones . DNA/plasmid moves from 1 cell into other cell
Long strands DNA can be transferred
What are lipopolysaccharides
Found in G-ve cells - in the outer cell membrane -
How do prokaryotes reproduce
- Binary fusion- grow and divide - replicating their DNA that stays same in each cell
- Conjugation - a form of horizontal gene transfer then 1 cell transfers DNA ( usually a plasmid ) to another cell thru pilus
- Endospores- in G+ve cells
what’s an endospore
In G+ve cells -produced then dormant under stressful conditions that reactivate and generate further viable bacteria once conditions improve
What colour do G+ve bacteria stain
Violet purple
What colour do G-ve bacteria stain
Pink
Give 3 reasons Why are G-ve bacteria have more resistance to antibiotics than Gram +ve
- Less peptidoglycan in outer membrane so less absorption antibiotic
- have a outer membrane with porins ( that can decrease number or alter structure ) so less antibiotic penetration
- Have LPS ( lipopolysaccharides) in outer membrane ) so maintain a barrier and decrease diffusion of hydrophobic solutes ( eg antibiotics )
List similarities between eukaryote and prokaryote cells
Both have cell membranes and ribosomes
List differences between eukaryote and prokaryote cells
Eukaryote Prokaryote
Cell wall - no LPS/petidoglycans. Have LPS/peptidogl
Nucleus - No true nucleus
Linear DNA in nucleus Single circular DNA
( not in a nucleus) &
Plasmids- small
circular DNA seperate
from main
chromosome
Contain membrane No membrane bound
bound organelles: organelles
Golgi
Lysosomes
endoplasmic reticulum
Mitochondria -
Ribosome 80S. Ribosome 70S
Mitosis for cell division Binary fusion
/endospores
/conjugation cell division
What do mitochondria do
Energy production
Name 4 organelles in eukaryote not prokaryote cells
Golgi/lysosomes /endoplasmic reticulum/Mitochondria
What do endoplasmic reticulum do
Protein synthesis
What do lysosomes do
intracellular digestion
What do Golgi apparatus do
protein modification
What cell has ribosomes of 70s
Prokaryote
What cell has ribosomes 80S
Eukaryote
Name 2 main components in prokaryotes and not eukaryotes and why this is therapeutically important
Prokaryotes have
1. petidoglycans in cell wall for cell rigidity shape - antibiotics that inhibit peptidoglycan synthesis won’t harm eukaryote cells as not contain these ( eg penicillin )
- Lipopolysaccharides in outermembrane G-ve so if disrupt this lipid component ( polymyxins ) membrane breaks and contents leak out and cell dies
( ( not in eukaryote cells so not harmed )
By targeting these components only in bacteria cell walls can kill bacteria cell but not damage host cells )
