Cell structure midterm 2 Flashcards
What is the difference between nucleoid, nucleus, nucleolus
Nucleoid
- Prokaryotic cell, where the circular DNA is, it is concentrated
Nucleus
- In a eukaryotic cell
Nucleolus
- Inside the nucleolus in the eukaryotic cell
- Main function is ribosome synthesis, ribosomes are made in the nucleolus
- Ribosome is made of protein and DNA, RNA specifically, all RNA is made in the nucleus, DNA is made in the cytoplasm
- mRNA is for translation, to bring the ribosomes out of the nucleus in order to make DNA
what are the bacterial cell envelope and their phyla?
- Gram negative
- has a thin cell wall
- but has both the inner and outer cell membrane
- Phyla: Proteobacteria - Gram positive
- has a thick and firm cell wall but has no outer membrane
- Phyla: Firmicutes
what is the cell wall made of?
Peptidoglycan (murein)
How is the cell wall linked together?
the glycan chains are cross-linked via short peptide bonds by a enzyme called transpeptidase
peptide bond attaches to the DAP –> D-ala and it cleaves off the other D-ala
What are the types of amino acids in bacteria?
4 types
- L-Alanine (L-ala)
these are unique to bacteria - D-Glutamic acid (D-Glu)
- Diaminopimelic acid (DAP)
- D-Alanine (D-ala)
How does lysozyme work?
It is part of your immune system, innate
it washes things out
it is a protein, enzyme that cleaves the glycan backbone, so this prevents the formation of cell wall
it targets bacteria with a more exposed cell wall (gram positive cells)
gram negative cells have plasma membrane that protects them from things like lysozyme
What does transpeptidase do?
it moves the amino acid from one amino to another amino acid
they cross link the glycan together, so they shift the amino acids to create a peptide bond
What do gram positive cells have?
Teichoic acids and lipoteichoic acid
S layer
no outer membrane
what is teichoic acids and lipoteichoic acids?
Teichoic acids are chains of glycerol linked by phosphodiester bonds (anionic)
it provides strength
What is a S-layer?
tough layer outside of the peptidoglycan wall, many copies of a single protein
some archaea and gram negative bacteria have it
what is the periplasm?
it was inbetween the inner membrane and cell wall of both the gram negative and positive cell
What does the periplasm contain?
6 things
2 proteins
- receptor proteins
- nutrient-binding proteins
3 enzymes
- digestive enzymes
- detoxifying enzyme
- enzyme for cell wall assembly
1 system
- secretion system
What does the gram negative bacteria contain?
Porin
- Membrane transport proteins which allow in hydrophilic molecules
Lipopolysaccharide phospholipid
- only found in the outer leaflet
What is the structure of lipopolysaccharide?
Top to bottom:
repeating O antigens
Chain of 5-sugars, core polysaccharides
Lipid A, fatty acids
- endotoxin
What are repeating O antigens
hydrophilic
sugar vary
antigenic, causing an immune system to recognize it
specific to the bacteria
creates protection
What are lipid A
two sugars
fatty acids
highly toxic, if you get infected with a gram negative bacteria you will have very specific symptoms
endotoxin (internal)
What are the gram negative bacteria infection symptoms?
Intravascular coagulation (blood clots in blood vessels)
hemorrhage (bleeding)
shock
What do lipopolysaccharides do?
activate macrophages
- this causes pyrogens (fever)
- macrophages are white blood cells and they are highly sensitive to endotoxins and so they release pyrogens
activate complement cascade
- this causes inflammation
- it is made up of proteins so one protein activates another and another
what are acid fast bacteria and what is their genus?
mycobacterium (genus)
they cause tuberculosis and leprosy and they stain differently than other bacteria
they have no outer membrane like gram positive bacteria but they have mycolic acid which is a hydrophobic waxy surface and thus the stain cannot enter
thick cell walls and mycolic acid makes it hard to stain
How do you stain mycobaterium
the acid fast staining procedure, 3 steps
- use heat to drive pink stain into cell
-They don’t let the stain come out - decolorized with acid-alcohol
-it takes the stain out of everything else but not the mycobacterium - counterstain with methylene-blue
- Why will this not stain the mycobacteria, because we are not heating it up so the stain will not go in
- Gram positive and gram negative will always looks blue (it will stain everything)
what does flagella do and what are the different types?
it enables bacteria to swim
it is made up of flagellin protein
there’s 4 types of structures
1. Monotrichous
- one flagella
- Lophotrichous
- multiple flagella at one end - Amphitrichous
- flagella at both ends - Peritirichous
- flagella everywhere
How does flagella move and what makes it move?
To move straight it must move counter clockwise thus all the flagella (if it has multiple) must move to one side and move in the same direction
if the flagella moves clockwise it will tumble
The flagella moves to where the chemical signal via chemotaxis
What is chemotaxis?
A chemical signal that the bacteria is drawn to and they start swimming, but if the signal gets stronger than it keep running until the signal gets weaker
then they tumble and pick a random direction and hope they ran correctly
What is phototastic
bacteria that are drawn to light
