bacterial anatomy Flashcards
define amphipathic
hydrophilic and hydrophobic in different areas
Define passive diffusion (3)
- transporter independent
- the combined concentration of solutes passively tries to reach equilibrium
- uptake increases in a linear fashion, but will plateau when inside conc. reaches outside
define facilitated diffusion
- independent of membrane permeability
- example is a porin, which is proteins that make a hole through the membrane, allowing molecules up to a certain size through
- uptake levels will rise as outer conc rises, but will reach max saturation. uptake will plateau when inner and outer conc. reaches equilibrium
the lower the km,
the higher the affinity of the channel, more activity
is active transport dependent on a transporter?
yes
Define the kinetics of active transport
uptake will plateau at a point. however, concentration inside can go above outside concentration
what do uni-, sym, and antiporters have in common?
all are unidirectional, any kind of transport
define uniporters
They move one specific substance in one direction
Used for either facilitated diffusion or active transport
define symporters
They move two specific molecules in one direction at the same time
Used for either facilitated diffusion or active transport
define antiporters
Two specific molecules are transported in opposite directions
Used for either facilitated diffusion or active transport
what are two functions of the cell wall?
resist osmotic pressure caused by the entry of water, and define cell shape
define periplasm
gap between cell wall and interior plasma membrane
What is the difference between peptidoglycan units on gram positive and negative units?
Gram negative have DAP on their string of amino acids, while gram positive uses Lys in the same spot
bridges between layers of the peptidoglycan in gram negative
direct peptide bond between the amino acid chains of each layer
bridges between layers of the peptidoglycan in gram positive
indirect bonding between layers through a bridge of glycenes
how does the cell wall grow? (3 steps)
- preformed units are brought to the cell wall
- autolysin comes in and cuts the cell wall, allowing new units to be added to the cell wall
- bridges are then formed between the layers through transpeptidation
how penicillin works
when the cell wall is growing, beta lactams in penicillin prevent new transpeptidation linkages between layers of the peptidoglycan layer.
why does penicillin only work on gram + bacteria
Gram - bacteria have the glycocalyx that protects them from penicillin, since it is a large molecule
how does lysozyme work?
it cleaves the beta 1-4 linkages between N-glucosamine and acetyl-muramic acid. it works on cell that are growing, and cells that are not. it cuts the linkages between peptidoglycan units
What is the significance of Lipid A to the body?
only found on the LPS layer, no body cell have LPS, the body knows there is an intruder
what is the LPS impermeable to?
larger proteins, ploysaccharides, and H+
