Gram Negative Bacteria-Mycobacteria and cytoplasmic membrane II

What are the two types of membrane proteins?

1. Integral

2. Peripheral

Where are integral proteins found? How can they be removed?

Embedded in the membrane. Removed with detergents or solvents

Where are peripheral proteins found? How can they be removed?

Attached to the membrane surface. Removed with salt solutions

What are the 7 essential functions of membrane proteins?

1. Solute transport

2. Electron transport

3. ATP synthesis

4. Protein secretion

5. Motility

6. Sensing environmental signals

7. Biosynthesis of cell wall polymers and lipids

What is an example of a protein for solute transport?

ABC transporter for nutrient uptake

What is an example of a protein for electron transport?

Cytochrome C

What is an example of a protein for ATP synthesis?

ATPase

What is an example of a protein for protein secretion?

Secretory translocase

What is an example of a protein for motility?

Flagella rotor

What is an example of a protein for sensing environmental signals?

Histidine kinase two component-regulatory system

What types of molecules can cross the cell membrane?

Small hydrophobic molecules and small uncharged polar molecules

Why do we need transporters in the membrane?

To get large uncharged polar molecules and ions across

How can you tell if its passive or facilitated diffusion?

If you increase the concentration and more drug gets in because with facilitated you can completely saturate the carrier so that the rate of transport plateaus (concentration of drug is not as much inside cell)

What is passive transport?

It transports solutes across the membrane based on a concentration gradient from high to low and requires no energy expenditure W

What are the 3 types of passive transport?

1. Simple diffusion

2. Facilitated diffusion

3. Osmosis

What is simple diffusion?

Movement of solutes down their concentration gradient from an area of high concentration to an area of low concentration

What is facilitated diffusion?

It is where proteins act as channels or carriers to allow certain molecules to diffuse into or out of the cell along their electrochemical gradient

What is osmosis?

It is the diffusion of water molecules across a selectively permeable membrane in response to differing concentrations of solutes

What do active processes require?

Cells to use energy in the form of ATP to move solutes across the plasma membrane against their concentration gradient

What is used to move substances across the cytoplasmic membranes?

Trans-membrane permeable proteins

What are uniport proteins?

They transport one substance in one direction

What are antiport proteins?

They transport two substances at once in the opposite direction

What are symports?

They transport two substances at once in the same direction

What is group translocation?

It causes chemical changes to the substance being transported. The membrane is now impermeable to the altered substance, therefore trapping it

What can pump antibiotics out of the cytoplasmic membrane?

Efflux pumps

What does the bacterial cytoplasmic membrane do?

It maintains a concentration and electrical gradient

What creates an overall electrochemical gradient across the membrane?

A relative concentration of chemicals inside and outside the cell and of the corresponding electrical charges (achieved through the proton motive force)

What is active transport?

It is when a cytoplasmic membrane can use the energy inherent in its electrochemical gradient to transport substances into or out of the cell.

How can we determine if the cell is dependent on the proton motive force?

1. Poke a hole in the membrane to disrupt the proton motive force

2. See if transport is still occurring or not

What are 2 antibiotics that disrupt membrane function?

1. Polymyxins (such as colistin)

2. Daptomycin

Is colistin for gram positives or negatives?

Gram negatives

What does colistin do? What is its structure? When is it used?

It is a basic polypeptide with a fatty acid tail that disrupts membranes rich in phosphatidylethanolmine. For multi-resistant bacteria

Is daptomycin for gram positives or negatives?

Positive

What does daptomycin do?

It is a new antibiotic that inserts into the bacterial membrane resulting in depolarization (kills cells)