Microbio 6

to get nutrients into the cell

Water can freely pass the membrane in both directions because it is small and weakly polar

Can only transport solutes down a gradient

Can transport sollutes against the electrochemical gradient, uses energy (ATP)

By the concentration gradient alone, not the electrochemical gradient

Transporters are saturable, so their rate has an upper limit based on how many transporters are in the membrane

In multicellular organisms, nutrients can be acquired by means of diffusion or facilitated diffusion

In unicellular organisms, including prokaryotes, nutrients are usually acquired by active transport

Transport systems are highly specidic; a single molecules or a class of closely related molecules

• The binding of the substrate on one side of the membrane induce a conformation change in the carrier in such a way that the carrier open to the other side. The concentration of te substrate is lower there
• The substrates is released and diffuse away from teh carrier

• Chanel
• Carrier

Open in, or open out

Carriers are substrate specific

When the protein is open to the side with the higher concentration of substrate, a phosphate binds to it and changes the shape, this pushes the substrate out of the protein, and allows something else to bind to it

Transports one molecule at a time

1 molecule in and 1 molecule out at the same time

2 molecules in the same direction at the same time

Simple transport

• Simple transport
• Group translocation
• ABC transport

Driven by the energy of the proton motive force

Cjemical modification of the transported substance driven by phosphoenolpyruvate

Periplasmic binding proteins are involved and energy comes from ATP

ETC pushes protons out, a terminal electron acceptor is present, proton motive force is generated

• ATPases can be used to generate the pmt, ATPases work in reverse
• pmf-dependant transporter are smporter or antiporter that use the proton gradient
• Pmf can be used to generate a gradient of Na+ that is used by some transporters as a soure of energy

Sodium gradient is apparent in sea water and is used by bacterias in the sea

• ATP-binding cassette, 3 components:
• A membrane spanning protein, the active transport carrier (not a channel)
• An ATP-hydrolyzing proteins that provide the energy for active transport
• A substrate-specific binding proteins that has very high affinity for a specific substrate (or a class of substrtes)

High affinity allows it to bind in very low concentration

In the periplasm

Anchored in the cytoplasmic membrane