Membrane transport and communication (physio lecture 2)

What are the different kinds of membrane transporters?

Channel proteins - create a water filled pore and allows for passive transport (no atp)

Carrier proteins - only open from one side and never form an open channel (kinda like an enzyme with binding site, conformation change occurs)

Different types of carrier proteins?

1. Uniport carrier: transports one specific substructure (diffusing)

2. Synport carrier: carries two or more substrates in the same direction. Both/all substrates involved are absolutely required for conformation change to occur!

3. Antiport carriers: moves substrates across the membrane in different directions, against the gradient. Requires ATP!!!

Co transport: SGLT

• Sodium dependent glucose transporter

• The extracellulat environment is the lumen of the intestine or kidney

1. sodium binds to the carrier, which is open towards the lumen. There is high Na+ and low glucose in the lumen

2. Na binding creates a high affinity site for glucose, so gluclose attaches

3. Glucose binding changes the conformation of the transporter protein, so now it is open towards the cytosol or ICF

4. Sodium releases into the cytosol, meaning there is no more high affinity site for glucose, so it gets released into the cytosol of the cell. Conformation is restored to original tingy

Signaling pathway - basic cascade

signal molecule binds to membrane receptor protein activates intracellular signal molecules alter target proteins create response

Enzyme linked receptors

when extracellular signal molelcue binds to the receptor and directly activates an enzymatic activity on the intracellular side

G protein coupled receptors

Large family of cell surface proteins that span the membrane ~7 times to detect external signals and trigger internal cellular responses

Focal adhesion complex

• specialized molecular structures that anchor the inside of a cell to its outside environment

• feels how stiff/soft environment is and triggers chemical signals inside the cell to control things like growth/survival/behavior