Membrane Protein transport - Week 8

Membrane Proteins and transport across membranes

Define facilitated transport

Membrane transport where proteins transfer specific molecules in and out of the cell

What type of molecules NEVER pass through the membrane

Ions (any sort of charged atoms/ molecules)

_________ ___________ Molecules are the easiest molecules to pass though the bilayer

Small non polar

Molecules move form areas of ______ to ____ concentration ______ the concentration gradient.

High, low, down

Which two types of molecules are impermeable

1. Large uncharged polar molecules

2. Ions

Larger uncharged polar molecules and ions need _______ _______ to pass through the bilayer

transport proteins

Define Transmembrane transport proteins

Create a protein lined path for transport through the cell

What are the 2 types of membrane transport proteins?

1. Channel proteins

2. Transporter proteins

Chanel proteins select molecules based on their _____ and ___________ ______

size and electric charge

Transporter proteins experience a series of ________ changes for transport

Conformational

True Or False: Solutes fit into the binding site of transporter proteins

True

Define: passive transport

Transport through the membrane using diffusion (NO ENERGY)

3 methods of Passive transport

1. Diffusion

2. Channel proteins

3. Transporter proteins

Define: Active Transport

Transport using ATP to pump molecules through the membrane

True Or False: Active transport pumps molecules along the concentration gradient

False, it pumps them AGAISNT the concentration gradient

Define electrochemical gradient

Concentration gradient + Membrane potential

Explain what is meant by membrane potential

The difference in charges on the outside of the cell compared to the inside

The inside of the cell is more _______ charged while the outside is more ______ charged

Negatively, Positively

Channel proteins have a _______ pore (where the molecules pass through)

hydrophylic

True Or False: Transporter proteins are faster than channel proteins

False, Channel proteins are faster than transporter proteins

Define: Non-gated Ion channels and their role

• Always open

• K+ (potassium) moves out of the cell

Define Gated ion channels

• Selects specific type of ions

• Requires a signal for channel opening

What is the effect of signals on non-gated channels

Causes the channel to remain open for long periods of time (think of it as a door wedge)

List the 4 type of gated ion channels

1. Mechanically gated

2. extracellular ligand (Ligand-gated)

3. Intracellular Ligand (Ligand-gated)

4. Voltage-gated

How is a mechanically-gated channel signaled

External stressed placed on it (Mechanical stress)

How is a extracellular ligand channel signaled

Signals attach to the exterior at the top

How is a Intracellular ligand channel signaled

Signals attach to the exterior on the bottom

How is a voltage-gated channel signaled

Signaled by a change in voltage across the membrane

True Or False: Transporter proteins are uniport

True

True Or False: The direction of Transporter proteins is not reversible

False, It is

Define: Symport Vs. Antiport

Symport: Two solutes moved in the same direction

Anti: 2 solutes in opposite directions