U1: KA3 - Membrane proteins Flashcards
(29 cards)
Describe the structure of the plasma membrane.
Fluid mosiac model
composed of phospholipids and proteins
Describe phospholipids.
Charged head that is hydrophillic
Uncharged non-polar tail which is hydrophobic
What gives the membrane its fluid quality?
Phospholipids constantly changing position.
The membrane is embedded with proteins which forms what?
A patchy mosaic.
What functions can proteins in the membrane have?
Active transport proteins
Channel forming proteins
Enzymes
Receptors
Attachment proteins for the cell cytoskeleton
What are the 2 types of protein in the plasma membrane?
Integral protein
Peripheral protein
What are integral proteins?
Found within the membrane.
Transmembrane, meaning they span entire width of membrane
Interact with the hydrophobic region of membrane - phospholipids. Allowing hydrophobic interactions holding integral membrane proteins within the bilayer.
What are peripheral proteins?
Found on the surface of the membrane have hydrophilic R groups bound to surface of membrane mainly by ionic and hydrogen bond interaction.
Many interact with the surfaces of integral membrane proteins.
What is facilitated diffusion?
Passive transport of substances across the membrane through specific transmembrane proteins.
Why are some channel proteins gated?
change conformation to allow or prevent diffusion
they respond to stimulus which causes them to open or close.
What are channel proteins?
Multi-subunit proteins with subunits arranged to form water-filled pores that extend across the membrane. Most channel proteins are highly selective.
What do ligand gated channels do?
Control binding of signal molecules. When the correct signal molecule binds the gate opens allowing ions to flow through.
How do voltage gated channels work?
Controlled by change in ion concentration
How do transporter proteins work?
Bind to specific substance to be to be transported and undergo a conformational change to transfer the solute across the membrane.
Why do transporters alternative between two conformations?
So binding site for a solute is sequentially exposed on one side of the bilayer, then the other side.
How do protein pumps work?
Active transport uses them to transfer substances across the membrane against the concentration gradient.
Pumps that mediate active transport are what?
Transporter proteins coupled to an energy source
What is the concentration gradient?
Difference in concentration of a solute across the plasma membrane.
What is the Electrical potential difference?
Membrane potential - difference in electrical charge on the two sides of the membrane.
The sodium-potassium pump transports ions ….. a steep concentration gradient.
Against
How many ions are actively transported out of the cell and how many are in?
3 Sodium ions out
2 Potassium ions in
What combines to form the electrochemical gradient and what does it determine?
Concentration gradient and the electrical potential difference.
Determines the transport of the solute.
