Membrane Proteins 1.3 Flashcards
what is the cell membrane composed of?
proteins and phospholipids
what is the function of the cell membrane
controls entry and exit of materials into and out of the cell
what do regions of hydrophobic R groups allow?
strong hydrophobic interactions that hold integral membrane proteins within the phospholipid layer
what can integral proteins be?
transmembrane proteins
what do peripheral proteins have?
hydrophilic R group on they surface and are bound to the surface membranes mainly by ionic and hydrogen bonds
what do many peripheral membrane proteins interact with?
the surfaces of integral membrane proteins
what is the phospholipid bilayer?
barrier to ions and most uncharged polar molecules
what molecules can pass through the bilayer by simple diffusion?
oxygen and carbon dioxide
what is facilitated diffusion?
passive transport of substances across the membrane through specific transmembrane proteins
why do different cell types have different channel and transporter proteins?
to perform specialised functions
most channel proteins in animal and plant cells are what?
highly selective
why are some channel proteins gated and change conformation?
to allow or prevent diffusion
what are ligand-gated channels controlled by?
binding of signal molecules
what are voltage-gated channels controlled by?
changes in ion concentration
why do transporter proteins bind to specific substance?
to be transported and undergo a conformational change to transfer the solute across the membrane
what does active transport use?
pump proteins that transfer substances across the membrane against their concentration gradient
what is required for active transport?
a source of metabolic energy
what determines the transport of a solute carrying a net charge?
the concentration gradient and the electrical potential difference combine to form the electrochemical gradient
what energy does the sodium-potassium pump use?
energy from the hydrolysis of ATP to establish and maintain ion gradients
describe the transportation of ions in the sodium-potassium pump
it transports ions against a steep concentration gradient using energy directly from ATP hydrolysis
what does the sodium-potassium pump transport?
actively transports 3 sodium ions out of the cell and 2 potassium ions into the cell
where is the sodium-potassium pump found?
in most animal cells - accounting for a high proportion of the basal metabolic rate in mainly organisms
what does the sodium-potassium pump drive in the small intestine?
transport of glucose
what is the glucose transporter responsible for?
glucose symport transports sodium ions and glucose at the same time and in the same direction
describe the generation of an ion gradient
- the pump has high affinity for sodium ions inside the cell
- binding occurs-
phosphorylation by ATP - conformation changes
- affinity for sodium ion decreases
- sodium ions released outside of the cell
- potassium ions bind outside the cell - dephosphorylaton
- conformation changes -> potassium ions taken into cell
- affinity returns to start
what do some active transport proteins do?
they hydrolyse ATP directly to provide the energy for the conformational change require to move substances across the membrane
