lecture 3 - membrane transport Flashcards
P-type ATPases
phosphorylate themselves (use the phosphorylation of ATP to provide energy to move something from high to low)
eg Na-K pump
Na-K pump
3 binding sited for Na and K
K ions larger
Na fits into domains easier
hence 3:2 Na:K stoichiometry
- Na enters the channel
- conformational change to move N domain across
- N domain phosphorylates P domain releasing
ADP and energy - energy used to shut gate on one side and open gate on other side
- Na released
- K enters and fills pockets in channels
- causes conformational change to release phosphate from P domain through actuator domain
- regenerated ATP binds N domain, energy used to open gate
- K exits
- cycle repeats
gibbs donnan effect
describes the unequal distribution of permeant ions on either side of a membrane which occurs in the presence of impermeant charged ions
negatively charges proteins hold onto positive ions in the cell which causes
low water potential there fore water enters and na/k ATPase lowers the number of dissolved particles in the cell which counter GD effect
if we inhibited na/k pump the cell would
burst
secondary active transport
transport one solute down a concentration gradient, coupled to the transport of another against concentration gradient
symporters
move two things in the same direction
e.g. sodium glucose transporter
antiporter
transport of two or more molecules or ions in opposite directions
active transporters
ABC transporters, transport small molecules and use ATP as they do it
E.G. CFTR
osmolarity
total concentration of dissolved particles in a litre of solution
osmolality
the number of dissolved particles per unit mass
1M sucrose has an osmolarity of
1 osmolar
1M NaCl has an osmolarity of
2 osmolar
1M CaCl2 has an osmolarity of
3 osmolar
