Physiology Flashcards
What is facilitated diffusion?
Diffusion that uses a carrier protein to facilitate passive diffusion
What is active transport?
Requires energy to pump molecules against their concentration gradient
What is primary active transport and what is an example?
When energy is used directly to move substance against the concentration gradient
Sodium potassium pump
What is secondary active transport?
Solute moves against its concentration gradient facilitated by the passive movement of an ion down a concentration gradient
What is a symport?
Solute and ion move in the same direction
What is an antiport?
Solute and ion move in opposite directions
What is the process of the sodium potassium pump?
- 3 Na from inside cell bind
- ATP hydrolysed to ADP and Pi, providing energy to change conformation
- 3 Na released outside of cell, 2 K bind
- Pi released from pump, which reverts back to original cell, 2 K released into cell
What is the membrane potential?
-70mV
What is the process of an action potential?
- Resting membrane potential - voltage-gated Na channels in resting state and voltage-gated K channels closed
- Stimulus causes opening of Na channels - depolarisation of cells
- Once threshold reached more Na channels open
- Na channels close and K channels open - repolarisation
- Hyperpolarisation - more K channels open, Na channels in resting state - refractory period
Which factors affect rate of diffusion?
Surface area Membrane thickness Concentration gradient Lipid solubility Molecular weight
What is endocytosis?
‘Pinching off’ and engulfing to take molecule into cell
What is exocytosis?
Vesicle bind to plasma membrane then release its contents into extracellular fluid
What is pinocytosis?
Engulfing with fluid around the area
What is osmolarity?
The concentration of osmotically active particles in a solution
What is tonicity?
The effect a solution has on cell volume