Mod2-Obj2: Passive transport and active transport Flashcards
Types of transport: Passive transport
No energy (ATP) required
- Substances move down concentration gradient
- Simple and facilitated diffusion
Types of transport: Active transport
Requires ATP
-Primary active transport
Concentration gradients
Atoms and molecules move from an area of high concentration to an are of low concentration
- Down or along a concentration gradient
- Once equilibrium is reached, there is no further net movement
Simple diffusion
Movement in and out of cell, no ATP required
- Solutes move down concentration gradient
- High to low
- Speed is influenced by size, the smaller the molecule the faster the rate of diffusion
- Lipid-soluble substance
Facilitated diffusion
Assisted movement in and out of cell, no ATP required
-Solutes move down concentration gradient
-High to low
-Carrier proteins to faciliate the passage of lipid-insoluble (polar) solutes across the plasma membrane i.e.) glucose
-Protein channels
+leakage channels and gated channels
i.e.) sodium (Na+) and potassium (K+)
Carrier-mediated facilitated diffusion
Via protein carrier specific for one chemical; binding of substrate causes transport protein to change shape
Channel-mediated facilitated diffusion
Through a channel protein; mostly ions selected on basis of size and charge
Leakage channel
Are always open and simply allow ions or water to move according to concentration gradients
Gated channel
Are controlled (opened or closed) by chemical or electrical signals
Facilitated diffusion: Voltage gated channels
Voltage-gated channels open in response to changes in t membrane potential
Osmosis
Net diffusion of water through a selectively permeable membrane, from an area where there is more water, to an area where there is less
- One solute molecule, displaces one water molecules
- Water moves from an area where there is less solute, to an area where there is more solute, to balance out the concentration gradient
- Through an aquaporin or through the lipid bilayer
Diffusion and osmosis are…
Passive and non-energy requiring
Tonicity
The ability of a solution to affect cell shape by altering water volume
Tonicity: Isotonic solution
Same concentration of solutes and water
-No change in volume or shape
Tonicity: Hypertonic solution
Higher concentration of solutes, lower concentration of water
-Cell volume decreases, cell shrinks
Tonicity: Hypotonic solution
Lower concentration of solutes, higher concentration of water
-Cell volume increases, cell swells
Tonicity: Clinical importance
- Never use plain water in an IV drip, as net movement of water inside and outside of a cell should not occur
- Use saline in an IV drip
- Never drink sea water
- You drink water when thirsty
Primary active transport
Plasma membrane can actively move substances against their concentration gradients
- Low to high
- Mediated by carrier proteins (uses ATP to drive movement)
- Maintains concentration differences either side of membrane
Hydrolysis of ATP changes…
Shape of carrier protein -Pump solutes (ions) E.g.) K+/Na+ pump -Moves Na+ out of the cell -Move K+ into the cell -Maintains membrane potential
Endocytosis and Exocytosis
Used to move particles too large to cross the membrane
-Involves vesicles and the cell membrane
Endocytosis
Into the cell (phagocytosis and pinocytosis)
Exocytosis
Out of the cell (i.e. proteins from golgi apparatus)