Bio Cell Function Notes

Passive Transport

- Does not require energy (ATP)

- Occurs in situations where there are areas of different concentration of a particular substance

- Movement of the substance occurs from an area of high concentration to an area of low concentration

- Movement is said to occur along a "concentration gradient"

- SIMPLE DIFFUSION (e.g. oxygen moving through membrane)

o High low concentration

o Substances other than water move between the phospholipid molecules/ proteins

o Involves the membrane

- FACILITATED DIFFUSION (glucose moving into cells)

o Non- channel protein carriers change shape to allow movement of substances OTHER than water

o Carrier changes shape but doesn't require energy

- OSMOSIS

o Movement along the concentration gradient

o Involves only the passive movement of WATER molecules across a partially permeable membrane (a membrane that only allows certain substances through)

o "hyperosmotic solution" has a higher concentration of total solutes than the "hyposmotic solution"

 Hypo  where the water is from (high concentration of water)

 Hyper where the water is going (low concentration of water)

- Pass through Membrane: small, non- polar substances

- DO NOT PASS: polar and large substances (e.g. chloride ions, potassium ions, sodium ions, glucose, sucrose)

- *passive transport continues until there is an equal concentration of substance in both areas involved equilibrium

Active Transport

- Requires energy

- Moves AGAINST the concentration gradient, so energy and expenditure must occur

- This process allows the cell to maintain interior concentrations of molecules that are different from exterior concentrations

- Sodium- potassium pump

Endocytosis and exocytosis

- Processes that allow larger molecules to move across the plasma membrane

- Endo allows macromolecules to enter the cell, while Exo allows molecules to leave

- Both processes depend on the fluidity of the plasma membrane

o ENDO occurs when a portion of the plasma membrane is pinched off to enclose macromolecules or particulates

 VESICLES