Movement of Substances

Define diffusion

Net movement of particles down a concentration gradient until equilibrium is reached

Define osmosis

Net movement of water molecules down a water potential gradient through a partially permeable membrane

What is rate of diffusion and osmosis affected by?

• Concentration / water potential gradient

• Diffusion distance

• SATV ratio

Define active transport

The process in which cellular energy (ATP) is used to move particles of a substance against a concentration gradient across a membrane with protein pumps

What substances are taken up by protein “pumps” during active transport?

Selected substances are taken up as most membrane “pumps” are specific to particular substances

Define bulk transport

Movement of vesicles of matter across the cell surface membrane with ATPP

*Gradient does not matter

What is rate of active transport affected by?

• Temperature

• pH

• Concentration gradient

• Amount of ATP present

What is exocytosis?

Process by which cells export products like enzymes via vesicles

What is endocytosis?

Process by which substances are brought into the cell

What is phagocytosis?

Wholesale import of solid matter

What is pinocytosis?

Bulk import of fluids

What happens to a plant cell in a solution with higher water potential?

1. Cell sap has lower water potential than surrounding solution

2. Net movement of water molecules into cells via osmosis

3. Cells expand and become turgid

4. Cellulose cell wall prevents cell from bursting as cytoplasm volume increases

What happens to a plant cell in a solution with lower water potential?

1. Cell sap has higher water potential than surrounding solution

2. Net movement of water molecules out of the cell via osmosis

3. Cell becomes flaccid 

4. Cell surface membrane pulls away from the cellulose cell wall and cell becomes plasmolyse

What happens to an animal cell in a solution with higher water potential?

1. Cytoplasm has lower water potential than surrounding solution

2. Water molecules enter the cell via osmosis

3. Cell expands and bursts

What happens to an animal cell in a solution with lower water potential?

1. Cytoplasm has higher water potential than surrounding solution

2. Net movement of water molecules out of the cell via osmosis

3. Cell shrinks in size and becomes crenated (spiky)