Cellular Transport Unit Passive Transport = movement of substances across the cell membrane without any input of energy by the cell

Passive Transport

Types 1) Diffusion = movement of molecules from high to low [ ] (concentration) - driven by the concentration gradient - spreads out evenly till dynamic equilibrium is reached - spreads out evenly till dynamic equilibrium is reached

Diffusion

2) Osmosis = diffusion of water A solution may be one of the following: (compared to a cell) - isotonic solution: same [ ] of water and solute - hypotonic solution: lower [ ] of solute, a lot of water - hypertonic solution: higher [ ] of solute, less water

Isotonic Solution (Red Blood Cells) A solution is isotonic to a cell if it has the same concentration of solutes as the cell. Equal amounts of water enter and exit the cell, so its size stays constant.

Hypotonic Solution (Red Blood Cells) A hypotonic solution has fewer solutes than a cell. Overall, more water enters a cell in a hypotonic solution, causing the cell to expand and even burst.

Hypertonic Solution (Red Blood Cells) A hypertonic solution has more solutes than a cell. Overall, more water exits a cell in a hypertonic solution, causing the cell to shrivel and even die

Direction of Osmosis Outside the Cell Inside the Cell Net Movement of Water Isotonic Isotonic None Isotonic Isotonic None Hypotonic HypertonicInside the Cell Hypotonic HypertonicInside the Cell Hypertonic Hypotonic Outside the Cell Hypertonic Hypotonic Outside the Cell ** If the solution outside the cell is hypotonic, then inside the cell is hypertonic and vice versa ** Water tends to diffuse from hypotonic to hypertonic

- Plasmolysis = cells shrink when turgor pressure is lost - the reason plants wilt

- Cytolysis = cell bursts due to water entering the cell

3) Facilitated Diffusion = move molecules across the cell membrane through carrier/transport proteins - are specific for the type of molecule they help diffuse

Facilitated Diffusion (Open Channels)

Facilitated Diffusion (Proteins Change Shape)

Diffusion vs. Facilitated Diffusion Diffusion Facilitated Diffusion Diffusion Facilitated Diffusion

Active Transport = substances can cross the cell membrane with an input of energy from the cell

Active Transport

1) Endocytosis = the process by which cells ingest “stuff” - vesicle holds the “stuff” - two types: 1) pinocytosis - solutes and fluids 2) phagocytosis - large particles or whole cells

Endocytosis

2) Exocytosis = the process by which cells release “stuff” - is essentially the reverse of endocytosis

Exocytosis