Cellular Transport

Objectives:-Summarize the structure & function of the plasma membrane -Summarize passive transport and the four main types-Summarize active transport and the three main types-Relate cell transport to homeostasis

Selectively Permeable Membrane

Passive TransportFour types:

diffusionosmosisfacilitated transportion channels

Common characteristics: -No addition of energy (ATP) required.-molecules move from high concentrations to low

concentrations.

1. Diffusion-Simplest type of passive transport.

-No energy required

-Movement of molecules from a high concentration to a low concentration.

-Substances being diffused: lipids, gases, fat-soluble molecules

Diffusion

2. Osmosis

-Passive transport…no ATP needed

-Function: diffusion of water across a selectively permeable membrane, high concentration to low concentration.

-Substance being diffused: water

Osmosis

Cells are subject to Osmosis because they are surrounded by water solutions.

1. Isotonic Solutions-outside concentration = inside concentration.

2. Hypotonic Solutions-Concentration (of sugar) is lower outside than inside

the cell.

This means water wants to move into the cell. Cells begin to swell and may burst. (cytolysis)

3. Hypertonic Solution-Concentration (of sugar) is higher outside of the cell

than inside.

Water tends to flow out of the cell causing animal cells to shrivel and plant cells to wilt.

*Remember…it’s just water moving!

Some cells have developed ways to rid themselves of water.

Contractile vacuoles (unicellular orgs.)

Turgor Pressure, Plasmolysis, Cytolysis

Turgor Pressure Plasmolysis

Contractile Vacuole

3. Facilitated Diffusion

-Passive transport…no ATP needed

-Function: transports sugars and amino acids using membrane transport proteins that are specific to the molecules that need to pass.

-Common molecules…sugars & amino acids

4. Ion Channels

-Passive transport…no ATP needed.

-Function: transports ions using membrane transport proteins that are specific to the ions that need to pass.

Examples of Ions: Cl- Na+ Ca2+ K+

Active Transport

Active Transport- movement against a concentration gradient from “low to high”.

-requires input of energy (ATP) and membrane transport proteins.

1. Cell Membrane Pumps: Sodium-Potassium Pump (move K inside the cell, move Na outside the cell.) -Used in the human muscular and nervous systems.

Active Transport

Active Transport

Types of Active Transport:

2. Endocytosis: cell membrane surrounds and takes in material from its environment.

-pinocytosis-fluids -phagocytosis-large particles or cells

Pinocytosis Phagocytosis Endo & Exo

3. Exocytosis: the expulsion or secretion of materials out of a cell.-works with the golgi apparatus in forming vesicles to remove large molecules such as proteins, waste products, and toxins out of the cell.

Endocytosis Exocytosis