Bio Lesson 5 - Cell Transport

Cell Transport

• Mechanisms that cells use to transport across the cell membrane

• Creates a set of internal conditions different from the surroundings — i.e. homeostasis

Passive Transport

• Requires no additional energy

  • moves ALONG the concentration gradient—from high to low concentration

Simple Diffusion

Small, hydrophobic molecules pass through the phospholipid bilayer

Facilitated Diffusion

molecules transported by channel proteins

Osmosis

movement of a solvent from low solute concentration to high solute concentration

• basically, the movement of water to balance out the concentration

Levels of Tonicity

describes how the solute concentration of a solution compares to the concentration of the cell

Hypotonic

• Lower concentration outside the cell caused water to diffuse into the cell which swelled up

Movement: Water moves into the cell

Animal cells: Cytolysis (Bursts)

Plant cells: Turgid (Normal/Firm)

Isotonic

• Equal concentration in and out the cell caused no net movement, change in cell size nor shape

Movement: Balanced; water still moves

Animal cells: Normal (Healthy)

Plant cells: Flaccid (Limp)

Hypertonic

• Higher concentration outside the cell caused water to diffuse out of the cell, which shrunk

Movement: Water leaves the cell

Animal cells: Shriveled (Shrinks)

Plant cells: Plasmolyzed/Plasmolysis (Membrane shrinks away)

ATP

Adenosine Triphosphate

• the primary energy-carrying molecule that acts as the "rechargeable battery" of the cell, powering almost every cellular activity and chemical reaction.

Active Transport

• Requires energy in the form of ATP

• moves AGAINST the concentration gradient—from low to high concentration

Protein pumps

proteins on the membrane pump molecules in or out of the cell

Bulk transport

mechanisms of cell transport in very large quantities or sizes

Exocytosis

exit of materials from the cell

Endocytosis

entry of materials into the cell

Phagocytosis

“cell eating”

• engulfs solid material

• The cell membrane extends outward using pseudopodia ("false feet") to surround, trap, and engulf large solid particles or whole bacteria.

pseudopodia: temporary, arm-like extensions of a cell’s membrane and cytoplasm that are used for movement and capturing food.

Pinocytosis

“cell drinking”

• engulfs liquid material

• The cell membrane folds itself inward to suck in extracellular liquid and whatever random materials happen to be floating in it.

Receptor-mediated

very specific pinocytosis

• engulfs material that requires receptors

• The cell membrane has receptor proteins that wait for specific target molecules to land on them, which triggers the membrane to fold inward and suck them in.

receptor proteins: specialized chemical receivers embedded in a cell's membrane (or sitting inside the cell) that pick up molecular signals from the outside world and tell the cell how to respond.