Untitled Flashcard Set

Cell Transport

Cell Membrane

  • The cell membrane controls what enters and leaves the cell.

  • It is selectively permeable, meaning some substances can pass through while others cannot.

  • Cell transport is the movement of substances across the cell membrane.

Concentration Gradient

  • A concentration gradient is a difference in the concentration of a substance between two areas.

  • High → Low concentration = moving WITH the concentration gradient.

  • Low → High concentration = moving AGAINST the concentration gradient.

Passive Transport

  • Passive transport does NOT require energy (ATP).

  • Substances move from high concentration → low concentration.

  • Types of passive transport:

    • Diffusion

    • Osmosis

    • Facilitated diffusion

Diffusion

  • Movement of particles from high concentration → low concentration.

  • Does not require ATP.

  • Continues until equilibrium is reached.

  • Equilibrium means particles are evenly distributed.

Osmosis

  • Osmosis is the diffusion of water across a selectively permeable membrane.

  • Water moves from an area of high water concentration → low water concentration.

  • Does not require ATP.

Facilitated Diffusion

  • Moves substances from high concentration → low concentration.

  • Does not require ATP.

  • Uses transport proteins in the cell membrane to help substances cross.

  • Used for substances that cannot easily pass directly through the membrane.

Tonicity

Hypotonic Solution

  • There is more water outside the cell.

  • Water moves INTO the cell.

  • An animal cell swells and may burst.

  • Memory trick: HYPO = Hippo → big/swollen.

Hypertonic Solution

  • There is less water outside the cell.

  • Water moves OUT of the cell.

  • An animal cell shrinks.

Isotonic Solution

  • Concentrations are equal inside and outside the cell.

  • Water moves in and out at equal rates.

  • The cell stays about the same size.

Active Transport

  • Active transport requires energy (ATP).

  • Usually moves substances from low concentration → high concentration.

  • Moves substances against the concentration gradient.

  • Protein pumps are an example of active transport.

Endocytosis

  • Requires energy.

  • Moves large materials INTO the cell.

  • The cell membrane surrounds the material and forms a vesicle.

  • Think: ENDO = ENTER.

Exocytosis

  • Requires energy.

  • Moves large materials OUT of the cell.

  • A vesicle fuses with the cell membrane and releases its contents outside.

  • Think: EXO = EXIT.

Most Important Things to Remember

Diffusion = particles move High → Low

Osmosis = WATER moves across a membrane

Facilitated Diffusion = High → Low using PROTEINS

Active Transport = Low → High using ATP

Endocytosis = INTO the cell

Exocytosis = OUT of the cell

Hypotonic = water enters → cell swells

Hypertonic = water leaves → cell shrinks

Isotonic = equal movement → cell stays the same