Cells & Their Environment Diffusion & Osmosis

Homeostasis The ability of an organism to maintain a constant internal balance, regardless of its external environment. Ex. Maintaining a constant body temperature.

Homeostasis? Write down another example of homeostasis within our bodies or within the cells of our bodies.

Membranes Regulate the Traffic of Molecules Materials such as water, nutrients, dissolved gases & wastes must constantly move in two-way traffic across a cell’s plasma membrane. The Plasma membrane functions like gatekeepers, letting some molecules through but not others.

The Plasma Membrane The Plasma Membrane can be thought of as the edge of life-it is the boundary that separates the interior of a living cell from its surroundings. It regulates the traffic of chemicals into and out of the cell. (Semipermeable)

Homeostasis To maintain homeostasis, a cell uses: Passive Transport (no energy output required). Active Transport (energy output is required).

Passive Transport 1. Diffusion – molecules moving from a region of high concentration to an area of low concentration. Diffusion 2. Osmosis – diffusion of water through a selectively permeable membrane, from high to low concentration. Osmosis

Diffusion

Passive Transport 3. Facilitated Diffusion – diffusion of specific particles through selective pores (channel proteins) in the cell membrane. From High to Low concentration.

Solute & Solvent Solute – The substance dissolved in a solvent Solvent – The substance in which the solute is dissolved (usually water) ex. Salt (solute) dissolved in water (solvent)

A Cell in Water Solutions (See Pg 86-87)  Change Isotonic Solution – the same H2O concentration inside the cell as out. (Cell stays the same …Equilibrium) Or Same solute concentration in the solution as in the cell

A Cell in Water Solutions (See Pg. 86-87) Hypertonic Solution– Higher H2O concentration inside the cell – (H2O moves out …cell shrinks). Or Higher solute concentration in the solution than in the cell

A Cell in Water Solutions (See Pg 86-87) Hypotonic Solution – Lower H2O concentration inside the cell – (H2O moves in…cell expands). Or Lower solute concentration in the solution than in the cell

Isotonic Solution Which Direction will the water move? H2O Which Direction will the water move? Will the Cell expand or shrink? Is this a iso-, hyper- or hypo- solution?

Hypertonic Solution Which Direction will the water move? H2O Which Direction will the water move? Will the Cell expand or shrink? Is this a iso-, hyper- or hypo- solution?

Hypotonic Solution Which Direction will the water move? H2O Will the Cell expand or shrink? H2O H2O Is this a iso-, hyper- or hypo- solution?

Hypo, Hyper, or Iso

Hypo, Hyper, or Iso

Hypo, Hyper, or Iso

Animations Diffusion Osmosis Facilitated Diffusion Hypertonic, Hypotonic, Isotonic Another one Passive Transport Video

Endocytosis & Exocytosis Active Transport Movement of molecules from a low concentration to a region of high concentration. This process requires energy. These are: Active Transport Endocytosis Phagocytosis Pinocytosis Exocytosis Video Active Transport Endocytosis & Exocytosis

1. Active Transport Active Transport - this type of transport requires that the cell use energy, because substances are moving against the concentration gradient. Sodium Potassium Pump - the cell pumps out 3 sodium ions and takes in 2 potassium ions

2. Endocytosis The cell membrane surrounds and pinches off material as it brings it into the cell. Phagocytosis – bringing large particles into the cell. Pinocytosis – bringing small particles into the cell.

3. Exocytosis The process by which cells expel large particles.

Animations Endocytosis & Exocytosis Active Transport Video