1.7 and 1.8 Cells in Their Environment

and Osmosis

Text pages 22-28

The Big idea• How do substances move in and out of cells

Videohttp://www.youtube.com/watch?v=qotIWgL7zFs

http://www.youtube.com/watch?v=9QCxTf0QfTo&feature=related

1.7 Cells in Their Environment

• Permeable (all), semi permeable (some) and impermeable (none)

• Cell membrane: – Selectively permeable (pg 22)

• Diffusion– Molecules constantly move and collide, causing

them to spread out– Concentration= the amount of stuff in a specific

area– Molecules always move from an area of high

concentration to an area of low concentration– This is how things move in and out of cells (see

page 24)

1.8 Osmosis (page 25)

• Osmosis:– A type of diffusion involving to water– Water constantly moves in and out of cells

depending on concentration– See page 25 of text

Cells in solutions of different concentrations

• Solute = substance dissolved in another substance

• Solvent= stuff that does the dissolving– E.g., hot chocolate= water (solvent) and chocolate

(solute)• In cells salts and sugars = solutes, and water =

solvent

Examples of Osmosis (see page 26)Example 1: Equal movement of water in and out of cells

Example 2: More water moving into cells than is moving out

Example 3: More water moving out of cells than is moving in

Turgor Pressure

• the main pressure of the cell contents against the cell wall in plant cells.

• cells contain more water in vacuole than flaccid cells (osmotic pressure)

• gives the plant rigidity, and may help to keep it erect. Turgor can result in the bursting of a cell.