1.3 Diffusion, Osmosis, and the Cell Membrane

watch:

http://highered.mheducation.com/sites/0072495855/student

_view0/chapter2/animation__how_diffusion_works.html

1.3 Diffusion, Osmosis, and the Cell Membrane

• Diffusion: the movement of particles from an area of higher concentration to an area of lowerconcentration.

• Concentration [ ] is the amount of substance in a given space.

• Example: smell of fresh baked bread “spreading” throughout the room is an example of diffusion.

Diffusion and the Cell Membrane

• The cell membrane is a selectively permeable membrane.

It has many small openings that let some substances pass through it

but not others.

• One way that substances can move through the cell membrane is

by diffusion.

• When the concentration on both sides of the membrane is the

same, it is called equilibrium.

Osmosis

• Osmosis is the diffusion

of water through a

selectively permeable

membrane.

• Osmosis occurs when

water particles move

from a higher

concentration to a

lower concentration.

Osmosis and the Cell

• Cells contain water and need this water to survive.

• Osmosis is how the cell gains and loses its needed

water.

Explain how placing this wilted

flower in water will cause the flower

to “straighten up”.

Examples of Osmosis

Example 1: Equal movement of water in and out of cells

Examples of Osmosis

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

Examples of Osmosis

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

Cell reproduction/growth and

• Read the handout provided.

Answer the following questions

What are 2 reasons why cells divide rather than continue to

grow indefinitely.

Cells reproduce by cell division.

What are the phases of mitosis? Draw a diagram and label

what is happening in each step.

(c) McGraw Hill Ryerson 2007

(c) McGraw Hill Ryerson 2007

Early Prophase - nucleolus disappears and spindle fibres form

Late Prophase - spindle fibres attach to centromeres of

chromosomes

Metaphase - chromosomes align on equator of cell

Anaphase - spindle fibres pull sister chromatids to opposite poles of

cell

Telophase - in this final stage, spindle fibres disappear and a

nuclear membrane forms around each separated set of

chromosomes.

Cytokinesis is the separation of the nuclei into two daughter cells

• https://www.youtube.com/watch?v=ofjyw7ARP1c

(c) McGraw Hill Ryerson 2007

Assignment

• Cell lab next class

• Cell structure test Wednesday Oct. 26.

(c) McGraw Hill Ryerson 2007