Download notes

Cell Transport
Osmosis and Diffusion NOTES
Page 80-85

The cell membrane is selectively
permeable

Only some substances can pass through the
membrane while others cannot
What are some things that have to pass
the cell membrane?
 Cells need oxygen and food to enter the
cell and waste products must leave the
cell.

Diffusion

process by which molecules move from an
area of HIGH concentration to an area of
LOW concentration
What Causes Diffusion?


Molecules are always on the move
 They bump into each other
 As the bump they begin to spread out
What do you think the goal of diffusion is?
Goal is to get to equilibrium : Equal concentration on either side of the membrane
Osmosis
The diffusion of WATER through a
selectively permeable membrane
 Cells depend on water for many functions,
so osmosis is a very important process.

Salt

Salt is a SOLUTE, when it has a high concentration
(inside or outside the cell), it will draw the water in its
direction.
Passive vs. Active Transport

Passive transport: movement of
materials across the membrane without
using energy

Goes with the concentration gradient
 HIGH

TO LOW
Active transport: movement of materials
across the membrane using energy

Goes against the concentration gradient
 LOW
TO HIGH
Active Transport
Sometimes proteins in the cell membrane
need to help move substances into the cell
 Active transport: can pedaling up hill, need
a lot of energy.

Engulfing
When
a cell membrane
surrounds, engulfs or encloses,
a particle; a type of active
transport
Why are cells SO small?

As a cell’s size increases, more of its
cytoplasm is located farther from a cell
membrane
Takes too long to get materials entering the
cell to their destination
 Takes too long to remove wastes from inside
the cell


With you lab group, discuss how osmosis,
diffusion, and active transport are
connected to homeostasis
Elodea Leaf w/ Fresh Water
Elodea Leaf w/ Salt Solution
Label the parts:
A. Cell Wall
B Chloroplast