Date: November 23, 2015
Happy Birthday
Alexandra &
Cameron!!!!
Aim #29: How can the process of diffusion and
the structure of the cell membrane help the cell
maintain homeostasis?
Do Now: Warm-Up Notebook
Date
Title of Activity
Page #
11/23
Other Organelles
52
HW:
1) Cell Web Quest due Tuesday 12/1
2) QUIZ- Tuesday/Wednesday (Aim #’s 24-26)
3) Unit 3 Test- Monday (12/7)/Tuesday (12/8)
Aim #29: How can the process
of diffusion and the structure of
the cell membrane help the cell
maintain homeostasis?
1) What is diffusion?
The net movement of particles
from where they are more
concentrated to where they are
less concentrated.
2) What do we mean when we say concentration?
The amount of a particular substance
It’s all about concentration
3) The reason
diffusion occurs
is because
molecules are
always…
MOVING
Why are particle always moving?
ENERGY
Particles are in constant motion because they have
energy
4) What is the end result of diffusion?
The number of particles are now evenly distributed
This is called: Dynamic Equilibrium
Dynamic Equilibrium
At this point, the number of particles have spread
themselves out equally throughout the beaker.
5) Are the particles still moving after dynamic equilibrium
has been reached?
YES
An illustration of diffusion:
6) What are the two Conditions for diffusion
to occur?
1)There must be a concentration
gradient
2) There must be no barrier blocking
the movement of particles.
What is a concentration gradient?
The difference in concentration
between a region of high
concentration and a region of
lower concentration.
Does this picture illustrate a concentration gradient?
What do we mean by a barrier?
Will diffusion take place?
YES
Will diffusion take place now?
NO
The particles must be free to move down their
concentration gradient in order for diffusion to
occur.
Does diffusion take place across the cell
membrane?
Yes, the cell is:
Selectively Permeable
Why do some things get through
the cell membrane?
Small molecules are more likely to get
through the cell membrane compared to
big molecules
Cell Membranes are:
Selectively Permeable
A selectively permeable membrane allows some
substances to cross the membrane more easily
than others and blocks the passage of other
substances altogether.
8) What is facilitated diffusion?
• transport proteins help move
materials from high to low
concentration
9) What is the main job of the cell membrane?
HOMEOSTASIS & TRANSPORT
• Cell membranes helps organisms maintain
_____________ by controlling what substances may
enter or leave cells
• To stay alive, a cell must exchange materials such
as food, water, & wastes with its environment