Download The Cell in Its Environment

The cell In It’s Environment
• Function of the cell membrane?
– To regulate what enters and leaves the cell.
• Structure of the cell membrane
– Double layer of lipids with carbohydrates and proteins
scattered throughout.
The Cell in Its Environment
•
The cell membrane is selectively permeable:
– means some substances can pass through
it while others cannot.
Balloon
The Cell in Its Environment
• Three ways substances can move in
and out of the cell
1. Diffusion - no energy required
2. Osmosis – no energy required
3. Active Transport – energy required
Diffusion
• Diffusion:
• The movement of molecules from an area
of higher concentration to an area of lower
concentration.
– Caused by molecules in motion.
– Collisions cause molecules to spread out.
http://www.stolaf.edu/people/giannini/flashanimat/transport/diffusion.swf
Air freshener
Food dye in water
Diffusion
• Concentration gradient - Created when
different concentrations are in contact with one
another
High
Low
Diffusion
• Substances naturally move with the gradient
High to low concentration is like going
down hill – with the gradient.
Diffusion
– Example in living organisms – movement of oxygen
from water into cells.
Osmosis – A special type of diffusion
•
Osmosis is the diffusion of water
molecules across a selectively
permeable membrane
– Water moves from high to low concentration
What are three ways
substances can pass across
the cell membrane?
Diffusion
Osmosis
Active transport
Movement Across the Cell Membrane
•
Passive Transport

•
Moving materials across a cell membrane
WITHOUT using energy
Two examples of passive transport:
• Diffusion
• Osmosis
Movement Across the Cell Membrane
•
Active Transport

Movement of materials across a cell
membrane which requires energy
Active Transport
• Sometimes molecules must move against the
concentration gradient (from low to high or
uphill) and this requires energy.
http://highered.mcgrawhill.com/sites/0072495855/student_view0/chapter2/animation__
mitosis_and_cytokinesis.html
Methods of Active Transport
•
Two ways that the cell moves things by active
transport.
1. Transport proteins
2. Engulfing
Transport Proteins – Active Transport
 Transport proteins in the cell membrane act as
channels through the membrane
http://highered.mcgrawhill.com/sites/0072495855/student_view0/chapter2
/animation__how_the_sodium_potassium_pump_
works.html
http://www.youtub
e.com/watch?v=S
TzOiRqzzL4
Engulfing – Active Transport
 Engulfing: cell membrane surrounds and then engulfs
a particle (amoeba and white blood cells).
http://www.youtu
be.com/watch?v
=W6rnhiMxtKU
http://www.youtube.com/watch?v=STz
http://www.youtube.com/watch?v=s
0p1ztrbXPY&feature=related
OiRqzzL4&feature=related
Cell Size
•
Why are cells so small?
– Small size makes it easier to move materials
into and out of the center of the cell.
– Makes all cell processes more efficient.
Cell Size
•
How do cells maintain their small size?
When a cell reaches a certain size it
divides.
We call this cell division MITOSIS.
Let’s Review
 Explain the difference between osmosis
and diffusion?
•
•
Diffusion refers to the movement of
molecules from high concentration to low
concentration.
Osmosis is diffusion of WATER across a
selectively permeable membrane. Also from
high concentration to low concentration.
Let’s Review
 Do osmosis and diffusion require
energy?
•
•
No because they both are a form of Passive
transport.
Molecules or water (osmosis) move with the
concentration gradient (downhill).
Let’s Review
 Why does active transport require
energy?
•
Because the cell is trying to move molecules
against the concentration gradient – from
low to high concentration
 Why are cells so small?
•
To allow materials to move in and out quickly
making the cell more efficient.
Let’s Review
 What happens to a cell when it reaches a
certain size?
•
It divides to maintain its small efficient size
 What do we call this cell division?
•
Mitosis
Diffusion
http://www.youtube.com/watch?v=ULR79TiUj80
http://highered.mcgrawhill.com/sites/0072495855/student_view0/chapter2/animation__
mitosis_and_cytokinesis.html
http://www.stolaf.edu/people/giannini/flashanimat/transport/
diffusion.swf
Osmosis and salt
http://www.stolaf.edu/people/giannini/flasha
nimat/transport/osmosis.swf