Download Cellular Transport

Cellular Transport
Ch. 1 Sec. 4
Why transport?
• Cells need to
–take in supplies
–get rid of wastes
–send out products
Control of transport
• Cell membrane
–Selectively permeable
–Some things can pass through
–Others cannot
Types of transport
• Diffusion
• Osmosis
• Active transport
Concentration
• The amount of substance in a
given volume
• Like density
High concentration Low concentration
Diffusion
• The movement of molecules
from areas of high
concentration to areas of low
concentration
Why does it happen?
• Molecules are always moving
• higher concentration  bump
into one another more
• When they bump they spread
out
• Demo
Result
• Diffusion happens until
molecules are evenly distributed
Osmosis
• The diffusion of water
• Based on the concentration of
water molecules
• More “stuff”  lower water
concentration
Animal cells
If the concentrations are the
same on both sides of the
membrane then water
moves equally in both
directions
Outside
Cell
Plant cells
Animal cells
If the concentration of stuff is
higher outside the cell then
there is movement of water
outside causing the cell to
shrink.
Outside
Cell
Plant cells
Animal cells
If the concentration of stuff is
lower outside the cell then
there is a net movement of
water inside the cell, causing
swelling or breakage.
Outside
Cell
Plant cells
Animal cells
Outside
Cell
Outside
Cell
Outside
Cell
Plant cells
Active Transport
• When energy is needed to get
materials through the
membrane
• Osmosis and diffusion =
passive transport
Active Transport
• Needed when:
–Molecules needs to move from
areas of low concentration to
areas of high concentration
–Molecules are too large to fit
through membrane
Active Transport
• Cells use special
proteins in the
membrane to
help get things in
and out =
transport proteins
• Need energy to
make protein
work
Video
Active Transport
• Large molecules can enter the cell
by being engulfed
• Also requires energy
Why are cells so small?
1. If they get too big, there
isn’t enough cell membrane
to let in enough nutrients
and materials
• Volume (inside) grows faster
than surface areas (outside)
Why are cells so small?
2. Once through the
membrane, materials spread
through cell by cytoplasm
streaming
• Would take too long in big
cells for stuff to reach center
Why are cells so small?
3. There would be too much
activity going on for one
nucleus to control
• If they get too big divide
into two cells or die