Download 8. Passive Transport Across Membrane

PASSIVE
TRANSPORT
ACROSS A
MEMBRANE
1
Passive & Active Transport
Overview
Cell
Transport
Passive
Transport
Active
Transport
molecules enter or leave one at a time
Diffusion
Osmosis
Facilitated
Diffusion
• no cell energy needed
• molecules move with the
concentration gradient (high
to low) due to random
molecular motion
Carrier
Proteins
many molecules enter or leave
together i.e. bulk transport
Endocytosis
Exocytosis
• cell energy needed
• molecules move against the
concentration gradient (low to
high)
Passive Transport
Diffusion:
• even spreading of molecules from an
area of high concentration to an area
of lower concentration
• move with the concentration
gradient
Osmosis:
• diffusion of water molecules across a
selectively permeable membrane
• move with the concentration
gradient
Isotonic solution:
• contains the same concentration of solute as an
another solution
Hypotonic solution:
• contains a low concentration of solute relative to
another solution
Hypertonic solution:
• contains a high concentration of solute relative to
another solution
http://www.tvdsb.on.ca/WESTMIN/science/sbi3a1/cells/Osmosis.htm
Isotonic
Hypotonic
Hypertonic
Solution
Cell Types
•same amount of water
enters & leaves
1.Plant
Cell
no change
• water enters the
cell by osmosis
• turgor pressure
develops
• helps support plant
• water leaves the
cell by osmosis
• loss of turgor
pressure
• plant wilts
• plasmolysis
2. Animal
Cell
no change
cytolysis – cell bursts
cell shrinks
Red Blood Cells
• H2O enters by osmosis
• cell membrane can’t
withstand pressure
∴ all
• bursts - cytolysis
• H2O leaves by
osmosis
• whole cell shrivels
intravenous medication
must be:
• isotonic or blood cells will
die
LETS SEE WHAT YOU
REMEMBER???
• 1. Which bag would you predict to
show the least change in mass at the
end of the experiment?
• a. The bag in Beaker 1
b. The bag in Beaker 2
c. The bag in Beaker 3 Correct
d. The bag in Beaker 4
e. The bag in Beaker 5
C
2. After the experiment has run for 30
minutes, which bag loses the most mass
which gains the most mass? List the bag
that gains the most mass first.
a. 1, 2, 3, 4, 5
b. 1, 5, 2, 3, 4
c. 4, 3, 2, 5, 1
d. 3, 2, 1, 4, 5
e. 2, 1, 5, 3, 4
Correct
e
Passive Transport
• turgor pressure pushes
cell membrane against
cell wall
• cell becomes turgid - stiff
• loss of turgor pressure
• cell membrane pulls away
from cell wall
• cell becomes flaccid
• plasmolysis
Passive Transport
higher concentration outside
1. directly
1
2
3
through
phospholipid
bilayer
• ex.
• O2
• CO2
• H2O
2. protein channels
• charged ions & water
• ex. Na+, Ca2+, K+, Cl-
3.carrier protein
• called facilitated diffusion
• larger molecules
• ex. glucose, amino acids
Facilitated
Diffusion
used for molecules that are too big to
pass directly through cell membrane
or protein channel
high concentration outside
lower concentration inside
a) molecule bounces b) carrier protein
into a specific
binds molecule
carrier protein
d) carrier protein
resumes its shape
c) carrier changes
shape & flips
over, bringing
molecule into
cell
Cell Transport Overview
Single Molecules
protein
channel
facilitated
diffusion
VIDEO
Homework
• Page 64 # 1 – 8
• Quiz tomorrow on nutrients and
enzymes
• Time to ask questions