Chapter 8-Cellular Transport
& the Cell Cycle
Section 8.1-Cellular Transport
•
•
•
•
Osmosis: Diffusion of
Water
Plasma membrane can act as a pump or a dam for
water soluble molecules
Plasma membrane doesn’t limit the diffusion of
water
Diffusion-def-pg.194- the movement of
particles from an area of higher concentration to
an area of lower concentration.
Osmosis-def-pg194-the diffusion of water
across a selectively permeable membrane
•
Regulating the water flow through the plasma membrane is
an imp factor in maintaining homeostasis within the cell
What controls osmosis?
•
•
Concentration gradient
is one factor that
controls osmosis
Concentration
gradient-def-pg196the unequal distribution
of particles
•
•
How osmosis affects
cells?
Remember that cells are subject to osmosis because
they are surrounded by water solutions
3 types of solutions:
1.
2.
3.
Isotonic solution
Hypotonic solution
Hypertonic solution
How osmosis affects
cells?
A. Cells in an isotonic solution
•
Isotonic solution-def-pg196-the concentration of
dissolved substances in the solution is the same as the
concentration of dissolved substances inside the cell
•
•
Fig 8.2
this also means that the concentration of water in the solution
is the same as the concentration of water inside the cell.
Results-cells in an isotonic soln experience osmosis but
because the concentrations of water are both the same
inside the cell as outside the cells keep their shape.
How osmosis affects
cells?
B. Cells in a hypotonic solution
•
•
Hypotonic solution-def-pg.196- the concentration of
dissolved substances is lower in the solution outside the cell
than the concentration inside the cell
–
this means more water outside the cell than inside
–
Ex/ Animal (Red blood cells) cells may not stand the increased
internal pressure and burst
Ex/Plant cells- contain a rigid cell wall that supports the cell and it
won’t burst in a hypotonic soln-rather the cells will get firm
Ex/ grocery stores & fruit & water moisture
Results-cells in a hypotonic soln will swell & the internal
pressure increases
–
–
Fig 8.3
C.
How osmosis affects
cells?
Cells in a hypertonic solution
•
Hypertonic solution-def-pg196- the concentration of
dissolved substances outside the cell is higher than the
concentration inside the cell
–
•
Results- this means water is flowing out of the cell due
to osmosis
–
–
Fig 8.4
This means that there is more water inside the cell than
outside
Ex/ Animal (red blood cells) cells- in a hypertonic soln will
shrivel up because of the decreased pressure in the cells
Ex/Plant Cells-in a hypertonic soln the cells will lose
water, mainly from the central vacuole & cytoplasm & cell
membrane will shrink from the cell wall-explains wilting
Passive Transport
–
•
Passive transport-def-pg.198-the movement of particles
across the membrane without use of energy.
Passive transport by proteins
•
•
–
–
Facilitated diffusion-def-pg.198-passive transport of materials
across the membrane using transport proteins
Types of transport proteins:
Channel proteins- transport proteins that
form channels that allow specific
molecules to flow through the plasma
membrane, this movement happens with
the concentration gradient & doesn’t
require any energy from the cell
Carrier proteins-another type of
transport protein, that changes shape to
allow a substance to pass through the
plasma membrane, this movement happens
with the concentration gradient & doesn’t
require any energy from the cell
Passive Transport
Active Transport
•
•
•
Active transport-def-pg.199-the movement
of materials through a membrane against a
concentration gradient & it requires energy
from the cell
Allows for particle movement into or out of a
cell against a concentration gradient
Active transport is required for a cell to
maintain homeostasis
1.
How active transport
occurs
A transport protein (carrier protein)
binds with a particle of the substance
to be transported.
»
Each carrier protein has a shape to fit a
specific molecule or ion
2. When the proper molecule binds w/the
protein, chemical energy allows the cell
to change the shape of the carrier
protein so that the particle to be
moved is released on the other side of
the membrane
3. Once particle is released the protein’s
original shape is restore
Transport of Large
Particles
•
–
–
–
–
•
•
–
–
Endocytosis-def-pg.200-the process by which a cell surrounds and takes in
material from its environment.
During endocytosis material doesn’t pass directly through the cell membrane
How endocytosis works?
Material is engulfed & enclosed by a portion of the cell’s plasma membrane
Portion of the membrane breaks away & the resulting vacuole with the material moves to
the inside of cell
See fig 8.7
Exocytosis-def-pg.200-the expulsion or secretion of materials from a cell.
1.
2.
Cells use this:
to get rid of waste
secrete substances like hormones produced by the cell
Both endocytosis & exocytosis are types of active transport & require energy from
the cells