Transcript In PLANT CELLS… - Laurel County Schools

PLASMA MEMBRANE
 The
Plasma Membrane is the
outer membrane that covers
the cell
 The cell activity will depend
on the materials that enter
and exit the cell.
SEMI-PERMEABLE

The membrane
is said to be
semi-permeable
which means it
only allows
certain materials
to enter and exit
the cell.
SEMI-PERMEABLE

Only 4 items can
pass through
the membrane at
any time!
CO2
O2 N,
H2O
HOMEOSTASIS
 CELLS
ARE STRIVING TO
REACH A STATE OF
BALANCE—HOMEOSTASISBOTH INSIDE AND OUTSIDE
OF THE CELL
STRUCTURE OF PM
STRUCTURE OF PM
It is made of two fatty acids joined
tail to tail
 Membrane Proteins are found
embedded throughout the PM. They
are gateways for various molecules
to enter/exit the cell
 Cholesterol is also found
throughout….they will provide
structure and support for the
membrane.

The PM is very flexible and
therefore has the ability to
move easily. Proteins and
cholesterol have the ability to
move left to right (sideways)
throughout the membrane.
Because of this ability it is
called the
FLUID MOSAIC MODEL!!
RANDOM MOTION OF
MOLECULES

Robert Brown in
1927 observed
what he called the
Brownian Motion.
He made the
observations that
molecules are
always in motion.
IMPORTANT TERMS
 Solvent-a
 Solute-
substance that
has another
substance
dissolved in it.
 Ex: water
substance
being dissolved
in another
substance
 Ex: Sugar, salt,
etc...
DIFFUSION
 Some
molecules can move
directly through the membrane.
The net movement of
molecules from an area of high
concentrations to an area of low
concentration.
DYNAMIC EQUILIBRIUM
 DYNAMIC
EQUILIBRIUM- The
condition in which there is
continuous movement but NO
overall change.
 This is a key characteristic of
homeostasis.
OSMOSIS
 The
diffusion of water across a
semi-permeable membrane. This
works from a area of high
concentration to an area of low
concentration.
 Often said to go with the
concentration gradient.
CONCENTRATION
GRADIENT
 The
difference between
concentrations across space.
 There MUST be a difference in the
CG for diffusion to occur.
 Substance will go from High to low
or with the gradient.
WATER MOVEMENT

Water can move
easily through a cell
at any point..
 Some substance
cannot (sugar salt).
 Therefore the water
must move in or out
of the cell until
homeostasis is
reached.

Three major types
of solutions we
will discuss
 Hypertonic
 Hypotonic
 Isotonic
HYPERTONIC
The concentration of solutes outside
the cell is higher than the
concentration of solutes inside the
cell.
 As a result water will leave the cell
and the cell will shrink
 Ex: Lettuce in saltwater.


http://www.youtube.com/watch?v=GOxo
uJUtEhE&feature=player_embedded
HYPOTONIC
The concentration of solutes is
higher inside the cell than the
concentration of solutes outside the
cell.
 As a result, water will go into the cell
and the cell will swell
 Keep lettuce in distilled water…it will
stay crisp.

ISOTONIC
The concentration of solutes is the
SAME both inside and outside the
cell.
 Water still moves in and out but no
OVERALL CHANGE
 Cell is said to be in a state of
equilibrium.
 Most solutions that are injected in our
bodies are isotonic.


A simple rule to remember is:

Salt is a solute, when it is concentrated
inside or outside the cell, it will draw the
water in its direction. This is also why
you get thirsty after eating something
salty.
In PLANT CELLS…
 Turgor
Pressure- Internal
pressure in a cell.
 When the turgor pressure inside
the cell increase the PM will push
outward and cause the cell wall to
become very rigid—this gives
plants their shape.
In PLANT CELLS…
If the plant cell does NOT have enough
water the opposite will happen.
 No Water
Turgor Pressure
decreases
No shape
Wilting plant.

In PLANT CELLS…
 Loss
of water from a cell
resulting in a drop of Turgor
Pressure is called Plasmolysis.
In ANIMAL CELLS…
There is not a cell wall in animal cells
so sometimes the cell will continue
to grow and could possible burst.
 Some cells can survive in a
hypotonic solution because they
have the ability to adapt by forming
Contractile Vacuoles- Here the
excess water is squeezed out of the
cell through the membrane.

• NORMAL CELL
• After placing in salt
PASSIVE TRANSPORT
 H20,
lipids, and
lipid soluble
substance pass
through the
plasma
membrane by
diffusion.
 The
cell uses
NO energy to
move the
particles that is
why it is called
Passive.
 Usually from
High to Low
FACILITATED DIFFUSION
is
the passive transport of
materials across the
membrane by transport
protein.
ACTIVE TRANSPORT
The transport of materials against a
concentration gradient that requires
energy.
 Sometimes cell requires nutrients
and materials that are available in the
environment but would be going
from an area of low concentration to
an area of high concentration.

ENDOCYTOSIS
The process in which a cell surrounds
and takes in material from its
enviroment….. Taking in materials by
means of infolding, or pockets of the cell
membrane.
 Some cells take in large molecules,
groups of molecules, or even whole
cells.
 Materials do not pass through the
membrane…it engulfs the materials

ENDOCYTOSIS
 There
are two types of
endocytosis
–Phagocytosis
–Pinocytosis
Phagocytosis
Phagocytosis means “cell eating”.
Extensions of the cytoplasm surround a
particle and package it within a food
vacuole
 Amoebas use this method of taking in
food.
 Requires lots of energy

Pinocytosis
Pinocytosis – this process is similar to
phagocytosis.
 Cells take up liquid from the
surrounding environment. Tiny packets
form along the cell membrane, filled
with liquid, and pinch off to form
vacuoles within the cell.
 Pinocytosis means “cell drinking”


Cell Eating!
Phagocytosis

Cell drinking
EXOCYTOSIS
The reverse process of endoycytosis.
 This process is used to expel waste
from the interior to the exterior of the
cell
 This method can be used to secrete
substances produced by the cell. (EX:
hormones)

ACTIVE TRANSPORT
BOTH
Endocytosis and
Exocytosis are examples
of ACTIVE TRANSPORT