About Cell Membranes
• All cells have a cell
membrane
• Functions:
a.Controls what enters and exits the cell to maintain an internal balance
called homeostasis
b.Provides protection and
About Cell Membranes
•
The cell membrane is
constantly moving
•
Proteins, and other
structures move about
What is the purpose of cellular
transport?
•
The
cell membrane
regulates the
passage of materials into and out of
the cell
– Needed materials move in
• Glucose, oxygen, amino acids, etc.
– Excess materials move out
• Carbon dioxide, digested materials,
How?
• A cell membrane is semipermeable
(selectively permeable), meaning that some
substances can pass directly through the cell membrane while other substances
cannot.
• Materials can enter or exit through the cell
membrane by passive transport or active
transport.
sugar lipids salt waste
So what needs to get across the membrane?
Types of Cellular
Transport
•
Passive Transport
*cell does not use energy
1. Diffusion
2. Facilitated Diffusion 3. Osmosis
•
Active Transport
*cell does use energy
1. Protein Pumps 2. Endocytosis
•Animations of Active Transport &
Passive Transport
•
cell
uses no energy
•
molecules move
randomly
•
The random motion of molecules
occurs
along the concentration
gradient
meaning molecules
spread out
from an area of high
concentration to an area of low
concentration
.
•
(High
Low)
3 Types of Passive
Transport
1. Diffusion
– is the spreading out of
molecules across a cell membrane
until they are equally concentrated.
2. Facilitative Diffusion
– diffusion
with the help of transport proteins
Passive Transport:
1. Diffusion
• Diffusion: random movement of particles
from an area of high concentration to an area of low concentration.
• Diffusion continues until all molecules are
evenly spaced (equilibrium is reached)
• Note: molecules will still move around but
inside cell
Passive Transport:
1. Diffusion
Facilitated diffusion:
•diffusion of specific particles from high to low
concentration
•Help from transport proteins found in the
membrane
Passive Transport
:
2. Facilitated Diffusion
• http://bio.winona.edu/berg/ Free.htm
HIGH
LOW
Passive Transport
:
2. Facilitated Diffusion
inside cell
• Channel Protei ns
• Osmosis: diffusion of
water through a
selectively permeable membrane
• Water moves from a high
concentration of water
to a low concentration of
water
Osmosis
animation
Active Transport
•
Requires the cell to
use energy
•
Actively moves
molecules
to where
they are needed
•
Molecules move
against
the
concentration gradient -
from an area
of low concentration to an area of
high concentration
Types of Active
Transport
1. Protein Pumps -transport proteins that require energy to do work
Sodium Potassi um Pumps
(Active
Transport using proteins)
Protein
changes shape
to move
molecules: this requires
Types of Active Transport
2.
Endocytosis: takingbulky material into a cell by forming a vesicle
• Uses energy
• Cell membrane in-folds around food particle
• “cell eating”
• forms food vacuole &
digests food
Types of Active Transport
3.
Exocytosis
:
Forces
material out of cell
in
bulk
• Membrane surrounding
the material fuses with
cell membrane
• Cell
changes shape
–
requires
energy
• Ex:
Hormones
or
wastes
released from
cell
Endocytosis & E xocytosis
• Osmosis: diffusion of
water through a selectively permeable membrane
• Water moves from a high
concentration of water to a
low concentration of water
• Because water is so small and in such abundance, the cell cannot control its movement through the cell membrane.
Osmosis
animation
Revisited:
Passive Transport:
Effects of Osmosis on Life
•
Water moves
freely
through through pores
(blue and white molecules)
•
Solute (green) too
large
to move across.
•
Reminder:
–Solute: what is being dissolved
–Solvent: what dissolves the solute
Hypotonic Solution
Hypotonic: The solution has a lower
concentration of solutes and a higher
concentration of water than inside the cell.
(Low solute; High water)
Result: Water moves from the solution to
inside the cell): Cell Swells and bursts open (lyse)!
• Osmosis
Animations for isotonic, hypertonic, and
Hypertonic Solution
Hypertonic: The solution has a higher
concentration of solutes and a lower
concentration of water than inside the cell.
(High solute; Low water)
Result: Water moves out of the cell into the
solution: Cell shrivels!
• Osmosis
Animations for isotonic, hypertonic, and
hypotonic solutions
Isotonic Solution
Isotonic: The concentration of solutes in the
solution is equal to the concentration of
solutes inside the cell.
Result: Water moves equally in both
directions and the cell remains same size!
• Osmosis
Animations for isotonic, hypertonic, and
In what type of solution are these
cells?
A
B
C
Hyperto nic
Isoton ic
About Cell Membranes
• All cells have a _____
__________________
• Functions:
a.Controls what enters and exits the cell to maintain an internal balance called
_________________
b.Provides protection
About Cell Membranes
•
The cell membrane is constantly
_______________
•
Proteins, and other structures move
What is the purpose of cellular
transport?
•
The
cell membrane
regulates the
passage of materials __________ and
_______ of the cell
–
Needed materials move
_____
• Glucose, oxygen, amino acids, etc.
–
Excess materials move
_______
How?
• A cell membrane is _____________________
(selectively permeable), meaning that
__________ substances can pass directly through the cell membrane while other substances ___________
• Materials can enter or exit through the cell
membrane by __________ transport or
_________ transport.
Membrane movemen t animat ion
aa H2O
sugar lipids salt waste
So what needs to get across the membrane?
Types of Cellular
Transport
•
Passive Transport
*cell does ______ use energy
1. _______________
2. Facilitated Diffusion 3. ______________
•
Active Transport
*cell does use _________
1. Protein Pumps 2. Endocytosis
•Animations of Active Transport &
Passive Transport
•
cell
uses no energy
•
molecules move
__________________
•
The random motion of molecules
occurs
along the concentration
gradient
meaning molecules spread
out
from an area of _________
concentration to an area of
__________ concentration
.
•
(High
Low)
3 Types of Passive
Transport
1. Diffusion
– is the spreading out of
molecules across a cell membrane
until they are equally concentrated.
2. Facilitative Diffusion
– diffusion
with the help of _______________
_______________
Passive Transport:
1. Diffusion
• Diffusion: ____________ movement of
particles from an area of high
concentration to an area of low concentration.
• Diffusion continues until all molecules are
evenly spaced (___________________ is reached)
• Note: molecules will still ____________
inside cell
Passive Transport:
1. Diffusion
Facilitated diffusion:
•diffusion of specific particles from high to low
concentration
•Help from _____________ ______________found
in the membrane
•These molecules cannot pass through the
membrane alone
Passive Transport
:
2. Facilitated Diffusion
• http://bio.winona.edu/berg/ Free.htm
HIGH
LOW
Passive Transport
:
2. Facilitated Diffusion
inside cell
• Channel Protei ns
• Osmosis: diffusion of
_____________ through a selectively permeable membrane
• Water moves from a
_________ concentration of
water to a __________
concentration of water
Osmosis
animation
Active Transport
•
Requires the cell to
use ________________
•
Actively moves
molecules
to where
they are needed
•
Molecules move
against
the
concentration gradient -
from an area
of __________ concentration to an
area of __________ concentration
•
(Low
High)
Types of Active
Transport
1. ____________ Pumps
-transport proteins
that require energy to do work
Sodium Potassium Pumps (Active Transport using
proteins)
Protein
changes shape
to move
molecules: this requires
Types of Active Transport
2.
__________________: taking bulky material into a cell by forming a vesicle• Uses energy
• Cell membrane in-folds around food particle
• “_____________________”
• forms food vacuole &
digests food
Types of Active Transport
3. Exocytosis:
Forces
material out of cell
in bulk• Membrane surrounding the material ____________ with cell membrane
• Cell changes shape – requires energy
• Ex: Hormones or
wastes released from cell
• Osmosis: diffusion of water
through a selectively permeable membrane
• Water moves from a high
concentration of water to a
low concentration of water
• Because water is
so___________and in such
abundance, the cell
__________control its
movement through the cell membrane.
Osmosis
animation
Revisited:
Passive Transport:
• Osmosis: diffusion of
water through a selectively permeable membrane
• Water moves from a high
concentration of water to a
low concentration of water
• Because water is so small and in such abundance, the cell cannot control its movement through the cell membrane.
Osmosis
animation
Revisited:
Passive Transport:
Effects of Osmosis on Life
•
Water moves_________
through pores
(blue and white molecules)
•
Solute (green) too
__________
to move across.
•
Reminder:
–Solute: what is being dissolved
–Solvent: what dissolves the solute
Hypotonic Solution
Hypotonic: The solution has a ____________
concentration of solutes and a higher
concentration of water than inside the cell.
(Low solute; High water)
Result: Water moves from the solution to
___________ the cell): Cell ____________ and
bursts open (lyse)!
• Osmosis Animations for
isotonic, hypertonic, and
Hypertonic Solution
Hypertonic: The solution has a _____________
concentration of solutes and a ___________
concentration of water than inside the cell.
(High solute; Low water)
Result: Water moves ___________the cell into
the solution: Cell
_____________!
• Osmosis Animations for
isotonic, hypertonic, and
hypotonic solutions
Isotonic Solution
Isotonic: The concentration of solutes in the
solution is ___________ to the concentration of
solutes inside the cell.
Result: Water moves _____________ in both directions and the cell remains same size!
• Osmosis Animations for
isotonic, hypertonic, and
In what type of solution are these
cells?
A
B
C
How Organisms Deal with
Osmotic Pressure
• Bacteria and plants have cell walls that
prevent them from over-expanding. In plants the pressure exerted on the cell wall is called turgor pressure.
• A protist like the paramecium has contractile
vacuoles that collect water flowing in and pump it out to prevent them from over-expanding.
• Salt water fish pump salt out of their
specialized gills so they do not dehydrate. • Animal cells are bathed in blood. Kidneys
keep the blood isotonic by remove excess salt and water.
• Paramecium (protist)
