which cellular structure separates the cytoplasm from the external environment in all cells? a....
TRANSCRIPT
Which cellular structure separates the cytoplasm from the external environment in all cells?
A. Cytoskeleton
B. Nuclear membrane
C. Cell wall
D. Plasma membrane
Why do you think a snail shrivels up and dies when you add salt to it??•You should be able to give me a scientific explanation after these notes
Cell transport = the movement of molecules in, out, and throughout cells
To stay alive, a CELL MUST EXCHANGE Materials such as Food and Waste With Its environment and these materials must cross the cell membrane
Transporting materials across the cell membrane helps the cell keep a balance of water, pH, and nutrients (________)homeostasis
Solutions
A solution is a mixture of a solute and a solvent.
A solute is dissolved in the solvent.For example: Salt is dissolved in
water.○ salt is the solute ○ water is the solvent
Cell Membrane
• Cell membranes separate cells from extracellular fluid, from other cells, and from the environment
• The main parts of membranes are the lipid bilayer with membrane proteins embedded throughout it
Permeability• A material is permeable if it allows molecules to
pass through.• The cell membrane is selectively permeable.
(Only some molecules can freely cross the membrane)
Is the membrane permeable to ?Is the membrane permeable to ?
No
Yes
Passive Transport Passive Transport is the movement of molecules
across the membrane that requires No Energy. Both Osmosis and Diffusion are types of passive
transport because both are movement of molecules from high concentration to low concentration.
high
low
Weeee!!!
Diffusion The passive movement of molecules from an
area of high concentration to an area of low concentration is called diffusion.Ex. Perfume diffusing through the airFood coloring diffusing in water
Diffusion• Molecules are never
stationary but are in constant motion.
• Collisions cause the molecules to disperse until the molecules are evenly distributed throughout the available space.
Which direction will flow? ??
??
Which direction will flow?
Osmosis Osmosis is the diffusion of water
molecules across a permeable membrane.
In osmosis, like diffusion, water molecules move from an area of high concentration to low concentration.
70% water30% salt
Semi-permeable membrane
Where is the greatest concentration of salt?
in the beaker? in the bag?
Where is the greatest concentration of
70% water30% salt
Semi-permeable membrane
Where is the greatest concentration of water?
in the beaker? in the bag?
Where is the greatest concentration of
70% water30% salt
Semi-permeable membrane
from the bag into the beaker? from the beaker into the bag?
Which arrow indicates the correct direction of water flow?
OR
70% water30% salt
Semi-permeable membrane
Water flows from the beaker into the bag.
Salt does not flow through the selectively permeable membrane.
Semi-permeable membrane
What happens to the bag?
The bag swells.
Hypotonic Solution: (less solute)
What happens to the cell?Solution:100% water0 % solute
Cell:90% water10% solute
Osmosis
Where will the water go?
Osmosis Hypotonic solutions contain a lower concentration of solute, and therefore a higher concentration of water than a solution to which it is being compared.
If a cell is in a solution that is hypotonic to the cell, the cell will take in water.
Red blood cell placed in distilled water
OsmosisHypertonic Solution: (more solute)
What happens to the cell?Solution:50% water50% solute
Cell:90% water10% solute
Where will the water go?
Osmosis Hypertonic solutions contain
a higher concentration of solute, and therefore a lower concentration of water than the solution to which it is being compared
If a cell is in a hypertonic solution than water will diffuse out of the cell and into the hypertonic solution
Red blood cell placed in salt water solution
Isotonic Solution: (same solute)
What happens to the cell?Solution:90% water10% solute
Cell:90% water10% solute
Where will the water go?
Osmosis
Osmosis• Isotonic solutions
– When the concentrations of solute inside the membrane and out are equal.
– An isotonic solution is at equilibrium
– In an isotonic solution there is no net change in the cell, water flows in and out of cell
Red blood cell in an isotonic solution
“Passive transport requires energy”A. True
B. False
“Osmosis and diffusion do not require energy”
A. True
B. False
If a cell has 30% solute and the extracellular solution has 50% solute, will water move into or out of the cell?
A. Out and the solution is hypertonic to the cell
B. Out and the solution is hypotonic to the cell
C. In and the solution is hypertonic to the cell
D. Out and the solution is hypotonic to the cell
Important Osmosis Concepts: Water moves from high to low
concentration of water through a membrane (diffusion)
Increasing the concentration of solute in a solution lowers the concentration of water
Water moves from a hypotonic solution to a hypertonic solution until both solutions are isotonic to each other and at equilibrium
A B C D E
1. Which is the most hypertonic solution?
2. Which is the most hypotonic solution?
3. Which solution is isotonic?
Osmosis
Cellular Transport
When molecules cannot move through hydrophobic membrane
Some molecules must undergo passive transport by traveling across the membrane through a transport protein.
This is called: facilitated diffusion and still requires NO ENERGY because the molecule still moves from high to low concentration.
Water moves through special transport proteins called aquaporins
Transport Proteins
There are two types of transport proteins:
1. channel proteins
2. carrier proteins
Channel Proteins Channel proteins
are tubelike and provide openings through which particles can diffuse.
Carrier Proteins Carrier proteins have
a specific shape that fits a specific molecule.
When the proper molecule combines with the protein, it changes shape and moves the molecule across the membrane.
Active Transport Can a cell ever move particles from a region of
lesser concentration to a region of greater concentration?
Yes, but it requires an input of cellular energy (ATP)!
high
low
This is gonna be
hard work!!
Membrane Pump The transport of materials against a
concentration gradient requires energy (ATP) and is called ACTIVE TRANSPORT.
Active Transport uses ATP
Endocytosis Some cells can
take in large molecules, groups of molecules, or even whole cells through ENDOCYTOSIS. requires an input of ATP
Exocytosis The reverse
process of endocytosis is EXOCYTOSIS. Cells use this to expel wastes, and secrete cellular products. Requires an input of ATP
Review Passive Transport
No energyMolecules move from
an area of high concentration to an area of low concentration
Examples:○ Osmosis○ Diffusion○ Facilitated Diffusion
Active TransportRequires energyExamples:
○ Membrane pumpMolecules move from
an area of low concentration to an area of high concentration
○ Endocytosis○ Exocytosis
Back to the snail…. Why does a snail shrivel up and die when
you pour salt on it?Draw a diagramUse content vocabulary