Which cellular structure separates the cytoplasm from the external environment in all cells? A. Cytoskeleton B. Nuclear membrane C. Cell wall D. Plasma.

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