EXCHANGE WITH THE ENVIRONMENT

The Cell in Action

HOW DO YOU PREVENT UNWANTED THINGS FROM COMING THROUGH A

WINDOW?

WHAT PART OF A CELL DOES THE SAME THING?

“Close that window! Do you want to let in all the

bugs???

Moving Cellular Materials

Cells take in food, oxygen and other substances from their environments.

They also release waste materials into their environments.

What organelle works as a gatekeeper to let materials in and out of a cell?

Gatekeeper = Cell membrane

. Found in both plant and animal cells, the exchange of materials between a cell and its environment takes place in the cell membrane.

D I F F U S I O N

O S M O S I S

PA S S I V E T R A N S P O R T

A C T I V E T R A N S P O R T

Small particles cross the cell membrane by way of

To understand how materials move in and out of a cell, you need to know about diffusion….

Click icon to add pictureDiffusion is the movement of particles from areas of high density to areas of lower density.When the molecules are evenly spread, equilibrium occurs.

Diffusion occurs in ….

Solids

Liquids

Gasses

Example of a diffusion in a solid:You put a metal spoon into hot tea or

coffee and the entire spoon is hot after a few minutes.

Example of diffusion in a liquid:Adding a more dense liquid (such as

corn syrup) to water

Example of diffusion in a gas:Someone puts on too much Axe Body

Spray after PE. You can smell him before AND after you see him

Osmosis

Click icon to add pictureOsmosis is a special example of diffusion. It is the diffusion of water through a semi-permeable membrane .Semi = partialPermeable= go through, cross

Osmosis

Osmosis is the process by which water enters our tissues.

All of our cells are surrounded by a membrane that selectively allows anything the cell needs, but prevents unwanted molecules from entering.

How osmosis works

This works because the membrane contains lots of tiny holes that will let anything smaller through but obviously will stop big molecules from entering the cell.

Water is small enough to get through and enters by diffusion.

Water will enter until equilibrium is achieved.

Osmosis

If cells weren’t surrounded by water that contains few dissolved substances, the water in the cells would diffuse out of them.

Plants=wilting

However, the dissolved substances (solutes), such as salts, sugars, and other substances in the water that surrounds cells, prevent this from happening. Equilibrium

Active Transport Passive Transport

The movement of substances across the cell membrane that requires using energy by the cell

Endocytosis and Exocytosis Low concentration to

high concentration Riding a bike up a hill!

The movement of substances across the cell membrane without using energy by the cell.

Diffusion and Osmosis High to low

concentration Coasting down a hill on

your bike

Active and Passive Transport

Endocytosis

The cell membrane surrounds a particle and encloses this particle in a vesicle to bring the particle into the cell

A hughttp://www.youtube.c

om/watch?v=HndmASfmI8Y

Endocytosis

Exocytosis

The cell membrane encloses a particle in the cell in a vesicle, then moves to the surface, fuses with the cell membrane, and expels the particle.

Shoving someone

Hypertonic, Hypotonic and Isotonic

A hypertonic solution is a solution(mixture) containing more solute than solvent A lot of salt (solute) dissolved in water (solvent)

A hypotonic solution is a solution containing more solvent than solute Purified water --- almost no solute dissolved in the solvent

(water)An isotonic solution is a solution where the solute

and solvent are equally distributed. Cells normally want to remain in an isotonic solution, where

the concentration of liquid inside is the same as the concentration of the liquid outside of it. Equilibrium!