CHAPTER 2 SECTION 1

EXCHANGE WITH THE ENVIRONMENT

IN AND OUT OF THE CELL

•Cells need to get nutrients in and wastes out•The exchange of materials between a cell and its environment occurs at the cell membrane.

DIFFUSION

HIGH LOW

Movement of particles from an area where their concentration is high to

an area where the concentration is low

DIFFUSION IN CELLS• Diffusion can occur across

cell membranes or outside of cells.

• Cells do not require energy for diffusion to occur

EXAMPLES OF DIFFUSION

• Spraying air freshener in a room• Adding a drop of food coloring to

water

DIFFUSION• HTTP://HIGHERED.MCGRAW-HILL.COM/SITES/

0072495855/STUDENT_VIEW0/CHAPTER2/ANIMATION__HOW_DIFFUSION_WORKS.HTML

OSMOSISThe diffusion of

water through a cellular

membrane

ANIMATION OF OSMOSIS

• HTTP://WWW.TVDSB.ON.CA/WESTMIN/SCIENCE/SBI3A1/CELLS/OSMOSIS.HTM

MOVING SMALL PARTICLES• Many small particles (water and oxygen)

can diffuse directly through the cell membrane due to their size

• However, not all of the small particles a cell needs can do this. Sugar and amino acids aren’t small enough to diffuse through the cell membrane.

• These types of particles must travel through protein “doorways” within the cell membrane.

MOVING SMALL PARTICLES

ACTIVE TRANSPORT

• MOVEMENT OF PARTICLES AGAINST THE DIRECTION OF DIFFUSION

• LOW HIGH

• REQUIRES ENERGY (ATP)

PASSIVE TRANSPORT

• MOVEMENT OF PARTICLES IN THE DIRECTION OF DIFFUSION

• HIGH LOW

• NO ENERGY REQUIRED

ACTIVE / PASSIVE TRANSPORT• HTTP://WWW.BROOKSCOLE.COM/CHEMISTRY_D/

TEMPLATES/STUDENT_RESOURCES/SHARED_RESOURCES/ANIMATIONS/ION_PUMP/IONPUMP.HTML

MOVING LARGE PARTICLES

• Diffusion, passive transport and active transport are good methods of moving small particles into and out of cells.

• In order to move large particles in and out cells use endocytosis and exocytosis.

ENDOCYTOSIS• During endocytosis, the cell

membrane surrounds a particle and encloses it in a vesicle.

• This process moves large particles into the cell.

EXOCYTOSISWhen a large particle must be

removed from the cell, it is packaged in a vesicle at the endoplasmic reticulum then travels to the cell

membrane for release.