Cell Transport

This is known as diffusion Particles Move From Areas of Greater or Higher Concentrations to Areas of Lower or Lesser Concentrations This is known as diffusion

HIGH  LOW

Animation of How Diffusion Works http://highered.mcgraw-hill.com/sites/0072495855/student_view0/chapter2/animation__how_diffusion_works.html

A Cell Membrane

Membranes control what comes in or out of a cell and maintains a balance in the cell called homeostasis

Membranes are Selectively Permeable or Semi-Permeable Some materials can pass through membranes, but others cannot. Due to the chemical make up of the membrane and the diffusing particles. The size and charge of the particle determine if a membrane will be permeable to the particle.

Animation of Diffusion Through a Semipermeable Membrane http://zoology.okstate.edu/zoo_lrc/biol1114/tutorials/Flash/Osmosis_Animation.htm

MEMBRANES ARE SELECTIVELY PERMEABLE Some particles diffuse by themselves. Others (ions) have to go through proteins. Others (if they’re too large) will not diffuse at all. MEMBRANES ARE SELECTIVELY PERMEABLE

Diffusion is Important to Cells See what happens to red blood cells if the water and solute concentrations are not equal in blood cells and surrounding plasma! https://www.youtube.com/watch?v=A8cI6FkcG4c

The diffusion of water in or out of cells is so important, we have a special term for it – osmosis

Plant Cells Don’t Rupture Due to Osmosis Because of the Cell Wall

https://www.youtube.com/watch?v=zVvHn6Sj9PQ

The pressure of water in the vacuole of plant cells press up against the cell wall and is called turgor (or tugor pressure)

Terms You MUST Know and Understand! Hypertonic – the SOLUTE concentration is high Hypotonic – the SOLUTE concentration is low Isotonic – the SOLUTE concentrations are equal (at equilibrium)

PLANT CELL IN A HYPOTONIC SOLUTION PLANT CELL IN A HYPERTONIC SOLUTION PLANT CELL IN AN ISOTONIC SOLUTION

You can’t always predict which direction solutes move!!!! It depends if the cell membrane is permeable to the solute!!!!

Some unicellular organisms that are very hypertonic to their surroundings have a special vacuole, a contractile vacuole that pumps excess water out of the cell. https://www.youtube.com/watch?v=pahUt0RCKYc

You can always predict which way water will diffuse Water moves from hypOtonic solutions TO hypERtonic solutions

Ions Pass Through Membranes by Using Proteins When particles pass through proteins, this is called facilitated diffusion http://highered.mcgraw-hill.com/sites/0072495855/student_view0/chapter2/animation__how_facilitated_diffusion_works.html

If the Cell Uses Its Own Energy to Transport Materials Through the Cell Membrane, This is

In active transport, particles are moved from lower to higher concentrations This is known as going UPHILL or AGAINST the concentration gradient Protein pumps in the cell membrane are used in active transport

Video on Active Transport https://www.youtube.com/watch?v=2-icEADP0J4

When cells do not use their own energy for transport, it’s known as passive diffusion or transport. Particles are moved down the concentration gradient

Very Large Particles or Groups of Particles are Transported by Vesicles

Large Particles Move Into Cells by Endocytosis and Out by Exocytosis

A Review of Cellular Transport (click on SC, then GO to get this to work) http://www.classzone.com/cz/books/bio_07/resources/htmls/animated_biology/unit2/bio_ch03_0093_ab_cellmem.html