Plasma Membrane & Cellular Transport

http://www.i-sup2008.org/images/venue_transport.jpg

Cell Transport

A cell has to move food and wastes into and out of the cell. Materials must move through the plasma membrane which maintains homeostasis in the cell.

food

waste

food

foodfood

waste

waste

waste

Cell Transport

The Plasma Membrane surrounds the cell. How does it work?

Plasma Membrane

Boundary between the cell and its environment1. Allows nutrients into the cell2. Removes wastes and excess materials3. Maintains homeostasis: a stable internal

environment

Plasma MembraneHow does it work?1. Selectively permeable: only allows some

molecules in the cell, keeps others out

http://media3.washingtonpost.com/wp-dyn/content/photo/2006/10/15/PH2006101500491.jpg

Plasma Membrane2. Fluid Mosaic Model: membrane is flexible,

made of many pieces working together

http://www.youtube.com/watch?v=Qqsf_UJcfBc

Molecules are able to move around within each layer of the membrane.

FluidMolecules moving around on surface create different patterns.

Mosaic

Plasma Membrane3. Phospholipid Bilayer: membrane is 2 layers,

made of phospholipids with proteins mixed in

http://www.utm.utoronto.ca/~w3bio315/lecture2.htm

Plasma Membrane PartsPhosphate heads – hydrophilic (like water), outside and

inside membraneFatty Acid Tails – hydrophobic (fear water), inside

membrane, like OREO creamCholesterol – prevents fats from sticking together,

stabilize membraneTransport proteins – move molecules into and out of

cellIdentification proteins – outside cell, “nametag”Support proteins – inside cell for framework, “skeleton”Carbohydrates – serve as markers or “nametags”

1. Diffusion - molecules move from an area of high concentration to low concentration

http://iweb.tntech.edu/mcaprio/diffusion-animated.gif

NO ENERGY required, moves molecules from high concentration to low concentration

Passive Transport

http://schools.moe.edu.sg/chijsjc/Biology/Diffusion&osmosis/osmosis.gif

2. Osmosis – diffusion of water molecules across a selectively permeable membrane

Passive Transport – no energy required

Solutions

Isotonic solution – equal concentrations of solute (salt) inside and outside cell

http://www.biologycorner.com/resources/isotonic.gif

Solutions

Hypotonic solution – less solute in solution, more solute in cell, WATER FOLLOWS SALT, cells swell

http://www.biologycorner.com/resources/hypotonic.gif

Solutions

Hypertonic solution – more solute in solution, less solute in cell, WATER FOLLOWS SALT, cells shrink

http://www.biologycorner.com/resources/hypertonic.gif

Osmosis in blood cells

http://aryatiabdul.files.wordpress.com/2008/07/osmosis2.gif

Solutions – how transport affects animals and plants

http://kentsimmons.uwinnipeg.ca/cm1504/Image130.gif

Transport in PlantsHealthy plant cells are crisp due to TURGOR PRESSURE

Wilted plant cells are flaccid due to lack of water

Passive Transport – no energy required

3. Facilitated Diffusion – movement of molecules from high concentration to low concentration with help of membrane transport proteins

http://www.biology.arizona.edu/CELL_BIO/problem_sets/membranes/graphics/CHANNEL.GIF

High concentration

Low concentration

Active Transport

Requires energyMoves molecules against concentration gradientMoves molecules from area of low concentration

to area of high concentrationExamples:

gated channels, sodium/potassium pumps, endocytosis, exocytosis

Active TransportEndocytosis and Exocytosis

http://media-2.web.britannica.com/eb-media/38/8038-004-A29C9C02.jpg