Transport Across Membranes 2.4

Importance of Transport intake of nutrients removal of wastes communication with environment & other cells blocking passage of harmful substances

Passive Transport the movement of materials across the cell membrane without the use of chemical energy (ATP) occurs because of diffusion

Diffusion the net movement of a substance from an area of higher concentration to an area of lower dynamic equilibrium Image from: http://arditobook.pbworks.com/w/page/11348839/Diffusion

Simple Diffusion substances move across membrane unassisted small non-polar molecules (O2, CO2, steroid hormones, some drugs) and small polar molecules (H2O, glycerol) larger molecules and ions can not pass through membranes unassisted

Image from: http://schoolworkhelper

Facilitated Diffusion diffusion across membrane assisted by integral membrane proteins called transport proteins channel proteins vs. carrier proteins ions, water, amino acids, sugars, etc.

Osmosis the diffusion of water across a membrane water follows concentration gradient until equilibrium

Osmosis direction of osmosis changes depending on type of solution surrounding the cell: isotonic solution hypotonic solution hypertonic solution

Cell in Isotonic Solution The Plasma Membrane 4/25/2017 Cell in Isotonic Solution 10% NaCL 90% H2O ENVIRONMENT CELL NO NET MOVEMENT 10% NaCL 90% H2O What is the direction of water movement? equilibrium The cell is at _______________. copyright cmassengale 10 G. Podgorski, Biol. 1010 10

Cell in Hypotonic Solution The Plasma Membrane 4/25/2017 Cell in Hypotonic Solution 10% NaCL 90% H2O CELL 20% NaCL 80% H2O What is the direction of water movement? copyright cmassengale 11 G. Podgorski, Biol. 1010 11

Cell in Hypertonic Solution The Plasma Membrane 4/25/2017 Cell in Hypertonic Solution 15% NaCL 85% H2O ENVIRONMENT CELL 5% NaCL 95% H2O What is the direction of water movement? copyright cmassengale 12 G. Podgorski, Biol. 1010 12

Cells and Tonicity Image from: http://chemistry.about.com/b/2010/11/09/osmotic-pressure-and-tonicity.htm

Red Blood Cells Image from: http://www.esu7.org/~lweb/Lakeview/science/sea.htm

copyright cmassengale The Plasma Membrane 4/25/2017 isotonic hypotonic hypertonic hypertonic isotonic hypotonic copyright cmassengale 15 G. Podgorski, Biol. 1010 15

How does this impact… …a single-celled organism living in a freshwater environment? …a single-celled organism living in a salt-water environment? …the roots of a plant in the spring after salt has been sprinkled during the winter?

More applications… Why can’t you water a plant with salt water? Why do vegetables in the grocery store get sprayed with water periodically? (What would happen if they were sprayed with salt water?)

Active Transport Image from: http://thebasisoflife.wikispaces.com/Membrane+Structure+and+Function

Active Transport the movement of materials against the concentration gradient requires cellular energy (ATP)

Primary Active Transport pumps move positively charged ions (H+, Ca2+, Na+, K+) across membranes creates electrochemical gradient Image from: http://www.daviddarling.info/encyclopedia/A/active_transport.html

Secondary Active Transport uses gradient established by a primary active transport pump Image from: http://apbrwww5.apsu.edu/thompsonj/Anatomy%20&%20Physiology/2010/2010%20Exam%20Reviews/Exam%201%20Review/Ch03%20Active%20Transport.htm

Bulk Transport movement of larger substances across a cellular membrane requires energy (ATP) exocytosis & endocytosis

Endocytosis Image from: http://kentsimmons.uwinnipeg.ca/cm1504/membranefunction.htm

Exocytosis Neurotransmitters Image from: http://library.thinkquest.org/C004535/molecule_transport.html Neurotransmitters

Credits Slides #10, 11, 12, and 15 taken from Powerpoint presentations created by Cheryl Massengale, educator extraordinaire & creator of http://www.biologyjunction.com/