Transport Across Membranes Image from: http://schoolbag.info/chemistry/mcat_biochemistry/49.html 2.4

Importance of Transport intake of nutrients removal of wastes communication with environment & other cells blocking entry of harmful substances Cell membrane is selectively permeable.

Passive Transport the movement of materials across the cell membrane without the use of chemical energy (ATP) movement is due to diffusion

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

Simple Diffusion substances move unassisted small non-polar molecules, small uncharged polar molecules larger molecules & ions need assistance Image from: http://biology4alevel.blogspot.ca/2014/09/25-passive-and-active-transport-across.html small non-polar molecules (O2, CO2, steroid hormones, some drugs) and small polar molecules (H2O, glycerol)

Facilitated Diffusion diffusion across membrane assisted by integral membrane proteins called transport proteins channel proteins form hydrophilic pathways for water & ions; ion channels are usually voltage-gated carrier proteins usually have specificity

Facililated Diffusion Image from: http://biology4alevel.blogspot.ca/2014/09/25-passive-and-active-transport-across.html

Carrier Proteins Image from: https://www.quora.com/How-do-carrier-proteins-transport-specific-proteins

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 11/24/2018 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 _______________. 11 G. Podgorski, Biol. 1010 11

Cell in Hypotonic Solution The Plasma Membrane 11/24/2018 Cell in Hypotonic Solution 10% NaCL 90% H2O CELL 20% NaCL 80% H2O What is the direction of water movement? 12 G. Podgorski, Biol. 1010 12

Cell in Hypertonic Solution The Plasma Membrane 11/24/2018 Cell in Hypertonic Solution 15% NaCL 85% H2O ENVIRONMENT CELL 5% NaCL 95% H2O What is the direction of water movement? 13 G. Podgorski, Biol. 1010 13

Animal Cells Prefer Isotonic Environments 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

Plant Cells Prefer Hypotonic Environments

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

Active Transport the movement of materials against the concentration gradient (from low to high concentrations) 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