Transport Across Cell Membrane 2.4

Passive Transport the movement of materials across the cell membrane without the use of cell energy (ATP) simple diffusion (including osmosis) facilitated diffusion (using carrier proteins)

Simple Diffusion Image from: http://arditobook. pbworks the movement of molecules from an area of higher concentration to an area of lower concentration CO2, O2, H2O

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

Osmosis movement of water into and out of cells is important in life processes direction changes depending on type of solution: 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 6 G. Podgorski, Biol. 1010 6

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 7 G. Podgorski, Biol. 1010 7

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 8 G. Podgorski, Biol. 1010 8

Cells and Tonicity Image from: http://chemistry. about

Red Blood Cells Image from: http://www. esu7

copyright cmassengale The Plasma Membrane 4/25/2017 isotonic hypotonic hypertonic hypertonic isotonic hypotonic copyright cmassengale 11 G. Podgorski, Biol. 1010 11

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?)

Facilitated Diffusion Image from: http://schoolworkhelper protein carrier molecules assist in diffusion of molecules across cell membrane e.g. glucose into red blood cells

Active Transport Image from: http://thebasisoflife. wikispaces

Active Transport the movement of materials against the concentration gradients requires cellular energy (ATP) primary & secondary active transport important for reabsorption in kidneys, muscle contractions, nerve impulses, etc.

Active Transport often accomplished through protein channels movement of larger substances through endocytosis and exocytosis

Endocytosis Image from: http://kentsimmons. uwinnipeg

Exocytosis Image from: http://library. thinkquest Neurotransmitters

Credits Slides #12, 13, 14, and 17 taken from Powerpoint presentations created by Cheryl Massengale, educator extraordinaire & creator of http://www.biologyjunction.com/

Homework #1 Your biology study partner asks you a question about the concentration gradient of water. What is meant by the term “concentration gradient”? Is your study partner using the term correctly in reference to water? Explain why or why not.

Homework #2-3 Facilitated diffusion is specific. What does this mean? A red blood cell was placed in a beaker of solution. The cell immediately began to swell and finally burst. Explain what happened, referring to the cytosol of the cell and the solution in the beaker.

Homework #4,5 Distilled water is considered hypotonic to body cells. Explain. Compare the energy requirements of passive transport, primary active transport, and secondary active transport.

Homework #7 How does the concentration of a solute on the two sides of a membrane affect passive transport? How does this concentration affect primary and secondary active transport?