Solution concentration can be described in terms of tonicity. solutions are hypertonic, isotonic, or hypotonic to cells. a hypertonic is one that has a greater concentration of solute outside the cell and therefore a lower concentration. water will leave the cell, to the outside environment. this is one reason why organisms that live in fresh water cannot survive in salt water, the ocean. water will leave the organism’s cells and eventually the cells will undergo plasmolysis and the organisms will die. an isotonic solution is a balanced solution. that is, the solution concentration is balanced with the solution inside the cell. finally, when a cell is surrounded by a hypotonic solution, concentration of solute is greater inside the cell, concentration of water greater outside. water moves into the cell and the cell swells. if enough water enters, the cell can burst. on day 2, the egg was placed in 10% salt water. based on the student data, what type of solution would we label 10% salt water in this case? a) hypertonic b) hypotonic c) isotonic d) saline

With the description of the different cell walls, membranes, and associated proteins set in the students' minds, you now need to introduce them to the idea that the cell wall can also act as a foundation to build things upon. bacterial appendages require a strong foundation that will offer the support needed to move and function in a dynamic world. for example, flagella are long, whiplike protein structures that are used by many gram-positive and gram-negative bacteria for locomotion. in order to function effectively, a flagellum must be firmly anchored to the cell wall. how will you be able to get across the idea that the peptidoglycan cell wall is strong enough to support such a mechanism? with a protein rod that passes through the cell wall and protein rings used to anchor it in the membranes, these basal bodies are the rudimentary biological motors that use atp power to spin the hook and the flagella attached to it. bacterial flagella have a biological motor that spins within the cell wall and is powered by atp. this allows the flagella to spin in a whiplike motion to propel the bacterium.

Why do leaves change color in the fall? green pigments break down and no longer mask the color of chlorophyll. chlorophyll breaks down and no longer masks the colors of other pigments. red- and yellow-colored pigments grow and mask green-colored chlorophyll. green-colored chlorophyll breaks down and turns red and yellow.

What organ systems are working to you cool down after a workout?