What is the rule that governs the direction of diffusion?

In which of the following ways is the function of the surface of a microsphere similar to the function of an actual cell membrane? a. both make it possible for the conditions in the interior to be different from the conditions outside. b. both provide a barrier that keeps water from flowing across it so the interior remains dry. c. both separate the rna that forms in the interior from any rna that might form in the environment. d. both can actively move molecules into the interior or out into the surrounding environment.

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.

The distant ancestors of tigers may have had bodies without stripes. use the theory of natural selection to explain how tigers may have evolved to have stripes.