The Chemistry of Life, Pt. 3. Bio 10: Intro to Biology Instructor: Paul Nagami Laney College. August 30 , 2013. Agenda. Administrative Stuff Essay Outline Instructions Review: Wednesday’s Chemistry Lesson Elements of Life, continued More on pH, Acids , and B ases Buffers
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Life, Pt. 3
August 30, 2013
On your index card, write your name and try to draw how the electrons of nitrogen (N) are arranged in shells.
Make a guess (what do you recall?)
What are we made of? On your index cards, try to rank the following elements by the mass of them in your body, from most to least.
A solution is when one substance is mixed perfectly evenly with another, no matter how hard you try to separate them!
Solvent: The major part of the solution. Solute: What gets dissolved by the solvent.
More OH- means less H+, and vice-versa.
Acid = proton “donor”
Base = proton “acceptor”
Why do we say that acidic solutions with a lot of H+ have low pH?
There isn’t that much H+ dissociation. Pure water has only .0000001 M of H+. (M = Molar, a unit of concentration)
A strong acid might have .1 M of H+. A strong base might have only .00000000000001 M of H+!
So we count how many places we need to move the decimal point!
How many M of H+ are there in a solution with pH of 5?
What is the pH of a solution with .000000001 M of H+?
Which solution has more H+? Which is more acidic? Which is more basic?
Buffers prevent the pH of a solution from changing too easily.
Bicarbonate buffer system:
All living things need nitrogen to make DNA and protein!
Dry air is about 80% nitrogen by volume.
But those nitrogen atoms are stuck together in pairs!
All living things need phosphorus
Usually found as phosphate ions.
Every year, the General Sherman sequoia adds on over a cubic meter of wood – enough to make a new 15-meter (50-foot) tall tree!
Where does all of this dry mass come from?
Take a guess:
Most of the General Sherman tree’s dry mass is derived from….
A) Water and minerals from the soil.
B) Organic matter from the soil.
C) Energy from the sun.
D) Gas from the air.