Bio 10: Intro to BiologyInstructor: Paul Nagami

Laney College

August 30, 2013

The Chemistry

of Life, Pt. 3

Agenda

• Administrative Stuff• Essay Outline Instructions• Review: Wednesday’s Chemistry

Lesson• Elements of Life, continued• More on pH, Acids, and Bases• Buffers• The Pieces that Make DNA• The Forest and the Trees

• Wrap-up

Essay Outline• Don’t forget that your essay outline

is due in lecture a week from Wednesday

• Useful sources for articles on relevant research:• http://www.sciencedaily.com/• http://www.sciencemag.org/• http://www.nature.com/

• If you have questions, please ask sooner than later!

Simplifying the Table

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.

P) Phosphorus

N) Nitrogen

S) Sulfur

H) Hydrogen

O) Oxygen

C) Carbon

Fe) IronCa) Calcium

What’s a Solution?

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.

pH, continued

OH- vs. H+

More OH- means less H+, and vice-versa.

Acid = proton “donor”Base = proton “acceptor”

pH, continuedWhy 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!

Understanding pH

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

Buffers prevent the pH of a solution from changing too easily.

Bicarbonate buffer system:

Nitrogen (N)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!

Phosphorus (P) All living things

need phosphorus

Usually found as phosphate ions.

Elements of DNA

PhosphorusOxygenNitrogenCarbonHydrogen

What Are Trees Made Of?

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.

Review