Bio 10: Intro to BiologyInstructor: Paul Nagami

Laney College

August 28, 2013

The Chemistry of Life, Pt. 2

(Image credit: Wikimedia commons)

Agenda• Administrative Stuff• Review: Friday’s lesson on water• Understanding the Periodic Table• Atomic Symbols, Atomic Numbers• Valence Electrons• Ions

• Elements of Life• An introduction to pH, acids, and bases

• Wrap-up

Administrative Stuff

• The course webpage is in progress.

• Please turn in your completed (or incomplete) checklists with your index cards at the end of class today.

Quick Review:On your index

card, write your name and draw

three molecules of water and any interactions

between them.

Last time…• We introduced the parts of atoms (protons, neutrons, and electrons)…

• …and how those atoms can make molecules by sharing electrons.

• We discussed how unequal sharing of electrons can allow hydrogen bonds to form…

• And we explored how such properties cause some substances to be hydrophilic (water-loving) or hydrophobic (water-fearing), and how this relates to protein structure!

But what about elements that aren’t hydrogen or oxygen?

Reading a Periodic Table

Atomic Symbol = Abbreviation for element.C = Carbon (CO2= 1 Carbon, 2 Oxygen)

Atomic Number = Number of Protons

Carbon has 6 protons per atom.

Valence Electrons

What’s going on here?!

Make a guess!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. (Hint: Oxygen is heavier than hydrogen.)P) Phosphorus

N) Nitrogen

S) Sulfur

H) Hydrogen

O) Oxygen

C) Carbon

Fe) IronCa) Calcium

Simplifying the Table

Ions: Charged Particles!

Oxygen (O) Found as O2, never

as a single O atom!

Carbon (C)

Organic chemistry is thechemistry of carbon compounds! Every complex molecule in your body contains carbon!

Hydrogen (H) Pure hydrogen gas

doesn’t occur much in the body, but it’s part of other molecules.

Hydrogen ions in solution are very important, though!

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

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!

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 (revisited):

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: