Lecture AP Biology Chapter 2 The chemical context of life

Identify the four major elements; distinguish between the following pairs of terms: neutron and proton, atomic number and mass number, atomic weight and mass number; distinguish between and discuss the biological importance of the following: nonpolar covalent bonds, polar covalent bonds, ionic bonds, hydrogen bonds, and van der Waals interactions.

Ch 2 Warm-Up

1 What is the difference between an

atom, element and compound?

2 What are the 3 main components of

an atom? What are their charges?

3 What type of bond is found in:

 H 2 O?

 KCl?

 C 6 H 12 O 6 ?

 N 2 ?

 Ba(OH) 2 ?

Chapter 2

The Chemical Context

of Life

Ants & the Duroia Trees

Ants use formic acid to prevent other plants from growing so that the Duroia trees can serve as

their home.

You Must Know

• The three subatomic particles and

their significance

• The types of bonds, how they form,

and their relative strengths

I Matter vs Energy

Matter

 Has mass &

takes up space

 Affected by

gravity

 Consists of

elements and

compounds

Energy

 Moves matter

 Potential,

kinetic

 Ability to do

work

 Conversions

 Sound, light,

heat

 “ pure” substance

 Can’t be broken

down by

“ ordinary” means

to another

substance

 Ex hydrogen

(H), nitrogen (N)

Compound

different elements combined in a fixed ratio

Elements of Life

• 25 elements

elements (ex: Fe, I)

Hint: Remember CHNOPS

II Atomic Structure

• Atom = smallest unit of

matter that retains

properties of an element

• Subatomic particles:

Mass

(dalton or AMU)

Location Charg

e

neutron 1 nucleus 0

proton 1 nucleus +1 electron negligible shell -1

4

Atomic # (protons or electrons)

Mass # (protons + neutrons)

protons

(follow molecules, medical diagnosis)

III Chemical Bonds

Strongest Bonds:

that differ in electronegativity

III Chemical Bonds

Strongest Bonds:

(givers/takers)

- Affected by environment (eg

water)

Weaker Bonds:

molecule bonds to

electronegative atom of other polar covalent molecules

Weaker Bonds:

slight, fleeting attractions

between atoms and molecules close together

 Weakest bond

 Eg gecko toe hairs + wall surface

All important to life

Form cell’s

H bonds to other electronegative

atoms

Made and broken by chemical reactions

All bonds affect molecule’s

SHAPE

 affect molecule’s

FUNCTION

 Similar shapes = mimic

mimic endorphin (euphoria, relieve pain)

Chemical Reactions

forward and reverse reactions offset

one another exactly

reactants/products