Biology 12 Name: _________________________________ Block: _________ Date: _______________

Unit 1 – Homeostasis; Chapter 2 – The Molecules of Cells

2.1 – Basic Chemistry AND 2.2 Molecules and Compounds (p24-29) – STUDENT NOTES

Why study Chemistry in Biology Class?

All life is made up of ____________

Matter is anything that _______________________________________________

All matter ( ________________________________) is made up of _______________________________

Definitions:

Element =

Atom =

Ion =

o Cation

o Anion

Chemical Bonds:

Atoms of a molecule are held together by ____________________________________

The likelihood than an atom will form a chemical bond with another atom depends on ____________________

__________________________________________________________________, also called the valence shell.

Stability (and full valence shells) is the goal.

Stability is obtained by _____________________________ or ________________ electrons.

Three Types of Chemical Bonds

1) _________________ Bonds Formed between ____________________

and _________________ atoms.

An ionic bond is a ___________________ of electrons from

_____________( _____________ ion) to

a __________________ (_______________ ion)

2) ________________ Bonds

Formed between ____________________ and _________________ atoms.

Atoms of molecules ___________________ pairs of their valence electrons.

i. _____________ _____________ bond = sharing one pair of electrons

ii. _____________ _____________ bond = sharing two pair of electrons

iii. _____________ _____________ bond = sharing three pair of electrons

There are 2 types of Covalent Bonds:

a) __________________ covalent bonds

= share electrons _______________.

One atom doesn’t attract the shared electrons more

Than the other atom.

b) __________________ covalent bonds

= ___________ sharing of electrons between atoms

In a water molecule, oxygen has the greater

Electronegativity and attracts the H electrons

More strongly.

A comparison: covalent vs. ionic bonding

3) Third type of Chemical Bond = ____________________ Bonds

H is covalently bonded with one atom to form a molecule (e.g H2O, NH3)

Then the H in the covalently bonded molecule is attracted to another atom (usually O, N or F) of a

different molecule

H bonds form weak intermolecular bonds; and serve as links between molecules.

i. For example H-bonds between water molecules, DNA nitrogenous bases, proteins.

H bonds help determine the three-dimensional shape of molecules

H bonds are ALWAYS represented by dotted lines

Examples shown below – water and DNA molecule

If you need more Chemistry review … check out:• www.KhanAcademy.org the Chemistry section• https:// cnx.org/contents/jVCgr5SL@14.2:xVWiZWMF@10/Atoms-Isotopes-Ions-and-Molecules-The-

Building-Blocks Open Stax, Biology 2e, Chapter 2.1 Atoms, Isotopes, Ions, and Molecules: The Building Blocks

• YouTube – Discover Science Now - Bio12 – Biochem Playlist, videos # 1, 3, and 4

Now we can finish these definitions ...

Molecules =

Compounds =