1

Chapter 2: Chemistry

BIO 105

What does chemistry have to do with biology?

Vocabulary

1. Matter – anything that takes up space and has

mass

2. Mass – measure of how much matter is

contained within an object

3. Atom – smallest unit of matter that cannot be

broken down by ordinary chemical

means

Atoms are the smallest

units of matter that can participate in chemical

reactions

2

Elements

Definition – an element is a “pure” form of

matter that contains a single type of atom

Of all of the elements listed on the periodic

table, only 20 or so are represented in the

human body.

3

The Periodic Table

• Atomic #

• Atomic mass

• Element symbol

Practice

Element # protons # neutrons # electrons

C

H

O

P

Mg

K

Practice

Element # protons # neutrons # electrons

C 6 6 6

H 1 0 1

O 8 8 8

P 15 16 15

Mg 12 12 12

K 19 20 19

4

Isotopes & Radioisotopes

Although all the atoms of a particular element contain the same number of protons, they do not

necessarily all have the same number of neutrons.

Atoms that have the same number of protons but differ in # of neutrons are called isotopes.

i.e. C12, C13, C14

Radioisotopes are unstable, radiation-emitting

isotopes.

Uses of RadiationChemical bonds

When atoms from two or more different

elements are combined to form a new chemical substance, a compound is

formed.

The atoms that make up these compounds are held together by chemical bonds.

5

Covalent bonding

Covalent bonds form when two or more

atoms share electrons in their outer orbitals.

The number of bonds an atom can form

depends on how many “empty spots” exist in the outer shell.

Each pair of electrons is shared equally between the carbon and individual hydrogen atoms.

6

A molecule is a chemical structure held together bycovalent bonds. It may be composed of atoms of

one or more elements.

Ionic bonding

Ionic bonding results from the mutual

attraction of oppositely charged ions.

Ion = charged atom

Hydrogen bonding

Hydrogen bonding is the result of polar

covalent bonds. Atoms may have a slight negative or positive charge depending on

electron distribution.

7

Polar molecules

Water as a solvent

Water is considered the best polar solvent, due to its ability to form hydrogen bonds with other

molecules.

Properties of water

• Solvent

• Transport medium

• High heat capacity

• High heat of vaporization

• Lubricant

8

Dehydration Synthesis

When dehydration reactions occur, a larger

product is formed. In the process, one molecule of H2O is produced.

Dehydration Synthesis example

Hydrolysis Reactions

These types of reactions occur when we are

breaking down a large molecule into smaller pieces.

9

Acids, bases, and salts

When an acid is added to water, it dissociates into H+ and one or more ions.

The concentration of hydrogen ions is increased.

H2CO3 ↔ H+ + HCO3-

Acids, bases, and salts cont.

Bases, on the other hand, remove H+ from solution and are therefore proton acceptors.

HCl + NaOH → H+ + Cl- + Na+ + OH- → NaCl + H2O

Bases decrease the amount of free H+ present in an aqueous solution.

pH scale

• The pH scale is a measure of the concentration of free H+ in a solution in moles/L.

• pH is the negative logarithm of the H+

concentration in a solution

• pH = - log10[H+]

10

pH

A solution with a H+ concentration of 1 x 10-4 has a pH of _____________. Is this classified as an acid or a base?

**A change of one whole number on the pH scale represents a tenfold change in the H+

concentration.**

Which solution has the highest

concentration of H+?

a. pH = 9

b. pH = 7

c. pH = 3

d. pH = 1

11

A solution with a pH of 6:

a. is an acid

b. is a base

c. has 10 times more H+ ions than a solution with

a pH of 5

d. both a and c above

Buffers

A buffering system is composed of a mixture of two compounds

* One substance can yield free H+ when [H+]

drops

* One substance binds with free H+ when

[H+] increases

Bicarbonate/carbonic acid buffering system

CO2 + H2O ↔ H2CO3 ↔ H+ + HCO3-

What are the four classifications of macromolecules?

Macromolecules

Each type of macromolecule is made up

repeating subunits called monomers.

When these monomers are attached together in a chain they are referred to as

polymers.

12

Carbohydrates

Composed of three types of atoms:

Ratio between the atom types:

Monomer = monosaccharides (simple sugars)

have from 3-9 carbons within their

structure

Monosaccharides

13

Disaccharides

Disaccharides are formed by the covalent

linkage of two monosaccharides.

Common disaccharides

Maltose =

Sucrose =

Lactose =

PolysaccharidesFunctions of carbohydrates

1. Energy storage

2. Energy production

3. Cell recognition

14

Lipids

Biological molecules that are insoluble in water (hydrophobic) but soluble in organic solvents

Simplest type of lipid is called a fatty acid.

Saturated vs. unsaturated fats

15

Lipid subclasses

1. Triglycerides

2. Phospholipids

3. Steroids

Triglycerides

Triglycerides

• Long-term energy storage

• Stored in the cells of adipose (fat) tissue

• Protection

• Insulation

16

Phospholipids Steroids

17

Proteins

Proteins are made up of monomers called

amino acids.

Peptide bond formation

18

Protein formation

Sickle Cell Anemia

19

Protein functions

1. Structural

2. Hormones

3. Contraction

4. Transport

5. Immune

6. Enzymes

20

Nucleic acids

Nucleic acids are made of monomers called

nucleotides.

Sugars that make up nucleotidesNitrogenous bases

Cytosine (C) Thymine (T) Uracil (U)

Adenine (A) Guanine (G)

21

Deoxyribonucleic acid (DNA)

double-stranded molecule

sugar = deoxyribose

nucleotides = A,T,C,G

specific base pairing

A & T

G & C

RNA Structure

Differs from DNA

– single stranded

– uracil replaces thymine

Types of RNA within the cell, each with a specific

function

– messenger (m)RNA

– ribosomal (r)RNA

– transfer (t)RNA

22