Section 2.3 Carbon-Based Molecules and 2.4 2014
Chemical Reactions.
Section 2.3: Carbon-Based Molecules
 Carbon atoms have unique bonding properties. It is often called the building block of life
because carbon atoms are the basis of most molecules that make up living things.
 Each carbon atom has four unpaired electrons in its outer energy level. Therefore, carbon
atoms can form covalent bonds with up to four other atoms, including other carbon atoms.
 Monomer – molecular subunit of a polymer
 Polymer – a large, carbon-based molecule formed by monomers.
The Four Macromolecules
POLYMER
MONOMER
ELEMENTS
Carbohydrates
Simple Sugar or Monosaccharide
C-H-O
 Glucose – C6H12O6 is a monosaccharide.
C6H12O6 + H2O + O2 -> Energy + H2O + CO2
 Two monosaccharides make a disaccharide i.e. table sugar:
mono – mono = disaccharide
 Many glucose molecules can be linked to make a polysaccharide: mono – mono – mono –
mono n = polysaccharide. Starch is an example of a polysaccharide. Starches are made and
stored by plants.
o
Lipids
Cellulose is somewhat different from starch. The cellulose molecule is a major building
block in plant cell structure. You have eaten cellulose in the stringy fibers of vegetables
such as celery, so you know that it is tough to chew and break up.
Fatty Acids
C-H-O

Most animal fats are saturated fats (solid), which means they have the maximum number
of hydrogen atoms possible. All Carbon-Carbon bonds are single. C is ‘saturated’with H

Unsaturated fats (oils) tend to have fewer hydrogen atoms because there is at least one
double bond between carbon atoms.
Proteins
Amino Acid (sequence determined by DNA)
Nucleic Acids
Nucleotide
NOCH
Sugar – Phosphate – Base
 DNA (DeoxyriboNucleic Acid) stores the information for putting amino acids together to
make proteins.
 RNA (RiboNucleic Acid) helps build proteins
Mr. Lesar
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Section 2.3 Carbon-Based Molecules and 2.4 2014
Chemical Reactions.
Section 2.4: Chemical Reactions
Key Terms/concepts
 Chemical reactions change substances into different substances by breaking and forming
chemical bonds.

C6H12O6
+
H2O
(REACTANTS)
+
O2
->
direction
Energy
+
H2O
+
CO2
(PRODUCTS)
 Reactants are the substances changed during a chemical reaction.
C6H12O6 + H2O + O2
 Products are the substances made by a chemical reaction.
Energy + H2O + CO2
 Bond Energy is the amount of energy that will break a bond between two atoms
 Equilibrium is reached when both the reactants and products are made at the same rate.
 Activation energy is the amount of energy that needs to be absorbed for a chemical reaction to
start. It is like the energy you would need to push a rock up a hill. Once the rock is at the top of
the hill, it rolls down the other side by itself.
 Exothermic – a type of chemical reaction that releases more energy than it absorbs.
o
o
o
o
The products have a lower bond-energy than the reactants.
The difference in bond energy between the reactants and products is usually given off
as heat or light.
Example – Cellular respiration
Aka – an exergonic reaction.
 Endothermic – a type of chemical reaction that absorbs more energy than it releases.
o Its products tend to have higher bond energy than the reactants.
o Example – photosynthesis
o Aka – an endergonic reaction.
Mr. Lesar
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