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2.3 Carbon-Based Molecules
KEY CONCEPT
Carbon-based molecules are the foundation of life.
2.3 Carbon-Based Molecules
Carbon atoms have unique bonding properties.
• Carbon forms covalent bonds with up to four other atoms,
including other carbon atoms.
• Carbon-based molecules have three general types of
structures.
– straight chain
– branched chain
– ring
2.3 Carbon-Based Molecules
• Many carbon-based molecules are made of many small
subunits bonded together.
– Monomers are the individual subunits.
– Polymers are made of many monomers.
2.3 Carbon-Based Molecules
Integrating Chemistry – Types of reactions
• Some polymers form through a process of dehydration, that
is, a molecule of water is released as one or more monomer
bonds to another. One provides a hydrogen (H) and the other
provides a hydroxyl group (OH).
• Some polymers can also
be broken down in a
reverse reaction called
hydrolysis. The bonds
between the monomers
are broken by the addition
of water molecules (H2O).
2.3 Carbon-Based Molecules
Four main types of carbon-based molecules are found in
living things.
• Carbohydrates are made of carbon, hydrogen, and
oxygen.
– C, H and O are combined in a ratio of 1:2:1
2.3 Carbon-Based Molecules
Four main types of carbon-based molecules are found in
living things.
• 1. Carbohydrates are made of carbon, hydrogen, and
oxygen.
– Carbohydrates include
sugars and starches.
– Monosaccharides are
simple sugars like glucose
and fructose.
– Disaccharides include
sucrose, maltose and
lactose
– Polysaccharides include
starches, cellulose, and
glycogen.
2.3 Carbon-Based Molecules
• Carbohydrates can be broken down to provide
energy for cells (starch and glycogen). Glycogen is
made by animals and stored in their liver.
• Some carbohydrates are part of cell structure (cellulose).
Polymer (starch)
Polymer (cellulose)
monomer
Starch is a polymer of
glucose monomers that
often has a branched
structure. Starch is
made and stored by
plants. They break it
down for energy.
Cellulose is a polymer
of glucose monomers
that has a straight, rigid
structure. It is used and
the building block of
plant cell structure. It is
the tough outer
covering of plant cells.
2.3 Carbon-Based Molecules
• 2. Lipids are nonpolar molecules that include fats, oils,
and cholesterol.
– Many contain carbon chains called fatty acids.
– Fats and oils contain fatty acids bonded to glycerol.
Triglyceride
2.3 Carbon-Based Molecules
• Lipids have several different functions.
– broken down as a source of energy (fats and oils)
– make up cell membranes (phospholipids and cholesterol)
– used to make hormones (cholesterol makes steroid
hormones like testosterone and estrogen)
2.3 Carbon-Based Molecules
• Fats and oils have different types of fatty acids.
– saturated fatty acids (common in animal fats)
– unsaturated fatty acids
2.3 Carbon-Based Molecules
• Phospholipids make up all cell membranes.
– Polar phosphate “head”
– Nonpolar fatty acid “tails”
Phospholipid
How would the polar head of a phospholipid respond to
water molecules?
How would the nonpolar tails respond to water
molecules?
2.3 Carbon-Based Molecules
• 3. Proteins are polymers of amino acid monomers.
– Twenty different amino acids are used to build proteins
in organisms.
– They are the most varied of the carbon-based
molecules and function in movement, eyesight or
digestions and many other things.
Fig. Serine is
one of 20 amino
acids that make
up proteins in
organisms
2.3 Carbon-Based Molecules
• Proteins are polymers of amino acid monomers.
– Twenty different amino acids are used to build proteins
in organisms.
– Amino acids differ in side groups, or R groups.
2.3 Carbon-Based Molecules
• Proteins are polymers of amino acid monomers.
– Twenty different amino acids are used to build proteins
in organisms.
– Amino acids differ in side groups, or R groups.
– Amino acids are linked by peptide bonds.
2.3 Carbon-Based Molecules
• Proteins differ in the number and order of amino acids.
– Amino acids interact to give a protein its shape. Primary structure
(amino acid chain), secondary structure (folds, alpha or beta), tertiary
structure (overall shape).
Hemoglobin
hydrogen bond
– Incorrect amino acids change a protein’s structure
and function.
2.3 Carbon-Based Molecules
Hemoglobin and Sickle Cell Anemia
• Hemoglobin in red
blood cells transports
oxygen. Just one
amino acid change
causes red blood cells
to have the curved
shape characteristic of
sickle cell anemia.
(colored SEM;
magnification 3500 X)
2.3 Carbon-Based Molecules
• 4. Nucleic acids are polymers of monomers called
nucleotides.
• They carry detailed instructions to build proteins.
2.3 Carbon-Based Molecules
• Nucleic acids are polymers of monomers called
nucleotides.
– Nucleotides are made of a sugar, phosphate
group, and a nitrogen base.
A phosphate group
deoxyribose (sugar)
nitrogen-containing molecule,
called a base
2.3 Carbon-Based Molecules
• Nucleic acids are polymers of monomers called
nucleotides.
– Nucleotides are made of a sugar, phosphate
group, and a nitrogen base.
– DNA stores genetic
information.
DNA
– RNA builds proteins. RNA
Apply: What is the
relationship between
proteins and nucleic acids?