2.3 Carbon-Based Molecules
CARBON BASED MOLECULES
2.3 Carbon-Based Molecules
KEY CONCEPTS
Carbon-based molecules are the foundation of life.
Lipids are one class of organic molecules. This group
includes fats, oils, waxes, and steroids. Lipids are
made of C, H, and a little bit of O.
Lipids are not water soluble. This unique chemistry
makes them ideal for building things like the cell
membrane, commonly called the phosphlipid bilayer.
2.3 Carbon-Based Molecules
KEY CONCEPTS
We will be examining these types of lipids:
-Basic Hydrocarbons
23_541
-Triglycerides (fats and oils)
-Phospholipids
-Steroids, including hormones and cholesterol.
2.3 Carbon-Based Molecules
• Lipids have several different functions.
– broken down as a source of energy
– make up cell membranes
– used to make hormones
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 (not covered on exam)
– ring (not covered on exam)
2.3 Carbon-Based Molecules
Here are some examples of straight chain hydrocarbons.
2.3 Carbon-Based Molecules
Here are some examples of straight chain hydrocarbons.
2.3 Carbon-Based Molecules
There is a shorthand for drawing molecules:
• To simplify a hydrocarbon, we draw a kinked line
where each bend (and each end) is a carbon.
2.3 Carbon-Based Molecules
Practice
• Try drawing the kinky model of ethanol (seen below).
2.3 Carbon-Based Molecules
Practice
• Try drawing the kinky model of ethanol (seen below).
2.3 Carbon-Based Molecules
Practice
• Try drawing the kinky model of ethanol (seen below).
2.3 Carbon-Based Molecules
• Lipids are nonpolar molecules that include fats, oils,
and cholesterol (which is a steroid).
– Many contain carbon chains called fatty acids.
– Fats and oils contain 3 fatty acids bonded to
1 glycerol.
– These fatty acids (hydrocarbon chains) are
hooked to the glycerol by taking water out. When
they join it is called a dehydration synthesis
reaction.
Triglyceride
2.3 Carbon-Based Molecules
On your own, draw a triglyceride
(one glycerol + 3 fatty acids).
2.3 Carbon-Based Molecules
• Fats and oils have different types of fatty acids.
– saturated fatty acids (single bonds)
– unsaturated fatty acids (at least one
double bond)
2.3 Carbon-Based Molecules
Saturated fats and unsaturated fats have different
properties because of how the molecules pack
together.
2.3 Carbon-Based Molecules
Real Fatty acids…do not memorize. More double bond
means lower melting point (more likely to be liquid at
room temperature)
O
OH
stearic acid (18:0)
m.p. 70ºC
OH
oleic acid (9-18:1)
an -9 fatty acid
m.p. 16ºC
O
O
OH
linoleic acid (9,12-18:2)
an -6 fatty acid
m.p. -5ºC
OH
linolenic acid (9,12,15-18:3)
an -3 fatty acid
m.p. -11ºC
O
2.3 Carbon-Based Molecules
Saturated fats pack well and tend to be solid.
Unsaturated fats do not pack well and tend to be
liquid.
Saturated
Unsaturated
2.3 Carbon-Based Molecules
Peanut Butter separates into both types!
Saturated
Unsaturated
2.3 Carbon-Based Molecules
• Phospholipids make up all cell membranes.
– Polar phosphate “head”
– Nonpolar fatty acid “tails”
Phospholipid
2.3 Carbon-Based Molecules
• Phospholipids make up all cell membranes.
2.3 Carbon-Based Molecules
• Phospholipids make up all cell membranes.
2.3 Carbon-Based Molecules
Steroids are a class of lipids. Steroids include hormones
and cholesterol. Steroids consist of 4 interconnected
rings of carbon.
2.3 Carbon-Based Molecules
Steroids are a class of lipids. Steroids include
hormones and cholesterol. Steroids consist of
interconnected rings of carbon.
Hormones
Cholesterol
• A chemical messenger
that carries a signal from
one cell to another.
• Helps keep the cell
membrane fluid at a wide
range of temperatures.
• Ex) Testosterone, or
epinephrine
2.3 Carbon-Based Molecules
Lipids section is over. Continue for polymers.
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.
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.
– Carbohydrates include
sugars and starches.
– Monosaccharides are
simple sugars.
– Polysaccharides include
starches, cellulose, and
glycogen.
2.3 Carbon-Based Molecules
• Carbohydrates can be broken down to provide
energy for cells.
• Some carbohydrates are part of cell structure.
Polymer (starch)
Starch is a polymer of
glucose monomers that
often has a branched
structure.
Polymer (cellulose)
monomer
Cellulose is a polymer
of glucose monomers
that has a straight, rigid
structure
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
Polymers are analogous to trains, necklaces, or
anything else made of similar repeating parts.
In the case, the monomers are the…
2.3 Carbon-Based Molecules
2.3 Carbon-Based Molecules
• Proteins are polymers of amino acid monomers.
– Twenty different amino acids are used to build 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.
Hemoglobin
hydrogen bond
– Incorrect amino acids change a protein’s structure
and function.