Chapter 3
Lecture Outline
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Organic Chemistry
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All organic molecules contain carbon.
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Inorganic molecules do not contain carbon.
Biochemistry is the chemistry of living things.
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Carbon: The Central Atom
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Carbon is the central
atom in all organic
molecules.
Carbon has unique
bonding properties.
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Can combine with other
carbon atoms in long
chains
Can form ring structures
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Carbon: The Central Atom
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Carbon atoms
participate in four
covalent bonds.
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Has four electrons in the
outer energy level
Can double bond with
oxygen
Can triple bond with
other carbon atoms
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Isomers
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Several factors determine the properties of an
organic molecule.
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The types of atoms in the molecule
The 3-D arrangement of atoms within the molecule
Organic molecules can have the same number and
composition of atoms, but can have different
arrangements.
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These are called isomers.
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Molecules with the same empirical formula but different
structural formulas
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Hexose Isomers
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The Carbon Skeleton
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All organic molecules have a carbon skeleton.
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This determines the overall shape of the molecule.
Organic molecules differ in these ways:
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The length and arrangement of the carbon skeleton
The kinds and location of atoms attached to it
How the attached atoms are combined together
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These combinations are called functional groups.
Functional groups determine the chemical nature of the
molecule.
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Functional Groups
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Macromolecules of Life
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Macromolecules are very large organic
molecules.
The most important organic compounds
found in living things are:
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Carbohydrates
Proteins
Nucleic acids
Lipids
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Polymers
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Carbohydrates, proteins and nucleic acids are
polymers.
Polymers are combinations of smaller building blocks.
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The building blocks are called monomers.
Polymers are built via dehydration synthesis.
Polymers are broken apart via hydrolysis.
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Polymers
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Carbohydrates
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Organic molecules composed of carbon, hydrogen
and oxygen
All have the general formula CH2O
Names end in –ose
Serve as the primary energy source for most living
things
Also serve as structural support
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Important components of nucleic acids
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Plant cell walls
DNA and RNA
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Simple Sugars
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Simple sugars are described by the number
of carbons in the molecule.
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Examples of simple sugars:
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Triose-3 carbons
Pentose-5 carbons
Hexose-6 carbons
Glucose
Fructose
Galactose
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Complex Carbohydrates
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When two or more simple sugars are
combined, they form complex carbohydrates.
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Formed via dehydration synthesis
Disaccharides
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Two simple sugars
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Trisaccharides
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Sucrose
Lactose
Maltose
Three simple sugars
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Polysaccharides
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Contain many simple sugars
Examples of polysaccharides:
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Starch and glycogen
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Used for energy storage in plants (starch) and animals
(glycogen)
Cellulose
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Important component of plant cell walls
Humans cannot digest cellulose; it is the fiber in our diet.
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Helps facilitate movement of food through the digestive
tract
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Complex Carbohydrates
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Proteins
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Proteins are polymers
made of amino acids.
An amino acid contains:
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Central carbon
Amino group
Carboxyl group
Hydrogen
There are 20 different
amino acids.
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The Structure of Proteins
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Amino acids are joined via dehydration synthesis.
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The bond formed between amino acids is called a peptide
bond.
Several amino acids joined together form
polypeptide chains.
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Primary Structure
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The sequence of amino acids in a polypeptide
constitutes the primary structure of the protein.
This sequence is dictated by information in genes
(DNA).
All levels of protein structure depend on the primary
sequence.
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Secondary Structure
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Polypeptides twist and fold
into their secondary structure.
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Some sequences of amino
acids twist into a helix.
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Some sequences of amino
acids remain straight and
fold back on themselves.
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This is called an alpha helix.
This is called a beta-pleated
sheet.
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Tertiary Structure
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The various alpha
helices and beta
pleated sheets interact
to form a globular
structure.
This globular structure
is unique for each
polypeptide.
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Quaternary Structure
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Some proteins contain more
than one polypeptide chain.
Each of these polypeptides
has its own unique tertiary
structure.
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These polypeptides interact
to form a more complex
globular structure.
Quaternary structure can be
stabilized by disulfide bonds.
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Form and Function
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The protein’s overall shape
determines its job.
If a protein is not shaped
properly, it likely will not work
properly.
Example:
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Denaturation:
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Sickle cell anemia
A mutation in the gene causes
the protein to have a different
shape.
This shape change results in a
change in function.
When heat or other
environmental conditions break
the bonds that stabilize tertiary
structure.
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Types of Proteins
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Structural proteins
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Regulatory proteins
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Determine what activities will occur in a protein
Enzymes and hormones
Carrier proteins
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Important in maintaining the shape of cells and
organisms
Collagen
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Transport molecules from one place to another
Lipoproteins
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Nucleic Acids
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The largest biological
molecules
Store and transfer
information within a cell
Include DNA and RNA
Are made of
nucleotides
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5-carbon sugar
Phosphate group
Nitrogenous group
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Nucleotides
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DNA
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Each DNA molecule is made of two strands.
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Held together by hydrogen bonds between the nitrogenous
bases
The bases pair according to base pair rules.
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The two DNA strands are twisted on each other, forming
a double helix.
Each DNA strand is divided into segments.
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Each segment forms a gene.
Genes are the recipes for proteins.
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Adenine - thymine
Cytosine - guanine
The sequence of nucleotides in a gene dictate the order of amino
acids in a polypeptide.
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The Structure of DNA
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DNA and Chromosomes
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Each DNA strand has many genes.
Each DNA strand is called a chromosome.
Human cells have 46 chromosomes in each
cell.
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Each cell copies all of these chromosomes before
it divides to pass along to daughter cells.
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The Functions of DNA
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DNA is able to:
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Replicate itself
Store information and transmit it to offspring
Direct synthesis of proteins
Mutate (change chemically)
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The Functions of DNA
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RNA
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RNA is a single-stranded molecule.
Contains uracil instead of thymine
Base pairs with itself and DNA
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RNA is found in three different forms:
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A-U
G-C
mRNA (messenger RNA)
rRNA (ribosomal RNA)
tRNA (transfer RNA)
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DNA vs. RNA
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Lipids
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Commonly called fats
Large and nonpolar
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Usually have very few oxygen atoms
There are three main types of lipids:
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Do not dissolve in water
Dissolve in other nonpolar molecules like acetone
True fats (e.g., pork chop fat and oils)
Phospholipids (membrane components)
Steroids (most hormones)
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True (neutral) Fats
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Used to provide energy
The building blocks of
fats
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A glycerol molecule
Three fatty acids
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Saturated vs. Unsaturated Lipids
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If the carbon skeleton of a fatty acid has as much
hydrogen as possible, the fat is called a saturated fat.
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If the carbons of a fat have double-bonded carbon
molecules in them, the fat is called unsaturated fat.
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Saturated fats are found in animal tissues and tend to be
solid at room temperature.
Unsaturated fats are frequently plant fats and are liquids at
room temperature.
A polyunsaturated fat has several double bonds.
Fats are important energy storage molecules.
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Saturated and Unsaturated
Fatty Acids
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Phospholipids
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Are complex organic
molecules that
resemble fats but
contain phosphate
groups
Phospholipids are the
major components of
cell membranes.
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Some are known as
lecithins.
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Steroids
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Nonpolar molecules that are arranged in rings of
carbon
Steroids are important components of cell
membranes.
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Steroids often serve as hormones and serve in
regulation of body processes.
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Cholesterol
Testosterone, estrogen
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Overview
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