Biomolecules
The Chemical Building
Blocks of Life
The Chemistry of Carbon
• Organic molecules contain carbon
• Carbon’s four valence electrons allow
it to form up to four covalent bonds
• Hydrocarbons consist only of C and H
– Propane CH8
• It can easily bond to itself and form
long chains
– Linear
- Cyclic
- Branched
Functional Groups
• Chemical properties and reactivity are a
result of functional groups
• Functional groups maintain chemical
properties no matter where they occur
• Polar molecules are hydrophilic
• Nonpolar molecules are hydrophobic
• The degree to which organic molecules
interact with water affects their function
• Hydroxyl group (-OH) is one of the most
common functional groups, it will make a
molecule water soluble
The Molecular Logic of Life
Small molecules, common to
all organisms, are arranged
into unique macromolecules
(Campbell p. 62)
Macromolecules – The
Sum of the Parts
Many complex biological activities require
large macromolecules
Macromolecules are polymers
poly: “many”
mer: “units”
ex: proteins, nucleic acids, starches
Polymers are built by covalently linking
together small similar (or in some
cases, identical) subunits/building
blocks called monomers
mono: “one”
mer: “unit”
ex: amino acids, nucleotides,
monosaccharides
4 Classes of Organic Compounds, or
“Biomolecules”- necessary for an
organism to survive:
Proteins are polymers of amino acids
Nucleic acids are polymers of
nucleotides
Starches are polymers of simple
sugars called monosaccharides
Lipids aren’t REALLY polymers, since
they don’t have repeating chains. BUT
they are important biomolecules. The
building blocks (monomers) of some
types of lipids are glycerol and fatty
acids
Condensation
It’s not just for the water cycle anymore!
This is how we link monomers together to create
polymers
• Macromolecules are constructed by
covalently bonding monomers by
condensation reactions where water is
removed from the functional groups of the
monomers
• Dehydration synthesis (water is removed)
• A hydroxyl (-OH) from one monomer and a
hydrogen (-H) from another are removed
• Anabolic reaction- requires energy
Hydrolysis
• Hydrolysis is the reverse of condensation
• Results in the break down of polymers
• Hydration reactions add water and break
bonds, releasing energy-- catabolic
animation
Macromolecules- why
are they so important?
• Each macromolecule performs complex
tasks with precision
• The basic structure and function of each
class of macromolecules is similar in all
organisms (from the simplest bacteria
to complex humans)– indicates an
evolutionary link.
Classes of Biomolecules
• Carbohydrates
•Lipids
•Proteins
•Nucleic Acids
Basic Function
Carbo’s
Lipids
N. Acids
Energy
Storage
Structure
Strength
Long term
storage
Insulation
Protection
Hormones
Sugars
Fats
DNA
Oils/Waxes
RNA
Phospholipids ATP
Steroid
hormones
(glucose)
Starch/
Glycogen
Cellulose/
Chitin
Inheritance
Blueprint for
metabolism
Proteins
Catalysts
Hormones
Structure
Defense
Proteins
Enzymes
Carbohydrates
How Sweet It Is!
• General formula (CH2O)n
• Simple sugars or large
molecules made of sugar
monomers
• Monosaccharides (monomer)
are covalently linked by
condensation reaction to form
polysaccharides (polymers)
Sugars
• Monosaccharides
– Five carbon: Ribose
– Six carbon: glucose and fructose
•Disaccharides
–Sucrose
–Lactose
•Polysaccharides
–Starch
–Glycogen
–Chitin
–Cellulose
Polysaccharides
Two Types for Storage
1. Glycogen – animal energy storage product
that accumulates in the liver/muscles
- Highly branched
GlucoseGlycogenglucosebloodstream
2. Starch – plant energy storage
- Helical
- Easily digested by animals through
hydrolysis
Two Types for Structure:
1. Cellulose
Polysaccharide found in plant cell walls
• For humans cellulose is indigestible and
forms dietary fiber
• Made up entirely of β glucoses
– Structure is constrained into straight
microfibrils
• Not an energy source for animals
2. Chitin – insect exoskeletons
So what’s the difference between
condensation and hydration
reactions?
• animation
Lipids
Functions:
1. Long-term energy
storage/insulation (fats)
2. Structural components of cells
(phospholipids)
3. Cellular messengers (hormones)
More FAT
• Triglycerides are composed of three fatty
acids covalently bonded to one glycerol
molecule
•Fatty acids are composed of CH2 units and
are hydrophobic- contain tons of energy in
their hydrocarbons!
•Fatty acids can be saturated (all single bonds)
or unsaturated (one or more double bonds)
•A fat (mostly saturated) is solid at room
temp., while an oil (mostly unsaturated) is
liquid at room temp.
•Glycerol is a molecule with
three carbons in a row, each
with a hydroxide group
•Fatty acid chains are
hydrocarbons
• that is, they are
composed of mostly
carbons and hydrogens.
• This is a molecule that is
VERY hydrophobic.
•When glycerol combines with
the fatty acid chains it forms
a carboxyl group between
them
•They link by the loss of a
water molecule.
animation
video
Carbon can bond to four
different substances, but
sometimes it will share
more than one pair of
electrons.
Phospholipids
• Important structural component of
cell membranes
• Phosphate group (head) is polar
and water soluble (hydrophilic)
• Two fatty acid tails are
hydrophobic
•This allows the phospholipids to
form bilayers and membranes
• Steroids
Other Lipids
– Insoluble in water
– Built around a four ringed skeleton
• Cholesterol
– Component for animal cell membranes
– Formation of myelin sheath covering nerves
• Hormones
– Chemical messengers
• Waxes
– Many fatty acids linked to a long backbone
– Waterproofing in plants, ears, beehives
overview
Proteins
• 50% dry weight of body
• Mammal cell contains 10,000 proteins
• Enzymes (regulate chemical reactions)
• Structural elements (cell membrane,
muscles, ligaments, hair, fingernails)
• Carriers (regulate what goes into/out
of cells)
• Send and receive messages
(hormones)
• Movement
Building Blocks of Proteins
Amino Acids
• Amino acids (monomers) are linked
together to form proteins (polymers)
– Each unique sequence of amino acids forms a
different protein
– All living things (even viruses) use the same 20
amino acids
• 20 different Amino Acids
–
–
–
–
Amino end (NH2)
Carboxyl end (COOH)
Hydrogen
R group – variable component
Amino Acids
• Amino Acids are grouped by
whether R- group is polar or nonpolar
•Positively charged side chain
•Negatively charged side chains
•Polar but uncharged side chains
•Hydrophobic side chains
•Special cases
Protein Assembly
• AA’s are linked together by joining
the amino end of one molecule to
the carboxyl end of another
•Peptide bond forms a chain called a
polypeptide
http://www.biotopics.co.uk/
as/aminocon.html
Protein Structure
• Primary structure
– Specific linear sequence of AA’s in a
polypeptide
– Determined from code in inherited
genetic material
– Changes in primary structure can
alter proper functioning of the protein
Hormone: Insulin
• Frederick Sanger (1940s, 50s), discovered
the amino acid sequence of Insulin
• Causes cells to take up more glucose, and
liver and muscle cells to create glycogen
• Diabetes is a deficiency of insulin
Carrier: Hemoglobin
-Protein that carries
oxygen to your cells
-Iron an important cofactor, iron deficiency
=anemia
Sickle Cell Disease
Spider silk: a structural protein
Spider Silk Video
Enzyme: Salivary Amylase
• Hydrolyzes starch while chewing
Enzyme: Rubisco
Catalyzes first step of
carbon fixation in
photosynthesis
Movement: Actin and Myosin
• Secondary structure
- the tendency of the
polypeptide to coil or
pleat due to H-bonding
between R- groups
- -helix, -pleated sheet,
or random coil
• Tertiary structure
- shape of entire chain; folded, twisted, or
– globular
- shape related to function and properties
• Quaternary structure
- more than one polypeptide chain
Nucleic Acids
• Polymers composed of monomer
units known as nucleotides
• Information storage
– DNA (deoxyribonucleic acid)
• Protein synthesis
– RNA (ribonucleic acid)
• Energy transfers
– ATP (adenosine tri-phosphate) and
NAD (nicotinamide adenine
dinucleotide)
Nucleotides
• Structure
– Phosphate
– Nitrogenous base
 Purines (double-rings)
 Adenine and Guanine
Pyrimidines (single-rings)
 Cytosine, Thymine, and Uracil
– Sugar – either ribose or deoxyribose
 pentoses in ring form
Deoxyribose lacks one oxygen
Functions of Nucleic Acids
• DNA – Physical carrier of genetic
information
– Restricted to nucleus
• RNA – key component of protein
synthesis
– Messenger RNA (mRNA) – blueprint
for construction of a protein
– Ribosomal RNA (rRNA) – construction
site where the protein is made
– Transfer RNA (tRNA) – truck
delivering the proper AA to the site of
construction
The End