Molecules of Life
Dr. Anderson
GCIT
Cells and Molecules
• Atoms
• Molecules
– Polymers
• Organic Molecules
– Carbohydrates
– Lipids
– Proteins
– Nucleic Acids
Molecules
• Other important molecules to life
– O2
– CO2
– Ions
• Ca, I, Cl-, Fe+, Na+, K+, etc.
• Why are these important?
Bonding
• Covalent Bonds
– Electrons are shared between atoms
• Ionic Bonds
– Electrons are “donated” to atoms depending on
their electronegativity
Covalent Bonds
• Covalent bonds are much stronger and
difficult to break
– CAN be manipulated in the body using enzymes,
which lower the activation energy needed for
chemical reaction to occur
– Creating bonds (building molecules) – anabolism
– Breaking bonds (splitting molecules) - catabolism
Molecular Characteristics
• Polar Covalent – unequal sharing of electrons
around the molecule
– Results in slightly positive or negative “ends”
– Examples?
• Non-polar Covalent– equal sharing of
electrons around the molecule
– Equal distribution of charge around the molecule
Ionic Bonds
• The “donation” of an electron changes the
charges between molecules
• Separation of these charges and their
recombination leads to electric charge!
– How can this happen?
– Where does this happen in the human body?
Ionic Bond Disassociation
• In water, ionic bonds can be separated so that
the individual ions (atoms) go into solution
• Examples?
NaCl
Na+ +
Cl-
Organic Molecules
• Contain carbon
• Carbohydrates
• Lipids
• Proteins
Carbohydrates
• Made of C, H, and O
• Sugars
– Monosaccharides
– Disaccharides
Monomer
• Starches
– Polymers of sugars
Polymer
Lipids
• Made of C, H, O
• How are fats
different from
carbohydrates?
• Saturated
• Unsaturated
Triglyceride
Special Lipids
• Phospholipids
– Make up cell membranes
• Steroids
– Hormones, cholesterol
• Eicosanoids
– Immune responses, blood clotting, etc.
Proteins
• Made of H, C, N, O, S
• Polymers of amino acids
• Extremely complex!!
– Examples?
• Shape dictates function in proteins
– Can protein molecules change shape?
Primary Structure
• Simple peptides – simple “string” of amino
acids”
Secondary Structure
• Alpha-helices
• Beta-pleated sheets
– Bonds between the “chains” form these structures
Beta-pleated sheet
Tertiary Structure
• Helices and Sheets
cause a complex
structure
– Globular proteins
• What affects the
shape?
Quaternary Structure
• Multiple polypeptide structures combine to
form a functional protein
Protein Shape
• What affects the shape of a protein?
• What does the shape of a protein affect?
• “Lock and Key” - enzymes
Enzymes
• Protein molecules that catalyze chemical
reactions
• Can either synthesize or decompose
molecules
Steps in Enzymatic Action
• 1. The enzyme’s active site bonds with the
substrate to make the enzyme-substrate
complex
• 2. Enzyme undergoes internal rearrangements
to initiate the reaction
• 3. Products are formed and released
Examples of Enzymes - Catabolism
• Often end in
“–ase”
Enzyme
– Lipase
– Protease
– Fructase
Breaks down polymers into monomers to be used
by cells in the body! (Catabolism)
Examples of Enzymes - Anabolism
• Dehydration Synthesis
– Water is produced when bond is made
Nucleic Acids
• The “blueprint of life” – the order of monomers
in the DNA molecule is the key
• DNA and RNA – polymers of sugar, nitrogen bases
and phosphates
• This is the core of to the central dogma of biology
• DNA
RNA
Proteins
DNA (Deoxyribonucleic Acid)
RNA
• Created from DNA
• Also a polymer
• Acts as a
messenger to
encode genetic
information for
protein synthesis
Important Biological Chemical
Reactions
• Synthesis – combination of smaller molecules
or atoms into larger molecules
• Decomposition – Breaking a large molecule
into smaller ones
• Exchange Reactions – parts of molecules
exchanged with others
Synthesis Reaction
(Dehydration Synthesis)
• A+B
AB
• e.g. - Sugar into starch
Decomposition Reaction
• Hydrolysis – water is used to separate amino
acids from proteins (peptides)
Protein
Ala
Lys
Arg
Phe
Trp
Leu
H2O +
enzyme
Free amino
acid
Exchange Reactions
• Molecular Partners are “swapped”
• E.g. Photosynthesis
• CO2 + H2O
Solar Energy
C6H12O6 + O2
What is the opposite of this reaction?
What affects chemical reaction rates?
• Temperature – increases in temperature cause an
increase in molecular motion, leading to faster
reactions
• The amount of reactants – reaction can be
limited because there are not enough raw
materials
• pH – highly acidic or alkaline (basic)
environments can increase or decrease reaction
rates, depending on the specific reaction
Example – Enzymes and pH
Where is the enzyme activity highest? Where is it lowest? Why?
Temperature Limited Reaction
• Asymmetrical activity
curve
• Why asymmetrical?
Reactant-Limited Reactions
In this example, an
enzyme is mixed with
the substrate that it
breaks down.
What is the limiting
factor here?
ATP – Rechargeable Cellular Battery
• Energy is stored in the
phosphate bonds of
ATP
• When bonds are
broken, (ATP
ADP)
energy is released
• When bonds are made
(ADP
ATP)
energy is stored