Water: A special molecule
The solvent in cells, tissues and organs is
water. Four special properties of water are:
1. Hydrogen bonding
Effects: cohesion, adhesion, surface
tension. More energy is needed to break
hydrogen bonds than other intermolecular
bonds, which gives water a high specific
heat capacity.
2. Density
Effects: Ice is the only solid that floats in its
liquid! This insulates water under ice.
Water: A special molecule
3. Polar nature of the bond
Effects: as a solvent, water allows polar
molecules and ionic compounds to
dissolve due to water’s polarity.
4. Dissociation of intramolecular bonds
Effects: 1 in 107 water molecules dissociates
to form H+ and OH- ions.
This is a pH of 7 = NEUTRAL.
Functional Groups
• Functional groups are parts of larger
molecules.
• They greatly influence biological
reactivity because they have
negative or positive regions that
react to form bonds.
Draw the structural formula.
Draw the structural formula.
Biochemical Reactions that
Make and Break Molecules
Macromolecules
Macromolecules are large organic molecules.
The four main types of macromolecules are
1.
2.
3.
4.
Carbohydrates – sugars and starches
Lipids – fats and hormones
Proteins – enzymes and structures
Nucleic acids – DNA and RNA
Macromolecules are also called polymers.
Monomers and Polymers
• “mono” means “one”
• “mer” means “unit”
• So a single unit of a large molecule is a
monomer
• “poly” means “many”
• So a polymer is a large molecule made of
many monomers
• For example:
sugar + sugar  starch
amino acid + amino acid  protein
Five Major Biochemical Reactions
Making and breaking bonds is important to
forming polymers from monomers.
1. Condensation or dehydration synthesis
2. Hydrolysis or decomposition with water
3. Neutralization of acids and bases
4. Redox or electron trading
5. Phosphorylation or adding a phosphate
group
1. Condensation Reactions
• A condensation reaction
joins monomers to form
polymers.
• When a bond is formed
between two monomers a
water molecule is also
produced.
• This reaction is also called
dehydration synthesis.
Example:
glucose + fructose  sucrose + H20
+
+ H20
2. Hydrolysis Reactions
• A hydrolysis reaction
breaks a polymer into
monomers.
• Water is added to a
molecule which causes a
bond to break.
• The H+ is added to one
monomer and the OH- to
the other monomer.
Example:
sucrose + H20  glucose + fructose
3. Neutralization Reactions
• Acids have a -COOH or H+ group.
• Bases have a –OH or –NH2 group.
• A neutralization reaction occurs when acids and
bases react to produce a salt and water.
• Buffers are molecules that react to minimize pH
changes in a cell.
• Buffers absorb excess H+ (acids) or OH- (bases)
4. Redox Reactions
•
•
•
•
Redox stands for reduction – oxidation reactions
“LEO goes GER”
Loss of Electrons is Oxidation
Gain of Electrons is Reduction
• Common in metabolic
reactions like
photosynthesis and
cellular respiration.
• The electrons are
carrying energy.
5a. Substrate-level
Phosphorylation
ATP, adenosine triphosphate, is the energy molecule of all
cells. The bond formed by adding a 3rd phosphate group to
adenosine diphosphate (ADP) is an important energy
storage location.
Substrate-level phosphorylation uses the energy released
from breaking a phosphate group off another molecule to
attach the phosphate to ADP to form ATP.
5b. Oxidative phosphorylation
Oxidative
phosphorylation
is a metabolic
reaction that uses
energy released by
the oxidation of
glucose to produce
ATP in cellular
respiration.
5c. Photophosphorylation
Photophosphorylation is the
production of ATP using the energy of
sunlight during photosynthesis.