Biochemical
Reactions
First… a Summary

Macromolecules
 Monomers

+ functional groups
Four types of macromolecules of interest
to us:
 Carbohydrates
 Proteins
 Lipids
 Nucleic Acids
Carbohydrates

Monomer: simple
sugar
 Ex.

Glucose
Functional group(s):
 Carboxyl
 Hydroxyl

Polymer: complex
CHO
 Starch,
glycogen
Proteins

Monomer: amino
acids
 20
total, 8 or 9
essential

Functional group(s):
 Carboxyl
 Amino

Polymer
 Polypeptide
 Protein
Lipids


Monomer: Fatty acid
Functional group(s):
 Carboxyl

Polymers: many –
depending on the
type of lipid
 Phospholipid,
triglyceride
Nucleic Acids

Monomer: nucleotide
 A,

T (or U), C, G
Functional group(s):
 Phosphate
 Amino
 Hydroxyl

Polymer:
 DNA and
RNA
Biochemical Reactions



Chemical reactions associated with biological
processes
Often involve a combination of more than one
type of reaction
Four main types of reactions:
 Neutralization
 Oxidation-Reduction
 Condensation
 Hydrolysis
Acid-Base Reactions

Acid: produces H+ ions in water
 pH

Base: produces OH- ions in water or
accepts H+ ions
 pH

value less than 7
value more than 7
Neutralization Reaction: interaction of an
acid and a base to form a salt (an ionic
compound) and water
Neutralization Reaction


Necessary to maintain a constant pH state within
the body
Buffers: resist changes in pH
H+ ions when fluid is too basic
 Take up H+ ions when fluid is too acidic
 Release
Oxidation-Reduction Reactions

Involves the transfer of electrons
 Oxidation:
loss of electrons
 Reduction: gain of electrons

Electrons are highly reactive and don’t exist on
their own in cells
 If
oxidation occurs to one molecule in the cell,
reduction must immediately to another molecule

The entire reaction is often called a redox
reaction
Condensation Reactions

Involved in the assembly of all
four types of macromolecules
 An
H atom is removed from a
functional group on one molecule,
and an OH group is removed from
another molecule
 Result: a larger molecule + water
(water out, monomer in)
 Also
known
as
dehydration
synthesis
Hydrolysis Reactions

Involved in the breakdown
of macromolecules into their
monomers
 Water
is added to break the
bonds between monomers
(water in, monomer out)
 H from the water is added to
one molecule, and the OH
group is added to the adjacent
monomer
 Covalent bond between
monomers breaks to form two
smaller molecules
Role of Enzymes

An enzyme is a biological catalyst
 Speeds
up a biochemical reaction, but is not
used up in the reaction

Enzymes are proteins
 Have
a specific shape
 Each enzyme fits specifically with a substrate
(the reactant for the reaction) to form an
enzyme-substrate complex

Like a lock and key!
Enzyme-Catalyzed Reactions

Enzymes prepare substrates for reaction by
changing the substrate, its environment, or both,
in some way
 Causing
bonds to stretch or bend (making them more
fragile)
 Bring two substrates together
 Transfer electrons to or from the substrate (i.e. reduce
or oxidize it), making it less stable
 Add or remove H+ ions to or from the substrate (i.e.
act like an acid or base), destabilizing it
Enzyme Denaturation

Proteins are called denatured when they have lost their
shape.


Caused by changes in temperature, pH, environmental factors,
etc.
Because shape is so important to protein function, denatured
proteins are no longer able to carry out their proper function
Liver Functions
Importance of Catalase

H2O2 (hydrogen peroxide) is a harmful byproduct
of many of the metabolic processes that take
place in the liver
 Must
be removed quickly
 This is the responsibility of the enzyme catalase
Factors Affecting the Action of
Catalase

What might our liver
be exposed to that