Proteins
Proteins Do
Everything!!
Proteins
• All proteins are polymers of
amino acids.
• There are only 20 amino acids
and they are used by organisms
to make every known protein.
• There are approximately two
million known proteins.
The Amino Acids
20 different R groups form 20 different amino acids
Amino Acid structure
Amino Acids have
3 Groups
– Amino group
(NH2)
– Carboxyl Group
(COOH)
– Side group (“R”
group)
Amino acids join together to
form peptides, polypeptides,
and polypeptide chains.
Linking Amino Acids
• Condensation reaction links amino group of one
amino acid with carboxyl group of next
• Forms a peptide bond
Water forms as a by-product
Forming A Protein
• Peptide bonds – bond
between 2 amino
acids. (Dehydration
Synthesis= water lost
in process)
• A bunch of amino
acids together =
protein or
polypeptide.
Bonding in Proteins
• 2 amino acids  dipeptide
• More than 2 amino acids  polypeptide
• DNA determines the sequence of amino acids
in a protein or polypeptide chain.
• Sequence of amino acids is unique to each
protein
Functions of proteins
• Movement
–Actin & myosin in
muscles
• Structure
–Collagen in skin
(or lip injections
Example: Angelina
Jolie)
Functions of proteins
Antibodies - are specialized proteins
involved in defending the body
from antigens (foreign invaders).
One way antibodies destroy
antigens is by immobilizing them so
that they can be destroyed by white
blood cells.
Storage Proteins - store amino acids.
Examples include ovalbumin and
casein. Ovalbumin is found in egg
whites and casein is a milk-based
protein.
Functions of proteins
Hormonal Proteins - are messenger
proteins which help to coordinate
certain bodily activities. Examples
include insulin, oxytocin, and
somatotropin.
Insulin regulates glucose metabolism by
controlling the blood-sugar
concentration.
Oxytocin stimulates contractions in
females during childbirth.
Somatotropin is a growth hormone that
stimulates protein production in muscle
cells.
Proteins
Function
Example
Structure/support
collagen
Fight infection
antibodies (immune system)
Transport
hemoglobin carries O2
Catalyst
enzyme
Movement
actin & myosin in muscle
Functions of proteins
Enzymes
The controller of all CHEMICAL reactions
in your body
Chemical Control (Enzymes)
-at all times there are billions of chemical reactions
taking place in any organism
-all organisms therefore need to control these
chemical reactions that make up metabolism
- Enzymes control chemical reactions and therefore
control Metabolism
There are over 2000 known enzymes, each of which is
involved with one specific chemical reaction
• Enzymes
Enzymes
– enzymes are proteins
– enzymes are referred to as organic catalysts
• catalysts - inorganic or organic substance which
speeds up the rate of a chemical reaction
– Chemical reaction = Dehydration Synthesis and Hydrolysis
• activation energy - the energy that must be
overcome in order for a chemical reaction to occur.
– enzymes lower the energy needed to start a chemical reaction.
(lower activation energy)
Activation Energy
Structure
• Structures of Enzymes
- enzymes are large, complex proteins
- all enzymes are either all protein or are protein
with non-protein parts called coenzymes
- coenzymes are often vitamins
- ASE
• Usually enzymes end in – ase
• Enzymes are named according to the substrate they are
specific to
– substrates are the chemicals that each enzyme acts upon
Example of Naming:
• The enzyme maltase (enzyme) breaks down (acts upon)
the dissaccharide maltose (substrate) into 2
monosacchardies
• The enzyme peptidase breaks the peptide bonds in
proteins
Active Site or Binding Site
• Active Site or Binding Site
-enzymes are usually much bigger than their
substrates
-enzymes have a specific pocket or site where
the substrate can fit and interact
-the specificity of the enzyme is dependent
upon its active site
“Lock and Key Theory”
"Lock and Key Theory”
– each enzyme is specific
for one and ONLY one
substrate
(one lock - one key)
Enzyme Substrate Complex
1. Enzyme forms a temporary association with
the substrate or substrates
2. The Enzyme and Substrate form a close
physical association between the molecules
called an enzyme substrate complex.
Enzyme – Substrate Complex
Enzyme Substrate Complex
3. While the enzyme substrate complex is
formed, the enzyme action takes place and
the substrate is broken down into its smaller,
simpler parts
4. After completion, the enzyme and the
products separate. The enzyme is then ready
to react with another substrate.
New Enzymes
• Although enzymes may be reused in cells,
they eventually are destroyed and new ones
must be synthesized.
• Enzymes begin to be destroyed above
45 C. (above this temperature all proteins
begin to be destroyed)
Factors Influencing Rate of Enzyme
Action
• pH - the optimum (best) in most living things
is close to 7 (neutral) -- high or low pH levels
usually slow enzyme activity
• Temperature - strongly influences enzyme
activity
– optimum temperature for maximum enzyme
function is usually about 35-40 C.
– reactions proceed slowly below optimal
temperatures
– above 45 C. most enzymes are destroyed
Denaturation
• An enzyme may change shape as a result of
high temperatures or extreme pH values. This
process is called denaturing
– Denaturing will cause an enzyme to become
useless