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Disassembly = hydrolysis
Break bonds between fatty acid & glycerol units
 Insert H + OH from water

A typical fat molecule has a two-part structure:


glycerol
fatty acid chains
Saturated or unsaturated fat?
 In a saturated fat,
carbon atoms are
surrounded by as many
hydrogen atoms as
possible.
 An unsaturated fat has
fewer hydrogen atoms
than it could have.
Monounsaturated =
presence of one double
bond, Polyunsaturated
= more than one
carbon-carbon double
bond. More reactive.
Types of
Lipids:
Triglycerides
Types of Lipids:
Phospholipids
 Phospholipids
 Derived from triglycerides
 Glycerol backbone
 Two fatty acids attached instead of three
 Third fatty acid replaced by phosphate group
 The fatty acids are nonpolar and hydrophobic
 The phosphate group is polar and hydrophilic
 Molecules self arrange when placed in water
 Polar phosphate “heads” next to water
 Nonpolar fatty acid “tails” overlap and exclude water
 Spontaneously form double layer & a sphere
Phospholipids Form Membranes
Types of Lipids:
Steroids
 Steroids
 Cholesterol, Testosterone,
Oestrogen , Vitamins A,D,E,K
 Skeletons of four fused
carbon rings
Figure 2: Cholesterol and three
substances made from it. The
substances have very similar
molecular structures. (Carbon and
hydrogen atoms in the molecules
have been omitted for clarity. The
lines represent carbon–carbon
bonds; there are carbon atoms at
each line junction).
Proteins

Amino acids are monomers

Functions

Support – Collagen, skin

Enzymes – Almost all enzymes are
proteins

Transport – Hemoglobin
membrane proteins

Defense – Antibodies

Hormones – Many hormones
regulate; insulin

Motion – Muscle proteins

Soluble due to Polar NH2 and COOH functional groups
Protein Subunits:
The Amino Acids
Glycine
 Proteins are polymers of amino
acids
 Each amino acid has a central
carbon atom (the alpha carbon) General
to which are attached
Formula:




a hydrogen atom,
H2N-CHZ-COOH
an amino group –NH2,
A carboxylic acid group –COOH,
Amino
and one of 20 different types of –
Acid
R (remainder) groups OR –Z
Structural
group
 There are 20 different amino
acids that make up proteins
 All of them have basically the
same structure except for what
occurs at the placeholder Z
Formula
Alanine
Structural Formulas
Z group is drawn in
red
You will notice each
amino acid has a
different Z group (or
R group)
Proteins:
The Polypeptide Backbone
 Amino acids joined together end-to-end
 COOH of one AA covalently bonds to the NH2 of the
next AA
 Special name for this bond - Peptide Bond
 Two AAs bonded together – Dipeptide
 Three AAs bonded together – Tripeptide
 Many AAs bonded together – Polypeptide
 Characteristics of a protein determined by
composition and sequence of AA’s
 Virtually unlimited number of proteins
Synthesis and Degradation of a
Peptide
peptide linkage
You may want to check out this animation
Peptide Linkages
A condensation
reaction between
two amino acids.
Note how the
carboxyl and
amine groups
react in forming
the dipeptide and
water.
Amino group can act as a
base
Carboxyl group can act as
acid
Zwitterion
Bases accept H+
Acids donate H +
Therefore
NH2 becomes NH3+ ion
COOH becomes COO- ion
At a particular pH, the
amino acid will become
H3N+ -CHZ-COOThe pH at which the
structure of the amino acid
becomes a zwitterion
depends on the Z (or R
group) of the AA
in an acidic solution
in an alkaline solution
in neutral solution
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Protein Molecules:
Levels of Structure
 Primary:


Literally, the sequence of amino acids. Controls entire shape
Looks similar to a string of beads (up to 20 different colors)
 Secondary:


The way the amino acid chain coils, pleats or folds
Parts of the chain attract each other
 Tertiary:


Overall three-dimensional shape of a polypeptide
Side groups (Z) of amino acids form bonds, may be hydrogen bonding,
dispersion (intermolecular forces) or much stronger ionic or covalent bonds
 Describing what a knot looks like from the outside
 Quaternary:


Consists of more than one polypeptide
Like several completed knots glued together
View an animation of protein folding here
Levels of Protein
Organization
Protein-Folding Diseases and
Protein Markers


Assembly of AA’s into protein extremely complex
Process overseen by “chaperone” molecules
 Inhibit incorrect interactions between R groups as polypeptide grows
 Defects in these chaperones can corrupt the tertiary structure of proteins
 Mad cow disease could be due to mis-folded proteins
On he other hand, correctly constructed proteins can be use to identify
the onset of disease. Proteins utilized in this way are called ‘protein
markers’. An increased level of protein markers in a persons blood can
also be used to monitor disease and test effectiveness of treatment.
Scientist identify protein markers thorough application of IR, NMR
and MS spectroscopy. Examples of protein markers are enzymes and
antigens.
In this emerging area of research, protein markers can be used to
diagnosis heart attacks and some cancer types. There can be
alternate reasons for elevated levels of protein markers in an
individual however.
Refer to p. 197 for further information about the specific diagnosis of
Enzymes
 Enzymes are biological catalysts
 Properties
 SPECIFICITY:
 1 enzyme  1 reaction
 LOWER ACTIVATION
ENERGY:
 increased reaction rate
 CONTROL (regulation):
 Enzymes can be “switched on”
or “off.”
Enzymes
 Only certain parts of a
protein are chemically
active.
 The tertiary shape of a
protein determines
which active sites are
exposed.
 Biological polymers (carbohydrates, lipids, proteins, nucleic
acids) must be assembled precisely!
 Chemical processes must occur in proper sequence.
 Chemical processes require energy (heat) for activation.
 Reactions occur very slowly at body temperature.
 Add heat to speed up reaction  undesirable reactions (proteins denature)
Enzymes speed up reactions by 1010 times, at normal body
temperatures and pressures and are vey selective compared
to inorganic catalysts.
Process of catalysis:
 Enzyme attaches
temporarily to
substrate(s) at active
site.
 Reaction occurs.
 Product released.
 See p.194 of your
textbook for a more
detailed explanation
Importance of enzymes
 Enzymatic
reactions occur in
sequence to make
natural products.
 Abnormal enzymes
can produce
abnormal products.
Sometimes enzymes become no
longer functional
Structure of
protein very
important. Because
the bonds that hold
the protein
(enzyme) in shape
may be weak
hydrogen or even
weaker dispersion
forces, altering
the conditions can
cause the shape of
the molecule to
change. This
renders the enzyme
as ineffective.
Clumping
(Coagulation)
Denaturation is the term used
to describe a change that
destroys the biological
activity of a protein.
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Enzyme activity
Different
Enzymes
operate at
varied
optimum pH
levels
Figure 12.35
Effect of pH on
enzyme activity.
Enzymes operate in
a small pH range.
Figure 12.34 Effect of
temperature on enzyme
activity.
Enzymes denature above
40◦C
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