Download Chapter 3-5 Organic Chemistry

Chapter 3
The Structure and Function of
Macromolecules
Introductory Terms
Macromolecule = “giant” molecule of
living matter
 Monomer = subunits that serve as the
building blocks of a polymer



Example: Lego block
Polymer = monomers linked together

Example: Lego castle
Macromolecular Reactions


Dehydration
Synthesis:


2 molecules
become
covalently bonded
to each other
through the loss of
water
Hydrolysis:

Water is used to
break up polymers
into monomers
Macromolecular Diversity

Diversity in polymers is due to
differing arrangements of
monomers…
Nearly infinite possibilities…
 Alphabet analogy

Carbohydrates

Structure:
C:H:O in a 1:2:1 Ratio
 Example: C6H12O6


Functions:

Short-term energy storage
• Pasta dinner before the big race, game,
etc.

Structural Support
Carbohydrates

Monosaccharides:



“one sugar”
C:H:O Ratio =
1:2:1
Glucose
(C6H12O6) is a
monosaccharide
Carbohydrates

Disaccharides:



“double sugar”
2 monosaccharides
joined together by a
glycosidic linkage
(covalent bond)
Sucrose = glucose +
fructose
Carbohydrates

Polysaccharides


Polymers in which a few
hundred to a few
thousand
monosaccharides are
linked together
Starch and glycogen are
examples
Carbohydrates

Structural Polysaccharides

Cellulose
• Major component of plant
cell walls
• Cannot be digested by
humans
• Fiber!

Chitin
• Used by arthropods to build
exoskeletons
• Cell wall of fungi
Lipids

Structure:
Made up of carbon, hydrogen, oxygen
 Do not dissolve in water


Functions:
Long-term energy storage
 Chemical messengers (hormones)
 Insulation
 Waxes

Lipids

Fats



Made of glycerol
and 3 fatty acids
Fatty acid has a
long carbon
skeleton and a
carboxyl group
C-H bonds
responsible for
hydrophobia of
fats
Lipids

Fats

Saturated Fat =
no double bonds
• Saturated with
hydrogen

Unsaturated Fat =
double bonds
• Not saturated with
hydrogen
Lipids

Phospholipids



Have only 2 fatty
acids
Instead of 3rd fatty
acid, they have a
phosphate group
Major component
of cell membrane
Lipids

Steroids


Made up of 4
interconnected
rings
Examples:
• Cholesterol
• Testosterone
• Estrogen
Proteins ***



Most of a cell is made up of proteins
Instrumental in almost everything organisms do
Structure:



All proteins are created from unique combinations of 20
different amino acids
C,H,O,N
Major Functions:







Structure (keratin in hair & nails)
Contraction/movement (actin & myosin in muscles)
Energy (last resort for humans) 4 Cal/g
Transport (hemoglobin transports oxygen)
Signaling (hormones can signal cells to respond)
Defense (antibodies)
Enzymes (speed up chemical reactions by lowering
activation energy)
Proteins

Amino Acids
Amino acids are the monomers of
proteins
 Organic molecules possessing both
carboxyl and amino groups
 20 types of AAs that make up 1000s
of different proteins
 AAs are linked together by peptide
bonds

Amino Acids
Proteins

A protein is one or more polypeptides precisely twisted, folded and
coiled into a molecule of unique shape (3-D)

4 Levels of Protein Structure

Primary Structure
• Unique sequence of AAs
• Example: Tryptophan-leucine-glycine-glycine-lysine-phenylalanine-serine-leucine
• Sickle Cell Anemia
Proteins



Secondary Structure:
Alpha helix (spiral) or
pleated sheet
H bonds between
components of amino
acids cause this coiling
or pleating.
Proteins




Tertiary Structure:
Helix or pleated sheet
twists into a 3D shape
(Like a slinky tied in
knots)
Caused by interactions
between R groups of
amino acids. (polar
interactions, disulfide
bridges, hydrophobic
interactions, ionic bonds)
Proteins



Quaternary Structure
Only in proteins with
more than one
polypeptide chain
Hemoglobin has 4
polypeptide chains held
together by a heme (iron
containing) group.
Proteins

Denaturation:




When pH, salt
concentration,
extreme heat, and/or
other environmental
factors are altered,
the protein may
unravel and lose its
shape
Biologically inactive
Structure + function
(A change in
structure alters
function)
Enzymes

Enzymes
Catalytic proteins
 Catalyst = a chemical agent that
changes the rate of a reaction without
being consumed by the reaction
 Speed up biological reactions

Enzymes

Activation Energy




The energy
required to break
the bonds in the
reactant
molecules
Heat helps… but
cannot be used in
cells
Why not?
Enzymes can only
hasten reactions
that would
eventually occur
anyways
Enzymes
Enzymes are VERY selective
 Substrate = the reactant an enzyme
acts on



Enzyme binds to the substrate(s) and
converts the substrate(s) to the
product(s)
Enzymes can distinguish its substrate
from closely related compounds so
each type of enzyme catalyzes a
particular reaction
Enzymes

Active site:


The part of the enzyme that actually
binds to the substrate
Induced Fit:

As a substrate enters the active site, it
induces the enzyme to change its
shape slightly so that the active site
fits even more snugly around the
substrate
Enzymes
Enzymes

Rate of Reaction:

Partly a function of the initial
concentration of a substrate
• More substrate = more frequently access
active sites of enzyme
• There is a limit to this…
• Sometimes all enzymes are “busy”
• Enzyme is said to be “saturated”

Every enzyme has an optimal
temperature and pH level
Enzymes

Enzyme Inhibitors:


Certain chemicals
selectively inhibit
the action of
specific enzymes
Competitive
inhibitors:
• Mimics that
compete with
normal substrate
molecules for
admission into the
active site
Enzymes

Noncompetitive
inhibitors:

Impede enzymatic
reactions by
binding to a part
of the enzyme
away from the
active site,
thereby making
the enzyme
change its shape
• Example: penicillin
Enzymes

Allosteric site:


A specific receptor site on some part of the enzyme
molecule remote from the active site where the
molecules that naturally regulate enzyme activity bind
to
“On/Off switch”
Enzymes

Feedback
Inhibition:


A metabolic
pathway is
switched off by its
end product,
which acts as an
inhibitor of an
enzyme within the
pathway
Thermostat
Nucleic Acids

Structure





Made up of
nucleotides
(One phosphate,
one pentose sugar,
& one nitrogen
base)
CHNOPS
Adenine & Guanine
are Purine bases.
Cytosine &Thymine
(Uracil) are
Pyrimidine bases
Nucleic Acids



RNA is single stranded; DNA is double
stranded
RNA has uracil instead of thymine
RNA has ribose sugar, & DNA has
deoxyribose sugar.
Functions:
DNA serves as the genetic code for production
of proteins.
RNA- DNA’s helper