Monomers, polymers, and
macromolecules
There are 4 categories of macromolecules:
Carbohydrates
Proteins,
Lipids,
and Nucleic acids
Carbon is the central element
• All biomolecules contain a Carbon chain or ring
• Carbon has 4 outer shell electrons (valence = 4)
• Therefore it’s bonding capacity is great
• It forms covalent bonds –hence, has strong bonds
• Once bound to other elements (or to other
Carbons), it is very stable
Carbon linkages
• Single chains
• Rings
CH4 =
Propane
The 4 types of biomolecules often
consist of large carbon chains
= C3H8
Carbon binds to more than just
hydrogen!!
• To OH groups in sugars
• To NH2 groups in amino
acids
• To H2PO4 groups of
nucleotides of DNA,
RNA, and ATP
Amino acid
OH, NH2, PO4 are called ‘functional groups’!
Fig. 3.1
Functional groups:
Isomers have the same molecular
formulas but different structures
• Structural isomer = difference in the C skeleton structure
• Stereoisomer = difference in location of functional groups
Enantiomers are special types of
stereoisomers
Enantiomers are mirror
images of each other
One such enantiomer
contains C bound to 4
different molecules and is
called a chiral molecule
Chiral molecules rotate
polarized light to the right
(D form) or to the left (L
form) molecules
Examples: amino acids (L
form)
sugars (D form)
Monomers and polymers
• Monomers are made into polymers via dehydration reactions
• Polymers are broken down into monomers via hydrolysis
reactions
Fig. 3.3
Carbohydrates (or sugars)
• Simple sugars
(monosaccharides)
• Only one 3-C, 5-C, 6C chain or ring
involved
Fig. 3.5
Examples of sugar monomers*
*Remember how C’s are counted
within the ring structures (starting
from the right side and counting
clockwise)
Carbohydrates (sugars)
• Double sugars
(disaccharides)
• Two 6-C chains or
rings bonded together
Carbohydrates (sugars)
• Complex carbo’s
(polysaccharides)
–
–
–
–
Glycogen to glucose
in animals
Starch
Cellulose
Glycogen
Chitin
Fig. 3.9
Polysaccharides
Starch structure vs Glycogen structure
Fig. 3.10
Polysaccharides: Cellulose structure
Proteins
• Composed of chains
of amino acids
• 20 amino acids exist
• Amino acids contain
–
–
–
–
Central Carbon
Amine group
Carboxyl group
R group
Fig. 3.20
The 20 Amino Acids
All differ with respect
to their R group
Peptide bonds occur between amino acids
• The COOH group of 1
amino acid binds to
the NH2 group of
another amino acid
• Forms a peptide bond!
Fig. 3.21
The chain (polymer) of amino acids forms a variety of
loops, coils, and folded sheets from an assortment of
bonds and attractions between amino acids within the
chain(s)
There are at least 7 functions of proteins
•
•
•
•
•
•
Enzyme catalysts – specific for 1 reaction
Defense – antibody proteins, other proteins
Transport- Hgb, Mgb, transferrins, etc
Support – keratin, fibrin, collagen
Motion – actin/myosin, cytoskeletal fibers
Regulation- some hormones, regulatory proteins
on DNA, cell receptors
• Storage – Ca and Fe attached to storage proteins
Fig. 3.18
There are four levels of protein
structure
• Primary = sequence of
aa’s
• Secondary = forms
pleated sheet, helix, or
coil
• Tertiary = entire length
of aa’s folded into a
shape
• Quaternary = several
aa sequences linked
together
Fig. 3.23
Motifs and Domains: Important features of 2° and 4°
structure
Nucleic acids: DNA and RNA
• DNA =
deoxyribonucleic acid
• DNA is a double
polymer (chain)
• Each chain is made of
nucleotides
• The 2 chains bond
together to form a
helix
DNA nucleotides
• Each nucleotide in
DNA contains:
– 5-C sugar
(deoxyribose)
– Phosphate
– Nitrogen base
-adenine (A)
-guanine (G)
-cytosine (C)
-thymine (T)
Fig. 3.14
One polymer of nucleotides on one “backbone” of nucleic acid
Fig. 3.15
The DNA “double helix”
Lipids: Hydrophobic molecules
• Central core of glycerol
• Bound to up to 3 fatty acid chains
• They exhibit a high number of C-H bonds –
therefore much energy and non-polar
• When placed in water, lipids spontaneously
cluster together
• They help organize the interior content of
cells  “phospholipids”
Glycerol and fatty acid chains
What specific bonds form between glycerol and
each fatty acid chain?
Would you think this to be an hydrolysis or a
dehydration synthesis rxn?
Saturated and unsaturated fats
The difference resides in the number of H’s attached
to C’s in the fatty acid chains; the amount of
“saturation” on the C’s
Saturated vs unsaturated fats and diet
• Saturated fats raise LDL-cholesterol levels in the
blood (animal fats, dairy, coconut oil, cocoa
butter)
• Polyunsaturated fats leave LDL-cholesterol
unchanged; but lower HDL-cholesterol (safflower
and corn oil)
• Monounsaturated fats leave LDL and HDL levels
unchanged (olive oil, canola, peanut oil, avocados)
• One variety of polyunsaturated fat (Omega-3 fatty
acids) guards against blood clot formation and
reduce fat levels in the blood (certain fish,
walnuts, almonds, and tofu)
Phospholipids and cell membranes
• P-lipids make up the majority of cell
membranes including:
–
–
–
–
–
The plasma membrane
Nuclear envelope
Endoplasmic reticulum (ER)
Golgi apparatus
Membrane-bound vesicles
Structure of single P-lipid
The 3 C’s of glycerol are bound to:
2 fatty acid chains
phosphate
Cell environment organizes P-lipid
bilayer to proper orientation
Hydrophilic (polar) “heads” of P-lipid oriented to the
exterior; hydrophobic (non-polar) “tails” oriented to
the interior