Chapter 5 notes
The structure and
function of
Macromolecules
Concept 5.1
Polymer: a long molecule consisting of
similar or identical building blocks
- like a train with many cars
- monomers: repeating units that are
the building blocks
Diversity of life is based around 40 or 50
polymers
Concept 5.1
Monomers are connected together by
dehydration synthesis (anabolic)
- covalent bond w/ the loss of H2O
Polymers are broken down by hydrolysis
(catabolic)
- reverse rxn. of dehydration synthesis
- “break with water”
Concept 5.1
HO
1
2
3
H
(a)
1
2
H
Unlinked monomer
Short polymer
Dehydration removes a water
molecule, forming a new bond
HO
HO
H2O
3
4
H
Longer polymer
Dehydration reaction in the synthesis of a polymer
Concept 5.1
HO
1
2
3
4
Hydrolysis adds a water
molecule, breaking a bond
HO
1
2
3
H
HO
H
H2O
H
Concept 5.2
Carbohydrates: include sugars and
polymers
Monosaccharides (monos = single;
sacchar = sugar)
- molecular formula is CH2O
- ex. Glucose (C6H12O6)
- most sugars are rings when aqueous
Concept 5.2
(a) Linear and ring forms
(b) Abbreviated ring structure
Concept 5.2
Disaccharide: two monosaccharides
joined by a glycosidic linkage
- formed by dehydration synthesis
- glucose + glucose = maltose + H2O
- glucose + fructose = sucrose + H2O
Concept 5.2
Glucose
Glucose
Maltose
(a) Dehydration reaction in the synthesis of maltose
Glucose
Fructose
Sucrose
(b) Dehydration reaction in the synthesis of sucrose
Concept 5.2
Polysaccharides: polymers w/ few
hundred to a few thousand monomers
-fcn. of a polysaccharide is determined
by monomers and positions of
glycosidic linkages
Concept 5.2
Storage polysaccharides
- starch: found in plants; consists only
of glucose monomers (1-4 linkage);
how plants store glucose (chloroplasts)
- glycogen: polymer of glucose found
in animals; stored in liver and muscle
cells
Concept 5.2
Structural polysaccharides
- cellulose: major component of plant
cell walls
- note: 2 ring structures of glucose
(alpha (a) and beta (b))
- cellulose is composed of all b glucose
- cellulose = “insoluble fiber”
Concept 5.2
a Glucose
(a) a and b glucose ring structures
b Glucose
Concept 5.2
Concept 5.2
Cell walls
Cellulose
microfibrils
in a plant
cell wall
Microfibril
10 µm
0.5 µm
Cellulose
molecules
b Glucose
monomer
Carbohydrates
Structural polysaccharides (cntd.)
- chitin: carbohydrate used by
arthropods to build exoskeletons
- also used to make decomposable
surgical thread
Concept 5.2
(a) The structure
of the chitin
monomer.
(b) Chitin forms the
exoskeleton of
arthropods.
(c) Chitin is used to make
a strong and flexible
surgical thread.
Concept 5.3
Lipids: little or no affinity for water; consist
mostly of hydrocarbons
- 3 families: fats, phospholipids, steroids
Fat: composed of 2 parts
- glycerol: 3 carbon alcohol w/ hydroxyl
- fatty acids: long carbon skeletons w/
carboxyl groups
Concept 5.3
Fatty acid
(palmitic acid)
Glycerol
(a) Dehydration reaction in the synthesis of a fat
Concept 5.3
Fatty acids can vary in length and in the
number and location of double bonds
- “saturated”: no double bonds; most
animal fats; solid at room temp.
- “unsaturated”: has one or more
double bonds which removes H atoms;
plants and fish; liquid at room temp.
Concept 5.3
Structural
formula of a
saturated fat
molecule
Stearic acid, a
saturated fatty
acid
(a) Saturated fat
Concept 5.3
Structural formula
of an unsaturated
fat molecule
Oleic acid, an
unsaturated
fatty acid
cis double
bond causes
(b) Unsaturated fat
bending
Concept 5.3
The major fcn. of fats is energy storage.
- 1g of fat stores more than twice as
much energy as 1g of a polysaccharide
- mammals stock food reserves in
adipose cells
Concept 5.3
Phospholipids: similar to fats but have
only 2 fatty acid tails; 3rd hydroxyl
group joins to a phosphate group
- show ambivalent behavior to water
- head= polar (hydrophilic); tail=
nonpolar (hydrophobic)
- arranged in a bilayer, or double layer
Hydrophobic tails Hydrophilic head
Concept 5.3
Choline
Phosphate
Glycerol
Fatty acids
(a) Structural formula
Hydrophilic
head
Hydrophobic
tails
(b)Space-filling model
(c) Phospholipid symbol
Concept 5.3
Steroids: lipids with a carbon skeleton
consisting of 4 fused rings
- differ in functional groups attached to
rings
- Cholesterol: found in animal cell
membranes; precursor for other
steroids
Concept 5.3
Concept 5.4
Proteins: account for more than 50% of
the dry weight of most cells
- used for structural support, storage,
transport, signaling, movement, and
defense
Concept 5.4
Proteins are polymers constructed from
the same set of 20 amino acids
- called polypeptides
- consist of one or more polypeptides
folded and coiled into specific
conformations
Concept 5.4
Amino acids are the building blocks of
proteins
- a carbon is bonded to an animo
group, a carboxyl group, a hydrogen
atom, and a variable (R)
- grouped according to side chains
(nonpolar, polar, acidic, basic)
Concept 5.4
Concept 5.4
Concept 5.4
Amino acids are bonded together by a
peptide bond
- carboxyl group of one amino acid
connects w/ the amino group of
another (dehydration synthesis)
Concept 5.4
Concept 5.4
Four levels of protein structure
- primary structure: unique sequence
of amino acids
- even a slight change can affect a
proteins conformation and ability to
function
- ex. Sickle-cell disease
Concept 5.4
Concept 5.4
- secondary structure: coils or folds that are
a result of hydrogen bonds at regular intervals
- a helix: delicate coil held together by
hydrogen bonding between every fourth
amino acid
- b pleated sheets: two or more regions
lie parallel to each other
Concept 5.4
Concept 5.4
- tertiary structure: irregular contortions
from interactions between side chains (R
groups)
- hydrophobic interactions: nonpolar
side chains cluster in the core, away from
water
- van der Waals interactions help hold
them together
Concept 5.4
- disulfide bridges: covalent bond
between two cysteine monomers
(have sulfhydryl groups)
- ionic bonds and hydrogen bonds
also contribute
Concept 5.4
Concept 5.4
- quaternary structure: overall
protein structure resulting from
combining of multiple subunits
The unique conformation endows each
protein with a specific function
Concept 5.4
Concept 5.4
Concept 5.4
The unique conformation endows each
protein with a specific function
- denaturation: protein unravels and
losses its conformation
- pH, [salt], temperature
Concept 5.5
Compounds that are responsible for
determining the amino acid sequence of a
polypeptide.
Two types of nucleic acids
- deoxyribonucleic acid (DNA)
- ribonucleic acid (RNA)
Flow of genetic information: DNA  RNA 
Protein
Concept 5.5
DNA
1 Synthesis of
mRNA in the
nucleus
mRNA
NUCLEUS
CYTOPLASM
mRNA
2 Movement of
mRNA into cytoplasm
via nuclear pore
Ribosome
3 Synthesis
of protein
Polypeptide
Amino
acids
Concept 5.5
Nucleotides are the monomers (building
blocks) of nucleic acids
-nucleotide = nitrogenous base +
pentose (5-carbon sugar) + phosphate
Concept 5.5
5 end
Nitrogenous bases
Pyrimidines
5C
3C
Nucleoside
Nitrogenous
base
Uracil (U, in RNA)
Cytosine (C) Thymine (T, in DNA)
Purines
Phosphate
group
5C
Sugar
(pentose)
Adenine (A)
Guanine (G)
(b) Nucleotide
3C
3 end
Sugars
(a) Polynucleotide, or nucleic acid
Deoxyribose (in DNA)
Ribose (in RNA)
(c) Nucleoside components: sugars
Concept 5.5
Two families of nitrogenous bases:
- pyrimidines: single ring; cytosine
(C), thymine (T), and Uracil (U)
- purines: double ring; adenine (A),
and guanine (G)
Concept 5.5
Difference between DNA and RNA is in
the sugar. DNA lacks an oxygen atom
attached to its number 2 carbon
Polynucleotide: nucleotides are joined
by phosphodiester linkage
Concept 5.5
DNA molecules have two polynucleotides
that form a double helix.
- Watson and Crick (1953)
- A binds to T; C binds to G; forms two
complementary strands