Download The Structure and Function of Macromolecules: Four Classes of

The Structure and Function
of Macromolecules:
Four Classes of Organic
Molecules
AP Biology Chapter 5
Biomolecule - Project
You are to become an expert in an
assigned biomolecule
 Organize the main structure and functions
of your biomolecule
 Models are good
 Note examples & interesting facts…
 Use visual of transparency / doc camera,
poster OR Power point
 Presentations - Tuesday

Polymers and Macromolecules:
Polymer: most macromolecules are
polymers…a single unit repeated many times,
hence “poly”mer
 Monomer: a single unit (“mono”mer) of a
polymer
 Macromolecule: a large organic molecule,
made of polymers
 Four classes of macromolecules (biomolecules)

–
–
–
–

Carbohydrates
Lipids
Proteins
Nucleic Acids
Each class of macromolecule possess
The principle of POLYMERS
How are monomers attached or detached?

Dehydration Synthesis: polymerization
reactions during which monomers are
covalently linked, producing net removal of a
water molecule for each covalent linkage

Hydrolysis is a reaction process that breaks
covalent bonds between monomers by the
addition of water molecules.
Carbohydrates




(p60-):
A monosaccharide (sugar) is the simplest kind
of carbohydrate. It consists of a single
molecule like fructose or glucose.
All sugar molecules have the formula (CH2 O)
n, where n is any number from 3 to 8.
For glucose, n is 6, and its formula is C6H12O6
The formula for fructose is also C6H12O6
ά –glucose and - glucose:
Two forms of glucose, seen below, differ
only in a reversal of the H and OH on the
first carbon.
 Even very small changes in the position of
certain atoms may dramatically change
the molecule

Disaccharides
Di (two) sacchar (sugar): a double sugar
that consists of two monosaccharides
joined by a glycosidic linkage.
 Glycosidic linkage: covalent bond formed
by a condensation/dehydration (water is
lost) reaction between two sugar
monomers, for example maltose:

Disaccarides
– Common Disaccharides:
 Maltose= Glucose+Glucose (beer)
 Lactose= Glucose+Galactose (milk)
 Sucrose= Glucose+Fructose (table
sugar/fruit sugar)
– All saccharides are storage molecules, they
store energy to be used by living system
Storage Polysaccharides

A polysaccharide consists of a series of
connected monosaccharides. A
polysaccharide is a polymer.

Cells hydrolyze storage polysaccharides into
sugars as needed.

Common storage polysaccharides are
STARCH, GLYCOGEN, CELLULOSE, and
CHITIN.
Starch:
Starch is an ά-glucose polymer that is an
energy storage molecule in plants
 Starch has two forms:
– Amylose and Amylopectin

Glycogen
Glycogen: an ά-glucose polymer that is a
storage polysaccharide in animal cells.
 Glycogen polymers are more tightly
branched than starch
 Glycogen is stored in the muscle and liver
of humans and other vertebrates

Cellulose
Cellulose is a polymer of - glucose
molecules.
 It serves as a structural molecule in the
walls of plant cells.
 Cellulose is the major component in wood.
 We are unable to digest Cellulose– Fiber in
out diet
 Termites??

Starch vs. Cellulose
What is the difference between starch and
cellulose?
 Starch - ά-glucose polymer
 Cellulose - - glucose molecules.

Figure 5.7x Starch and cellulose molecular models
 Glucose
 Glucose
Cellulose
Starch
Chitin
Chitin is a polymer similar to cellulose, but
each -glucose molecule has a nitrogen
containing group attached.
 Chitin serves as a structural molecule in
the walls of fungus cells, exoskeletons of
insects, and mollusks

Lipids (p 65-)
Lipids are a class of substances that are
insoluble in water, but are soluble in
non-polar substances (ether,
chloroform)
 Fats are energy storage molecules, they
store more energy per gram than
carbohydrates!

Lipids
 There
are three major groups of lipids:
– Triglycerides, phospholipids, and
steroids
– Triglycerides (fats, oils, waxes)
– They consist of 3 fatty-acids attached to
a glycerol molecule.
– Fatty acids are hydrocarbon chains with
a carboxyl group at one end of the chain
Triglyceride/Fatty Acid: (type of
lipid)
A saturated fatty acid has a single
covalent bond between each pair of
carbon atoms, and each carbon has 2
hydrogen bonded to it. The carbon is
“saturated” with hydrogen
 Unsaturated fatty acids have a double
covalent bond and each of the two
carbons in this bond have only one
hydrogen atom bonded to it.

Saturated vs. Unsaturated:
Phospholipids (type of lipid)
Phospholipids: look just like a lipid
except that one of the fatty acid chains
is replaced by a phosphate group
(hence, “phospho” lipid)
 A phospholipid is amphipathic,
meaning it has a hydrophobic “head”
and hydophilic “tail”
 Phospholipids are oriented in a
sandwich-like fashion formation with
the tails grouped together on the inside
(away from water)

Steroids: (type of lipid)
Steroids are characterized by a backbone
of four linked carbon rings.
 Examples include cholesterol (a
component of cell membranes),
hormones, testosterone and estrogen.

Proteins:

(p79-)
Proteins can be grouped according to their
functions:
 Structural proteins: keratin, hair, horns, collagen,
connective tissue, spider silk
 Storage proteins: casein in milk & ovalbumin in egg
whites
 Transport proteins: found on cell membranes that
transport materials into and out of cell, hemoglobin
 Defensive proteins: antibodies to fight infection
 Enzymes: regulate the rate of chemical reactions
Protein -- Model…

For a protein to function properly, it has
to be folded into a specific structure.
Protein folding has four levels of
“folding”
– Primary
– Secondary
– Tertiary
– Quarternary
Secondary Structure
Secondary structure of a protein is a 3D shape
that results from hydrogen bonding between the
amino and carboxyl groups of adjacent amino
acids.
 The bonding produces a spiral (alpha helix)
 The bonding produces a folded (pleated sheet)
 Proteins whose shape is dominated by these 2
patterns, form fibrous proteins

Pages 82-83
Tertiary Structure

Tertiary structure of a protein includes
additional 3D shaping. The following
factor contribute to tertiary “folding”
– Hydrogen bonding between R groups of
amino acids
– Ionic bonding between R groups of amino
acids
– Hydrophobic effect
– Disulfide Bonds, when the sulfur atoms in two
cysteine amino acids bond….”Disulfide Bridge”
Quaternary Structure

Quaternary structure describes a protein
that is assembled from two or more
separate peptide chain.
– Hemoglobin consists of 4 peptide chains held
together by hydrogen bonding, R-groups
interactions, and disulfide bonds
Nucleic Acids
The genetic information of a cell is
stored in molecules of DNA.
 The DNA, in turn, passes its genetic
instructions to RNA for directing various
metabolic activities of the cell
 DNA is a polymer of nucleotides:

– Nitrogen Base (A,T,C,G)
– 5-carbon sugar (deoxyribose)
– Phosphate group
Purines and Pyrimidines
The nitrogen bases are A, T, C, G
 A and G are “Purines” double-ring bases
 T and C are “Pyrimidines” single-ring
bases
 You can remember which bases are purine
because only the two purines end with
“nine”: adenine and guanine
 Remember base pairing rules A-T and C-G

Page 87
Nucleic Acids
The two strands of DNA are antiparallel,
that is, they run in opposite directions.
 One is arranged in the 5’3’ direction the
other in the 3’5’ direction

RNA

RNA differs from DNA in the following
ways:
– The sugar in RNA is ribose, not
deoxyribose
– The thymine does not occur in RNA, it is
replaced with uracil
– RNA is a single-stranded molecule and
does not form a double helix as DNA does.