Chp 2 (cont.) Organic Molecules
Spider’s web and close up of capture strand - spider silk protein
1!
Molecular Diversity is Based on Carbon
An organic molecule contains both
carbon and hydrogen. Ex: Methane a simple organic molecule
C atoms can bond to 4 other atoms –
chains, rings, branches
A chain of C atoms is called a carbon
skeleton Methane
What is the chemical formula for Butane and
Isobutane?
Ethane
Length.
Carbon skeletons vary in length.
Butane
Branching.
Propane
1-Butene
Skeletons may be unbranched or branched. Skeletons may have double bonds,
which can vary in location.
Double bonds.
Cyclohexane
Isobutane
Rings.
2-Butene
Benzene
Skeletons may be arranged in rings.
3!
Cells Make Lots of Large Molecules From a
Limited Set of Small Molecules
 Large
organic molecules are called macromolecules
– Aka. polymers b/c they are made from same units linked
together (draw train cars linked)
– The repeating units are called monomers
Nucleic acid
polymer
Monomer
Carbohydrate
polymer
Monomer
Monomer
Protein polymer
4!
 During
dehydration synthesis, an enzyme binds
two monomers, releasing a water molecule
H
OH
OH
OH
Short
Shortpolymer
polymer
H
H
Unlinked
Unlinkedmonomer
monomer
Dehydration
Dehydration
reaction
reaction
H 2O
OH
OH
H
H
Longer polymer
Building a polymer chain
5!
 Hydrolysis
is the reverse reaction, it breaks
polymers into monomers
H 2O
H
OH
Hydrolysis
H
OH
OH
Breaking a polymer chain
H
6!
Organic Molecules: Carbohydrates
 Carbohydrates
include
small simple sugars and
large polysaccharides
– Monosaccharides
are
the monomers of carbs
– Exs:
Glucose and
Fructose
Bees with honey, a mixture of 2
different monosaccharides
What do you think a chemical formula would be for
“carbo” “hydrate”?
7!
 Molecular
formula of a monosaccharide is
a multiple of CH2O
– Glucose
is C6H12O6
 Monosaccharides
are the main fuel for cellular
work
Monosaccharide structures
8!
 Two
monosaccharides can join to form one
disaccharide (a dehydration synthesis reaction)
– Glucose
bonding to fructose forms sucrose, table
sugar
– Glucose
linked to galactose = lactose, sugar
found in milk
What problem is associated with this disaccharide in
some people?
9!
 Starch
and glycogen = polysaccharides in plant
and animal respectively, storage of ___________
 Cellulose
= polysaccharide in plant cell walls,
structural support
Polysaccharides
are long chains
of
carbohydrates
10!
Organic Molecules: Lipids
  Lipids = hydrophobic (water
_________ )
– Long-term energy storage
– Not large
– Not built of monomers
Fats = lipids made from
glycerol and fatty acids
– Long hydrocarbon chains
– Saturated fatty acid vs.
unsaturated fatty acid
Formation of a fat molecule
11!
Phospholipids & Sterols are Also Lipids
 Phospholipids =
main component of
cell membranes
 Similar to fats, but
imp. differences
— Two
fatty acids
— Hydrophilic
head
and hydrophobic
tails
✶ Form stable bilayer in
water
13!
 Steroids
= lipids with 4
fused rings
 Cholesterol
=
common component of
animal cell membranes
– Starting
material for
sex hormones
– Too
much in the
blood can lead to
atherosclerosis
Fig. 3.9C Cholesterol, a type of steroid
14!
Atherosclerosis 15!
Organic Molecules: Proteins
 The
monomers of proteins
are amino acids
– Protiens; hair, cartilage,
muscle, antibodies, enzymes,
hemoglobin
– 3-D structure directly related
to function
– Made from genetic info
(DNA) found in the _______
of the cell
16!
H
H
Carboxyl
group
Amino
group
O
N
H
C
C
Amino acid
H
O
H
+
OH
R
Peptide
bond
N
C
Dehydration
reaction
H
C
H
R
N
OH
H 2O
H
Amino acid
H
O
C
C
R
H
N
C
H
R
O
C
OH
Dipeptide
Fig 3.11C Peptide bond formation
 Amino
acids structure: amino group, carboxyl group,
central carbon atom, and an R group
 Linked
 Links
– together by dehydration reactions
called peptide bonds
Carboxyl group bonded to amino group (C-N bond)
17!
Polypeptides must fold into a protein to work
 A polypeptide
chain has hundreds or thousands of aa’s
linked by peptide bonds
– Amino acid sequence of polypeptide determines shape
– Shape determines its specific function
Groove
Ribbon model of lysozyme
Groove
Space-filling model of lysozyme
18!
Four Levels of Protein Structure
Primary structure
Amino acids
Hydrogen
bond
Secondary structure
Alpha helix
Tertiary structure
Pleated sheet
Polypeptide
(single subunit
of transthyretin)
Quaternary structure
Transthyretin, with
four identical
polypeptide subunits
19!
 If
protein’s shape is altered, it may no longer
function
– Denaturation
= polypeptide chains unravel,
lose their shape, and lose their function
– Can
happen w/ changes in salt concentration,
heating, changes in pH
– Ex.
Frying an egg (egg white is protein)
20!
Organic Molecules: Nucleic Acids
 DNA
and RNA are
nucleic acids
 Monomers
of nucleic
acids are nucleotides
✶ Nucleotides
have 3 parts
– A 5-C sugar called
ribose in RNA and
deoxyribose in DNA
– A phosphate group
– A nitrogenous base
A nucleotide
21!
There are 5 types of nucleotides
Nucleotides form nucleic acids
22!
 DNA -
2 polynucleotide
strands wrap around each
other, double helix
– 2 strands are held together
by __________ bonds
– A pairs with T, and C pairs
with G, producing base
pairs
 RNA is
a single strand
Figure 15C DNA double helix
23!
Clicker Question #5
Which monomer is incorrectly
paired? A. protein: monopeptide
B. carbohydrate: monosaccharide
C. nucleic acid: nucleotide
D. lipid: no monomer
2.5 Mastering Concepts
Explain hydrolysis and
dehydration synthesis in
large molecules