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Ch. 4- Carbon and the Molecular Diversity of Life Structure and
Ch. 5- Function of Macromolecules
A. P. Biology
Chapters 4 and 5
Mr. Knowles
Liberty Senior High School
The Uniqueness of Carbon• Requires 4 electrons to fill its outer shell.• Will form tetrahedral molecules with other atoms.
Has equidistant bond angles of 109.5°.• Will readily form single, double and triple covalent
bonds.• Carbon forms a variety of chained and ringed
organic compounds.• Carbon is the backbone for many organic
compounds.
Carbon in a Tetrahedron!
Hydrocarbons:– Are molecules consisting of only carbon
and hydrogen.– Are found in many of a cell’s organic
molecules.
(a) A fat molecule (b) Mammalian adipose cells
100 µm
Fat droplets (stained red)
Figure 4.6 A, B
Functional groups are the parts of molecules involved in chemical reactions Functional groups
– Are the chemically reactive groups of atoms within an organic molecule.
Six functional groups are important in the chemistry of life–Hydroxyl–Carbonyl–Carboxyl–Amino–Sulfhydryl–Phosphate
Some important functional groups of organic compounds
FUNCTIONALGROUP
STRUCTURE
(may be written HO )
HYDROXYL CARBONYL CARBOXYL
OH
In a hydroxyl group (—OH), a hydrogen atom is bonded to an oxygen atom, which in turn is bonded to the carbon skeleton of the organic molecule. (Do not confuse this functional group with the hydroxide ion, OH–.)
When an oxygen atom is double-bonded to a carbon atom that is also bonded to a hydroxyl group, the entire assembly of atoms is called a carboxyl group (—COOH).
C
O O
C
OH
Figure 4.10
The carbonyl group ( CO) consists of a carbon atom joined to an oxygen atom by a double bond.
Some important functional groups of organic compounds
Acetic acid, which gives vinegar
its sour taste
NAME OF
COMPOUNDS
Alcohols (their specific
names usually end in -ol)
Ketones if the carbonyl group is
within a carbon skeleton
Aldehydes if the carbonyl
group is at the end of the
carbon skeleton
Carboxylic acids, or organic
acids
EXAMPLE
Propanal, an aldehyde
Acetone, the simplest ketone
Ethanol, the alcohol
present in alcoholic
beverages
H
H
H
H H
C C OH
H
H
H
HH
H
H
C C H
C
C C
C C C
O
H OH
O
H
H
H H
HO
H
Figure 4.10
Some important functional groups of organic compounds
FUNCTIONALPROPERTIES
Is polar as a result of the
electronegative oxygen
atom drawing electrons
toward itself.
Attracts water molecules,
helping dissolve organic
compounds such as sugars
(see Figure 5.3).
A ketone and an aldehyde may be structural isomers with different properties, as is the case for acetone and propanal.
Has acidic properties because it is a source of hydrogen ions.The covalent bond between oxygen and hydrogen is so polar that hydrogen ions (H+) tend to dissociate reversibly; for example,
In cells, found in the ionic form, which is called a carboxylate group.
H
H
C
H
H
C
O
OH
H
H
C
O
C
O
+ H+
Figure 4.10
Some important functional groups of organic compounds
The amino group (—NH2) consists of a nitrogen atom bonded to two hydrogen atoms and to the carbon skeleton.
AMINO SULFHYDRYL PHOSPHATE
(may be written HS )
The sulfhydryl group consists of a sulfur atom bonded to an atom of hydrogen; resembles a hydroxyl group in shape.
In a phosphate group, a phosphorus atom is bonded to four oxygen atoms; one oxygen is bonded to the carbon skeleton; two oxygens carry negative charges; abbreviated P . The phosphate group (—OPO3
2–) is an ionized form of a phosphoric acid group (—OPO3H2; note the two hydrogens).
N
H
H
SH
O P
O
OH
OH
Figure 4.10
Some important functional groups of organic compounds
Because it also has a carboxyl group, glycine is both an amine and a carboxylic acid; compounds with both groups are called amino acids.
Glycine EthanethiolGlycerol phosphate
O
C
HO
C
OHH
N
OH
OH
OH
C C SH
OH
OH OH
OH
OH
OH
C C C O P O
OOHOHOH
OH OOH
Figure 4.10
Some important functional groups of organic compounds
Acts as a base; can pick up a proton from the surrounding solution:
Ionized, with a charge of 1+, under cellular conditions.
(nonionized) (ionized)
N
H
H H
+N H
H
Two sulfhydryl groups can interact to help stabilize protein structure (see Figure 5.20).
Makes the molecule of which
it is a part an anion (negatively charged ion).Can transfer energy between organic molecules.
Figure 4.10
Functional groups give organic molecules distinctive chemical properties
CH3
OH
HO
O
CH3
CH3
OH
Estradiol
Testosterone
Female lion
Male lionFigure 4.9
Organic Compounds• Four major groups:
1. Carbohydrates2. Lipids3. Proteins4. Nucleic Acids
• Differ in their functional groups; Fig. 3.2, p.45.
Organic Compounds • Some organic compounds are small with
one or a few functional groups- monomers. (Ex. Glucose = monosaccharide).
• Other organic compounds are made from linking several simple monomers together in complex chains- polymers (1000’s of glucose monomers = starch, polysaccharide).
Monomers Polymers
Simple Complex
• Monosaccharides Polysaccharides
• Glycerol, Fatty Acids Lipids, Fats
• Amino Acids Proteins
• Nucleotides Nucleic Acids
Building Macromolecules• All polymers are formed by making
covalent bonds between two monomers.• The –OH group from one monomer is
removed and the –H from the other is removed – Dehydration Synthesis
• H2O is removed which requires energy.
Dehydration Synthesis
HHO HO H
ENERGYHOH
HO H
Dehydration Synthesis• When polymers are built from smaller
monomers- anabolic reactions (synthesizing). Requires energy.
• These reactions require the reactants to be held close together and chemical bonds to be stressed and broken-catalysis.
• Catalysis is caused by enzymes.
Hydrolysis Reactions• Cells may also disassemble polymers into
monomers- catabolic reactions (breakdown).• A molecule of H2O is added and split; a H is
added to one monomer and the OH is added to the other-hydrolysis (water splitting).
• Catabolic reactions release the energy stored in the bonds of the monomers.
Carbohydrates• Contain C, H, O atoms (CH2O)n
• Functions:Main source of energy- for
immediate use or for energy storage,Used for structure- on surfaces
of cell membranes (bacteria, eukaryotes), or support cell walls (plants).
Three Types of Carbohydrates
1. Monosaccharides- “mono”- single; simple sugars that are made of 3-6 C’s in a chain or ring.
Ex. C6H12O6 , Glucose, most abundant monosaccharide
Straight Chain or Rings
Monosaccharides- Isomers
Three types of isomers are:
– Structural
– Geometric
– EnantiomersH H H H H
H
H H H H H
H
H
HHHH
H
H
H
H
H
HH
H
H
H
H
CO2H
CH3
NH2
C
CO2H
H
CH3
NH2
X X
X
X
C C C C C
C
C
C C C
C C C C
C
(a) Structural isomers
(b) Geometric isomers
c) Enantiomers
H
Figure 4.7 A-C
Enantiomers:
Are important in the pharmaceutical industry.
L-Dopa
(effective against Parkinson’s disease)
D-Dopa
(biologically inactive)Figure 4.8
Isomers
Structural Isomers- monosaccharides with the same empirical formula but different structures.
Ex. Glucose and Fructose
Isomers• Stereoisomers –
monosaccharides that have the same empirical formula but they have functional groups as mirror images of each other.
• Ex. Glucose and Galactose
Monosaccharides of Nucleic Acids
Other Monosaccharides
• Fructose- commonly found in fruit.
• Galactose- found in milk.• Ribose- found in RNA.• Deoxyribose- found in DNA.
Monosaccharides• Most offer a number C-H bonds
as potential chemical energy.
• May also be used as monomers to build more complex polymers for energy storage or structural molecules.
2. Disaccharides• Are two monosaccharides that form
a glycosidic bond by removing a H2O molecule.
• Glucose + Fructose-->Sucrose (table sugar)
Sucrose- A Disaccharide (Umm!)
Disaccharides• Monosaccharides (glucose) is often
converted into a disaccharide before being transported around an organism’s body.
• Unable to be used in this form until it arrives at a tissue.
• Plants transport glucose as sucrose. (sugar cane)
Lactose (MOO!)
Lactose• Mammals use lactose to
transport glucose to infant.• Adults usually lack the enzyme,
lactase, which breaks down lactose glucose + galactose.
Other Disaccharides• Sucrose (Table Sugar)- Glucose +
Fructose
• Lactose (Milk Sugar)- Glucose + Galactose
• Maltose (Breakdown from Starch)- Glucose + Glucose
3. Polysaccharides• Formed when monosaccharides are
linked in chains by glycosidic bonds.
• They are polymers- long chains of monomers (building blocks).
• Polymer = polysaccharide,
• Monomers = monsaccharides
Polysaccharides• Two Basic Functions-
1. Storage Polysaccharides: May store 1000’s of monomers for energy. Usually stored in special storage structures.2. Structural: May form structural parts of cells and/or tissues.
Starch = Amylose
Chloroplast Starch
Amylose Amylopectin
1 m
(a) Starch: a plant polysaccharideFigure 5.6
Plant Storage- Starch• Amylose- hundreds of glucose molecules in a
long, unbranched chain.• The glycosidic bond is between the 1C-4C.• The chains coil in water and don’t form H
bonds, therefore not very soluble in H2O.• Only 20% of starch in potatoes is amylose.• 80% is amylopectin- short and branched
glucose chains. Is cross-linked.
Starch Storage
• Plants use special tissues called tubers.
• Also stored in bulbs of perennials.
Glycogen:– Consists of glucose monomers.
– Is the major storage form of glucose in animals.
MitochondriaGiycogen granules
0.5 m
(b) Glycogen: an animal polysaccharide
Glycogen
Figure 5.6
Animal Storage- Glycogen• Insoluble, branched amylose chains.• Longer and more branched than
starch.• Stored in liver and skeletal muscle.• Not transported in blood.
Starch
Cellulose
Cellulose has different glycosidic linkages than starch.
(c) Cellulose: 1– 4 linkage of glucose monomers
H O
O
CH2OH
HOH H
H
OH
OHH
H
HO
4
C
C
C
C
C
C
H
H
H
HO
OH
H
OH
OH
OH
H
O
CH2OH
H
HH
OH
OHH
H
HO
4OH
CH2OH
O
OH
OH
HO
41
O
CH2OH
O
OH
OH
O
CH2OH
O
OH
OH
CH2OH
O
OH
OH
O O
CH2OH
O
OH
OH
HO4
O1
OH
O
OH OHO
CH2OH
O
OH
O OH
O
OH
OH
(a) and glucose ring structures
(b) Starch: 1– 4 linkage of glucose monomers
1
glucose glucose
CH2OH CH2OH
1 4 41 1
Figure 5.7 A–C
Structural Polysaccharides• Cellulose- a chain of glucose molecules in
which the monomers alternate positions.• Similar to amylose but not recognized by
the same enzymes. Resistant. Compare in Fig. 3.7.
• A water-tight, structural molecule.• Plant cell walls
Cellulose- A Structural Polysaccharide of Plants
Plant cells
0.5 m
Cell walls
Cellulose microfibrils in a plant cell wall
Microfibril
CH2OH
CH2OH
OH
OH
O
OOH
OCH2OH
O
O
OH
OCH2OH OH
OH OHO
O
CH2OH
O
OOH
CH2OH
OO
OH
O
O
CH2OHOH
CH2OHOH
OOH OH OH OH
O
OH OH
CH2OH
CH2OH
OHO
OH CH2OH
O
O
OH CH2OH
OH
Glucose monomer
O
O
O
O
O
O
Parallel cellulose molecules areheld together by hydrogenbonds between hydroxyl
groups attached to carbonatoms 3 and 6.
About 80 cellulosemolecules associate
to form a microfibril, themain architectural unitof the plant cell wall.
A cellulose moleculeis an unbranched glucose polymer.
OH
OH
O
OOH
Cellulosemolecules
Figure 5.8
A major component of the tough walls that enclose plant cells
• Cellulose is difficult to digest:– Cows have microbes in their stomachs to
facilitate this process (relationship?).
Figure 5.9
Termite Colony
Koalas and EucalyptusI have
indigestion!
Polysaccharides and Clean Hair!
Chitin
• ChitinChitin, another important structural polysaccharide– Is found in the exoskeleton of arthropods.– Can be used as surgical thread.
(a) The structure of the chitin monomer.
O
CH2OH
OHH
H OH
H
NH
C
CH3
O
H
H
(b) Chitin forms the exoskeleton of arthropods. This cicada is molting, shedding its old exoskeleton and emergingin adult form.
(c) Chitin is used to make a strong and flexible surgical
thread that decomposes after the wound or incision heals.
OH
Figure 5.10 A–C
3. Chitin• Structural polysaccharide of Arthropods
(insects and crustaceans) and fungi.• Modified form of cellulose; has an added
nitrogen group to each glucose unit.• Hard, flexible, and water-tight.• Few organisms can digest.• Exoskeleton of Arthropods.
My Kind of Polysaccharide!
Biology Lab Manual, Lab #3, pp.29-31
Testing for Carbohydrates
Reactive Groups in Monosaccharides
Groups are Missing in Sucrose
The Benedict’s TestCu 2+ (Cupric Ions)
Reducing Sugar
Cu+ (Cuprous Ions)
Cu (Most Reduced Copper)
H
Heat and High pH
H
Benedict’s Test for Reducing Sugars
-+ ?
Positive and Negative Control for Starch
