SBI 3U7
The Chemical Basis of Life
The Chemicals of Life
Terms that you should know
1.
Organic Chemistry
 The study of organic compounds
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Organic Compounds
Compounds that contain both carbon (C) and hydrogen (H) atoms
Carbon backbone
Open-ended chains or loop-like rings
Atoms bond using covalent bonds
Examples:
o Carbohydrates
o Proteins
o Lipids
o Nucleic Acid
Carbon Atom
Atomic # 6, 4 valence eCompletes its outer shell by sharing 4 valence e- in 4 covalent bonds
Makes large complex molecules possible
Contributes to the complexity and diversity of organic molecules
Hydrocarbons
 Molecules containing only C, and H
 Are hydrophobic because C-C and C-H bonds are nonpolar
 (Although the En = 0.4, which makes this slightly polar, its geometric
symmetry in the molecule allows
it to be nonpolar, ie. Methane and larger
hydrocarbons)
 E.g. methane. Ethane, butane, benzene
Functional Groups
 Small characteristic groups of atoms frequently bonded to the carbon skeleton
of organic molecules
 Have specific chemical and physical properties
 Regions which are commonly chemical active
 Behave consistently from one organic molecule to another
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 Types:
Group
Hydroxyl
(-OH)
Alcohols
Carbonyl
(-CO)
Aldehyde
-CHO(-al)
The Chemical Basis of Life
Description
Examples/Names
Makes the molecule to which it is attached
Methanol
water soluble
Polar water molecules are attracted to the polar Ethanol
hydroxyl group which can form hydrogen bonds
Glycerol
Carbon atom double bonded to oxygen
Glycerolaldehyde
Polar water soluble
Formaldehyde
pentanal:
Acetone
Ketones
-CO(-one)
Carboxyl
(-COOH)
butanone
Polar water soluble
Has acids properties since donates hydrogens
Acetic acid
Formic acid
Amino
(-NH2)
Sulfhydryl
(-SH)
Phosphate
(-PO4)
Polarsoluble in water
Acts as a weak base
The unshared pair of electrons on the nitrogen
can accept a proton, giving the amino group a
“+ “charge
Helps stabilize the structure of proteins
Ammonia
Methylamine
Thiol
Polarsoluble in water
ATP/ADP
Important in cellular energy storage and transfer DNA / RNA
Glycerol phosphate
**The functional groups helps to create polar molecules to large non-polar hydrocarbons
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The Chemical Basis of Life
**Make sure you know the functional
groups
{ANSWER: P. 27 #1,
READ: ‘Did you know?: When it comes to
drugs, like dissolves like’}
5.
Monomer
 Subunit of a
polymer
 E.g. glucose,
amino acid
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Polymer
 Large molecule consisting of many identical or similar subunits connected
together
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Macromolecule
 Large organic polymers
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Polymerization Rxns
 Chemical rxns that link two or more small molecules to form larger molecules
with repeating structural units.
 Most of them are condensation (dehydration synthesis) rxns.
 Condensation reactions absorb energy when forming bonds.
 These reactions are also called anabolic reactions (obtaining a larger molecule
by putting together monomers)
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Hydrolysis reactions
 Uses water to break apart larger molecules
SBI 3U7
The Chemical Basis of Life
 Energy is released from breaking bonds
 These reactions are also called catabolic reactions (breaking down nutrient
macromolecules)
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Isomers
 A variation in the architecture of organic molecules can be seen in isomers compounds that have the same molecular formula but different structures and
hence different properties.
There are two different types of isomers:
 Types of Isomers:
1. Structural Isomers –
 Differ in the covalent arrangement of their atoms (They differ in how the
atoms are joined together.) They have different chemical properties.
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# of possible isomers ↑ as the carbon skeleton size ↑
What's the difference? Well besides the structural difference, biologically one
might be active but the other may not.
2. Optical Isomers – many molecules of biological importance (particularly
sugars and amino acids) have optical isomers (also called enantiomers –
mirror image). Optical isomers occur whenever a carbon atom has four
different atoms or groups attached to it. For example – your right and left
hands are "optical isomers". Just as a glove is specific for a particular hand,
some biochemical molecules found in biological systems can only interact
with a "SPECIFIC" optical isomer of a compound but are unable to "fit" the
other!
Ex. Amino acids are one such example. Amino acids can exist in two isomeric forms
called D-amino acids (right handed) and
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The Chemical Basis of Life
o L-amino acids (left handed). ONLY L-amino acids are commonly found
in most proteins of living things.
Ex. Hexose Sugars (See below)
Carbohydrates
 Carb: carbon (C); hydro: water (H2O)
 Made of C, H, and O in the ratio 1:2:1
 Empirical Formula: (CH2O)n (n represents the number of carbon atoms)
 Made of sugars and their polymers which are formed by condensation rxns.
 More easily digested than lipids so the energy stored by them can be released
more rapidly
 Soluble in water so are easier to transport
 Types:
Carbohydrates
Monosaccharides
Disaccharides
Polysaccharides
Monosaccharides
 Mono: one; saccharide: sugar
 Simple sugar (3-7 carbon atoms) in which C,H, and O occur in ratio of 1: 2:
1(CH2O)
 All have the same composition of atoms, although the arrangement of the atoms
differ
 Major nutrients for cells
 Most common glucose produced by photosynthetic organisms
6CO2 + 6H2O + sunlight C6H12O6 + 6O2
 Store energy in their chemical bonds which is harvested by cellular respiration
 Contain hydroxyl functional group and either an aldehyde group (aldose) or a
ketone group (ketose)
 The most common monosaccharides and chemical structures are:
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The Chemical Basis of Life
 The small difference b/w isomers affects molecular shape which gives the
molecules distinctive biochemical properties
 In aqueous solutions, many monosaccharides form rings
Hydroxyl at C 1 will be below
the plane of the ring
Hydroxyl at C 1 will be above
the plane of the ring
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The Chemical Basis of Life
Glucose
Source of energy for
virtually all cells
Fructose
Fruit sugar
Galactose
Component of lactose, milk
sugar
Disaccharides
 Di: two
 Composed of 2 simple monosaccharides joined by a glycosidic linkage (a covalent
bond formed by a condensation reaction b/w two sugar molecules)
o The most common linkages occur b/w carbon 1 on one monomer and either
carbon 4 and 6 on another
 An ether linkage is a linkage formed b/w two alcohols
 Types:
o Maltose  Glucose + glucose (sugar in beer)
o Sucrose  Glucose + fructose (table sugar)
o Lactose  Glucose + galactose (sugar in milk)
 Formation of maltose and sucrose
o
Maltose
 Glucose + glucose
o Sucrose  Glucose + fructose
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The Chemical Basis of Life
Oligosaccharides
 Contain three or four simple sugars
Polysaccharides
 Poly: many
 Too large to be absorbed by cells in the digestive system, therefore chemical
reactions break the bonds between the glucose subunits
 Complex carbohydrate
 Many (few hundred or thousand) monosaccharides linked together
 The difference b/w starch and cellulose structure
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The Chemical Basis of Life
 Helical glucose polymer with
1-4 linkages
 Stored as granules within plastids
 E.g.
o Amylose
o amylopectine
 storage polysaccharide in animals
 stored in the muscle and liver of
vertebrates
 is made of modified glucose molecules
linked together and similar to
amylopectine but is more highly
branched
Starch
Glycogen
Energy Storage
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The Chemical Basis of Life
Biological
Functions
Structural
Chitin
 Forms exoskeletons
of arthropods
Cellulose
 Major structural component
of plant cell walls
 Monomers connected with
linkage (-OH group on
carbon one is above the
ring’s phase
 Cannot be digested by most
organism b/c they lack an
enzyme that can hydrolyze
the linkage
{ANSWER: P. 34 #1-8, 10
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