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Organic Compounds
Introduction to Carbon based or Organic
Compounds
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Life’s structural and functional diversity results
from a great variety of molecules.
In addition to water, all other biological molecules
are organic or carbon based molecules.
Structural Ball-and-stick Space-filling
formula
model
model
Methane
The 4 single bonds of carbon point to the corners of a tetrahedron.
Life’s molecular diversity is based on the
properties of carbon
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Carbon is unparalleled in its ability to form
large, diverse molecules
The outer electron shell of Carbon has 4
electrons
Carbon completes its outer shell by sharing
electrons with other atoms (Carbon and
other elements) in 4 covalent bonds.
Organic compounds
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Organic molecules are characterized by having a
central “backbone” made of atoms of carbon linked to
each other like a “chain” of carbon atoms. In addition,
other atoms can link to the carbon backbone.
The unique properties of an organic compound
depend on the size and shape of its Carbon skeleton
(the chain of Carbon atoms, can be branched or
unbranched) and on the groups of atoms that are
attached to that skeleton.
Carbon
skeletons vary
in many ways
Propane
Ethane
Length.
Carbon skeletons vary in length.
Butane
Isobutane
Branching. Skeletons may be unbranched or branched.
1-Butene
Double bonds.
Skeletons may have double bonds,
which can vary in location.
Cyclohexane
Rings.
2-Butene
Benzene
Skeletons may be arranged in rings.
Organic Compounds
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There are chemical “groups” that are
important in the chemistry of life.
These groups, known as functional groups
(groups of atoms that always go together),
affect the molecules function by participating
in chemical reactions .
The most important groups are (these are all
polar):
Hydroxyl group Consists of a Hydrogen
bonded to an Oxygen (also known as
alcohol group).
Carbonyl group : Carbon linked by a double
bond to an Oxygen
Carboxyl group: A Carbon double-bonded to both
an Oxygen and a Hydroxyl group (also known as an
acid group)
Amino group : Composed of a Nitrogen bonded to
2 Hydrogen atoms and the Carbon skeleton
Phosphate group: Consists of a Phosphorus atom
bonded to 4 Oxygen atoms
Methyl group nonpolar and not
reactive,Carbon bonded to 3 Hydrogen
Organic Compounds
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How about a working example?
Male and female sex hormones differ
ONLY by functional group
This change in functional group may
seem subtle, but results in different
actions of these molecules, which help
produce the physical features
(characteristics) of males and females
Same structure, but
different functional
groups
Estradiol – female
sex hormone
Female Lion
Hydroxyl group
Methyl group
Testosterone –
male sex hormone
Carbonyl group (not on the list)
Male Lion
Biological Molecules
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In addition to water, all other biological molecules are
organic (carbon-based) molecules. There are many organic
molecules, but four of them are important to living
organisms: Carbohydrates, Lipids, Proteins and Nucleic
Acids.
Most of the large molecules in living things are
macromolecules called polymers.
A polymer is a ‘macromolecule’ because of its great size.
Polymers consist of many identical or similar building blocks
(monomers) strung together, much like a long train consists
of many individual cars
Polymers
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The variety of polymers made by a cell is
potentially endless
The arrangement and number of
monomers can lead to countless different
polymers
Many Carbohydrates and all lipids,
proteins and nucleic acids are polymers!
How do we build large molecules?
Cells link monomers to form polymers by
dehydration synthesis
1
2
3
4
Short polymer
Unlinked monomer
Removal of
water molecule
There is input of
Energy
1
2
Enzyme
catalyzes the
reaction
Longer polymer
3
4
This is an ENDERGONIC reaction. Why?
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Polymers are broken down to monomers by
the reverse process, hydrolysis
1
There is an energy
release
1
2
2
3
Addition of
water molecule
3
4
Enzyme
catalyzes the
reaction
4
This is an EXERGONIC reaction. Why?
Biomolecules
Carbohydrates
CARBOHYDRATES
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Carbohydrates are a class of molecules
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They include sugars, starches and fiber.
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Composed of the elements C, H and O
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Major source of energy from our diet
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Produced by photosynthesis in plants
Types of Carbohydrates
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Monosaccharides
Single monomer
Disaccharides
Contain 2 monosaccharide units
Polysaccharides
Contain many monosaccharide units
Monosaccharides are the
simplest carbohydrates.
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Monosaccharides are single-unit sugars
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Monosaccharides are the fuels for cellular work.
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We classify monosaccharides according to the
number of carbons involved in the carbon chain.
5C and 6C are the most important.
Examples of 6 C Monosaccharides
H
C O
H C OH
HO C H
CH 2OH
C O
HO C H
H
O
C
H C OH
HO C H
H C OH
H C OH
H C OH
H C OH
H C OH
CH 2OH
CH 2OH
CH2OH
D-Glucose
D-Fructose
HO C H
Galactose
Honey
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Honey is a sweet, thick sugary
solution made by bees. The
composition of honey consists of
varying proportions of fructose,
glucose, water, oil and special
enzymes produced by bees. It also
has gluconic acid hydrogen peroxide
that make honey inhospitable to
bacteria, mold, and fungi, organisms
we call microbes.
Hunter of bees, Arana, Spain
7000 BCE
Disaccharides
Disaccharides are two unit sugars
 Disachharides are more complex fuels for
cellular work.
 We form dissacharides using dehydration
synthesis
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Energy
Glucose + Glucose
H2O
Maltose
Enzyme
Enzyme
Energy
H2O
Energy
Glucose + Fructose
Energy
H2O
Enzyme
Enzyme
Sucrose
H2O
Energy
Glucose + Galactose
Energy
H2O
Enzyme
Enzyme
Lactose
H2O
What is sucrose? Table Sugar!
Primary Plant Sources of table sugar
Sugar Cane – Saccharum officinarum
Sugar Beet – Beta vulgaris
Sorghum – Sorghum bicolor
Palm – Phoenix dactylifera
Maple – Acer saccharum
The average USA sugar consumption per
capita per year is 60 lbs.
Oh Boy! All I
need now
is some sugar!
Sugar Cane
Saccharum officinarum – member
of Poaceae (Grass family)
Native to: Polynesia
Sugar Cane Fields, Queensland Australia, Spring 2006
Sugar Beet, the sugar of
temperate climates
Beta vulgaris – Chenopodiaceae
(Goosefoot Family)
Sugar Beet Fields. Cornwall England, Summer 2006
North American Sweetener
Acer saccharum – Sugar Maple
Maple Syrup
Sap is collected in early spring
Sap is boiled in “sugar house”
40 gallons sap  1 gallon syrup
 What is lactose?
Lactose is the dissacharide sugar
found in milk!
 What is lactose intolerance?
Are you lactose intolerant?
Do you know somebody who is?
 Lactose intolerance is a
condition that those who are
afflicted cannot digest milk.
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This is the normal hydrolysis reaction
Energy
Glucose + Galactose
Energy
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H2O
Enzyme
Enzyme
Lactose
H2O
A lactose intolerant person does not have
the enzyme that breaks down the lactose,
therefore lactose is indigetable and it
causes indigestion!
How sweet is sweet?
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Various types of molecules, including non-sugars, taste
sweet because they bind to “sweet” receptors on the
tongue.
Polysaccharides
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Polysaccharides are carbohydrates
composed of many monosaccharides.
There are two types of polysaccharides
Storage Polysaccharides: They store
energy
Structural Polysaccharides: These are
use for building cell structures.
Polysaccharides are long chains of
sugar units
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These large molecules are polymers of hundreds or
thousands of monosaccharides linked by dehydration
synthesis
Energy
1. Glucose + Glucose
H2O
Enzyme
Energy
Maltose
n(H2O)
2. Maltose + n(Glucose)
Polysaccharide
Enzyme
n = many
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Starch and glycogen are storage polysaccharides
that store sugar for later use.
Cellulose is a structural polysaccharide in plant
cell walls
Starch granules in
potato tuber cells
Glycogen granules
in muscle tissue
Cellulose fibrils in
a plant cell wall
Cellulose
molecules
Glucose
monomer
STARCH
GLYCOGEN
CELLULOSE
Starch is a storage polysaccharide composed entirely of
glucose monomers.
One unbranched form of starch, amylose, forms a helix.
 Branched forms, like amylopectin, are more complex.
 Animals that feed on plants rich in starch use it as a
source of energy.
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Fig. 5.6a
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Animals also store glucose in a polysaccharide
called glycogen.
Glycogen is highly branched, like amylopectin.
Humans and other vertebrates store glycogen in
the liver and muscles for a short period of time.
They only store one day supply.
Insert Fig. 5.6b - glycogen
Structural Polysaccharides
Other polysaccharides, structural polysaccharides serve
as building materials for the cell or for the whole
organism. The Best example is cellulose.
wood is mostly cellulose
plant cell with cell wall
individual
cellulose
molecules
close-up of cell wall
bundle of
cellulose
molecules
cellulose fiber
Cellulose
 Cellulose is a structural polysaccharide composed
entirely of glucose monomers.
 Cellulose is commonly known as fiber. Cellulose is the
most abundant organic compound on Earth; because it is
the main component of the cell wall of plants.
 Most animals (including humans) do not have enzymes
that can hydrolyze the glucose links in cellulose.
Cellulose in our food passes through the digestive tract
and is eliminated in feces as “insoluble fiber”.
 Nevertheless, as fiber travels through the digestive tract,
it abrades the intestinal walls and stimulates the
secretion of mucus which helps digestion and excretion.
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Cellulose, even though insoluble, is used by
many animals as a source of nourishment.
Ruminants (cows, sheep, goats, deer,
antelopes, bison, giraffes) first soften this plantbased food in their rumen or first stomach, and
regurgitated and re-chewed (“chewing their
cud”) – yum! The mass is re-ingested and
broken down by microbes that are able to
break down the cellulose
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Another important structural polysaccharide is
chitin, used in the exoskeletons of arthropods
(including insects, spiders, and crustaceans).
Chitin also forms
the structural
support for the
cell walls of
many fungi.