The Molecules of Life
Chapter 5
Section 5.1 Biomolecules
Objectives:
• Identify carbon skeletons and functional groups in organic
molecules
• Relate monomers and polymers
• Describe the processes of building and breaking down
polymers.
Organic Macromolecules “Biomolecules”
Large, carbon-containing molecules that are manufactured by living
things.
Categoies: Carbohydrates, Lipids, Proteins and Nucleic Acids
Approximately 60-90% of an organism is water.
The rest of an organism consists mostly of carbon-based
molecules.
“Organic Chemistry” is the study of carbon compounds.
Why are carbon atoms so common in living things?
Carbon is a versatile atom…..
Carbon Bonding
Carbon has 4 valence electrons.
Needs 4 more to be stable.
Tends to form covalent (sharing)
bonds.
Carbon Bonding
Carbon is relatively unique in that it
can form a variety of bond
combinations:
4 single covalent bonds
2 double covalent bonds
1 double and 2 single covalent bonds
1 triple and 1 single covalent bond
Carbon can use its bonds to:
Form an endless variety of
carbon skeletons from the
simplest single carbon
molecule (methane - CH4) to
long straight chains, to
branched chains or to rings.
Hydrocarbon - organic
molecules that are composed
of carbon and hydrogen only.
(fuels)
Carbon can also bond with
atoms of other elements.
What else can be found in organic molecules?
In addition to hydrogen, oxygen and nitrogen are frequently
found in organic molecules.
Frequently molecules contain groups of atoms that interact in
predictable ways with other molecules. These groups of
atoms are called Functional Groups.
Together, the carbon skeleton and the attached functional
groups determine the properties of the organic molecule.
HYDROPHYLIC
HYDROPHOBIC
Water loving
Attracted to water molecules
Polar
Water soluble/dissolves in
water
Water fearing
Repels water
Non polar
Water insoluble/doesn’t
dissolve in water
Example:
NaCl - ionic
0-H , S-H - polar covalent
Example:
C-C , C-H - nonpolar covalent
Some Common Functional Groups
(“R” denotes a group of atoms-the rest of the molecule)
Functional Groups are important because they:
-allow us to recognize the molecule as carbohydrate, lipid, protein,
or nucleic acid.
-allow us to predict the behavior of the macromolecule they are
part of.
Draw Functional Groups:
C–C–C–C–C–C–C–C–C–C–C–C
Macromolecule Composition
Large molecules are called polymers.
Polymers are built from smaller “building block” molecules called
monomers.
Every living cell has thousands of kinds of polymers.
Vary from cell to cell in an organism
Vary from organism to organism
Fewer than 50 monomers are used to make all polymers.
There are four main categories of Organic Polymers:
Carbohydrates
Lipids
Proteins
Nucleic Acids (DNA and RNA)
How do organisms build polymers?
by the Dehydration Reaction (condensation)
One water molecule is removed every time two monomers are linked
together. (H and OH)
End products: water and a polymer.
The same process is used to make all organic polymers!
MONOMER + MONOMER + MONOMER (ETC…) → POLYMER (+H2O)
How do organisms break down polymers?
by the Hydrolysis Reaction
To break the link (bond) between two monomers,
one water molecule is needed (H and OH).
Enzymes
Chemicals produced/used by living
organisms to reduce the amount of energy
needed to activate chemical reactions such
as the Dehydration Reaction or the
Hydrolysis Reaction. They speed up the rate
of chemical reactions.
Section 5.2:
Carbohydrates: Sugars and polymers of sugars
Objectives:
•Describe the basic structure and function of sugars.
•Name 3 mono-, 3di- and 3 polysaccharides and describe
their structure and function.
General Function: Provide or store energy for organisms, or function
as structural components of cells.
What do each of the following have in common?
Examples:
•
•
•
•
•
•
•
•
Potato
Slice of bread
Table sugar
Wood
Honey
Glass of Milk
Crustacean exoskeleton
Vertebrate animal blood
They all contain carbohydrates.
There are three main types of carbohydrates.
Monosaccharides
Disaccharides
Polysaccharides
Monosaccharides “simple sugars” or “simple carbs”
General Information
Function
Fuel for cells/ready-to-use energy, building-blocks for carbohydrate polymers
Composition
Carbon, Hydrogen and Oxygen in a 1:2:1 ratio
General Molecular Formula
(CH2O)n
where n is any whole number between 3 to 8.
ex. C6H12O6
C3H6O3
C5H10O5
C8H16O8
4 carbon monosaccharide =
Functional Groups
hydroxyl (-OH) (Polar)
carbonyl ( C=O) (Polar)
Properties
Water soluble due to functional groups polarity
Monosaccharide
Structure/Composition
(Chemical Formula)
Function
Glucose
C6H12O6
Fructose
C6H12O6
Found in blood
“blood sugar”
Fruit/Honey
Galactose
C6H12O6
Deoxyribose
C5H10O4
DNA
Ribose
C5H10O5
RNA
Examples of Important Monosaccharides:
Isomers: molecules with the same chemical formula,
but different structural formulas
Which monosaccharides are isomers?
glucose, fructose and galactose
In aqueous (water) solutions,
monosaccharides form ring structures
Disaccharides “Double sugars”
General Information
Function: transport energy
Composition: 2 monosaccharides
Formation: Dehydration Reaction
Molecular Formula of Disaccharides:
C6H12O6
+ C6H12O6
C12H24O12
H2O (dehydration reaction)
C12H22O11
NOT a 1:2:1 C:H:O ratio
but always a 2:1 H:O ratio (all carbs)
Disaccharides have the same functional groups
and properties as monosacharides.
Disaccharide
Structure/Composition
Sucrose
Cane/Table sugar
Glucose and Fructose
Lactose
Milk sugar
Maltose
Seed/Grain sugar
Function
Transports energy
from leaves (where it
is made) to other parts
of the plant
Glucose and Galactose Transports energy in
vertebrates (Mom to
baby)
Glucose and Glucose
Stores energy for seed
embryo to use when it
germinates
Polysaccharides “Complex Carbohydrates”
General Information
Function
Energy storage and structure
Composition
Carbon, Hydrogen and Oxygen
formed by joining monosaccharides together in long chains
(100s-1000s of monomers)
General Molecular Formula
2:1 H:O ratio
Functional Groups
hydroxyl (-OH) (Polar)
carbonyl ( C=O) (Polar)
Properties
Typically insoluble in water due to size
Some Important Polysaccharides:
Polysaccharide
Structure
Function
Cellulose
Multiple Glucose chains
bound together like a rope
Structural: Fibrous
support for plants-found
in cell wall
Starch
Unbranched, coiled chains of Energy storage in plants
glucose
Glycogen
Branched chains of glucose
Energy storage in
animals, found in liver
and muscle cells
Chitin
Nitrogen group replaces the
–OH in the glucose
monomers
Structural: Hard
Arthropod exoskeletons
and in
Fungi cell walls
Putting it all together…
Disaccharides and Polysaccharides are built form
monosaccharides through the process of
Dehydration Reaction
Polysaccharides and Disaccharides are broken down in
the process called
Hydrolysis
Remember that the correct enzyme is needed for each
reaction to occur.
Polysaccharide Formation
Glucose
Lactose Intolerance
The body does not produce the enzyme lactase that is needed to
hydrolyze lactose into glucose and galactose
When dairy products are consumed, bacteria in the digestive tract begin
to ferment the lactose, producing unpleasant symptoms such as gas,
bloating, and diarrhea.
Babies with lactose intolerance must have an alternative energy source
such as soy milk.
Soy milk is a good energy source alternative to lactose because it is
produced from soybeans which contain the disaccharide maltose
(glucose-glucose). (glucose is fuel for cells)
Can take the lactase enzyme with dairy products.
Some dairy products have the enzyme already added.
Hydrolysis of Polysaccharides
Vertebrate digestive systems have the ability to hydrolyze
starch and glycogen, however they do not produce the
enzyme needed for the hydrolysis of cellulose.
Cellulose passes through the digestive tract ‘undigested’ and
is considered fiber in your diet.
Cow’s source of nutrition is plants which consist mainly of
cellulose. How is it that cows can survive on a diet which is
mainly vegetarian, yet they cannot hydrolyze the cellulose?
They have microorganisms in their digestive tract produce the
necessary enzyme needed to ‘digest’ the cellulose. (Termites
do too.)
Sweetness of Various Carbohydrates
•Fructose
•
173
•
100
•
74
•
33
•
33
•
16
•Sucrose
•Glucose
•Maltose
•Galactose
•Lactose
•Lactase is the enzyme needed
for the hydrolysis of lactose.
•Why is milk with the lactase
enzyme sweeter than regular
milk?
Addition of the lactase enzyme causes the
hydrolysis of lactose into glucose and galactose.
Glucose is sweeter than lactose!
Venn Diagram
Dehydration Reaction
Summary:
Hydrolysis Reaction