Download Chapter 3: Cell Molecules

9/8/14
Molecules of Life
!  The dynamics of the diversity of life is due to the
proper functioning and interaction of the molecules
in each cell.
!  Inefficient molecules can cause cells or organisms
to become inefficient.
!  For example, diary products can cause issues in
some people. Why would this happen ?
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Molecules of Life
!  The diagram is an illustration
of the 3-dimensional structure
of the enzyme Lactase (a
protein with enzymatic
function).
!  The function of Lactase is to
break down Lactose (above),
a molecule made from 2
simple sugars.
!  Today, ~ 75 % of the world’s
population is lactose intolerant
due to the formation of a bad
enzyme in their intestinal wall.
Molecules of Life
!  Recent research has shown
that we humans acquired the
capacity to digest milk
products only ~ 7500 years
ago.
!  Data indicate that this occurred
in central europe , and from
here spread through other
human populations.
!  One of the reasons that
lactose intolerance is still high
in people of Asian, South
American, and African descent.
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Central role of Carbon
!  The diversity of all life is related to the diversity of its
chemistry, which in turn is all possible due to the variety
in which CARBON can react and form molecules.
!  All life forms on planet earth are carbon based
organisms.
!  Carbon-based molecules are referred to as organic
compounds.
!  Carbon always creates covalent bonds with other
carbons or other atoms to create simple to extreme
complex structures.
Central role of Carbon
!  The reason is the fact that carbon always makes 4
covalent bonds
!  If we look back at the Carbon atom, it has atomic
number 6. This means 6 protons, and 6 electrons. 4
of those electrons are in the outer-shell. It likes to get
4 more to get a full outer shell
!  Sharing its 4 electrons with 4 other ones thus creates
4 pairs of “shared” electrons ( thus 4 covalent bonds).
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Central role of Carbon
Formation of methane
4H + C
CH4
Central role of Carbon
Structural
formula
Ball-and-stick
model
Space-filling
model
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Central role of Carbon
Ethane
Propane
Carbon skeletons can vary in length.
By stringing carbons one after another, one creates
carbon chains or carbon skeletons. Obviously, this can
result in very large complexes.
Central role of Carbon
Butane
Isobutane
Skeletons may be un-branched or branched.
1-Butene
2-Butene
Skeletons may have double bonds, which can vary in location.
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Central role of Carbon
!  When a carbon chain only has carbons and hydrogens,
we call it a HYDRO-CARBON chain
!  The longer the hydrocarbon chain, the more
hydrophobic it becomes…. Thus not very soluble in
water !
!  Hydrocarbon chains are most often drawn in a
simplified, skeletal manner. Start, end and intersection
represent the carbon atoms, the hydrogens are not
shown, but assumed present according to the rules
known (that carbon can make 4 bonds and hydrogen
can only makes one bond).
Central role of Carbon
or
Butane
1-Butene
Ethane
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Molecular formula
Butane
Isobutane
C4H10
C4H10
Molecular formula tells us what atoms are in the molecule,
but it does not tell us the organization
The example above shows that both have the same
molecular formula. That’s why the chemical structure
becomes important.
Isomers
Butane
Isobutane
C4H10
C4H10
Molecules with the same molecular formula but
with a different chemical structure are called
ISOMERS.
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Isomers
!  The changes between Isomers can be very subtle and can be
the difference between being a biological active or non-active
molecule.
!  For example, if a group occurs on the left side or right side of a
carbon, it becomes spatially different like for example L and D
lactic acid. They are mirror images like your left and right hand
…. and thus not the same molecules. We humans make for
example L-lactic acid… we cannot metabolize D-lactic acid !
L-Lactic acid
D-Lactic acid
Optical Isomers
!  Such differences in being mirror molecules such as L or D form
are called Optical Isomers or Enantiomeres
!  For example : Bacteria can make D-Lactate in our body and we
have no way of neutralizing it. (our enzymes only break down Llactate).
!  In are cases, too much of
D-lacate can affect the
brain and has been
reported to result in
sleepiness, hallucinations,
clumsiness, blurred vision,
disorientation, dizziness,
lethargy, excessive
irritability,….
Lactobacilli (bad guys)
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Optical Isomers
!  Methamphetamine is another example, but with graver
consequences.
!  The L-isomer is just a decongestant and has no stimulant
activity. The D-form is known as speed/ice: it is a potent brain
stimulant and highly addictive
The face of a meth user
Functional groups
!  Functional groups refer to the side chains on carbon
chains
!  They are important because they convey functionality
to the molecules by creating regions for chemical
interaction with other molecules.
!  Many of the functional groups are polar because they
can be ionized and thus provide a hydrophillic
character to the molecule. The more such functional
group a molecule has, the more it becomes “waterloving” … (the exception is the methyl group).
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Functional groups
!  There are six (6)
important functional
groups in the chemistry
of life:
!  Hydroxyl group
!  Carbonyl group
!  Carboxyl group
!  Amino group
Functional groups
!  Phosphate group
!  Methyl group
All groups provide some
hydrophillic characteristic
to a molecule except for
the methyl groups (they
are hydrophobic).
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Functional groups
Estradiol
!  Just like subtle changes in
isomer structures can have
drastic effects, so does the
presence of functional groups
on certain molecules.
!  Look at the minor chemical
Female lion
Testosterone
differences of the functional
groups on these steroid
hormones …
!  and think on what effects they
have on the animal or human
body.
Male lion
MacroMolecules of Life
!  Cells can make a huge number of different carbon
molecules AND make larger molecules by combining
sets of small molecules (like playing with lego blocks)
!  Many of the molecules are very large
!  Those are called macromolecules or polymers
!  No matter what cell type, molecules of life can be put
into 4 major classes :
!  carbohydrates, lipids, proteins, and nucleic
acids
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MacroMolecules of Life
!  Cells make most of their large molecules by joining smaller
organic molecules into chains called polymers
!  Those smaller organic building blocks called are called
monomers
!  Cells link monomers to form polymers using a
dehydration reaction. ( a water molecule is removed and the two
parts are joined via a covalent bond)
!  It requires a very specific enzyme to perform this
reaction
MacroMolecules of Life
H
OH
OH
OH
Short polymer
H
H
Unlinked monomer
Dehydration
Dehydration
reaction
reaction
H 2O
OH
OH
H
H
Longer polymer
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MacroMolecules of Life
!  The breaking down of a large polymer into smaller building
blocks (monomers) occurs via a hydrolysis reaction.
!  In this case, water is inserted (by means of another specific enzyme)
between two monomers to break the covalent bond apart.
H 2O
H
OH
Hydrolysis
H
OH
H
OH
CarboHydrates
!  Carbohydrates are the sugar molecules
!  The basic building blocks (monomers) of
carbohydrates are the simple sugars; these are also
called the mono-saccharides
!  A monosaccharide has a formula that is a multiple of
CH2O (carbon with water… a carbo-hydrate).
!  It usually contains hydroxyl groups and a carbonyl
group, that make the molecule hydrophilic ( water
soluble) !
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CarboHydrates
H
O
H
C
H
C
OH
C
O
C
H
H
C
OH
HO
C
H
H
C
OH
H
C
OH
H
C
OH
H
C
OH
H
C
OH
H
C
OH
HO
H
Glucose and fructose are
examples of typical simple
sugars (mono-saccharides).
Both can be written as C6H12O6
Or C6(H2O)6… a multiple of CH2O
Their chemical structure is different and
thus they are isomers.
H
Glucose
Notice the many hydroxyl groups (-OH)
that provide a hydrophilic character to
sugars.
Fructose
CarboHydrates
•  Monosaccharides can also occur as ring
structures
6 CH2OH
H
5C
H
H
4C
OH
OH
3C
H
CH2OH
O
H
C 1
H
C2
OH
HO
O
H
OH
H
H
OH
H
O
OH
OH
Structural
formula
Abbreviated
structure
Simplified
structure
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CarboHydrates
!  Mono-saccharides are the main fuel molecules
for cellular work… the breakdown of sugars in cells
releases energy.
!  That is why sugar drink work very well as quick pep-
me-up’s … energy bars are usually filled with sugars
!  People that can’t eat orally get sugars supplied via
IV’s. (intra-venous bags)
!  The carbons from sugar breakdown can also be used
to make fats and proteins. (but…too many simple
sugars in a meal will quickly be turned into fat..)
CarboHydrates
CH2OH
CH2OH
O
O
H
H
H
H
OH
H
HO
H
H O
OH
H
H
OH
H
H
OH
OH
Glucose
OH
Glucose
H 2O
CH2OH
CH2OH
O
H
H
OH
H
H
OH
HO
H
H
O
Maltose
O
H
H
OH
H
H
OH
OH
When two mono-saccharides join we
get a di-saccharide.
The example here shows two
Glucose molecules linking up to form
Maltose.
Notice the dehydration synthesis
aspect of this reaction.
Where do we find maltose ?
Sucrose, table sugar, is a different disaccharide made from glucose and
fructose.
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Di-saccharides
What is the chemical formula for Sucrose or Lactose ?
CarboHydrates
How sweet are sugars ? Sweetness all depends on how well the
molecules trigger your sweet receptors on your tongue. .
Lugduname
~300,000 times sweeter
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CarboHydrates
What’s the deal with high fructose corn sugar (HFCS) ?
Many researchers claim that HFCS is the carbohydrate equivalent of
crack cocaine.
Researchers find that high-fructose corn syrup
prompts considerably more weight gain !
• 
• 
• 
Rats with access to high-fructose corn syrup gained
significantly more weight than those with access to
table sugar, even when their overall caloric intake
was the same.
In addition to causing significant weight gain in lab
animals, long-term consumption of high-fructose corn
syrup also led to abnormal increases in body fat
The normal molecule that regulates your appetite is
glucose. Evidence indicates that fructose does not
turn off your appetite but may stimulate it !
CarboHydrates
Wanna Supersize it ?
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CarboHydrates
!  When many monosaccharides link up we get a poly-
saccharide (a polymer of monosaccharides).
!  They Link together by dehydration reactions
!  Some polysaccharides are energy storage molecules
–  Starch in plants
–  Glycogen in animals
!  Some polysaccharides serve as structural compounds
–  Cellulose in plants
–  Chitin in exo-skeleton of insects/crustaceans
CarboHydrates
Starch granules in
potato tuber cells
Glycogen
granules in
muscle
tissues
Cellulose fibrils in
a plant cell wall
STARCH
Glucose
monomer
GLYCOGEN
CELLULOSE
Cellulose
molecules
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Cellulose in Plant Walls
Chitin in ExoSkeleton
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Chitin Technology
!  The nanofibers from chitin have
appealing physical and biological
features and have attracted intense
attention due to their excellent biological
properties related to biodegradability,
biocompatibility, antibacterial activity,
low immunogenicity and wound healing
capacity.
!  These nanofibrous materials have
tremendous potential to be used as
drug delivery systems, tissue
engineering scaffolds, wound dressing
materials, antimicrobial agents, and
biosensors.
CarboHydrates
!  We can eat and digest starch (from plants) and
glycogen (from animal muscle). They provide us
with a sugar source … glucose molecules.
!  Cellulose makes up the cell walls of plants. The
covalent bonds in cellulose are different then those
in starch and glycogen. Same goes for chitin….
!  We cannot break those bonds in cellulose and
chitin. Cows and termites have micro-organisms in
their gut to help with that process.
!  Thus grazing like cows will not get us any useful
carbohydrate supply !!
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