Download glucose - Y11-Biology-SG

Biological
Molecules
‘what you need to know!’
MONOMER – single repeating
units that……
……are joined together to form
POLYMER.
MONOMER
POLYMERISATION
POLYMER
Polymers
Monomers
Polysaccharides Glucose
Proteins
Amino acids
Lipids?
Glycerol &
fatty acids
CARBOHYDRATES
CARBOHYDRATES
MONOSACCHARIDES
DISACCHARIDES
POLYSACCHARIDES
MONOSACCHARIDES
- A single sugar unit
- Sweet and soluble
- Contain carbon, hydrogen & oxygen
- Classified according to the number
of carbons a molecule has:
-TRIOSE – 3 carbons
-PENTOSE – 5 carbons and
-HEXOSE – 6 carbons
MONOSACCHARIDES
Three common sugars share the same
molecular formula: C6H12O6. Because of their
six carbon atoms, each is a hexose. They are:
• glucose, the immediate source of energy for
cellular respiration
• galactose, a sugar found in milk
• fructose, a sugar found in honey and fruits.
MONOSACCHARIDES –
which is which?
MONOSACCHARIDES –
which formula?
Molecular formula – C6H12O6 or C3H6O3
or C5H10O5
Structural
formula –
Although galactose, glucose and fructose
share the same molecular formula (C6H12O6),
the arrangement of atoms differs in each
case. Substances such as these three, which
have
identical
molecular
formulas
but
different structural formulas, are known as
structural isomers.
Pentose and hexose sugars are drawn in two forms
straight chain forms
Ring forms
3D model
Carbon
Hydrogen
Oxygen
2D model
C6H12O6
Glucose: Going from chain to ring form
How the chain closes to form a ring in solution inside cells.
Observe the atoms involved (highlighted in colour).
GLUCOSE comes in 2 forms, according to
how the ring closes.
WARNING!
A single detail like this one makes all the difference.
The position of the OH group on C1
will determine the type of polysaccharide it will form
and in turn, the functions it will have in a cell. Remember this as
you study polysaccharides.
Here this H is
above
the carbon 1.
This is called
α (alpha) glucose.
Here this H
is below
the carbon 1.
This is called β
(beta) glucose.
Structural Isomers
Both these molecules are glucose.
Both have a molecular formula of C6H12O6.
But they are structurally different and will have
different functions in a cell.
Biological role of monosaccharides
As an energy source…..
•A large amount of energy is stored between the C-H bonds
•This is released to form ATP
•ATP is the energy currency of the cell
As building blocks…..
•Repeated glucose molecules build up; starch & glycogen
•Ribose (5C) forms part of RNA
•Deoxyribose (5C) forms part of DNA
•Vitamin C (ascorbic acid derives from glucose)
DISACCHARIDES
Two monosaccharides can be linked together to form a
"double" sugar or disaccharide. Three common
disaccharides:
sucrose — common table sugar = glucose + fructose
lactose — major sugar in milk = glucose + galactose
maltose — product of starch digestion = glucose + glucose
Although the process of linking the two monomers is
rather complex, the end result in each case is the loss of
a hydrogen atom (H) from one of the monosaccharides
and a hydroxyl group (OH) from the other. The resulting
linkage between the sugars is called a glycosidic bond.
The molecular formula of each of these disaccharides is
C12H22O11 (2 C6H12O6 − 1 H2O)
DISACCHARIDES
Two well-known examples: maltose (used in the making
of beer) and sucrose (table sugar)
Forming disaccharides: maltose
1. Two α glucose molecules meet.
2. The OH from C1 & H from C4 react to form a
molecule of water. This is called a condensation
reaction.
3. The C1 is joined to the C4 by the O left.
4. The bond between the two joined glucoses is called
glycosidic bond. In this case: α1,4 glycosidic bond.
Forming disaccharides: sucrose
1. An α glucose and a fructose molecule meet.
2. The OH from C2 in the fructose & the H from C1 in
the glucose react to form a molecule of water. This
is called a condensation reaction.
3. The C1 is joined to the C2 by the O left.
4. The bond between these two joined
monosaccharides is called glycosidic bond. In this
case: α1,2 glycosidic bond.
POLYSACCHARIDES
• Polymers with subunits of monosaccharides
• Made by repeated condensation reactions
• Normally thousands of monomers long
• Polysaccharides are not sugars
STARCH
CELLULOSE
GLYCOGEN
Starch
• Polymer of α-glucose.
• Plant storage polysaccharide.
• Made up of two types of substances:
1) Amylose
+
2) Amylopectin
Spiral structure of Amylose
Amylose
•Condensation reactions
between α glucose with 1-4
links.
•Formed from thousands of
condensation reactions that
form coiled springs.
Amylopectin
Mostly 1-4 links.
Some 1-6 links.
Amylopectin
• Condensation reactions
between α glucose (1-4 links).
• Coiled springs with a
branched structure are
formed (branches of 1-6 links).
1-6 links form
a branch structure
1-4 links form
a helical structure
Starch grains are a mixture of amylose & amylopectin
Starch is a polysaccharide
Starch it is a insoluble store of glucose
Starch is only found in plant cells,
the animal cells equivalent is called glycogen.
Glycogen
It has 1-4 links
and 1-6 links
the storage
polysaccharide in animals
found in liver and
muscles
Cellulose
• Present in plant cell walls.
• It is a polymer of β glucose.
• It is formed by parallel chains.
• Has a slow decomposition.
• It is mechanically very strong.
• It is the most abundant organic
molecule on the planet.
Cellulose
• C1-4 links make up this polysaccharide.
• When the C1 and react, one glucose molecule needs
flips through 180o.
• This structure has H bonds holding the parallel
chains together.
• This subtle difference makes cellulose so strong
Structural differences between starch,
glycogen and cellulose
CAN YOU STATE THREE
DIFFERENCES BETWEEN
STARCH AND CELLULOSE?
CAN YOU STATE THREE
DIFFERENCES BETWEEN
STARCH AND GLYCOGEN?
AND BETWEEN GLYCOGEN AND
CELLULOSE?