Biological Molecules
Bio
Do Now
Silently and independently:
Spend the next 10 minutes studying for the
quiz. The quiz will cover everything since our
last exam:
1.
2.
3.
Chemistry review
Water
Mono/disaccharides
Put away everything except a pencil and a cover sheet.
Once done
 Turn it in on my desk
 Pick up the handouts
 Tape the orange sheet in your LAB notebook
Today’s Announcements
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•
•
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Lab report: due Thursday NEXT TUESDAY
Lab makeups on Thursday
Reminder: no tutoring after school on Tuesdays
Pass back papers do NOT leave these in my room
please 
Warm-up
Can you…
Draw on the diagram where a glycosidic bond will form
and complete the diagram to show the disaccharide that
will be produced.
Can you…
Draw on the diagram where a glycosidic bond will form
and complete the diagram to show the disaccharide that
will be produced.
Review of Mono/disaccharides
The many forms of glucose:
Straight chain(linear) form
(least common/stable)
α-Ring form
Alpha-ring
(“OH” group is
below the ring)
β-Ring form
Beta-ring
(“OH” group
is above the
ring)
Cyclic Structure of Glucose: Rotation
Straight open-chain glucose is so reactive that
almost all molecules quickly rearrange their
bonds to form two new structures. These
structures are six-membered rings like those
below. The beta version is more stable.
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How are the two
monosaccharides joined?
Glycosidic Bond
Formed by
condensation
reactions
Recall: what molecule
is released when the
glycosidic bond
forms?
H2O
6C
12H
6O
6C
12H
6O
12C
22H
11O
How are the two
monosaccharides joined?
Glycosidic Bonds
+H2O
REDUCING SUGARS
What is a “reducing sugar”? How do we test for it?
Reducing sugars
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Can cause reduction chemical reactions
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Benedict’s Test: when a reducing sugar is added to
the reagent (copper sulfate dissolved in a base), it
reduces the reagent and makes a red-brown
precipitate
Include the following:
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ALL monosaccharides
SOME disaccharides
•
E.g. Maltose
SUCROSE is an important example of a disaccharide
that is NOT a reducing sugar
Which of the following would NOT
reduce Benedict’s Reagent?
A.
D.
B. Ribose
C.
E.
8 minutes- silent, independent work time
8 minutes- group work time
4 minutes- class review
Simple Sugar Practice Problems
Polysaccharides
Carbohydrates which are made from many linked monosaccharide
monomers form long chain-like molecules called polymers.
glycogen
starch
polysaccharides
- made from glucose
monomers
cellulose
Polysaccharides Derived from Glucose
There are three main types of naturally occurring
polysaccharides. They are cellulose, glycogen, and starch
that are of major importance.
What does cellulose do?
(Hint: recall cell structures)
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Polysaccharides
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Functions: storage, structure, recognition
Starch and glycogen are storage molecules
Chitin and cellulose are structural molecules
Cell surface polysaccharides are recognition
molecules
Starch
A plant storage polysaccharide
• Two forms: amylose and amylopectin
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Most starch is 10-30% amylose and 70-90%
amylopectin
Branches in amylopectin every 12-30
residues
Amylose has αβ(1,4) links and one
reducing end
Starch
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Amylose: compact, energetic spirals
of α-glucose molecules
Amylopectin: compact, branched,
energetic shapes of α-glucose
molecules
Polysaccharides Derived from Glucose
The unbranched structure of amylose.
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Polysaccharides Derived from Glucose
The branched structure of amylopectin.
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Polysaccharides Derived from Glucose
An important reaction during digestion is the hydrolysis
of starchy foods as shown below.
Starch is not soluble in cold water due to its large size and
will form a colloidal dispersion in hot water.
Starch solutions form a blue-black color in the presence of
free iodine.
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Polysaccharides Derived from Glucose
Glycogen is a carbohydrate polymer that is stored in the liver
and muscle tissues in animals. It is the energy-storage
carbohydrate in animals.
Glycogen has a structure similar to amylopectin (starch)
except that it is more highly branched with the a-1,6glycosidic linkages occurring more frequently along the
polymer chain.
Like amylopectin, glycogen gives a red-violet color with
iodine
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Carbohydrates: Summary
• Polysaccharides
– Storage:
• Plants: storage
• Animals: glycogen
• Polysaccharides
Structural:
Cellulose~ most abundant
organic compound;
Chitin~ exoskeletons; cell
walls of fungi; surgical thread
Polysaccharides Derived from Glucose
Cellulose, like starch and glycogen, is a glucosebased polymer.
The glucose units in cellulose are joined by -1,4glycosidic linkages instead of a-1,4-glycosidic
linkages.
There is extensive hydrogen bonding in cellulose.
Therefore, it’s a long strong chain of -Glucose
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Demonstration Time
Form human glucose polymers for:
• Amylose
• Amylopectin
• Cellulose
Cellulose
• Most abundant organic molecule.
• It’s very slow to decompose.
• Made of β glucose units.
• Every other β glucose is rotated through 180° - this makes the
chains straight, not coiled.
• Hydrogen bonding between monosaccharide molecules in the
chain gives strength.
• Hydrogen bonding between cellulose molecules cause bundles called
microfibrils to develop. These are held together in fibres.
• 20-40% of the plant cell wall.
• A cell wall will have several layers of fibres running in different
directions - gives great strength almost equal to steel.
• Provides support in plants and stops plant cells bursting.
• Freely permeable to water and solutes.
Figure 27.9 Two
representations of
cellulose. In the threedimensional model note
the hydrogen bonding
that links the extended
cellulose polymers to
form cellulose fibers.
Three-dimensional model of cellulose
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Which picture shows cellulose?
How are the polysaccharides formed?
Hint: Same type of reaction that forms a
disaccharide from monosaccharies
Condensation reactions
Which type of reaction (condensation or
hydrolysis) does this show?
Hydrolysis
Carb overload?
Let’s practice this all some
Sell that Saccharide Assignment
Review handout
When should this be due?
Options for saccharide
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Sell that Saccharide Example
Glucose is the most important of the monosaccharides. It is
an aldohexose and is found in the free state in plant and
animal tissue. Glucose is also known as dextrose and
grape sugar.
Glucose is a component of the disaccharides sucrose,
maltose, and lactose and is the monomer in the
polysaccharides amylose, amylopectin, cellulose, and
glycogen.
Glucose is the key sugar of the body and is carried by the
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bloodstream to all body parts.