Carbohydrates- IB Biology
Essential Idea- Compounds of carbon, hydrogen and
oxygen are used to supply and store energy.
Molecular Models Kits
• In your groups, you have a kit. We will be
making models with these over the next several
class periods.
• To begin, you will receive a handout with the
models to be made each day. I will instruct you
on which ones to build as we go through each
period. Please stay on task and do only the
ones required. You must get a stamp in order to
receive credit. No exceptions.
Review: Polymer Principles
•Four classes of macromolecules:
–Carbohydrates
–Lipids
–Proteins
–Nucleic Acids
•Polymers are made up of smaller parts called
monomers.
•Polymers are formed through condensation reactions.
•Polymers are broken apart through a hydrolysis
reaction.
General Information about Carbohydrates
•Carbohydrates are composed of C, H, and O
CH2O
(CH2O)x
C6H12O6
–“Carbo”-contains carbon
–“Hydrate”- Compound containing chemically
combined water.
•Often end in “-ose”
Is this a carbohydrate?
Is this a Carbohydrate?
Is this a carbohydrate?
Is this a Carbohydrate?
Carbohydrate Functions
–Immediate energy source for cells
–Energy storage for later use
–Raw material for building other
molecules
–Important role in cell membrane
recognition
About 17 KJ
of energy
per dry
gram. About
the same as
protein, but
½ that of
lipids
Monosaccharides
-one sugar unit (monomer)– are
the simplest carbohydrates
•Backbone of 3-7 carbon atoms
•Form ring structures in cells
•Characterized by sweet taste
•Have several polar -OH groups, so they are
soluble in water. (The many –OH groups can
hydrogen bond with water molecules)
Carbons
are
numbered
On your lab paper,
draw Glucose
Number the carbons
On your glucose, circle all the hydroxyl
(–OH) groups
Label the slight positive and slight negatives
on the highlighted O’s and H’s.
HINT: Remember polarity and unequal pull
of electrons
Using the molecular model kits,
build a model of glucose
Notice orientation of hydroxyl (OH) groups
Initial when complete
Glucose
• C6H12O6
• A product of
photosynthesis
• Main energy source
for cells- used in ATP
synthesis during
cellular respiration
Draw a water molecule hydrogen bonding
off of EACH highlighted H and EACH
highlighted O.
–Be sure you correctly orient the H’s and
O’s of the water molecule
–Show the hydrogen bond with a dotted line
(you should end up drawing 10 H2O’s)
Some example monosaccharides
•
•
•
•
Glucose
Ribose
Deoxyribose
Fructose
Deoxyribose and ribose are the building
blocks for nucleic acids.
Found in DNA
Found in RNA**
Fructose
• Found in fruits
• Used by plants to
attract animals to the
fruit for seed
dispersal.
Isomers
• Glucose and
fructose have the
same chemical
formula C6H12O6 but
different structural
arrangement of the
atoms (called
isomers)
The monosaccharides glucose, fructose, and
galactose are isomers.
• They contain the same atoms but in different
arrangements
All are C6H12O6
Disaccharides
• Di = 2
• Saccharide = sugar
Disaccharides are formed in
Condensation Reactions
http://kisdwebs.katyisd.org/campuses/MRHS/teacherweb/hallk/Teacher%20Docu
ments/AP%20Biology%20Materials/Chemistry%20of%20Life/Condensation%20
and%20Hydrolysis%20Reactions/conde_shell.html
2.3.1 Monosaccharide monomers are linked together by condensation
reactions to form disaccharides and polysaccharide polymers.
Disaccharide #1
Gosh! Isn’t it sweet?! The two glucose
molecules are holding hands.
Maltose: C12H22O11
(glucose + glucose –
H2O)
is a dimer of glucose. It
provides energy for
germinating seeds.
Maltose – between which carbon #’s
are the glucoses connected?
H2O
Using the molecular model kits:
BUILD MALTOSE
Notice orientation of hydroxyl (-OH) groups.
When finished with maltose
• Combine each group’s maltose’s to make
one long chain. Draw this. This is a
model of starch.
Sucrose (glucose + fructose) is a transport
form of sugar used by plants and harvested
by humans for food and used as table sugar.
Lactose (galactose and glucose) is
present in milk
Splenda: A modified
disaccharide
• Splenda is just a
modified form of
sucrose
• Notice the chloride
ions that replace
the hydroxyl
groups
Other sweeteners
Steviol
Complex Carbohydrates:
The Polysaccharides
•Polymers of hundreds
or thousands of
sugar monomers
–costs little energy to
build
–easily reversible =
release energy when
digested
Storage Polysaccharides
• What does it mean to store something?
Storage Polysaccharides
–Starch (polymer of glucose)
•Found in PLANTS
•Formed in roots and seeds as a
form of glucose storage
–Glycogen (polymer of glucose)
•Found in ANIMALS
•Formed in the liver and muscles as
a form of glucose storage
Structural Polysaccharides
•Cellulose (polymer of
glucose)
–Most abundant organic
compound on Earth
–Found in the cell walls
of plants
–Indigestible for most
animals due to
orientation of bonds
between glucoses
Structural Polysaccharides
•Chitin (polymer of modified glucose
units)
–Found in the outer coverings of
insects, crabs, and spiders
–Found in the cell walls of many fungi
Starch vs. Cellulose
Starch:
•Polymer of a-glucose
•Highly branched
•Has a 1-4 linkages
•Used for storage in
plants.
Cellulose
•Polymer of b-glucose
•Linear, does not branch
•Has b 1-4 linkages
•Most animals lack the
enzyme to break the b 14 linkages (so we can’t
digest it).
Digesting starch vs. cellulose
starch
easy to
digest
enzyme
cellulose
hard to
digest
enzyme
Cow
can digest cellulose well;
no need to eat other sugars
Gorilla
can’t digest cellulose well;
must add another sugar
source, like fruit to diet
Helpful bacteria
• How can herbivores digest cellulose so well?
– BACTERIA live in their digestive systems & help digest
cellulose-rich (grass) meals
Ruminants
ITell
eatme about
the rabbits,
WHAT!
again, George!
Summary of Carbohydrates
• Monosaccharides: Glucose, Fructose, Galactose,
Ribose
• Disaccharides: Lactose, Maltose, Sucrose
• Polysaccharides: Starch, Cellulose, Glycogen, Chitin
– Alpha (starch) & Beta (cellulose) linkages
– Chitin: exoskeleton, suture, and fungi (cell walls)
Starch Cut-Out Activity
1. Get in your lab groups, at each table
2. Each person pick up one color of the glucose
molecules, and 2 water drops.
3. Cut out the glucoses on the lines, and make
them even.
4. Attach the two glucoses with tape.
5. Write H, and OH on the water drops.
6. Affix the water below the O.
7. Attach all the glucoses at your table, with a
water in between each. Then connect the
entire class.