1. Carbohydrates
Biomolecule #1

2. Carbohydrates Structure
Compounds composed of carbon (C), hydrogen (H), and oxygen (O) are called carbohydrates. The monomer of a carbohydrate is a monosaccharide.
Carb = Carbon hydro = water Carbohydrate = carbon + water
general formula = CH2O; a ratio of 2 hydrogen to 1 oxygen like water H2O
ribose C5H10O5
glucose C6H12O6
sucrose C12H22O11
glycogen C24H42O21
Most commonly form ring shapes
but can also form straight chains.

3. Functions of Carbohydrates
Carbohydrates are a central energy source in organisms, as well as functioning as cellular support in plants, fungi, and animals.
Energy for metabolism (glucose)
Short term energy storage (glycogen/starch)
Structure: plants – cell wall (cellulose);
animals – exoskeleton (chitin)
Source of carbon for other molecules
Cell surface markers – cell identification

4. 1. Monosaccharide: Simple Sugars
Examples of Carbohydrates
1. Monosaccharide: Simple Sugars
Monosaccharides like glucose are the main source of energy in living things

5. 2. Disaccharides-2 sugars
2 monosaccharides linked together by a condensation reaction
Examples:
Sucrose – Table Sugar
glucose + fructose
Lactose – Milk Sugar
glucose + galactose
Maltose –
glucose + glucose

6. 3. Polysaccharides: Complex Carbs
Starch:
Used by plants to store excess glucose (energy);
Water soluble
Cellulose:
Used by plants as a cell wall building material (structure);
Water insoluble
Glycogen:
Used by animals to store excess glucose (energy);
Water soluble
Chitin:
Used by animals to create a hard outer covering;
Water insoluble

7.  Figure 5.8 About 80 cellulose molecules associate
Plant cells
0.5 m
Cell walls
Cellulose microfibrils
in a plant cell wall 
Microfibril
CH2OH OH O
Glucose monomer
Parallel cellulose molecules are
held together by hydrogen
bonds between hydroxyl
groups attached to carbon
atoms 3 and 6.
About 80 cellulose
molecules associate
to form a microfibril, the
main architectural unit
of the plant cell wall.
A cellulose molecule
is an unbranched 
glucose polymer.
Cellulose
molecules
Figure 5.8

8. Cellulose and starch are both polymers of glucose, but the bonds which hold them together are different
The difference in bonds creates differences in the molecules structure.
Structure = Function

9. Cellulose is difficult to digest
Animals can’t break the bonds between the glucose molecules –dietary fiber
Animals that eat plants have bacteria in their stomachs that can break the bonds of cellulose- allow their hosts to digest plants
Figure 5.9

10. Chitin, another important structural polysaccharide
Is a polymer of a form of glucose with an attached functional group
Is found in the exoskeleton of arthropods
(a) The structure of the
chitin monomer. O
CH2OH OH H NH C
CH3
(b) Chitin forms the exoskeleton
of arthropods. This cicada
is molting, shedding its old
exoskeleton and emerging
in adult form.
(c) Chitin is used to make a
strong and flexible surgical
thread that decomposes after
the wound or incision heals.
Figure 5.10 A–C

11. = S T R U C E F U N C T I O

12. 4. Other Uses for Carbohydrates
Cell surface markers – carbohydrates attached to parts on the cell membrane where they act to identify the cell
ABO blood groups
are identified by
carbohydrates on
their surface