AP Biology
Dr. Solis
Carbohydrates serve as fuel and
building material
Carbohydrates
Polymers of Sugars
Disaccharides
(double sugars)
Polysaccharides
(macromolecules)
Sugars
Monosaccharides
(simple sugars)
Carbohydrates
 Monosaccharides – simple sugars
Carbohydrates
 Disaccharides – double sugars
Carbohydrates
 Polysaccharides – polymers composed of many sugar
building blocks
Remember: Sugars are Carbs!
 Sugars are carbs
 Most names for sugars end in ose
 Glucose, fructose,
 Monosaccharides generally have molecular formulas
that are some multiple of the unit CH2O
Sugars? Nutritious?
 Glucose is a monosaccharide
 Is a major nutrient to the cell
 Important for: Cellular respiration
 Cellular respiration: Cells extract
energy in a series of reactions made
possible by glucose
 The carbon skeleton of glucose lays
a foundation for other the synthesis
of other molecules (amino acids,
fatty acids)
Disaccharide
 Disaccharide consists of two monosaccharides joined
by glycosidic linkage.
 Glycosidic linkage: simply – the dehydration
reaction formed by the molecules forming a covalent
bond.
Lactose is a disaccharide in
milk.
Maltose is a sugar in beer.
Sucrose is table sugar.
Polysaccharides
 Polysaccharides – macromolecules (a few hundred to a
few thousand monosaccharides joined by glycosidic
linkages.
 Serve as structures and building material for cells and
organisms
Polysaccharides
 Some are stored for
later use
 These are things like
‘starch’ in plants
 Stockpiling of surplus
glucose
 Sugar can be
withdrawn later
through hydrolysis
 Potatoes, grains, corn,
rice – starch in the
human diet
5.2 – Part 2 Important
Polysaccharides
 Review: Plants store sugar in the form of starch.
 Starch is a polysaccharide
 Human diets are made up mostly of starch.
Important Polysaccharides
 Glycogen – A polymer of glucose
 Animals (including humans and other vertebrates) store
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glycogen in liver and muscle cells
Hydrolysis in these cells release glucose when the demand
for sugar increases
Glycogen is stored; but not for long
In humans, glycogen is depleted in about a day unless it is
replenished.
Gives the animal much needed fuel when none other is
available.
How would this be a concern for people on a low-carb diet?
Glycogen has
30,000 glucose
units
Structural Polysaccharides
 Polysaccharides are also
important because:
 Organisms can build
strong materials from
them
 Cellulose is a
polysaccharide
Structural polysaccharides
 Cellulose is important
because:
 A major component of
the cell walls that
enclose plant cells
 Globally, plants produce
almost 100 billion tons of
cellulose per year.
 It is the most abundant
organic compound on
Earth
Cellulose Structure
 Cellulose is also a
polymer of glucose (like
starch)
 But it differs in its
structure
 In starch - all monomers
are in the same
orientation
 But in cellulose, every
other beta glucose
monomer is upside down
Cellulose
 In plant cell walls,
cellulose molecules held
together in a parallel way
are grouped into units
called microfibrils
 Cable like structures –
that are very strong
Cellulose
 Cellulose is the major
component of paper and
the only component of
cotton
Cellulose
 Normal enzymes are
unable to hydrolyze the
linkages in cellulose
 Most organisms cannot
digest cellulose
 Humans cannot digest
cellulose – so it passes
through our body
without being broken
down.
What animals can you name that can digest cellulose?