Carbohydrates
Pages 90 - 101
What is a Carbohydrate?
• Encompasses the polymer
polysaccharide (large molecule) made up
of monomers (small molecules) called
monosaccharides (one-sugar)
• Poly = Many
• Mono = One
• Saccharide = Sugar
Carbo-Hydrates?
• Carbohydrate chemical formula is generally
(CH2O)n
• n = the number of “carbon-hydrate” groups
• However, Carbohydrates are NOT carbon
atoms bonded to water atoms like the name
may sound!
• Instead, they are molecules with a Carbonyl
Group (=C=O) and several hydroxyl functional
groups (--OH), along with several to many
carbon-hydrogen bonds (C-H).
• This is even slightly confusing when viewing
the molecule, but the C is separating the 2Hs.
• H-C-OH
Carbon Hydrates
Carbohydrates = Sugars
• Sugars are essential for life
• They provide chemical energy in cells and
furnish some of the molecular building
blocks required for larger, more complex
molecules.
• Where do we find them?
• When should we eat them?
Why so many?
Numbering Your Carbs.
• The number of carbons vary within a
monosaccharide.
• They are numbered consecutively,
starting with the nearest end to the
carbonyl group
• Look at the three carbon sugars
(Called trioses) on page 91 for
numbering.
• The Pentose (5 carbon molecule)
ribose is found in nucleotides.
• Remember we numbered them from
right to left, starting at the carbonyl
group
What Carbs Look Like…
Polysaccharides
• Polysaccharides form when
monosaccharides are linked together
• The simplest Polysaccharide is when
two sugars link, called a disaccharide
• Simple sugars polymerize when a
condensation reaction occurs between
2 hydroxyl groups
• Look at page 93 where 2 glucose
become a maltose
• This polymerization occurs through a
process called Glycosidic Linkages
Many-saccharide
Starch
• When plants store their polysaccharides,
they store them as starches
• Basically a densely packed polysaccharide
• Page 94, table 5.1 show the different
polysaccharide structures
Different Polysaccharides 2 Know
• Starch- Storage of sugars in plants
• Glycogen- Storage of sugars in animals
• Cellulose- Makes up the cell wall of plants.
– The most abundant polymer on earth
• Chitin- Stiffens the cell wall of fungi and many
algae
– Very similar to cellulose
• Peptidoglycan- Found in bacteria cell walls
– The most complex polysaccharide
• Glycoprotein- used in cell recognition and cell
signaling
Chemical Evolution
• Even though they are the most plentiful
macromolecules on earth, it is very
unlikely the carbohydrates were the first
life forms
• They have virtually no templates for
forming base pairs or reproduction
• They lack functional groups
• Glycosidic linkages don’t catalyze very
well to release the needed energy
Carbohydrates as Energy
• Carbohydrates act as electron donors for
the redux reaction that releases energy
– The atom that receive an electron is redox
– The atom that loses an electron is oxidized
– (page 98-99) Read 1. & 2. on page 98
Function
• Used in building other molecules (Nucleic acids)
• Projects from th surface of the cell and displays
cells type and species
• Starch and Glycogen store sugars to be used
later to produce ATP
• Have reduced carbon atoms (C-H) that have
high free energy
• Chitin, cellulose, and peptidoglycan give
structural strength to the walls of cells