Food, glorious food
All about biological molecules
Four basic biological molecules
Carbohydrates
Proteins
Lipids
Nucleic Acids (Which we will
look at later)
Monomers and Polymers
“Mono” means “one.” “Poly” means “many.”
Large biological molecules are made up of smaller ones.
Carbohydrates
Sugars: the basic building
blocks of complex
carbohydrates.
Polysaccharides: long chains
of sugars. Some include:
starch
cellulose (“fiber”)
glycogen
Sugars
Sugars are the
simplest
carbohydrates.
Sugars can be
single-ring
(monosaccharides)
or double-ring
(disaccharides).
Glucose, a monosaccharide
Notice the ringshaped
structure.
Glucose is an
energy source
for all
eukaryotic
organisms. Your
brain uses 30%
of all glucose
you consume.
Maltose, a disaccharide
Notice the two-ring structure. Anything look
familiar?
Maltose is made up of two glucose molecules.
Forming Maltose
Notice that we’re about to lose an H from one glucose and
an OH from the other. Both glucose molecules will link to
one oxygen atom.
Because water (HOH) is lost, this is called dehydration synthesis.
Sucrose, a disaccharide
Note the components: glucose and fructose.
Starch
Starch is a
polysaccharide
A starch molecule
is a long chain of
hundreds of
glucose molecules.
Starch
Here is a model of starch (also called amylose). Notice
that dehydration synthesis happens here, also.
Cellulose
Here is a model of cellulose. What do you see here that was
different in starch?
The difference is small, but crucial.
Starch and Cellulose
See it now? That’s all it takes to make starch digestible
and cellulose (“fiber”) indigestible to humans.
Lipids
Lipids are fats,
waxes, and oils.
Lipids are made up
of fatty acid
chains and
glycerine
molecules.
Lipid molecule structure
The head of a
lipid molecule may
be polar,
attracting water.
Fatty acids,
being nonpolar, repel
water.
Saturated vs. Unsaturated
A side-by-side comparison of a saturated (hydrogenated)
and a monounsaturated fatty acid.
Saturated vs. Unsaturated
Saturated fatty
acids pack
together neatly,
making fats that
are solid at room
temperature.
Saturated vs. Unsaturated
The bent chains of
unsaturated fats
do not fit
together neatly.
Unsaturated fats
are liquid at room
temperature.
Thinking question
Shortening and
margarine labels
often brag that
their products are
made with healthy,
unsaturated
vegetable oils. So
why are they solid
at room
temperature?
Hint: Check the ingredients. What does “hydrogenated” mean?
Proteins
Egg whites are
made up of a
protein called
albumin.
Like all proteins,
albumin is
composed of
thousands of
amino acids.
Protein
Proteins are
polymers.
Proteins are long
chains of amino
acids.
Amino Acids
An amino acid has
three critical
parts:
amine group
carboxyl (acid)
group
R group (side
chain)
Proteins
As you can see, it takes many, many amino acids to
make up a protein such as albumin.
Proteins
Amino acids link together with peptide bonds.
As you can see, peptide bonding is a type of dehydration
synthesis.
An amino acid chain folds to form a protein.
Two types of proteins:
Structural proteins are used to build fibers
and tissues.
Enzymatic proteins take part in chemical
processes.
Recap
Starches and other polysaccharides are long
chains of sugars.
Proteins are made up of amino acids.
Lipids (fats, waxes, oils) are made up of
fatty acids and glycerol molecules.