Proteins, Carbohydrates and Fats
Learning Goals
 Student will be able to:
1) Understand that the building blocks of living
organisms are polymers
2) Explain the formation of proteins, simple
carbohydrates and fats from biological monomers
Success Criteria
 Students will be able to:
1) explain how proteins are constructed from amino
acids through a peptide bond (amide link)
2) explain how carbohydrates such as starch and
cellulose are created from simple sugars and
disaccharides.
3) explain how fats and oils are created from
triglycerides and fatty acids
Natural Polymers
 biological macromolecules – proteins, carbohydrates,
nucleic acids, fats and lipids of high molecular mass
 have a variety of physical and chemical properties
 the smaller monomers (amino acids, simple sugars,
glycerol and fatty acids) tend to be soluble which
allows them to be transported in our blood.
 the polymers are solids and form the structures of our
body
Proteins – Natural Polyamides
 proteins make up about one half of our dry body
weight – muscles, skin, cartilage, tendons, nails and
protein molecules like hemoglobin and enzymes.
 All proteins are constructed from the same set of
monomers called amino acids.
 there are 20 amino acids (see the diagram). You will
need to understand these in more detail in Biology.
 As the name suggests amino acids contain two
functional groups amines and carboxylic acids.
Amino Acids
 note the amine
group and the
carboxylic acid
group in the
generalized amino
acid structure
above
Find the amine and carboxylic acid
functional groups in these 8 simple
amino acids.
Amino Acids
 amino acids that our
bodies cannot
synthesize are called
essential amino
acids. These amino
acids must be
obtained by eating.
Amino Acids
 See page 118-119 in
Nelson 12
 There are 20 amino
acids in total.
 Notice the amine
group (NH2 or NH3+)
and the carboxylic
acid group (COOH,
COO-) on each
amino acid.
Amino Acids
 Line Drawings
 Notice the amine
group (NH2 or
NH3+) and the
carboxylic acid
group (COOH,
COO-) on each
amino acid.
Formation of proteins from amino acids
 The carboxylic acid group
of one amino acid links
with amine group of
another amino acid in a
condensation reaction.
 The link is called a peptide
bond, however you learned
it earlier as the amide link.
 A dipeptide is formed
from the reaction of two
amino acids
Formation of proteins from amino acids
 The first diagram shows glycine reacting with
alanine.
 The second diagram shows a few repeats of amino
acids.
…eventually enough amino acids
link up to form a protein
This is called the primary
protein structure
Chiral Molecules
Protein Structure
 Primary Structure of Proteins – a polymer chain
formed by linked amino acids (see previous page)
 Secondary Structure of Proteins - if you noticed
from the chart of 20 amino acids that some have polar
and non-polar groups. These groups attract each
other (Van der Waals, H-bonds, etc.) to form either an
alpha helix (like DNA) or a beta-pleated 2dimensional sheet.
 The tertiary structure developing from the secondary
and primary protein structure.
Protein Structure
 Tertiary Structure of Proteins – the alpha helix and
pleated sheets attract each other causing the protein to
coil into “twisted ribbon” shapes. Proteins like
hemoglobin and hormones twist into tight “balls” or
“globular shapes so that they can pass through narrow
blood vessels.
 Quaternary Structure of Proteins – several tertiary
structures attract each other to form complexes.
Hemoglobin is formed from 4 tertiary protein subunits.
Denaturing of Proteins
 Denaturing is the breakdown of proteins caused by the
breaking of weaker bonds like Van der Waals forces
and H-bonds.
 Denaturing is caused by heating, change of pH,
addition of organic solvents (acetone, formaldehyde,
etc.)
 The function of the protein is severely disrupted –
bonds within the tertiary and secondary structures of
proteins is lost along with its 3-D structure.
Polymers of Sugar
 Carbohydrates have the formula Cx(H2O)y, which
explains the derivation of the name – “hydrated
carbon”
 Glucose is C6H12O6 or C6(H2O)6 is a simple sugar called
a monosaccharide.
Monosaccharide structure
 Monosaccharides
fall into 2 groups –
aldoses like glucose
because they have an
aldehyde group
(like glucose) and
ketoses because
they have a ketone
group (like fructose)
3 simple monosaccharides often found in
food. Notice that they have 6 carbons
(hexoses). Some monosaccharides have 5
sugars (riboses)
Monosaccharide structure
 This shows monosaccharides in their more correct ring
structures.
Disaccharides
 Disaccharides form when
monosaccharides combine
in a condensation
reaction.
 Table sugar is sucrose.
 Enzymes are used to break
down disaccharides in the
body. people who lack the
enzyme lactase cannot
break down the sugar
lactose
Polysaccharides
 Carbohydrates can be
subdivided into three
levels based on their
number of saccharide
molecules – mono-,
di- and
polysaccharides.
 Polysaccharides are
long polymer chains
of saccharides.
Polysaccharides
 The three most
common
polysaccharides are
starch, cellulose
and glycogen.
Starch and Glycogen
 Starches are the main energy




storage for plants such as rice, corn
or wheat (seeds) and potatoes or
carrots (tubers)
Starch is a polymer of glucose.
Glycogen is produced by animals as
a ready energy source
Glycogen is stored in muscles and
the liver.
Our digestive tracts have enzymes
that can break down starch and
glycogen.
Cellulose
 Cellulose is also a polymer of
glucose but there are different
linkages.
 Cellulose is produced by plants
for support. It is insoluble.
 Humans cannot digest cellulose –
we often refer to it as dietary fiber
 Animals such as ants and cows
digest cellulose with the aid of
bacteria in their guts.
Nucleic Acids
Fats and Oils
 Fats and oils are triglycerides
which are esters formed from an
alcohol (glycerol) and longchained carboxylic acids called
fatty acids.
 Glycerol is an alcohol with 3
carbons and 3 –OH groups.
 3 fatty acid chains are attached
to the glycerol – they may or
may not be the same fatty acid –
usually they are different
Forming Fats
 Fatty acids usually have
even numbers in the
body as they are formed
from successive
addition of ethanoic
acid molecules in a
cyclic reaction.
 Fatty acids (which are
long chain carboxylic
acids) then react with
glycerol (a polyalcohol)
to form fats by creating
an ester link.
Lipids
 Lipids are formed when




glycerol (a polyalcohol) reacts
with fatty acids
Ester bonds are formed
between the alcohol group of
glycerol and the carboxylic acid
group of the fatty acid.
Monoglyceride = glycerol + 1
fatty acid
Diglyceride = glycerol + 2 fatty
acids
Triglyceride = glycerol + 3 fatty
acid – most fats fall into this
category
Saturated vs. Unsaturated Fats
Saturated vs. Unsaturated Fats
 If there are double bonds




somewhere along the
carbon chain of a fatty
acid, it is unsaturated.
If there are no double
bonds, the fatty acid or fat
is saturated.
unsaturated fats are mostly
better for your health
because they are easier for
our bodies to digest.
Mono-unsaturated fatty
acid is a fatty acid that has
just one double bond.
Polyunsaturated fatty
acids have multiple
double bonds.
Saturated vs. Unsaturated Fats
 The cis-isomer introduces a
kink into the molecule that
prevents the fats from
stacking efficiently as in the
case of fats with saturated
chains. This decreases
intermolecular forces
between the fat molecules,
making it more difficult for
unsaturated cis-fats to freeze;
they are typically liquid at
room temperature. Trans fats
may still stack like saturated
fats, and are not as
susceptible to
metabolization as other fats.
How are Hydrogenated Trans-Fats
Made?
 The process of hydrogenation forms saturated fats
(artificially) by blasting the polyunsaturated vegetable
oil with hydrogen atoms forming a trans-fat.
 This is called hydrogenation. A hydrogen atom is
bound to the backbone of the fat, making it more
stable and even solid at room temperature.
 This solid, creamy substance has an unnatural
chemical distribution rarely found in nature. In fact,
these fats are actually too stable and our body even has
trouble breaking them down.