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
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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
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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
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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.
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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.
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Amino Acids amino acids that our bodies cannot synthesize are
called essential amino acids. These amino acids must be obtained by
eating.
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Amino Acids See page 118-119 in Nelson 12 There are 20 amino
acids in total. Notice the amine group (NH 2 or NH 3 + ) and the
carboxylic acid group (COOH, COO - ) on each amino acid.
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Amino Acids Line Drawings Notice the amine group (NH 2 or NH 3
+ ) and the carboxylic acid group (COOH, COO - ) on each amino
acid.
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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
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Formation of proteins from amino acids The first diagram shows
glycine reacting with alanine. The second diagram shows a few
repeats of amino acids.
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eventually enough amino acids link up to form a protein This is
called the primary protein structure
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Chiral Molecules
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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 2- dimensional sheet.
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The tertiary structure developing from the secondary and
primary protein structure.
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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 sub- units.
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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.
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Polymers of Sugar Carbohydrates have the formula C x (H 2 O) y,
which explains the derivation of the name hydrated carbon Glucose
is C 6 H 12 O 6 or C 6 (H 2 O) 6 is a simple sugar called a
monosaccharide.
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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)
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Monosaccharide structure This shows monosaccharides in their
more correct ring structures.
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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
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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.
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Polysaccharides The three most common polysaccharides are
starch, cellulose and glycogen.
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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.
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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.
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Nucleic Acids
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Fats and Oils Fats and oils are triglycerides which are esters
formed from an alcohol (glycerol) and long- chained 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
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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.
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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
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Saturated vs. Unsaturated Fats
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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.
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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.
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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.