Chem 100 Unit 5 Biochemistry
Lipids
Lipids are large molecules that are not soluble in water. They are soluble in nonpolar solvents.
The most common lipid is fat. But steroids and fat soluble vitamins are also classed with lipids.
Function of lipids
Important part of almost all cells
Found in cell membranes and brain and nervous tissue
Long-term energy storage in the body
Serve as insulation of body’s organs against temperature change and shock
Fats and oils generally provide 9 Cal/g of energy in our diet. These can be converted to
glucose.
Classes of Lipids
Triglycerides
Phosphoglycerides
Sphingolipids
Glycolipids
Steroids
Fat Soluble Vitamins
The first four classes of lipids have at least one fatty acid
Fatty Acids
O
HO
C
C
H2
H2
C
C
H2
H2
C
C
H2
H2
C
C
H2
H2
C
C
H2
H2
C
C
H2
H2
C
C
H2
H2
C
C
H2
H2
C
CH3
Will be simplified to:
O
HO
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1
Fatty Acid
Saturated Fatty Acid Example: Stearic acid No double bonds
O
HO
Monounsaturated fatty acid Example: oleic acid 1 double bond cis
form puts a bend in the molecule
Melting
point
69oC
solid @RT
Source
14 oC
Liquid @
RT
from olive
oil
pig fat
O
C
HO
43 oC
Monounsaturated fatty acid1 double bond trans form no bend
OH
C
O
Polyunsaturated fatty acid 2 double bonds Example linoleic acid
-5 oC
liquid @
RT
OH
C
O
Polyunsaturated fatty acid 3 double bonds Example linolenic acid
-11 oC
liquid @
RT
OH
C
O
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Saturated fatty acids stack together very easily
so it is easy to form a solid so they are solid at
room temperature. Saturated fatty acids raise
the cholesterol in your blood.
O
HO
O
HO
O
HO
Cis Unsaturated fatty acids do not stack together
well at all so they tend to be liquids at room
temperature. Vegatable oils contain cis fatty
acids. The double bond tends to oxidize and the
oil becomes rancid. The oil can be
“hydrogenated” and then become more
saturated and resist oxidation.
HO
C
O
O
C
O
HO
C
HO
OH
C
O
OH
C
O
OH
C
O
Trans fatty acids stack together well like unsaturated fatty
acids. When cis fatty acids are hydrogenated some of the
cis double bonds become trans. Trans fatty acids raise the
levels of low density lipoproteins (LDL) in the blood
LDL contain cholesterol which accumulates in the arteries
leading to heart disease. These fatty acids are found in
milk, fried foods, butter, cookies, crackers and vegetable
shortening. Many restaurants are using less trans fatty
acids. You should limit these fatty acids in your diet
Hydrogenation
H
H
H
+ H2
OH
Catalyst
H
C
O
+
O
C
HO
O
HO
Both the saturated fatty acid and the trans isomer
are produced
Glycerol
H2C
OH
HC
OH
H2C
OH
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This is a triglyceride with three
unsaturated fatty acids that are cis.
The bend in the molecules make it
difficult for them to stack together and
form a solid
O
C
H2C
O
HC
O
O
C
O
H2C
O
C
O
H2C
OH
HO O
HC
OH
HO O
H2C
OH
HO
- 3 H2O
O
H2C
O O
HC
O O
H2C
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O
4
Saponification
The hydrolysis of a triglyceride with a strong base produces a molecule of glycerol and 3 salts of a
fatty acid
O
H2C
O O
HC
O O
O
H2C
+ 3 NaOH
O
3
Na+
+
O-
-
H2C
OH
HC
OH
H2C
OH
In this reaction glyceryl tristearate is hydrolyzed by sodium hydroxide to form sodium stearate
Soap
O
Na+
-
O-
Soap is the salt of a fatty acid. It is unique because it has an ionic end and a long tail that is
nonpolar. So it has both a water loving (hydrophilic) part and a water hating (hydrophobic)
part.
Na +
The polar “head” will be attracted to water.
The nonpolar “tail” will be attracted to oil.
This is how soap is able to wash away oil from
skin or dishes.
Oil droplet
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Non polar ends of molecules at the center
are attracted to the circular nonpolar
material. The negativiely charged groups
on the surface are attracted to the water
molecules
H
H
H
H
H
O
H
O
H
O H
O
H
O
H
O
H
H
H
O
H
H
O
H
H
O
H
H
O
H
H
O
H
H
H
H
O
H
H
O
H
H
H
H
O
H
H
H
O
H
O
H
H
H
O
O
O
A soap Micelle
Glycolipids
OH
O
H2C
HN
O
HO
CH
HO
O
C
H
OH
OH
Phosphoglycerides
CH3
H3C
N
CH3
O
CH2
O
H2C
O
P
O
CH2
O
H
C
H
C
O
C
O
C
O
H
Sphingolipids
CH3
H3C
N
CH3
OH
H2
C
O
C
H2
O
P
O
H2
C
O
CH
HN
O
C
Glycolipids Sphingolipids and phosphoglycerides have two hydrophobic “tails” and a
hydrophilic head.
One of the major functions of Sphingolipids and phosphoglycerides is forming the “lipid bilayer”
of cell membranes. Glycolipids are found in brain and nervous tissue.
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Hydrophilic head
Several of these molecules line up with each other so that on the
inside is a hydrophobic region, and on the outside are
hydrophilic regions.
Hydrophobic tail
These two layers of lipids form a
“lipid bilayer” of the cell
membrane. Water can be on
either side of the membrane but
not on the inner part of the
membrane. The parts that stick
through are proteins that only let
certain molecules through.
Another major function of sphingolipids is in forming the myelin sheath which protects or
insulates nerve tissue.
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Steroids
O
HO
O
H
H
H
OH
H
H
H
HO
O
cholesterol
cortisone
O
OH
H
H
H
H
HO
O
testosterone
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H
H
estrone
8
Carbohydrates
Carbohydrates make up ______% of our diet. They represent a major part of all of the matter on earth
that is organic.
Carbohydrates contain _______ functional groups
Carbohydrates are produced in the process called _________:
__________ + ____________ + energy
(CH2O)n + ________
n is usually 3, 4, 5, or 6.
Function of Carbohydrates
In animals and humans
1.
2.
3. Generally carbohydrates provide _____Cal/g of energy
In Plants
1.
2.
3.
3 Types of Carbohydrates
Monosaccharides
Disaccharides
Polysaccharides
Structures
Monosaccharides
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2 Types:
H
O
CH2OH
C
H
C
OH
H
C
OH
H
C
O
C
OH
CH2OH
CH2OH
_____________________
______________________
2 significant isomers:
H
O
H
C
O
C
HO
C
H
H
C
OH
H
C
OH
HO
C
H
OH
C
H
H
C
OH
OH
C
H
H
C
OH
CH2OH
CH2OH
_______________________
________________________
3 important monosaccharides:
CH2OH
H
O
H
C
O
C
C
O
HO
C
H
H
C
OH
H
C
OH
H
C
OH
HO
C
H
H
C
OH
H
C
OH
H
C
OH
H
C
OH
H
C
OH
H
C
OH
H
C
CH2OH
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CH2OH
OH
H
10
Glycosidic Linkage
Hemiacetal bond
H
H
O
H
O
C
H
C
H
C
OH
HO
C
H
C
OH
C
O
H
C
OH
H
HO
C
H
HO
C
H
C
OH
HO
C
H
H
C
OH
H
C
OH
H
C
OH
H
C
OH
H
C
OH
H
C
OH
H
C
H
H
OH
H
The Hemiacetal bond
H
R
H
R
C
O
+
H
O
R
C
O
R
1
OH
1
Ring Structures
CH2OH
CH2OH
H
C
O
C
O
H
H
O
H
C
C
C
OH
H
OH
OH
H
H
C
OH
H
OH
C
C
C
C
H
OH
H
OH
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H
11
α and β forms of glucose
CH2OH
CH2OH
C
C
O
H
OH
H
C
C
OH
H
H
OH
H
C
H
OH
O
C
OH
OH
C
C
C
C
H
OH
H
H
________________________
H
OH
_______________________
Glucose is a _________________sugar
These differ only in the position of one hydroxyl group. But starch foods like pasta, bread, and rice
contain the ______form. We can digest these foods. The _______form is found in wood and cellulose
which we cannot digest. We have an enzyme that can digest the ____form but not the ____form.
α and β forms of galactose
CH2OH
CH2OH
C
C
O
OH
OH
H
C
C
OH
H
H
O
OH
OH
H
C
H
C
OH
OH
H
C
C
C
C
H
OH
H
H
_____________________
H
_________________________
Galactose is a ____________________sugar.
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α and β forms of fructose
CH2OH
O
CH2OH
C
H
C
H
OH
OH
CH2OH
O
OH
C
H
C
H
OH
CH2OH
C
C
C
C
OH
H
OH
H
______________________
_____________________
Fructose is a ____________________sugar.
Reducing Sugars:
These are sugars that contain a free carbonyl group are known as reducing sugars. The oxygen
in the carbonyl can react with certain reagents that give a positive test for reducing sugars.
Benedict’s solution is one of those reagents. The three monosaccharides are reducing sugars.
Lactose and maltose are reducing sugars. Sucrose and the polysaccharides are not. But if those
non reducing sugars are hydrolyzed into monoscaccharides, then the product is a reducing
surgar. This reaction is also responsible for the browning of certain foods during the cooking
process.
Function of the monosaccharides glucose, galactose, and fructose.
1. Fructose
Found in fruits and honey
Sweeter than sucrose or glucose and other carbohydrates
Converted to glucose in the liver
2. Galactose
Obtained from the disaccharide lactose found in milk
Found on surfaces of cell membranes
3. Glucose
Main carbohydrate in our blood
Found in honey and fruit
It is the major building block of polysaccharides
The brain uses only glucose for fuel, but the brain does not store glucose so the
blood glucose level must be maintained. Below 25% of normal, coma can occur.
This could be caused by an overdose of insulin
Disaccharides
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The three important disaccharides are maltose, lactose and sucrose.
Function
Maltose
Obtained by hydrolyzing starch
Used in cereals, candy, and brewing beverages
Lactose
Found in milk (human milk 6-8% , cow milk 4-5%)
Some people do not have the enzyme needed to hydrolyze
lactose and are considered lactose intolerant.
Lactose is the least sweet sugar
Sucrose
Mostly obtained from sugar cane (20% sucrose) and sugar beets (15%
sucrose)
Commonly referred to as “table sugar”.
In the year 1700 Americans consumed _____lbs of sugar per person per
year. In 1780 it was______lbs. In 1960 it was_______. By 2005 Americans
consumed ________lbs per person pear year of sugar and other sweeteners!
Structure
Each of these disaccharides are made of 2 monosaccharides held together by a
glycosidic or ether bond.
glucose + glucose
glucose + galactose
glucose + fructose
maltose
lactose
sucrose
CH2OH
CH2OH
CH
OH
C
H
O
H
C
C
H
OH
CH
C
O
OH
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H
C
H
O
OH
H
C
C
H
OH
OH
C
H
14
CH2OH
C
O
H
H
H
C
C
OH
H
C
C
H
OH
OH
O
CH2OHO
C
H
C
H
OH
CH2OH
C
C
OH
H
CH2OH
CH
CH2OH
O
H
C
OH
OH
H
C
C
H
OH
CH
H
H
C
C
O
O
OH
C
OH
H
C
C
H
OH
H
Polysaccharides
Starch
Cellulose
Glycogen
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Starch
Function
1. Storage of carbohydrates in plants
2. Provides about 50% of the glucose in our diet
a. Found in rice, wheat, beans, breads, cereals, and potatoes.
Structure
Starch is made of 80% amylopectin and 20% amylose
__________________ a straight chain that coils up. It tends to be unbranched
chains of 200-4000 α-D-glucose units. Molecules are connected by α-1,4gylcosidic
bonds.
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__________________ is a branched structure of glucose units. A branch occurs every 25 glucose units
or so. Molecules are connected by α-1,4-gylcosidic bonds. . Branches are connected
by α-1,6-gylcosidic bonds.
Cellulose
Function
Structural Material in plants. It is found in the cell walls of plants.
Cotton is almost all cellulose. Wood and paper contain a great deal of cellulose
It is the fiber in our diet.
Structure
Cellulose does not coil like amylose. It forms in parallel rows.
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Cellulose
. Molecules are connected by β-1,4gylcosidic bonds. Our bodies have
enzymes that can hydrolyze the α-1,4gylcosidic bonds of starch but we do not have
enzymes to hydrolyze the β-1,4gylcosidic bonds found in cellulose . It is still and
important part of our diet.
The rows are held together by hydrogen bonds and then bundles of the rows of chains
are twisted into fibers. Cellulose is the fiber in our diet
Glycogen
Function
The way carbohydrates are stored in humans and animals
Helps maintain glucose level in blood and muscle tissue
Stored in the liver and in muscles
Structure
Glucose molecules are connected by α-1,4-gylcosidic bonds.
Branching occurs every 10-15 units. So there is much more branching
in glycogen than in amlopectin
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Glycogen
Amylopectin
Why is branching different?
Tasting Sweetness
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Sweetness scale
galactose
glucose
fructose
lactose
maltose
sucrose
sucralose (slpenda)
Aspartame (nutrasweet)
Saccharin (sweet’n low)
Standard (Sucrose = 100)
30
75
175
16
33
100
60,000
18,000
45,000
Metabolism
Proteins
Enzymes
DNA
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Proteins
Proteins are polymers of amino acids in a particular arrangement that allows them
to perfom a particular biological function.
Amino Acids
O
H 2N
CH C
OH
R
Amino Acids are amphoteric
O
+H N
3
Amino Acids are Zwitterions:
CH C
O-
R
Amino Acids act as buffers
O
O
+H N
3
CH C
+H
O-
+
R
3N
CH C
OH
R
H+
O
+H N
3
CH C
R
O
O-
H2N
+ OH
-
CH C
O-
R
Only the L-isomers of amino acids are found in nature
Amino Acids have a very high molecular weight. Insulin has a weight of 5,700
hemoglobin a weight of 64,000 and some virus proteins have a weight of 40 million
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Amino Acid Names and Structures
*denotes essential(must be obtained from your diet)
Amino Acid
Hydrophobic (water
fearing) nonpolar
Alanine
Amino Acid
Hydrophilic (water
loving) polar
Valine*
Serine
O
H 2N
CH C
OH
CH C OH
CH C
CH C
H2N
OH
CH C
OH
OH
H2N
CH C
C
OH
O
O
H2N
CH C
OH
H2N
CH2
CH2
CH2
O
C
NH2
OH
O
H2N
CH C
OH
H2N
O
H2N
CH C
CH C
CH2
CH2
HN
CH CH3
CH3
CH2
Lysine*
Histidine*
CH3
Isoleucine*
Phenylalanine*
O
CH C
Cysteine
O
OH
H2N
CH C OH
H2N
CH C
OH
H2N
CH C
N
SH
CH3
The 10 amino acids with a
*denotes essential(must be
obtained from your diet).
The other 10 amino acids
can be synthesized in the
body from lipids or
carbohydrates.
OH
CH2
CH2
CH2
NH2
O
O
CH2
CH CH3
OH
CH2
OH
CH OH
CH2
H2N
O
OH
O
C
OH
Threonine*
O
OH
CH C
CH2
C
Proline
O
Glutamate
HN
Leucine*
OH
Glutamine
CH2
CH2
H
CH2
O
O
OH
O
OH
Tryptophan*
CH C
Glycine
Aspartate
CH2
CH3
Methionine*
H2N
H2N
CH CH3
CH3
H2N
O
O
H 2N
O
NH
Asparagine
(hydrophilic)
Tyrosine
O
H2N
CH C
H2N
OH
CH C
CH2
O
OH
H2N
CH C
OH
CH2
CH2
CH2
C
Arginine*
O
CH2
O
NH
OH
OH
C
NH
NH2
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Peptide bonds.
The bond that holds amino acids together in a chain which becomes a protein is
called the peptide bond or amid linkage. This bond is between the amino group of
one amino acid and the carboxyl group of another amino acid
O
H2N
O
CH C
+
OH
H2N
CH3
CH C
O
OH
H2N
CH3
CH C
O
H
N
CH3
2 amino acids
CH C
OH
CH3
dipeptide
with amide linkage
If a polypeptide chain is hydrolyzed the products are amino acids
Types of proteins
Fibrous protein
Long, linear, polypeptide chains that are side by side
Insoluble in water
Structural proteins
Examples: hair, muscle
Globular Proteins
Polypeptide chains folded up
Attracted to water
These proteins can be moved from one place to another
Examples: enzymes, hemoglobin, insulin, antibodies
Structure: There are 4 levels of protein structure
Primary structure
The sequence/order of amino acids
Maintained by peptide bonds
Other levels of structure depend on primary structure
O
H2N
CH
R
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C
O
H
N
CH
R'
C
O
H
N
CH
R''
C
O
H
N
CH
R"""
C
O
H
N
CH
C
OH
R''''
23
Here is a peptide chain of 6 amino acids
O
H 2N
CH C
O
H
N
CH3
CH C
O
H
N
CH2
CH C
O
H
N
CH2
CH2
CH C
CH2
O
H
N
CH C
H
CH2
N
CH2
C
O
H
N
CH C
OH
CH2
CH2
O
S
NH
NH
C
OH
CH3
NH
NH2
Secondary Structure
The folding or other repeating pattern of the peptide chain.
Maintained by hydrogen bonds
Beta Pleated Sheet
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Alpha Helix
24
Alpha Helix
Beta Sheet
Examples are hair and wool and muscle
Example is silk
Globular proteins
Contain a combination of secondary structures giving rise to their tertiary structure
Fibrous proteins
Contain only one kind of secondary structure and no tertiary structure
Tertiary Structure 3o
The folding of the peptide chain
Maintained by hydrogen bonds, disulfide bonds (S-S), ionic interactions, hydrophobic
interactions all between different parts of the chain.
Only globular proteins have tertiary structure.
Quaternary Structure 4o
When different subunits of 3o structures are part of the same protein
4 Types of Structures of proteins
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Denaturing Protein
Breaking down the 3o, 3o and 4o structures but not the amino acid sequence.
Losing structure caused by the hydrogen bonds, disulfide bonds, folding, etc. The shape of the
protein is lost.
The peptide bonds are not broken so 1o structure stays the same.
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Effects
Protein is no longer biologically active
No longer soluble
Causes of denaturing
Extreme heat as in cooking
Extreme pH
+
+
+
Presence of certain heavy metal ions Ag , Pb2 , Hg2
Examples of Proteins
Enzymes
sucrase
lipase
protease
Storage Proteins
ovalbumin
casein
ferritin
Transport Proteins
hemoglobin
myoglobin
serum albumin
Contractile Proteins
myosin
actin
Protective Protein
antibodies
fibrinogen
Hormones
growth hormone
insulin
Structural Protiens
α-keratin
collagen
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Function
hydrolyzes sucrose
hydrolyzes lipids
hydrolyzes peptide bond
egg-white protein
milk protein
iron storage protein
transports oxygen in blood
transports oxygen in muscle
transports fatty acids in blood
thick filaments in muscle
thin filaments in muscle
form complexes with foreign proteins like viruses
protein used for blood clotting
stimulates growth of bone
regulates glucose in blood
Skin, hair, feathers, horns, nails, wool, hooves
Fibrous connective tissue: tendons, bone, cartilage
27
How Proteins are made
1. Nucleic Acids
Nucleic acids carry the information that is the blueprint needed to make the primary structure
of proteins
a. Nucleotides
Sugar + base + phosphate -> nucleotide
Nitrogen containing bases
1. Adenine (A)
2. Thymine (T)
3. Guanine (G)
4. Cytosine (C)
5. Uracil
(U)
DNA contains A, G, C, T
RNA contains A, G, C, U
b. Structure of Nucleic acids
Polymers of nucleotides
Base
Base
Base
|
|
|
Phosphate—Sugar—Phosphate--Sugar—Phosphate—Sugar--Phosphate
c. Double Helix
DNA is a spiral molecule in which to strands
of the polymer are hooked together by hydrogen
bonds.
Adenine hydrogen bonds with thymine
Guanine hydrogen bonds with cytosine
-A—C—G—A—T—C—T: : :
: : :
:
-T—G—C—T—A—G—A4/17/08
28
d. DNA Replication
e. Transcription
DNA mRNA
1. Types of RNA
Messenger RNA (mRNA)
Ribosomal RNA (rRNA)
Transfer RNA (tRNA)
2. The genetic code
The genetic information carried by the Nucleic acids to make proteins is coded. There are
only 4 bases in mRNA and there are 20 amino acids. The genetic code is a system of 3
bases in a particular order that corresponds to an amino acid.
Code
Guanine-guanine-cytosine (GGC) is the code for the amino acid gly. GAG is the code
for the amino acid glutamic acid.
There are 64 code words or codons for the 20 amino acids.
f. Translation
Initiation-Elongation-Termination
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g. Issues involving Nucleic Acids
1. Recombinant DNA technology
2. Muatations
X rays, UV sunlight,
Mutagens,
Viruses
DNA > alteration of DNA>defective protein>genetic disease (germ cells)
Cancer (somatic cells)
Normal Sequence
DNA
↓
mRNA
↓
Amino Acid
sequence
Mutation
ACA—CCC—AGG—TTT
ACA—CAC—AGG—TTT
UGU—GGG—UCC—AAA
UGU—GUG—UCC—AAA
Cys—Gly—Ser—Lys
Cys—Val—Ser—Lys
3. Viruses
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