Transcript Proteins

What are the molecules of
life?
• The forming and breaking of bonds is called a
chemical reaction.
• Organic molecules are long chains of carboncarbon bonds that form molecules including the
four major classes of macromolecules.
FOUR major types of
macromolecules
• Carbohydrates:
sugars, pastas,
breads,
starches, etc.
Lipids (fat)
• Lipid: fats,
wax, oils
Protein
• Protein: amino
acids, enzymes,
keratin, etc.
Nucleic acid
• Nucleic acids:
Deoxynucleic
acid (DNA),
Ribonucleic
acid (RNA)
Carbohydrates
• Carbohydrates are organic macromolecules
composed of carbon, hydrogen, oxygen.
• Carbohydrates are the main source of fuel
for human beings.
• Rice, corn, wheat, and oats provide 60% of
the calories consumed by human beings.
• These grains are also rich in protein,
vitamins, and dietary fiber when not
refined.
Refined grains
• Many times, the foods we eat
(polysaccharides such as white bread
or white rice) are refined or
bleached.
• This means that they have taken away
the bran and the germ part of the
grain kernel, leaving behind only the
endosperm
How does this work?
• A pollen tube then grows through the style
of the pistil and into the ovule, which
contains the egg.
• Double Fertilization occurs as one sperm
fuses with an egg and the other with two
nuclei.
• The sperm that fuses with the two nuclei
becomes a source of nutrient for the
embryo. This is the endosperm.
Double fertilization
Implication?
• We receive
less nutrients,
vitamins, and
minerals when
we eat refined
foods
compared to
whole grain.
What is the endosperm?
• The endosperm is the nutritive tissue that
makes up 85% of the kernel’s weight.
• It is primarily composed of starch, lipids,
and proteins. It is formed within ovule or
embryo sac of a seed plant.
• Endosperm constitutes the embryo’s main
food source for several days after
germination.
Balanced diet requires a
variety of foods
• Other food plants include legumes,
which are members of the pea (or
bean) family, sugar cane, potatoes,
vegetables, and fruits.
• We require a variety of food so that
we can acquire an adequate amount
vitamins, minerals, and essential
amino acids.
Types of carbs
• Monosaccharides-fructose, glucose, and
galactose. Ex: Fruit sugar
• Disaccharides—sucrose, which is table
sugar (glucose + fructose). Also lactose or
milk sugar (glucose + galactose)
• Polysaccharides-(sucrose + sucrose…)
starchy foods like potatoes, rice, etc.
These are called complex carbohydrates.
Cellulose, which makes up grass, are
polysaccharides that are indigestible for
human beings.
Polysaccharides
• Starches are found in plants and
glycogen in animals. Both are
polysaccharides usually used as
reserved for the organism.
Pasta contains lots of
polysaccharides. We
consume it and convert
it to glycogen when
not using it.
Structural Polysaccharides
• Cellulose, because of its Beta formation on
its Carbon-1, compared to Alpha in starch,
is not edible for human consumption but is
excellent for producing tough walls in
plants.
Cows have certain bacteria
in their stomachs that can
digest cellulose
Sugar chain formation
• These polymers (cellulose,
polysaccharides) are made up repeating
units called monomers. In the case of
sugar, monomers of monosaccharides make
disaccharides, chains of disaccharides
make polysaccharides.
• Condensation reaction or dehydration
reaction occurs whenever two monomers
are linked. In this case, a water is
removed whenever two monosaccharides
are put together to make a disaccharide.
Dehydration Synthesis
(condensation reaction)
• Water is removed. The 1,4 glycosidic
linkage brings the two monomers
together
•
What happens when I
consume lots of
carbohydrates?
Disassembling of
polymers to
monomers require
an addition of water
(with the help of
enzymes), or
hydrolysis. Hence,
it is just the
reverse of
dehydration
synthesis.
Is this a balanced diet?
• On a given day, 25% of the adult
American population visits a fast food
restaurant
– http://tuberose.com/Fast_Food.html
Do Americans eat a balanced
diet?
But we really consume this…
What is recommended
• According to the USDA, food consumption
in all of the five food groups is lower than
the recommended daily servings.
• In fact, about 30% of Americans are
obese. This does NOT include the amount
of Americans who are overweight.
Boyles, S. Web MD, Inc. 2002
Fats
• A fat molecule is made of glycerol and
THREE fatty acids. (Fig 5-10 pg 65).
When created, it is called
triacylglycerol, or triglyceride.
Phospholipids are formed
from TWO fatty acids
and a glycerol. They
are usually the skeleton
of a cell membrane
Bad fat
• Lipids are organic macromolecules that are
not soluble in water. These include fats,
steroids, & wax.
• Saturated fat—Fat that is fully bonded
with hydrogen carbon atoms. They tend to
be solid in room temperature. Ex: butter,
animal fat
Types of fats
• Unsaturated fat—
Fat that includes
many double bonds
in their carbon
chains. They tend
to be liquid at room
temperature. Ex:
vegetable oil
Type of fat
• Polyunsaturated fats: considered the
“healthier” fats. These can be found
in fish, soybean, sunflower seeds.
• Omega-3 fatty acids are considered
polyunsaturated. They are found in
flax oil, hemp oil, pumpkin seeds,
walnuts, and fishes.
Omega-3 fatty acids
• Omega-3 fatty acids are not generated by
your body. Hence, one needs to consume
it. Health benefits include prevention
from coronary heart disease, reduction in
hypertension, depression
What are trans-fats?
• Trans fatty acids are unsaturated fats
which have now become saturated through
hydrogenation.
• It is found in foods like vegetable
shortening, margarine, or fries. Research
has shown that they increase LDLs (or the
“bad cholesterol”), increase heart disease,
and clog arteries.
Why is it called trans-fat?
• In 3-dimensional shape of a fat, the
cis configuration is less stable than
the trans. However, if we
hydrogenate the oil, the cis
configuration will become trans.
cis
trans
Partially hydrogenated oils
Partially hydrogenated oils
Products of steroid
• Steroids are lipids characterized by a
carbon skeleton consisting of four rings
(Fig 5:14, pg 68). They include
cholesterol, which help make the plasma
membrane of the cell.
Recall that there are
two forms of
cholesterol. HDL
and LDL. Which
ones are better for
you?
Proteins
• Proteins are organic molecules composed of
polypeptides, or long chains of amino acids.
• Proteins play structural roles in organisms,
such as being a receptor in cells. Muscles
and hairs are made of protein.
• Proteins act as enzymes. Enzymes are very
sensitive to their surrounding environment.
For Ex: A change in temperature will
denature the structure on an enzyme.
Polypeptide synthesis
• When two amino acids are to be linked
together, a dehydration synthesis with the
help of enzymes create a peptide bond
between the two amino acids.
• When this is repeated over and over again,
a polypeptide is created. When various
kinds of polypeptides are linked together, a
basic molecule of protein is created.
Levels of protein
• The primary structure of a protein
indicates the unique amino acid
sequence. Fig 5-18, pg 71. This
uniqueness attributes each type of
protein.
•
Secondary Structure
• The segments of polypeptide chain that are
repeatedly coiled or folded in patterns
that contribute to the protein’s overall
conformation is the secondary structure
of the protein.
• Hydrogen bonds play an important role as
they form alpha helix and beta pleated
sheets found in protein secondary
structures.
Hydrogen bonding in
Secondary Structure
•
• Pleated sheet 
Alpha helix
Tertiary Structure
• Irregular contortions from bonding
between side chains of various amino acids
due to hydrophobic interactions and
disulfide bridges helps help make up the
tertiary structure.
• The accumulation of hydrogen bonds, ionic
bonds, and van der Waals interactions on
the side chains collectively strengthen the
protein conformation.
Tertiary Structure
Quaternary Structure
• When two or more polypeptide chains
aggregate into a functional
macromolecule, the quaternary
structure of the protein is formed.
EX: Collagen, hemoglobin
What denatures proteins?
• Heat, pH, chemicals can all change the shape of
the protein or denature it. Many times, the
denatured protein will go back to its original
conformation when the heat or chemical is
removed. However, excessive irritation may cause
irreversible damage.
• Chaperone proteins help in assisting the folding of
proteins acting as scaffolds or temporary braces
Why should a person keep
cool during a fever?
Nucleic Acids-informational
polymers
• Nucleic acid is the polymer that make
up genes in DNA which help program
the amino acid sequence of a
polypeptide.
• There are two types of nucleic acids,
deoxyribonucleic acid (DNA) and
ribonucleic acid (RNA).
A nucleic acid strand is a
polymer of nucleotides
• Nucleic acids are polymers or
monomers called nucleotides (usually
made up of a five-carbon sugar,
nitrogenous base, and phosphate
group).
Purines vs. Pyrimidines
• These are the larger nucleotides that
include adenine and guanine.
• The smaller nucleotides are pyrimidines,
which include cytosine, thymine, and uracil.
• Nucleic acid polymers (polynucleotide) are
joined by phosphodiester linkages between
the phosphate group of one nucleotide and
the sugar of the next.
• Fig 5-27, pg 78. Also look at the
difference between ribose and
deoxyribose
Phosphodiester linkages
• These phosphodiester linkages or
covalent bonds