Download ppt

Proteins
Bio 28: Nutrition
Instructor: Paul Nagami
Laney College
Proteins Do Almost Everything
Proteins are the “workhouses” of the cell, making chemical
reactions possible. For example, there are proteins to put
together DNA and to break apart starch. A protein that runs
a chemical reaction is called an enzyme.
Protein Structure
Strands of the protein keratin, a tough
protein in hair. Its shape, or structure,
contributes to its toughness.
Let’s zoom in even closer... what are
these helices (corkscrews) made out
of? What holds them together?
Proteins are made of amino acids
Amino acid
monomers!
Proteins are
polymers, like
carbohydrates!
Amino Acids
Amine functional
group (has N)
Acidic functional group (like
end of fatty acid)
The part in yellow is called the side chain. There are 20
different amino acid side chains in human proteins.
Assembling Proteins
Peptide bond = bond
between amino acids
It’s not easy to break this
bond, but we have enzymes
in on our stomach that can
break down proteins to
harvest the amino acids.
What Makes Proteins Different
from Each Other?
Proteins with different shapes can have different functions.
These shapes depend on their sequence of amino acids.
Proteins Are Amino Acid
Polymers (Chains)
Imagine unfolding
a protein chain…
You would be able to
look at the individual
amino acids.
Some of these amino
acids would stick to
each other. Others
would stick to water.
The side chains
(sticking out)
either stick to each
other or to
surrounding water
Hydrophilic amino acids end up on the outside of the protein,
hydrophobic amino acids end up on the inside of the protein.
DNA is the instructions for
protein
DNA’s function: Instructions to make proteins, such as lactase!
Differences in DNA code can lead to differences in lactase
production, causing lactose intolerance.
Essential Amino Acids
Although there are 20 different amino acids,
most people can make 11 of them.
The remaining 9 that we can’t make are
called essential amino acids.
To build complete protein, you must eat all 9
of these. Meat generally has all 9.
You can get them without meat if you
practice protein complementation.
By pairing foods that contain different amino
acids in the same day, you can eat healthy
without meat.
Making Complete Protein
Examples of complete protein: Rice + beans, rice + lentils,
potatoes + milk, whole-wheat bread + peanut butter.
Dangers of Excessive Protein
If you eat too much protein, it
is not stored. Instead, the body
eliminates the extra amino
acids in the urine.
In the long term, excessive
protein consumption can lead
to kidney stones and acidic
blood pH.
Some carbohydrates are necessary to break down
protein efficiently! If you eliminate carbs, you can’t
metabolize protein well.
Protein Malnutrition
Marasmus: Lack of both
protein and caloric intake in
general. Leads to wasting, very
common in infants.
Kwashiorkor: Lack of protein.
Common after 18 months; can
lead to edema/bloating, death.