PROTEIN
-
Proteins and Amino Acid
A.k.a: CHON
Gk word: “primary, holding first place”
Proposed by: Mulder, a Dutch chemist (proposed the
name in 1840)
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CHONS or proteins are components of every
living organisms.
In adult, CHON account 20% total weight.
o Almost ½ are in muscles
o 1/5 are in bones and cartilages
o 1/10 other tissues and bodily fluids.
Note: Every tissue and fluid in the body contains
CHON.
There are 20 known amino acids.
9 Essential amino acids- cannot be made by the
body and must be obtained through diet only.
o Histidine
o Isoleucine
o Leucine
o Lysine
o Methionine
o Phenylalanine
o Tryptophan
o Valine
11 non-essential amino
synthesized by the body.
o Alanine
o Arginine
o Asparagine
o Aspartic Acid
o Cysteine
o Glutamic acid
o Glutamine
o Glycine
o Proline
o Serine
o Tyrosine
acids-
can
be
CHON is Classified According to:
1) Types
a. Simple CHON
- Composed of only amino acids
and their derivatives.
- Albumin- plasma CHON
Insulin- hormones by the
pancreas.
- Histones- found in cell
nucleus.
- Globulins- found in myosin
and muscle CHON.
b. Conjugated CHON
- Simple CHON combined with a
non-CHON substance.
- NucleoproteinCHON
+
nucleic acid (e.g. DNA)
- Glycoprotein- CHO + CHON
(e.g. Mucin)
 Phosophoproteinsprotein + phosphorus
containing substance
other than
phospholipids or
nucleic acids (Casein in
milk).
- Chromoproteins- CHON + a
non- CHON pigment
(e.g., Hemoglobin)
- Lipoprotein- CHON + a
triglyceride or other lipid
(e.g., HDL)
- Metalloprotein- CHON + a
metal
(e.g., Ferritin)
2) Spatial and structural arrangements
a. Fibrous CHON
- Consist of long coiled or
folded chains of amino acids
bound together in parallel
lines.
- Myosin: a fibrous protein
- Found on the protective
tissues of animals like in body
structures:
 Skin
 Fins
 Tendons
 Scales of fish
 Hair
 Feathers
b. Globular CHON:
- Structure is coiled and tightly
wounded and is slightly
soluble in water.
-
Mobile, spherical molecules
that play crucial roles in
virtually
all
biological
processes.
- The perform rather than just
form structures.
 E.g.:
a. Antibodies: provides
immunity
b. Albumin: egg white
c. Hormones: regulates
growth and
development
3) Amino acid contents
a. Complete CHON:
- Has high biologic value
- Contains all the EAA in
amounts sufficient for growth
and maintenance of life.
- Generally, animal CHONs are
complete.
b. Partially complete CHON:
- Has low biological value
- Maintains life but do not
support growth
- Gliadin in wheat, legumin in
legumes
c. Incomplete CHON:
- Low biological value
- CHON that cannot support life
and growth
- Gelatin and most plant
sources.
Biologic Value:
d. Complete:
- High biologic value
- Maintains and grows
- Animal
e. Partial:
- Low biologic value
- Maintains, not grows
- Wheat, legumes
f. Incomplete:
- Low biologic value
- Does not maintain and grow
- Gelatin, most plants
4) Essentiality
a. Essential Amino Acids (Indispensable
AA)
- Cannot be synthesized by the
body from materials readily
available at a speed to keep up
with normal growth rate.
- They must be supplied readymade or preformed in the
diet.
- Sometimes termed as dietary
essential.
b. Semi-essential Amino acids
- An amino acid that can
maintain life processes for an
adult but not enough for
normal growth in children.
- Lowers the needs for a
particular EAA or partially
spares it.
- However, it cannot replace
the EAA.
c. Non-essential Amino acids (dispensable
AA)
- Can be synthesized by the
body
if
materials
are
adequate.
- Not dietary essential.
Functions of CHON and Amino Acids:
1. Body Building or Structural Role:
 Includes all living cells and tissues
 Integral part of cell nuclei and
protoplasm.
 Makes up the solid mass of soft tissues
like muscles, vital organs, glands and
blood cells.
 The supporting matrix for bones, teeth
and hair and nails.
 All enzymes, most hormones, other
bodily secretion and fluid (except bile)
 Also antibodies, thus aiding in bodily
resistance to infection.
2. Essential for growth:
 Needed by all living cells in the body
 To synthesize new CHON you need the
available 9 EAA and nitrogen
 For growth: the AA must be present in
amounts above your maintenance.
3. Source of energy:
 CHON 4 cal/ gram- more expensive
source of energy in terms of resources.
 Sole nutrient that supplies amino acids
for body building and repairing tissues.
 Secondary to the role of energy-giving.
4. Regulator of body process:
 Regulates osmotic pressure; hence
water balance and acid base balance.
 Helps in the exchange of nutrients and
other metabolites which pass between
cells and the intercellular fluids or
between tissues and the blood or lymph.
5. Source of Essential Amino acid:
 CHON has 8-10 EAA that play distinctive
physiological functions which cannot be
accomplished by other AA (Amino
Acids).
 Methionine:
o Methylating agent that is needed for
important substances in the body like
choline, heme portion of hemoglobin.
 Phenylalanine:
o Precursor for the AA tyrosine which both
are important in the production of the
hormones thyroxine and epinephrine.
 Phenylalanine and Tyrosine:
o Origins of melanin
 A pigment which occurs in the
hair, choroid lining of the eyes
and the skin.
 Tryptophan:
o The precursor of niacin as well as for
serotonin.
Evaluating CHON Quality:
Biologic Value:
 Refers to the percentage of absorbed nitrogen
retained in by the body.
 CHON with biologic values greater than 70% are
considered to be High Biologic Value protein and
able to support growth if calorie needs are met.
 Complete proteins: High
 Incomplete proteins: Low
Net protein utilization:
 Amount of protein that is actually available for
the body to use.
Protein efficiency ratio:
 The gram of body weight gained by a person per
gram of protein food taken in an adequate diet
over a specific period of time.
Factors affecting protein Utilization:
1. Amino acid balance:
 Right assortment of amino acids in
definite proportions for the particular
tissue to be formed should be present at
the proper site in order to be efficiently
utilized for tissue synthesis.
2. Immobility:
 Causes negative nitrogen balance even if
the diet is adequate in proteins.
 It has been noted that a healthy
individual who is immobilized or at rest
may lose as much as 18g of Nitrogen a
day.
3. Emotional Stress:
 Increases the production of epinephrine
in turn increasing nitrogen loss.
4. Caloric intake:
 If fat and carbohydrates sources of
calories are not present or insufficient,
protein will be deaminated and used for
energy.
5. Inborn errors of metabolism:
 PKU- loss of the enzyme necessary to
metabolize phenylalanine, which causes
mental retardation and slows down
growth.
i. Metabolism of Phenylalanine:
1. In a person without PKU:
a. Phenylalanine

Phenylalaninehydroxylase  Tyrosine
2. In a person with PKU:
a. Phenylalanine (3x)  (X)
no phenylalaninehydroxylase
i. Build up of
phenylalanine to
toxic levels.
Symptoms:
 Most babies with phenylketonuria appear
healthy at birth.
 Symptoms usually only develop due to
complications that arise if the condition is not
treated properly.
 If it isn’t treated, damage to the brain and
nervous system can lead to:
o Learning disabilities
o Behavioral difficulties
o Epilepsy
RA 9288:
 Known as “The Act of Promulgating a
Comprehensive Policy and National System for
Ensuring Newborn Screening”.
6. Food Processing:
 AA may be destroyed by heat and other
processing techniques.
 E.g. Lysine in bread decreases biologic
value when toasted.
Protein Deficiency:
Kwashiorkor:
 Syndrome of severe protein malnutrition
caused by inadequate intake of good quality
proteins.
 “The disease of the deposed baby when the
next one is born”.
 Cases about this occur in areas of famine or
poor food supply.
 Protein malnutrition leads to depigmentation,
desquamation, edema, hair color changes (black
hair becomes red and brown hair becomes
blonde) and nail thinning.
Marasmus:
 Condition of chronic protein and caloric
deficiency
 Aside from total food deprivation, the infant is
usually lacking in emotional and physical care.