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1. CHAPTER THREE
PROTEINS
By RAMEDAN ABDELLA
11/5/2023 1

2. Objectives
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Describe proteins (composition & structure)
Classify proteins and how they are digested,
absorbed and metabolized
Enumerate food sources of protein
Explain nitrogen balance
List RDA allowance of protein and health
problems related to over/under intake
Describe the function of protein
Describe the manifestation of protein
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3. definition
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Protein is a component of every living cell:
plant, animal, and even microorganism.
The human body contains more than a
thousand different proteins, which carry out
a variety of essential functions.
In the adult, protein accounts for 20% of
total weight. Almost half of the body's
protein is in muscle, one fifth in bone and
cartilage, one tenth in skin, and the rest in
other tissues and body fluids. With the
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4. COMPOSITION AND STRUCTURE
Proteins are large, complex molecules
composed of at least 100 individual
chemical building blocks known as amino
acids.
Like carbohydrates and fats, amino acids
contain carbon, hydrogen, and oxygen
atoms
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5. Of the 22 known amino acids, 9 must be
supplied in the diet because they cannot be
synthesized in the body.
These are known as indispensable or essential
amino acids.
The remaining amino acids are less important
because they can be manufactured in the body
from nitrogen and carbohydrate or fat.
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6. Table. 1. Essential and non-essential
amino acids
E.A.A. NON – E.A.A.
- Lysine
- Tryptophan
Histidine
Phenylalnine
Leucine
Isoleucine
Thereonine
Methionine
Valine
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Glycine
Alanine
Serine
- Norleucine
Aspartic acid
Glutamic acid
Hydroxy–glutamic acid
Proline
- Hydroxy – praline?
Cetrulline
Tyrosine
Cystine
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7. 1.Based on nutritional value
 Complete Proteins
Based on the relative quantities of amino
acids present, dietary proteins can be
classified as complete proteins, or high-
quality proteins,
if they provide all the essential amino acids
in adequate amounts and proportions
needed by the body for growth and tissue
maintenance.
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8. SOURCES OF PROTEIN
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Protein is found in
milk and milk products, vegetables, meat,
poultry, egg, fish, legumes and starches
Fruits contain only trace amounts of
protein, and
pure fats (e.g., oils, butter) contain none.
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9. SOURCES ….
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animal sources :-
are high quality protein
are complete protein
Eg. Meat, egg, milk , fish, lamp, beef etc
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10. SOURCE OF…
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Plant sources
mostly incomplete eg cereals,
Contain significant amount Eg. Soy
bean[baqela]
The values of plant food that must be eaten
to provide the amino acid values of one egg
is large. Where plants synthesize protein?
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11. 
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Types of Enzymes
Pepsinogen is secreted by the gastric juice
and activated by the Hydrochloric acid
Trypsinogen is secreted by pancreatic juice
and activated by entrokinase.
Chemotrypsinogen is secreted by
pancreatic juice and activated by the
active tripsin
Peptidase intestinal juice.
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12. • The principal site of protein digestion is the
small intestine, where protein hydrolysis
continues under the action of pancreatic
proteases (a generic term for enzymes that
break down protein).
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13. Factors Influencing Individual Protein
Requirement.
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Body size :The greater the size and weight of
the body, the greater the protein
requirements.
Age : Protein requirements per unit of body
weight decrease from infancy through
adulthood however, the elderly may require
more protein than younger adults to
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Sex: Although the RDA lists protein
allowances for all adults at 0.8 g/kg of body
weight, women actually need less protein
than men of the same age and weight
because of differences in body composition.
Women have smaller muscle masses and a
larger percentage of body fat.
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Nutritional status: Under nutrition increases
protein requirements.
Stress, infection, and heat: Emotional or
physical stress, infection, and high
environmental temperatures all increase
nitrogen losses and therefore increase protein
requirements.
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16. Functions of protein
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17. Function…
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Building the body and growth of new tissue
Maintenance of existing tissue
Synthesis of enzyme, hormones, and
antibodies
Provide essential amino acid
Fluid movement in the body : determine the
direction of movement of fluids by exerting
osmotic pressure eg plasma protein osmotic
pressure edema
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18. Deficiency state
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Protein energy malnutrition (PEM)
A range of disorders primarily characterized
by growth failure or retardation in children
PEM is today the most serious nutritional
problem in Africa and other developing
countries.
Its two clinical forms are Kwashiorkor and
Marasmus. Or mixed
The diseases occur mostly in children
between one and three years of age, after
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20. Causes of PEM
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Although there is no final clarity about the
etiology of kwashiorkor in biomedical terms,
it is nevertheless, clear that it is related to
nutritional deficiencies.
Therefore, all factors that could possibly
contribute to the child malnutrition in
general should be avoided.
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21. Causes ….
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Multifactorial
Having a number of interwoven factors
operating simultaneously
Three causes
Basic causes
Underlying causes
Immediate causes
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23. Cont…
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Underlying
Inadequate access to food (food)
Inadequate care to mothers and children
(care)
Vulnerable segments of the population need
someone to
Care for them
Feed them
Take them to the nearby health institution for
preventive and therapeutic care
Give them psychosocial support
Inadequate health services and unhealthy
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25. Cont…
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Basic
Related to the amount, quality, control and
use of various resources
Availability and control of human, economic
and organizational resources at different
levels of society
Divided into four groups
Ecological/technical conditions of production
Including the environment (soil and climate), level
of technology used, population resource ratio, level
of people’s skill
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26. Cont…
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Social conditions of production
Including ownership of the means of production, division of
labor, power relationships
Political factors
Including policies on employment, prices, incomes, subsidies,
health, education and agriculture, food and nutrition polices,
and the legal system as a whole
Ideological factors/socio-cultural factors
Including habits, beliefs, cultural preferences and all ideas
that legitimize actions in society
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27. 
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Other diseases may sometime play an
important role in precipitating the onset
of kwashiorkor in already malnourished
child. E.g.
Gastrointestinal tract infection
Diarrhea Intestinal worms share the diet
and cause other ill- health and poor
appetite
Constipation
Childhood diseases such as measles,
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28. cont….
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Forms of malnutrition
Clinical
milder
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Kwashiorkor
Characterized by symmetric edema is evident especially in
the lower limbs
Hair is sparse
Flaky paint rash on the buttocks, legs and arms
Marasmus
Shows a characteristic muscle wasting particularly evident
in the buttocks, the pinched face and anxious demeanor
Generally thought to be the result of cumulative, usually
slow, inadequate energy and protein intake
Mixed
Commonly coexist
Simple unified approach to clinical management of both
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30. 11/5/2023 30
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Marasmus
Progressive wasting of the body
and is associated with
insufficient intake or
malabsorption of nutrients
Characteristics
Occurs in children < 2 yrs of
age
Severe deprivation
Develops slowly
Severe weight loss
Severe muscle wasting
Low growth (<60%), Low
WAZ
No edema, no fatty liver
Anxiety, apathy
Possible good appetite
Hair thin, dry; skin dry
“Old Man“ face, wrinkled
appearance

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34. Nutritional Marasmus
There is a failure to thrive
Irritability, restlessness and diarrhea are
frequent.
Many infants are hungry, but some
anorexic.
There are little or no subcutaneous fats
The weight is much below the standard for
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35. The abdomen may be shrunken or distended
with gas.
Because of the thinness of the abdominal
wall, peristalsis may be easily visible.
The muscles are weak and atrophic and this
makes the limbs appear as skin and bone
Evidence of vitamin deficiencies may or may
not be found.
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36. 11/5/2023 36
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Kwashiorkor
Caused by lack of nutrients
including protein in the diet
Characteristics
1st to 3rd yrs of life
Edema; enlarged fatty
liver
Low protein, infections
Rapid onset
Some weight loss
Some muscle wasting
Growth: 60-80%
Mod low WAZ
Apathy, misery, irritable

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Signs and symptoms….
Growth failure occurs always
Wasting of muscle is also typical but may
not be evident because of edema
There may be mental change
Diarrhea and vomiting
Sign of other micronutrient deficiencies
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38. Cont…
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Skin changes
Mild: localized hyper
pigmentation and
skin cracks
Moderate: skin peals
off, desquamation.
Severe: superficial
ulceration, bleeding
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Hair changes
Hair changes are
classified into three
categories
Mild: beginning of
visible color and
structural changes
Moderate: color
and structural
changes, loss of
hair
Severe: loss of hair
together with
ulceration of head
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41. KWASHIORKOR
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Physiological functions of the various
systems are markedly disturbed with
Diarrhea
Electrolyte disturbance
Circulatory insufficiency
Metabolic imbalance
Poor renal functions
Hence the child with kwashiorkor should
be thought of as an emergency in need
of referral to the nearest health facility.
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43. Cont…
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Milder forms
Wasting
Thinness using weight for height (W/H)
Stunting
Linear growth retardation using height for age
(H/A)
Underweight
A result of wasting and/or stunting
Using weight for age (W/A)
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44. Public Health Consequences
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PEM
Susceptibility to mortality (death)
Susceptibility to acute morbidity
(disease)
Decreased cognitive development
Decreased economic productivity
Susceptibility to chronic diseases in
later life
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45. Malnutrition have intergenerational
effect
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46. Treatment Include:
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Diet. Treatment is often based on dried skimmed
milk (DSM) powder.
Formula Milk: F75 and F100
Ready to use therapeutic foods (RUTF)
Treatment of hypothermia.
Medication like antibiotics and deworming
Micronutrients: Vitamin A, folic acid, iron,
Follow up
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