PROTEIN Chap. 4 J. Pistack MS/Ed

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PROTEIN Chap. 4 J. Pistack MS/Ed

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Title: PROTEIN Chap. 4 J. Pistack MS/Ed

1
PROTEIN Chap. 4 J. Pistack MS/Ed
2
PROTEIN

Along with carbs and fats, proteins are energy
nutrients
Protein is nutritionally unique and cannot be
duplicated by carbs and fats
Proteins are the building blocks of tissues and
organs
Second only to water in amount present in the body

3
Composition of Protein

Carbon
Hydrogen
Oxygen
Nitrogen
Nitrogen is the element that distinguishes
protein from carbs and fats
The four elements are arranged in building blocks
called amino acids

4
Protein

Note Neurologic crippling results from
inadequate dietary protein and/or incorrect food
processing techniques

5
Amino Acids

Linked together in an exact order to form a
particular protein by a special bond called a
peptide bond
A chain of two or more amino acids by peptide
bonds is called a poly peptide
Really? It is estimated that there are 50,000
proteins in the body and only about 1000 have
been identified

6
Amino Acids

Proteins eaten are disassembled in the digestive
process into their component amino acids
Absorption occurs mostly in the duodenum and
proximal jejunum with the essential amino acids
being absorbed more quickly than the nonessential
ones
23 amino acids have been identified as being
important to the body's metabolism

7
Amino Acids

Essential Amino Acids
Cannot be synthesized in the body in sufficient
amounts to meet metabolic needs
Conditionally and/or Acquired Essential Amino
Acids
Can become essential, depending on the
biochemical needs of the body
Nonessential Amino Acids
Ordinarily can be built by the body in sufficient
quantities to meet its need

8
Functions of Protein in the Body

Structure
Maintenance and growth
Regulation of body processes
Immunity
Circulation
Energy source

9
Structure

Provide much of the body's mass
Contractile proteins (actin and myosin) are found
in skeletal muscle, smooth muscle and cardiac
muscle
Fibrous proteins like collagen, elastin, and
keratin are found in blood vessels, bone,
cartilage, hair, nails, tendons, skin, and teeth

10
Maintenance and growth

Because protein is a part of every cell, any
person requires an adequate supply of protein
Protein is required for growth and development
As cells of the body wear out they must be
replaced and protein is required for that process

11
Maintenance and growth

Anabolism the building of tissues as in growth
or healing
Catabolism the breaking down of tissues into
simpler substances
Both processes happen simultaneously

12
Maintenance and growth

A healthy body requires nitrogen, which as
mentioned earlier is found in protein
Nitrogen is excreted in urine, feces, sweat, and
can also be lost in bleeding or vomiting
Since it is lost in normal body processes, it
must be replaced
Nitrogen balanceAmount of nitrogen eaten is
equal to the amount excreted

13
Regulation of Body Processes

Hormones are chemicals secreted by various organs
to regulate/control body processes
Enzymes are chemicals that aid in body processes
Many times, enzymes speed up processes that
would take too long and are known as catalysts

14
Regulation of Body Processes

Nucleoproteins regulatory complexes found in
the nucleus of cells
Deoxyribonucleic acid (DNA) and ribonucleic acid
(RNA) are nucleoproteins involved with protein
synthesis
A gene is a part of the DNA that carries the code
to direct the synthesis of a single protein

15
Immunity

A protein called an antibody is produced in the
presence of a foreign substance or pathogen

16
Circulation

Albumin the main protein in the blood
Albumin helps maintain blood volume/pressure by
pulling back fluid into the veins from body tissue

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Energy source

Glucose is the most efficient energy source
Protein (and fat) can be used as backup sources
Once liver glycogen stores are depleted, the
glucose needs of the body cause the sacrificing
of amino acids from protein
The amino acids are converted into glucose
through a process called gluconeogenesis
The amount of energy from a gram of protein is
equal to a gram of carbohydrate (4 kilocalories)

18
Classification of Food Proteins

Complete protein - Food that supplies all
essential amino acids in sufficient quantity to
maintain tissue and support growth
Most complete proteins are from animal sources
such as meat, poultry, fish eggs, milk, and
cheese
Based on absorption of amino acids, animal
proteins are 90 to 99 digestible
Soybeans are a plant source of complete protein

19
Classification of Food Proteins

Incomplete protein - Food that lacks one or more
of the essential amino acids
Most plant foods are not complete proteins
because they lack at least one of the amino acids
The term incomplete does not mean its a bad food
Grains, legumes, vegetables, nuts, and seeds
contain incomplete protein and are 70 to 90
digestible

20
Incomplete Proteins

Limiting amino acidessential amino acid
undersupplied in a food
Complementationcombining of incomplete proteins
(grain and legume) so that all essential amino
acids are supplied

21
What?

Endogenous protein sources from the digestive
tract include shed mucosal cells yielding about
50 grams a day
An additional 17 grams of protein comes from
enzymes and glycoproteins

22
Vegetable Sources of Protein

Legumes are plants having roots having
nitrogen-fixing bacteria that lock the nitrogen
into the plants structure
Common legumes are peas, beans, lentils, and
peanuts

23
Vegetarian Diets