PROTEIN Chap. 4 J. Pistack MS/Ed

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PROTEIN Chap. 4 J. Pistack MS/Ed
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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

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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

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Protein

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

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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

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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

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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

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Functions of Protein in the Body

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

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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

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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

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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

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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

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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

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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

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Immunity

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

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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)

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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

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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

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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

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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

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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

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Vegetarian Diets

• Ovolactovegetarianno meat, fish, or poultry
• Lactovegetarianno meat, fish, poultry, or eggs
• Ovovegetarianno meat, fish, poultry, or dairy
• Strict vegetarian (vegan)no animal products
• Fruitariannothing but raw fruits, nuts, seeds,
  and berries
• There are many individual variations of these