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Proteins: Crucial Components of All Body Tissues

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... minerals zinc and iron Protein-Energy Malnutrition Protein-energy malnutrition: caused by inadequate protein and energy intake Common forms: ... – PowerPoint PPT presentation

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Title: Proteins: Crucial Components of All Body Tissues


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Proteins Crucial Components of All Body Tissues
2
What Are Proteins?
  • Proteins large, complex molecules found in cells
    of all living things
  • Dictated by genetic material (DNA)
  • Contain carbon, hydrogen, oxygen, nitrogen
  • Made from 20 different amino acids

The Building Blocks of Proteins
3
Amino Acids
  • Nine essential amino acids
  • Cannot be produced in sufficient quantities to
    meet physiological needs
  • Must be obtained from food
  • Nonessential amino acids
  • Can be synthesized in sufficient quantities

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Amino Acids
  • Transamination
  • Transfer amine group from an essential amino acid
    to a different acid group and R group
  • Conditionally essential amino acid
  • Nonessential amino acid becomes essential
  • Phenylketonuria (PKU) tyrosine becomes a
    conditionally essential amino acid that must be
    provided by the diet

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How Are Proteins Made?
  • Proteins are long chains of amino acids
  • Peptide bonds join amino acids together
  • Gene expression is the process by which cells use
    genes to make proteins
  • Gene segment of deoxyribonucleic acid (DNA) that
    serves as a template for the synthesis
    (expression) of a particular protein

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How Are Proteins Made?
  • Transcription messenger RNA copies the genetic
    information from DNA
  • Translation the genetic information in RNA is
    converted into the amino acid sequence of a
    protein

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How Are Proteins Made?
  • Protein turnover
  • Existing proteins are degraded to provide the
    building blocks for new proteins
  • Amino acid pool includes amino acids from food
    and cellular breakdown
  • Protein organization determines function
  • Sequential order of the amino acids
  • Spiral shape from twist in amino acid chain

Protein Synthesis
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Protein Denaturation
  • Proteins uncoil and lose their shape
  • Damaging substances heat, acid, base, heavy
    metal, alcohol
  • Protein function is lost
  • Denatured enzyme
  • High fever
  • Blood pH out of normal range
  • During digestion

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Protein in the Diet
  • For protein synthesis, all essential amino acids
    must be available to the cell
  • Limiting amino acid
  • Essential amino acid that is missing or in the
    smallest supply
  • Slows down or halts protein synthesis
  • Inadequate energy consumption
  • Limits protein synthesis

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Protein in the Diet
  • Incomplete protein (low quality) insufficient
    essential amino acids
  • Does not support growth and health
  • Complete protein (high quality) sufficient
    amounts of all nine essential amino acids
  • Derived from animal and soy protein

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Protein in the Diet
  • Mutual supplementation combine two or more
    incomplete protein sources to make a complete
    protein
  • Complementary proteins two or more foods are
    combined to supply all nine essential amino acids
    for a complete protein

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Protein Digestion
  • Protein digestion begins in the stomach
  • Hydrochloric acid denatures protein strands and
    activates pepsin
  • Pepsin enzyme breaks down proteins into short
    polypeptides and amino acids
  • Gastrin hormone controls hydrochloric acid
    production and pepsin release

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Protein Digestion
  • Digestion continues in the small intestine
  • Pancreatic enzymes (proteases) complete protein
    digestion
  • Special sites (small intestine) transport amino
    acids, dipeptides, tripeptides
  • High doses of individual amino acid supplements
    can lead to amino acid toxicity and deficiencies

Protein Digestion
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Protein Quality
  • Methods for estimating protein quality
  • Chemical score
  • Protein digestibility corrected amino acid score
    (PDCAAS)
  • Animal protein and many soy products are highly
    digestible (90 absorption)

Protein Absorption
27
Functions of Proteins
  • Cell growth, repair, maintenance
  • Enzymes and hormones
  • Fluid and electrolyte balance
  • Acid-base balance
  • Immune system
  • Energy source
  • Nutrient transport and storage

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Protein Adequacy
  • Nitrogen balance determines protein needs
  • Positive nitrogen balance
  • Negative nitrogen balance
  • In nitrogen balance

Nitrogen Balance
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RDA for Protein
  • RDA 0.8 g per kg body weight per day
  • Recommended percentage of energy is 10-35 of
    total energy intake
  • Protein needs are higher during growth and
    development (children, adolescents, and
    pregnant/lactating women)

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Too Much Protein Can Be Harmful
  • High cholesterol and heart disease
  • Animal-protein-rich diets are associated with
    high blood cholesterol levels (saturated fat)
  • Contribution to bone loss
  • High-protein diets increase calcium excretion and
    possibly lead to bone loss

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Too Much Protein Can Be Harmful
  • Kidney disease
  • High protein intakes are associated with an
    increased risk among susceptible individuals
  • People with diabetes have higher rates of kidney
    disease and may benefit from a lower-protein diet
  • Maximum of 2 g of protein per kilogram body
    weight each day is safe for healthy people

Fat Synthesis from Excess Protein
37
Protein Sources
  • Meats
  • Milk-based products
  • Soy products
  • Legumes
  • Whole grains
  • Nuts
  • Quorn

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Vegetarian Diets
  • Vegetarianism restricting the diet to foods of
    plant origin
  • People chose vegetarianism for
  • Health benefits
  • Ecological reasons
  • Religious reasons
  • Ethical reasons
  • Concerns over food safety

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Health Benefits of Vegetarianism
  • Lower fat and total energy intake
  • Lower blood pressure
  • Reduced risk of heart disease
  • Fewer digestive problems
  • Reduced risk of some cancers
  • Reduced risk of kidney disease, kidney stones,
    and gallstones

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Challenges of Vegetarian Diets
  • Can be low in some nutrients
  • Associated with disordered eating
  • Varied and adequate diet planning
  • Soy and complementary proteins
  • Vegetarian Food Guide Pyramid
  • Special attention to vitamins D, B12, and
    riboflavin (B2) minerals zinc and iron

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Protein-Energy Malnutrition
  • Protein-energy malnutrition caused by inadequate
    protein and energy intake
  • Common forms
  • Marasmus
  • Kwashiorkor

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Marasmus
  • Grossly inadequate energy and nutrient intake
  • Consequences of marasmus
  • Wasting and weakening of muscles (heart)
  • Stunted brain development and learning
  • Depressed metabolism
  • Stunted physical growth
  • Deterioration of the intestinal lining (anemia)
  • Severely weakened immune system
  • Fluid and electrolyte imbalances

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Kwashiorkor
  • Disease resulting from low protein intake
  • Kwashiorkor symptoms include
  • Some weight loss and muscle wasting
  • Retarded growth and development
  • Edema resulting in distention of the belly
  • Fatty degeneration of the liver
  • Loss of appetite, sadness, irritability, apathy
  • Skin problems and hair loss

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Genetic Disorders
  • Numerous disorders are caused by defective DNA
  • Genetic disorders include
  • Phenylketonuria
  • Sickle cell anemia
  • Cystic fibrosis

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