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Chapter 6 The Proteins and Amino Acids
Nutrition: Concepts & Controversies, 12e Sizer/Whitney
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Learning Objectives Describe why some amino acids are essential, nonessential, or conditionally essential to the human body, and state the outcome should any one of them be lacking in the diet. Compare the digestion of protein and transport of amino acids with digestion and transport of lipids in the body. Discuss the roles that various proteins and amino acids can play in the body.
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Learning Objectives Describe the fate of amino acids consumed with a balanced diet versus a carbohydrate-poor diet. Discuss the concept of nitrogen balance and compute the amount of protein needed for a healthy college student.
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Learning Objectives Identify the major forms of protein malnutrition, and discuss reasons why consuming too much protein is not recommended. Summarize the health advantages and nutritional risks of a vegan diet. Develop a lacto-ovo vegetarian diet plan that meets all nutrient requirements for a given individual.
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The Structure of Proteins
Difference from carbohydrates and fats Amino acids Carbon atom with amine group and acid group Side chain Essential amino acids Conditionally essential Recycling Priority system
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How Do Amino Acids Build Proteins?
Peptide bonds Link amino acids Strands of amino acids do not remain straight Coils Folds Side chain electrical charge Activation
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The Coiling and Folding of a Protein Molecule
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The Structure of Hemoglobin
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The Variety of Proteins
Protein shapes enable performance of different tasks Examples Protein strands – alone or in association Inherited amino acid sequences Alterations to sequence Sickle-cell disease Nutrients and gene expression
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Normal Red Blood Cells and Sickle Cells
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Protein Synthesis
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Denaturation of Proteins
Denaturing agents Digestion Stomach acid Dangers of denaturation
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Protein Digestion Stomach Small intestine Common misconceptions
Denatures protein in food Uncoil protein’s strands Enzymes attack peptide bonds Small intestine Polypeptides Further break down Common misconceptions
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A Dipeptide and Tripeptide
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How Protein in Food Becomes Amino Acids in the Body
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Amino Acid Absorption Absorbed by cells of small intestine
Larger molecules Hormones or allergens Separate sites for absorption Released into the bloodstream Carried to the liver
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The Importance of Protein
Amino acids must be continually available Building of new proteins Amino acids are needed each day Protein turnover
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Roles of Body Proteins Regulation of gene expression
Providing structure and movement Muscle tissue Other structural proteins Building enzymes, hormones, & other compounds Building antibodies
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Enzyme Action
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Amino Acid Sequence of Human Insulin
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Roles of Body Proteins Transporting substances
Hemoglobin and lipoproteins Maintaining fluid and electrolyte balance Edema Maintaining acid-base balance Blood clotting Providing energy and glucose
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Proteins Transport Substances Into and Out of Cells
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Amino Acids to Glucose Protein can help maintain blood glucose levels
No storage compound for protein Dismantle tissue proteins Oversupply of amino acids Remove amine group Use of residues
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Three Different Energy Sources
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Amino Acids to Glucose Fate of an amino acid Cellular use
Build protein Make a needed compound Dismantle amino acid for component parts Wasting of amino acids Preventing waste
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Protein and Amino Acid Supplements
Protein supplements Do not improve performance Not effective for weight loss Amino acid supplements Body designed to work with whole proteins No safe level of amino acid supplementation
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People Most Likely to Be Harmed by Amino Acid Supplements
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How Much Protein Do People Really Need?
DRI Depends on body size Infants and growing children Recommended intake Vegetarians Minimum amount Upper limit Body’s health Quality
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Nitrogen Balance Nitrogen excreted as compared to nitrogen eaten
Levels in healthy adults Variation in nitrogen balance Positive balance Examples Negative balance
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Nitrogen Balance
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Which Foods Provide High Quality Protein?
High-quality proteins Enough of all essential amino acids Limiting amino acids Complementary proteins Mutual supplementation Protein digestibility Animal proteins Legumes
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Complementary Protein Combinations
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Protein Deficiency and Excess
World’s leading form of malnutrition Combined with energy deficiencies Protein-energy malnutrition (PEM) Locations of prevalence Effects of PEM Children and adults Two forms
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Protein Deficiency and Excess
Marasmus Common in children Muscle wasting Impairments Disease conditions Preventing death Heart failure
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Protein Deficiency and Excess
Kwashiorkor Weaning of babies Fluid balance is diminished Changes in body Risk of infection PEM at home
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Protein Deficiency and Excess
Overconsumption of protein-rich foods Possible health risks U.S. protein intakes Heart disease Homocysteine Kidney disease Adult bone loss Cancer
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Getting Enough but Not Too Much Protein
Protein-rich foods Protein is critical to nutrition Displacement of other necessary foods Advantages of legumes Protein Vitamin and mineral source Soybeans
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Top Contributors of Protein to the U.S. Diet
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A Legume
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Vegetarian and Meat-Containing Diets: What Are the Benefits and Pitfalls?
Controversy 6
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Vegetarian Diets Reasons to choose a vegetarian lifestyle
Categorization of vegetarians By foods they choose to eat Reasons why meat eaters choose to eat meat
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Terms Used to Describe Vegetarians and Their Diets
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Positive Health Aspects of Vegetarian Diets
Other health behaviors associated with being vegetarian Obesity Heart disease Blood lipids Hypertension Cancer Other health benefits
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Positive Health Aspects of the Meat Eater’s Diet
Critical times in life Examples Pregnancy and infancy Childhood Adolescence Aging
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Planning a Vegetarian Diet
Vegetarian food guides Ensure adequate intakes Protein Iron Zinc Calcium Vitamin B12 Vitamin D Omega-3 fatty acids
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My Vegetarian Food Pyramid
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Nutrients in Nonfat Milk and Light Soy Milk
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