chapter62013
TRANSCRIPT
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Protein: Amino Protein: Amino AcidsAcids
Chapter 6Chapter 6
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The ChemistThe Chemist’’s View of Proteinss View of Proteins
• Atoms• Carbon, hydrogen, oxygen, nitrogen
• Amino acids• Carbon• Hydrogen• Amino group• Acid group• Side group or side chain
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The ChemistThe Chemist’’s View of Proteinss View of Proteins
• More complex than carbohydrates or fats• Twenty amino acids
• Different characteristics• Essential amino acids• Nonessential amino acids
• Conditionally essential
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Amino AcidsAmino Acids
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Examples of Amino AcidsExamples of Amino Acids
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The ChemistThe Chemist’’s View of Proteinss View of Proteins
• Proteins• Peptide bonds link amino acids
• Condensation reactions
• Amino acid sequencing• Primary structure – chemical bonds
• Secondary structure – electrical attractions
• Tertiary structure – hydrophilic & hydrophobic
• Quaternary structure – two or more polypeptides
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Amino Acid Sequence of Amino Acid Sequence of Human InsulinHuman Insulin
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The Structure of HemoglobinThe Structure of Hemoglobin
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The ChemistThe Chemist’’s View of Proteinss View of Proteins
• Protein• Denaturation
• Disruption of stability
• Uncoil and lose shape
• Stomach acid
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Protein DigestionProtein Digestion
• Mouth • Stomach
• Hydrochloric acid denatures proteins• Pepsinogen to pepsin
• Small intestine• Hydrolysis reactions • Peptidase enzymes
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Protein Digestion in the GI Protein Digestion in the GI TractTract
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Protein AbsorptionProtein Absorption
• Transport into intestinal cells• Uses of amino acids by intestinal cells
• Unused amino acids transported to liver• Enzyme digestion• Predigested proteins
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Protein SynthesisProtein Synthesis
• Uniqueness of each person• Amino acid sequences of proteins
• Genes – DNA
• Diet• Adequate protein
• Essential amino acids
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Protein SynthesisProtein Synthesis
• DNA template to make mRNA• Transcription
• mRNA carries code to ribosome• Ribosomes are protein factories
• mRNA specifies sequence of amino acids• Translation • tRNA
• Sequencing errors
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Sickle Cell Compared with Sickle Cell Compared with Normal Red Blood CellNormal Red Blood Cell
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Protein SynthesisProtein Synthesis
• Gene expression and protein synthesis• Capability of body cells• Protein needs
• Dietary influence on gene expression• Disease development
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Roles of ProteinsRoles of Proteins
• Structural materials• Building blocks for most body structures
• Collagen
• Replacement of dead or damaged cells
• Enzymes• Break down, build up, and transform
substances • Catalysts
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Stepped Art
Enzyme Enzyme Enzyme
AB
BA
BANew compound
The separate compounds, A and B, are attracted to the enzyme’s active site, making a reaction likely.
The enzyme forms a complex with A and B.
The enzyme is unchanged, but A and B have formed a new compound, AB.
Figure 6-9 p175
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Roles of ProteinsRoles of Proteins
• Hormones• Messenger molecules• Transported in blood to target tissues
• Regulators of fluid balance• Edema
• Acid-base regulators• Attract hydrogen ions
• Transporters – specificity
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Examples of Hormones and Examples of Hormones and Their ActionsTheir Actions
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An Example of Transport An Example of Transport ProteinProtein
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Roles of ProteinsRoles of Proteins
• Antibodies• Defend body against disease• Specificity
• Immunity – memory
• Energy and glucose• Starvation and insufficient carbohydrate
intake
• Other roles
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Preview of Protein MetabolismPreview of Protein Metabolism
• Protein turnover & amino acid pool• Continual production and destruction• Amino acid pool pattern is fairly constant
• Used for protein production
• Used for energy – if stripped of nitrogen
• Nitrogen balance• Zero nitrogen balance• Positive and negative nitrogen balance
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Preview of Protein MetabolismPreview of Protein Metabolism
• Making other compounds• Neurotransmitters• Melanin• Thyroxin• Niacin
• Energy and glucose• Wasting of lean body tissue
• Adequate intake of carbohydrates and fats
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Preview of Protein MetabolismPreview of Protein Metabolism
• Making fat• Energy and protein exceed needs• Carbohydrate intake is adequate• Can contribute to weight gain
• Deaminating amino acids• Stripped of nitrogen-containing amino group
• Ammonia
• Keto acid
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Preview of Protein MetabolismPreview of Protein Metabolism
• Make proteins & nonessential amino acids• Breakdown of proteins• Keto-acids• Liver cells and nonessential amino acids
• Converting ammonia to urea• Liver – ammonia and carbon dioxide• Dietary protein
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Transamination and Synthesis Transamination and Synthesis of a Nonessential Amino Acidof a Nonessential Amino Acid
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Urea SynthesisUrea Synthesis
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Preview of Protein MetabolismPreview of Protein Metabolism
• Excreting urea• Liver releases urea into blood
• Kidneys filter urea out of blood
• Liver disease• Kidney disease• Protein intake and urea production
• Water consumption
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Urea ExcretionUrea Excretion
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Protein Functions in the BodyProtein Functions in the Body
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Protein QualityProtein Quality
• Two factors• Digestibility
• Other foods consumed
• Animal versus plant proteins
• Amino acid composition• Essential amino acid consumption
• Nitrogen-containing amino groups
• Limiting amino acid
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Protein QualityProtein Quality
• Reference protein• Preschool-age children
• High-quality proteins• Animal proteins• Plant proteins
• Complementary proteins• Low-quality proteins combined to provide
adequate levels of essential amino acids
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Complementary ProteinsComplementary Proteins
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Health Effects of ProteinHealth Effects of Protein
• Protein deficiency• Consequences • Protein-energy malnutrition• Marasmus and kwashiorkor
• Heart disease• Animal-protein intake• Homocysteine levels• Arginine levels
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Health Effects of ProteinHealth Effects of Protein
• Cancer• Protein-rich foods; not protein content of diet
• Osteoporosis• Increase in calcium excretion• Animal proteins
• Weight control• Kidney disease
• Acceleration of kidney deterioration
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Recommended Intakes of Recommended Intakes of ProteinProtein
• Need for dietary protein• Source of essential amino acids• Practical source of nitrogen
• 10 to 35 percent of daily energy intake• RDA
• Adults = 0.8 grams / kg of body weight / day• Groups with higher recommended intakes
• Assumptions
• Adequate energy
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From Guidelines to GroceriesFrom Guidelines to Groceries
• Protein foods• One ounce equals 7 grams of protein• USDA Food Patterns• Recommended sources
• Milk and milk products
• Fruits, vegetables, and grains
• Read food labels• Current US and Canada intakes• Moderation
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Protein and Amino Acid Protein and Amino Acid SupplementsSupplements
• Protein powders• Muscle work vs. protein supplements
• Athletic performance
• Whey protein• Impact on kidneys
• Amino acid supplements• Potential risks associated with intake• Lysine & tryptophan