Date post: | 11-May-2015 |
Category: |
Technology |
Upload: | nutritionteach |
View: | 701 times |
Download: | 0 times |
Protein: Amino Protein: Amino AcidsAcids
Chapter 6Chapter 6
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
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
Amino AcidsAmino Acids
Examples of Amino AcidsExamples of Amino Acids
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
Amino Acid Sequence of Amino Acid Sequence of Human InsulinHuman Insulin
The Structure of HemoglobinThe Structure of Hemoglobin
The ChemistThe Chemist’’s View of Proteinss View of Proteins
• Protein• Denaturation
• Disruption of stability
• Uncoil and lose shape
• Stomach acid
Protein DigestionProtein Digestion
• Mouth • Stomach
• Hydrochloric acid denatures proteins• Pepsinogen to pepsin
• Small intestine• Hydrolysis reactions • Peptidase enzymes
Protein Digestion in the GI Protein Digestion in the GI TractTract
Protein AbsorptionProtein Absorption
• Transport into intestinal cells• Uses of amino acids by intestinal cells
• Unused amino acids transported to liver• Enzyme digestion• Predigested proteins
Protein SynthesisProtein Synthesis
• Uniqueness of each person• Amino acid sequences of proteins
• Genes – DNA
• Diet• Adequate protein
• Essential amino acids
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
Sickle Cell Compared with Sickle Cell Compared with Normal Red Blood CellNormal Red Blood Cell
Protein SynthesisProtein Synthesis
• Gene expression and protein synthesis• Capability of body cells• Protein needs
• Dietary influence on gene expression• Disease development
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
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
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
Examples of Hormones and Examples of Hormones and Their ActionsTheir Actions
An Example of Transport An Example of Transport ProteinProtein
Roles of ProteinsRoles of Proteins
• Antibodies• Defend body against disease• Specificity
• Immunity – memory
• Energy and glucose• Starvation and insufficient carbohydrate
intake
• Other roles
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
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
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
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
Transamination and Synthesis Transamination and Synthesis of a Nonessential Amino Acidof a Nonessential Amino Acid
Urea SynthesisUrea Synthesis
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
Urea ExcretionUrea Excretion
Protein Functions in the BodyProtein Functions in the Body
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
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
Complementary ProteinsComplementary Proteins
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
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
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
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
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