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Protein: Amino Acids Chapter 6
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The Chemist’s 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 Chemist’s View of Proteins
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The Chemist’s 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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The Chemist’s View of Proteins
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The Chemist’s View of 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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The Chemist’s View of Proteins
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The Chemist’s View of Proteins
Denaturation Disruption of stability Uncoil and lose shape Stomach acid
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Protein Digestion Mouth Stomach Small intestine
Hydrochloric acid denatures proteins Pepsinogen to pepsin Small intestine Hydrolysis reactions Peptidase enzymes
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Protein Digestion
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Protein 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 Synthesis Uniqueness of each person Diet
Amino acid sequences of proteins Genes – DNA Diet Adequate protein Essential amino acids
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Protein 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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Protein Synthesis
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Protein 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 Proteins Growth and maintenance Enzymes
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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Roles of Proteins
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Roles of Proteins Hormones Regulators of fluid balance
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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Roles of Proteins
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Roles of Proteins Antibodies Energy and glucose Other roles
Defend body against disease Specificity Immunity – memory Energy and glucose Starvation and insufficient carbohydrate intake Other roles
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Preview 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 or equilibrium Positive and negative nitrogen balance
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Preview 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 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 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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Preview of Protein Metabolism
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Preview of Protein Metabolism
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Preview of Protein Metabolism
Excreting urea Liver releases urea into blood Kidneys filter urea out of blood Liver disease: blood ammonia will be high Kidney disease: blood urea will be high Protein intake and urea production Water consumption
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Preview of Protein Metabolism
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Protein Quality Two factors Digestibility Amino acid composition
Other foods consumed Animal vs. plant proteins Amino acid composition Essential amino acid consumption Nitrogen-containing amino groups Limiting amino acid
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Protein Quality Animal proteins (complete proteins) Reference protein
Preschool-age children High-quality proteins Animal proteins (complete proteins) Plant proteins (incomplete proteins) Complementary proteins Low-quality proteins combined to provide adequate levels of essential amino acids
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Protein Regulations for Food Labels
Quantity of protein in grams Percent Daily Value Not mandatory Protein claims Consumption by children under 4 years old Quality of protein
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Protein-Energy Malnutrition (PEM)
Insufficient intake of protein, energy, or both Prevalent form of malnutrition worldwide Impact on children Poor growth Most common sign of malnutrition Impact on adults Conditions leading to PEM
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Protein-Energy Malnutrition (PEM)
Marasmus Chronic PEM Children 6 to 18 months Poverty Little old people – just “skin and bones” Impaired growth, wasting of muscles, impaired brain development, lower body temperature Digestion and absorption
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Protein-Energy Malnutrition (PEM)
Kwashiorkor Acute PEM Children 18 months to 2 years Develops rapidly Aflatoxins Edema, fatty liver, inflammation, infections, skin and hair changes, free-radical iron Marasmus-Kwashiorkor mix
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Protein-Energy Malnutrition (PEM)
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Protein-Energy Malnutrition (PEM)
Infections Degradation of antibodies Dysentery Heart failure and death Rehabilitation Rehydration and nutrition intervention Add protein slowly
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Health Effects of Protein
High-protein diets Heart disease Animal-protein intake Homocysteine levels Arginine levels Cancer Protein-rich foods; not protein content of diet Kidney disease Acceleration of kidney deterioration
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Health Effects of Protein
High-protein diets Osteoporosis Calcium excretion increases Ideal ratio has not been determined Animal protein intake Weight control Satiety
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Recommended Intakes of Protein
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
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Recommended Intakes of Protein
Protein in abundance Intake in U.S. and Canada Dietary sources Serving sizes Key diet principle – moderation
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Protein and Amino Acid Supplements
Protein powders Muscle work vs. protein supplements Athletic performance Whey protein Impact on kidneys Amino acid supplements Potential risks associated with intake Lysine & tryptophan
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Highlight 6 Nutritional Genomics
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Nutritional Genomics New field Nutrigenomics Nutrigenetics
Nutrients influence gene activity Nutrigenetics Genes influence activity of nutrients Human genome
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Nutritional Genomics
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A Genomics Primer DNA Gene expression Epigenetics 46 chromosomes
Nucleotide bases Gene expression Genetic information to protein synthesis Gene presence vs. gene expression Epigenetics DNA methylation
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A Genomics Primer
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Genetic Variation and Disease
Genome variation About 0.1 percent Goal of nutritional genomics Customize recommendations that fit individual needs Single-gene disorders Phenylketonuria (PKU)
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Genetic Variation and Disease
Multigene disorders Study expression and interaction of multiple genes Sensitive to environmental influences Example Heart disease Single nucleotide polymorphisms (SNPs)
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