Protein: Amino Acids

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Protein Amino Acids

• Chapter 6

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The Chemists 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 Chemists View of Proteins
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The Chemists 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 Chemists View of Proteins
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The Chemists 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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The Chemists View of Proteins
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The Chemists View of Proteins

• Protein
• Denaturation
• Disruption of stability
• Uncoil and lose shape
• Stomach acid

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Protein Digestion

• Mouth
• Stomach
• 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
• 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
• 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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The separate compounds, A and B, are attracted to
the enzymes 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.
Stepped Art
Fig. 6-9, p. 181
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Roles 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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Roles of Proteins
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Roles 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 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 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
• Kidney disease
• Protein intake and urea production
• Water consumption

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Preview of Protein Metabolism
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Protein Quality

• Two factors
• Digestibility
• 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

• 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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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
• 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
• 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)