2. The ChemistThe Chemist’s View of Proteins’s View of Proteins
• Atoms
• Carbon, hydrogen, oxygen, nitrogen
• Amino acids
• Carbon
• Hydrogen
• Amino group
• Acid group
• Side group or side chain
3. The ChemistThe Chemist’s View of Proteins’s View of Proteins
• More complex than carbohydrates or fats
• Twenty amino acids
• Different characteristics
• Essential amino acids
• Nonessential amino acids
• Conditionally essential
9. The ChemistThe Chemist’s View of Proteins’s View of Proteins
• Protein
• Denaturation
• Disruption of
stability
• Uncoil and lose
shape
• Stomach acid
10. Protein DigestionProtein Digestion
• Mouth
• Stomach
• Hydrochloric acid denatures proteins
• Pepsinogen to pepsin
• Small intestine
• Hydrolysis reactions
• Peptidase enzymes
12. Protein AbsorptionProtein Absorption
• Transport into intestinal cells
• Uses of amino acids by intestinal cells
• Unused amino acids transported to liver
• Enzyme digestion
• Predigested proteins
13. Protein SynthesisProtein Synthesis
• Uniqueness of each person
• Amino acid sequences of proteins
• Genes – DNA
• Diet
• Adequate protein
• Essential amino acids
14.
15. 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
16. Sickle Cell Compared withSickle Cell Compared with
Normal Red Blood CellNormal Red Blood Cell
17. Protein SynthesisProtein Synthesis
• Gene expression and protein synthesis
• Capability of body cells
• Protein needs
• Dietary influence on gene expression
• Disease development
18. 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
19. Stepped Art
Enzyme Enzyme Enzyme
A
B
BA
BA
New
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
20. 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
22. An Example of TransportAn Example of Transport
ProteinProtein
23. Roles of ProteinsRoles of Proteins
• Antibodies
• Defend body against disease
• Specificity
• Immunity – memory
• Energy and glucose
• Starvation and insufficient carbohydrate
intake
• Other roles
24. 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
25. 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
26. 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
27. 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
30. 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
36. 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
37. 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
38. Recommended Intakes ofRecommended 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
39. 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
40. Protein and Amino AcidProtein 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
Editor's Notes
Figure 6-9 Enzyme Action Each enzyme facilitates a specific chemical reaction. In this diagram, an enzyme enables two compounds to make a more complex structure, but the enzyme itself remains unchanged.
