proteins & amino acids chapter 6. where do we get it? animal foods –also provide b vitamins...
TRANSCRIPT
Proteins & Amino Proteins & Amino AcidsAcids
Chapter 6
Where do we get it?
Animal foods– Also provide B vitamins and minerals such
as iron, zinc and calcium Plant foods
– Also provide B vitamins, iron, zinc, fiber and calcium, but in less absorbable forms
Differences in fiber and fat content
Protein’s Building Blocks: Protein’s Building Blocks: Amino AcidsAmino Acids
Variety in Amino Acid Variety in Amino Acid StructureStructure
Chemist’s View of Proteins
More complex than carbohydrates or fats
Twenty amino acids Different
characteristics 9 essential amino
acids The rest are either
nonessential or conditionally essential
Chemist’s View of Chemist’s View of ProteinsProteins
Peptide bonds link amino acids Condensation reactions Multiple amino acids linked together: polypeptide Protein: one or more polypeptide chains
Amino acid sequencing and protein structure Primary structure – chemical bonds Secondary structure – electrical attractions Tertiary structure – hydrophilic & hydrophobic Quaternary structure – two or more polypeptides
Primary Structure: Amino Primary Structure: Amino Acid SequenceAcid Sequence
Secondary Structure: Secondary Structure: Alpha Helix and Beta Alpha Helix and Beta SheetSheet
Tertiary and Quaternary Tertiary and Quaternary StructureStructure
Tertiary Structure
Primary through quaternary structure
Protein Shape Protein Shape and Functionand Function
Denaturation Disruption of stability Uncoil and lose
shape Occurs with
exposure to acid or high heat
Mutations: deviations in primary structure
Mutations: Sickle Cell Anemia
If structure is altered, shape and function may be affected
Protein Protein Digestion & Digestion & AbsorptionAbsorption
Use of Amino Acids in Use of Amino Acids in BodyBody
Protein SynthesisProtein Synthesis
Basis of uniqueness of each person DNA is the template
Holds the code for amino acid sequences Structural proteins give us our shape Enzymes give us our metabolism
Protein synthesis happens in every cell Diet can influence gene expression Sequencing errors can affect function
DNA DNA Transcription & Transcription & Translation into Translation into
ProteinProtein
Sequencing Errors: Point Sequencing Errors: Point MutationMutation
Roles of ProteinsRoles of Proteins
Growth and maintenance Building blocks for most body structures
Collagen Replacement of dead or damaged cells
Enzymes Assist in break down, build up, and transform
substances Catalysts: speed up chemical reactions
Stepped Art
Enzyme Enzyme Enzyme
AB
BA
BANew compound
Fig. 6-9, p. 181
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.
Roles of ProteinsRoles of Proteins Hormones
Messenger molecules Transported in blood to target tissues
Regulators of fluid balance Hold fluid in the blood Without these proteins:
edema Acid-base regulators
Function as buffers Transporters – specificity
Insulin: A Protein Insulin: A Protein HormoneHormone
Protein Transporter: Protein Transporter: The Sodium-Potassium The Sodium-Potassium PumpPump
Roles of ProteinsRoles of Proteins Antibodies
Defend body against disease
Energy and glucose Alternative glucose
source during starvation and insufficient carbohydrate intake
Movement: contractile proteins in muscle
Energy from Energy from ProteinProtein
Protein MetabolismProtein Metabolism Protein turnover & amino acid pool
Continual production and destruction Need dietary protein to maintain supply
If needed for energy and glucose Wasting of lean body tissue
Can lower BMRExtreme deprivation: organ proteins compromisedPrevented by adequate intake of calories,
carbohydrates, and fats
Protein MetabolismProtein Metabolism Making proteins & nonessential amino acids
If essential amino acid needed, body breaks down its own proteins Rate of protein synthesis may be compromised Limiting amino acid
Nonessentials can be synthesized Making other compounds
Neurotransmitters, hormones Melanin
Nonessential Amino Acid Synthesis When a nonessential amino acid is not
available from the diet, it can be made in the body by the process of transamination.
Protein MetabolismProtein Metabolism Making fat
Energy and protein exceed needs Carbohydrate intake is adequate Can contribute to weight gain Creates nitrogenous waste
Nitrogenous waste In liver – ammonia converted to urea Filtered out of blood and excreted in
urine by kidneys
Nitrogenous Waste: UreaNitrogenous Waste: Urea
Protein intake and urea production
Production increases in proportion to dietary protein Water consumption important in high protein diets
Two factors Digestibility
Animal proteins Plant proteins
Amino acid composition Essential amino acid consumption Nitrogen-containing amino groups Limiting amino acid
Protein Protein QualityQuality
Health Effects of ProteinHealth Effects of Protein High-protein diets
Heart disease Increase risk correlated with high animal-
protein intakeDifferences among protein selections
CancerCertain protein-rich foods, not protein
content of diet, influence risk Individuals with kidney disease
Acceleration of kidney deterioration
Health Effects of ProteinHealth Effects of Protein High-protein diets
OsteoporosisCalcium excretion increasesHigh animal protein intake more closely
correlated with bone mineral loss Ideal amount has not been determined,
and there are multiple influences on bone health
Weight controlSatiation and satiety
Recommended Recommended Intakes of ProteinIntakes of Protein
Intake in U.S. and Canada typically adequate or more than adequate
Dietary sourcesServing sizes: what we get vs. what we
needWhat is a standard serving size of meat?
Key diet principle – moderation Leave room on the plate for other good stuff!
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