Chapter #6 Protein: Amino AcidsLearning ObjectivesThe Chemist’s View of ProteinsSlide 4Examples of Amino AcidsSlide 6Amino AcidsSlide 8Amino Acid Sequence of Human InsulinThe Structure of HemoglobinSlide 11Protein DigestionProtein Digestion in the GI TractProtein AbsorptionProtein SynthesisSickle Cell Compared with Normal Red Blood CellProtein Functions in the BodyProtein Turnover and Amino Acid PoolProtein Metabolism- Nitrogen balanceProtein QualitySlide 21Complementary ProteinsProtein DeficiencySlide 24Health Effects of ProteinSlide 26Recommended Intakes of ProteinCalculating Protein IntakesFrom Guidelines to GroceriesProtein and Amino Acid SupplementsChapter #6 Protein: Chapter #6 Protein: Amino AcidsAmino AcidsDr. Alisha RovnerDr. Alisha RovnerNTDT200NTDT200Fall 2013Fall 2013Learning ObjectivesLearning Objectives•Recognize the chemical structures of amino acids and proteins.•Summarize protein digestion and absorption.•Describe how the body makes proteins and uses them to perform various roles. •Explain the differences between high-quality and low-quality proteins, including notable food sources of each. •Identify the health benefits of, and recommendations for, protein.The ChemistThe Chemist’’s View of Proteinss View of Proteins•Atoms- carbon, hydrogen, oxygen, nitrogen•Amino acids (“building blocks of proteins”)•Carbon (C)•Hydrogen (H)•Amino (“nitrogen containing”) group (NH2) •Acid group (COOH)•Side group or side chainThe ChemistThe Chemist’’s View of Proteinss View of Proteins•More complex than carbohydrates or fats•All amino acids share a common structure but they differ in the following:•Size•Shape•Electrical charge and •Other characteristics because of difference in their side groupsExamples of Amino AcidsExamples of Amino AcidsAmino acids consist of a central carbon (C) with a hydrogen (H), an amino group (NH2) and an acid group (COOH). The difference is the side group.The ChemistThe Chemist’’s View of Proteinss View of Proteins•20 amino acids:•Essential amino acids- amino acids the body cannot make at all or cannot make in sufficient quantity to meet its needs•Nonessential amino acids- amino acids the body can synthesize•Conditionally essential amino acids- sometimes a non-essential amino acid become essential under certain circumstances (eg. Tyrosine)Amino AcidsAmino AcidsThe ChemistThe Chemist’’s View of Proteinss View of Proteins•Cells link amino acids end-to-end in a variety of sequences to form thousands of proteins•Peptide bonds link amino acids •Condensation reactions connect amino acids•2 bonded together- dipeptide•3 bonded together- tripeptide•10+ bonded together- polypeptideAmino Acid Sequence of Amino Acid Sequence of Human InsulinHuman InsulinInsulin is a relatively small protein made up 51 amino acidsThe Structure of HemoglobinThe Structure of HemoglobinThe ChemistThe Chemist’’s View of Proteinss View of Proteins•Denaturation•Change in protein’s shape and consequent loss of function •Examples of denaturation•Hardening of egg white when cooked•Curdling of milk when acid added•Stiffening of egg white when whippedProtein DigestionProtein Digestion•Mouth•Crushed and moistened•Stomach•Hydrochloric acid denatures proteins•Pepsinogen to pepsin•Small intestine•Hydrolysis reactions •Peptidase enzymesProtein Digestion in the GI Protein Digestion in the GI TractTractProtein AbsorptionProtein Absorption•Transport into intestinal cells•Uses of amino acids by intestinal cells•Unused amino acids transported to liver•Enzyme digestion•Predigested proteinsProtein SynthesisProtein Synthesis•Uniqueness of each person due to small differences in body’s proteins•Differences determined by amino acid sequences of proteins, which in turn are determined by genes•Protein synthesis depends on a diet that provides adequate and essential amino acidsSickle Cell Compared with Sickle Cell Compared with Normal Red Blood CellNormal Red Blood CellAmino acid sequence of normal hemoglobin Val- His- Leu- Thr- Pro-Glu-GluAmino acid sequence of sickle-cell hemoglobinVal- His- Leu- Thr- Pro-Val-GluProtein Functions in the BodyProtein Functions in the BodyProtein Turnover and Amino Protein Turnover and Amino Acid PoolAcid Pool•Within each cell, proteins continually being made and broken down (protein turnover)•When proteins break down they free amino acids which mix with amino acids from dietary protein to form “amino acid pool” with in cells and circulating blood•These amino acids can be used to make body proteinsProtein Metabolism- Nitrogen Protein Metabolism- Nitrogen balancebalance•Nitrogen equilibrium: N in = N out•Positive nitrogen: N in > N out •Body synthesizes more than it degrades•Growing infants, children, adolescent, pregnant women•Negative nitrogen: N in < N out•Body degrades more than it synthesizes•Person who is starving, burns, infectionsProtein QualityProtein Quality•Two factors that affect protein quality(1) Digestibility•Animal proteins high (90-99%)•Plant proteins (70-90%)(2) Amino acid composition•Essential amino acid consumption•Nitrogen-containing amino groups•Limiting amino acidProtein QualityProtein Quality•Reference protein•Standard against which to measure the quality of other proteins •Quality of protein is determined by comparing it’s amino acid composition with the essential amino acid requirements of preschool-age childrenComplementary ProteinsComplementary Proteins•Complementary proteins- Low-quality proteins combined to provide adequate levels of essential amino acidsProtein DeficiencyProtein Deficiency•Protein-energy malnutrition (PEM)•1. Marasmus-Reflects severe deprivation of food over a long period of time-Most commonly in children 6-18 months living in poverty, severe weight lost and muscle wasting2. Kwashiorkor -Reflects sudden and recent deprivation of food-More common in children 18 months -2 years-Limbs and abdomen swollen with edemaProtein DeficiencyProtein DeficiencyRehabilitation of PEM1.Rehydration•Diarrhea may have caused dramatic fluid and mineral losses that need to be replaced 2. Nutrition Intervention•Protein and energy given in small quantities•Intake gradually increased •Recovery typically better with an initial diet that’s relatively low in protein (10% of kcal)Health Effects of ProteinHealth Effects of Protein•Heart disease•High
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