Chapter 6 protein and amino acids


Published on

protein metabolism

Published in: Education, Technology, Business
1 Like
  • Be the first to comment

No Downloads
Total views
On SlideShare
From Embeds
Number of Embeds
Embeds 0
No embeds

No notes for slide

Chapter 6 protein and amino acids

  1. 1. 1 Proteins (amino acids) Normal body functions and health Obesity Human diseases Chapter 6: Protein and Amino Acids* proteins can come from different sources: red meat, white meat (fish and bairds), legumes * proteins/AA are the main contributor to building up of muscles and other prots. in the body
  2. 2. A. The Chemist’s View of Proteins • Proteins are made from 20 different amino acids, 9 of  which are essential.  • Each amino acid has an amino group, an acid group, a  hydrogen atom, and a side group.  -It is the side group that makes each amino acid unique:   size, shape, and electrical charge • The sequence of amino acids in each protein determines  its unique shape, function and complexity.
  3. 3. -carbon R R = = R R = -CH2COOH R = CH3 proteins ar the main source of nitrogen in the diet
  4. 4. The Chemist’s View of Proteins • Amino Acids – Nonessential (dispensable) amino acids are ones the  body can create, given the amino group and carbon  back‐bone sources – Essential (indispensable) amino acids must be supplied  by the foods people consume.  – Conditionally essential amino acids: nonessential but  become essential under certain conditions • Tyrosine • Glutamine * it is made from one of the essential AA "phenylalanine" *any defect in the process of conversion --> affect the amount of produced tyrosine * e.g., in phenylketonuria: lacking the enzyme that does the conversion from phenylalanine to tyrosine > those indv. must consume tyrosine in their diet >those indv. must watch the amount of consumed phenylalanine that can accumulate in the blood causing brain damage. the body can't produce them at all or in sufficient amounts *used by the immune system as source of energy * become essential when indv is sick, and a higher amount of Glu is needed
  5. 5. made from Meth *the one in red boxes are branched-chain AA * the ones in pink boxes are conditionally essential AA *most of prot. supplements contain Val, Iso, Leuc, b/c they are stimulate muscle prot. synthesis
  6. 6. The Chemist’s View of Proteins • Proteins  – Amino acid chains are linked by peptide bonds in  condensation reactions. • Dipeptides: have two amino acids bonded together. • Tripeptides: 3 amino acids bonded together. • Polypeptides: >3 amino acids bonded together.   – Amino acid sequences are all different, which allows  for a wide variety of possible sequences.
  7. 7. Condensation rxn:
  8. 8. The Chemist’s View of Proteins • Proteins – Protein Shapes: • Dependent on the amino acid composition  > Hydrophilic side groups are attate to water. > Hydrophobic side groups repel water. – Protein denaturation is the uncoiling of protein that  changes its ability to function. • Proteins can be denatured by heat and acid. • After a certain point, denaturation cannot be  reversed. the primary structure found in outside of the prot. found inside of the prot. those properties determine how prot. folds (tertiary stuctre), in turn determine prot. function
  9. 9. Human insulin Hemoglobin Quaternary Structuresinteraction of several polyeptides together
  10. 10. B. Digestion and Absorption • Proteins in diets need to be digested and absorbed. • In the Stomach • Protein is denatured by hydrochloric acid. • Pepsinogen (a proenzyme): converted into its active form pepsin by hydrochloric acid. • Pepsin cleaves proteins into smaller polypeptides. help to increase the surface area of enzymatic action
  11. 11. * most of the enzymes are produced in inactive form b/c it prevent internal digestion of the compartment walls. * there are many digestive enzymes b/c most of them are selective to type of peptide bond. know the names of all enzymes and the function of only pepsin and trypsine
  12. 12. Digestion and Absorption of Protein • Protein Digestion –In the Small Intestine • Proteases hydrolyze protein into short peptide chains (oligopeptides), which contain 4 to 9 AAs. • Peptidases split tri- and dipeptides into AAs.
  13. 13. Protein Absorption – Transporters / carrier proteins (?) on membranes of mucosal cells transport AAs and a few peptides into the cells of the intestine. – Absorbed amino acids are • Used by intestinal cells: synthesis of proteins or necessary compounds, energy • Excess is transported to the liver – Taking enzyme supplements or consuming predigested proteins is unnecessary they need to be carried b/c of they are hydrophobic, b/c of their low concentration gradient within the intestinal lumen, and b/c of the selective property of the cell membrane tripeptides at max e.g., glutathion: antioxidant it might be nesessary only when parts of the intestine are removedd due to cancer tratment
  14. 14. Points to remember & understand: •Proteins differ from other macronutrients: they contain nitrogen; and are more complex •Proteins are important because of the amino acids they contain •Amino acids can be designated as essential, non- essential or conditionally essential •Dietary proteins need to be digested and absorbed before our bodies can use them
  15. 15. C. Proteins in the Body • Proteins are versatile and unique • The synthesis of protein is determined by genetic information. • DNA (gene) • DNA is transcribed to messenger RNA, mRNA (Transcription, in the Nucleus) proteom: the 30000 type of prots. an average indv. have in their body
  16. 16. • Protein is constantly being broken down and synthesized in the body (Protein Turnover). –Nitrogen Balance • Synthesis • Breakdown (Proteolysis) • Excretion a measure of how efficiently the body uses the prots. it consumes
  17. 17. • Protein Synthesis – Sequencing errors: altered proteins. • e.g., sickle-cell anemia: incorrect AA sequence interferes with the cell’s ability to carry oxygen. –Nutrients and Gene Expression - Cells regulate gene expression to make the type of protein needed for that cell. –Regulation by nutrients –Protein Synthesis/Degradation? –Nutritional Regulation of Protein Turnover? –Nutritional Genomics and Proteomics? = although that all cells have the same genetic material (DNA), but diff genes get expressed in diff cells
  18. 18. Consequences of Defects in Protein Synthesis
  19. 19. Functions of Proteins 1)Building Materials for Growth and Maintenance • Collagen: filled with minerals to provide strength to bones and teeth. • Replaces tissues including the skin, hair, nails, and GI (gastrointestinal) tract lining 2)Enzymes: facilitate anabolic (building up) and catabolic (breaking down) chemical reactions –Digestive enzymes –Enzyme in metabolism: e.g. formation of glucose from AAS
  20. 20. 3)Hormones regulate body processes and some hormones are proteins. • Blood glucose & Metabolism: Insulin & glucagon. • Metabolism: Thyroxin promotes the appearance of glucose in blood produced in thyroid gland NOT ALL HORMONES ARE PROTEINS !!
  21. 21. Functions of Proteins in the Body 4)Regulators of Fluid Balance • Plasma (?) proteins attract water, and maintain volume of body fluids to prevent edema • Edema can happen because –Excessive protein losses caused by kidney diseases, inflamation or large wounds –Inadequate protein synthesis caused by liver disease –Inadequate protein intake • Maintain the composition of body fluids the swelling of the body the blood vessles become permable --> plasma proteins leak out of the blood vessels into the tissues (between the cells)
  22. 22. Blood
  23. 23. p. 182 Edema
  24. 24. Functions of Proteins 5)Acid-Base Regulators –Act as buffers by keeping solutions acidic or alkaline • Acidosis: high acidity in blood & body fluids. • Alkalosis: high alkalinity in blood & body fluids. 6)Transporters (?) –Lipids, vitamins, minerals & oxygen in the body –Act as pumps in cell membranes, transferring compounds from one side of the cell membrane to the other the -ve charge of prots. balance the acidic H+
  25. 25. Fig. 6-10a, p. 183 Key: Cell membrane Outside cell Inside cell Transport protein The transport protein picks up sodium from inside the cell. Sodium Potassium Membrane transport
  26. 26. Functions of Proteins 7) Antibodies (immunoglobulins) –Fight antigens fragment of bacteria and viruse –Provide immunity to fight an antigen more quickly the second time exposure occurs 8) Source of energy and glucose if needed • Other Roles • Blood clotting: fibrin • Vision: Opsin in the retina Without sufficient protein, though, the body cannot maintain its army of antibodies to resist infectious diseases, thus indv. with malnutrition are more susceptible to diseases. only when there is no sufficient carbohydrates/ calories in the body (NOT GOOD)
  27. 27. D. A Preview of Protein Metabolism –Protein Turnover and the Amino Acid Pool • Continual making & breaking down of protein. • Pattern of AA pool is fairly constant, irrespective of intake and/ or rate of protein breakdown. –Exogenous amino acids –Endogenous amino acids –Nitrogen Balance: balance of protein intake and output • used to estimate protein requirement dietary AA: digestion and absorption of prots. made by the body: making nonessential AA from essential AA
  28. 28. • Protein turnover & nitrogen balance go hand in hand. –Zero nitrogen balance is nitrogen equilibrium, • N intake = N output in urine • Protein synthesis = protein breakdown –Positive nitrogen balance: nitrogen consumed> nitrogen excreted. • Growing infants, children, adolescents, pregnant women, people recovering from protein deficiency or illness –Negative nitrogen balance: nitrogen excreted > than nitrogen consumed • Burns, injuries, infections, fever • Protein synthesis < protein breakdown
  29. 29. Proteins in the Body • A Preview of Protein Metabolism –Amino Acids • Make Proteins or nonessential AAs (?) • Make other compounds –Tyrosine: Neurotransmitters epinephrine and norephinephrine. –Tyrosine: melanin pigment & metabolic hormone thyroxine. –Tryptophan: »Niacin, and serotonin (neurotransmitter). • Energy and Glucose: no storage of proteins regulates sleeping
  30. 30. Proteins in the Body • A Preview of Protein Metabolism –Deaminating Amino Acids • Nitrogen-containing amino groups are removed. >Ammonia is released into the bloodstream. –Ammonia is converted into urea by the liver. –Kidneys filter urea out of the blood. >Carbon backbone is used in other metabolic pathways: glucose, fat –Using Amino Acids to Make Fat • Excess protein is deaminated and converted into fat; Nitrogen (NH3) is excreted. keto acid toxic compound
  31. 31. Deamination of AAs
  32. 32. Transamination & synthesis of non-essential amino acids Can essential amino acids be made by this process? What will happen if dietary supply of EAA is not adequate? e.g.,glutamic acide.g., pyruvate e.g., alanine e.g., alpha ketoglutarate No to break down the prots. in the muscles and other tissues in the body
  33. 33. Preview of Protein Metabolism: Urea synthesis
  34. 34. Fig. 6-14, p. 187 Bloodstream To bladder and out of body Kidney Urea Bloodstream Urea Liver Ammonia (NH3) + CO2 Amino acids Urea Liver disease: high ammonia Kidney disease: high urea a measure of [ammonia] and [urea] in the blood can determin a defect in liver or kidney
  35. 35. 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 Implication for weight loss diets * high consumption of prot. --> high production of urea * excretion of urea needs high amount of water for solivilbiization
  36. 36. Points to remember & understand: • Link between genetic information and protein synthesis –DNA, gene, mRNA, tRNA, rRNA –Consequences of ‘mistakes’ in the process • Functions of proteins –Protein turnover and nitrogen balance • Fates of amino acids: deamination, transamination, keto acids, ammonia, urea
  37. 37. E. Protein in Foods • Protein Quality: All proteins are not the same 1) Digestibility • Depends on protein’s food source –Animal proteins are 90-99% absorbed. –Plant proteins are 70-90% absorbed. > Soy and legumes are 90% absorbed. • Other foods consumed at the same time can affect digestibility e.g., eating fibers can reduce the transient time / accibility time for the enzymes to the prots. --> less digestion
  38. 38. Protein in Foods: protein quality 2) Amino Acid Composition • The liver can produce nonessential AAs. • Cells must dismantle to produce essential AAs if they are not provided in the diet. • Limiting amino acids (?) –Reference Protein is the standard by which other proteins are measured. • Based on their needs for growth and development, preschool children are used to establish this standard. essential AA ‫ﻳﻔﻜﻚ‬ The rationale behind this: if a protein will effectively support a young child’s growth and development, then it will meet or exceed the requirements of older children and adults.
  39. 39. Protein in Foods Protein Quality –High-Quality Proteins • Contains all the essential AAs >Animal foods contain all the essential AAs. >Plant foods: diverse in content & tend to be missing one or more essential AAs. –Complementary Proteins: combining plant foods that together contain all the essential AAs • Used by vegetarians
  40. 40. Assessing Protein Quality • Scarcity of proteins in some regions of the world –not in Canada • Measures of Protein Quality (Appendix D) –1) Amino Acid scoring –2) Protein digestibility-corrected amino acid score (PDCAAS) –3) Biological Value (BV) –4) Net Protein Utilization (NPU) –5) Protein Efficiency Ratio (PER) READ THAT!!! * how many of EAA are present in the food * even if have high score might not be a good quality b/c it might have poor digestibiity Animal:100%, Soy:94%, other plants 50-60%
  41. 41. Protein Regulation for Food Labels –Food labels must list protein quantity in grams –% Daily Values is not required but reflects quantity and quality of protein using PDCAAS. must be indicated if product is marketed to children or has specific claim
  42. 42. F. Health Effects and Recommended Intakes of Protein • Protein deficiencies arise from –protein-deficient diets and –energy-deficient diets. • Worldwide malnutrition problem, especially for young children. Other groups? • High-protein diets have been implicated in several chronic diseases no enough energy--> body brake up its prots. and use them as source of energy at places of war, developing countries, homeless people, elder pople
  43. 43. • Protein-Energy Malnutrition (PEM); also called protein-kcalorie malnutrition (PCM) • Chronic PEM: the child is short for his/ her age and • Acute PEM: child is thin for his/her height • Maramus, kwashiorkor, or a combination of the two
  44. 44. PEM Copyright © 2013 by Nelson Education Ltd. Table 6.3, p. 187*liver is the place of lipid metabolism * child has no prot. necessary --> can't take up the lipids from the liver--> lpid accumulation in liver --> liver enlargement
  45. 45. Health Effects & Recommended Intakes of Protein • PEM – 1. Marasmus: – Chronic PEM ‘Little old people’ –2. Kwashiorkor: Acute PEM • Older infants and young children, 18 months to 2 years of age prot. deficiency prot. and/or energy deficiency Kwashiorkor is a Ghanaian word that refers to the birth position of a child and is used to describe the illness a child develops when the next child is born. When a mother who has been nursing her first child bears a second child, she weans the first child and puts the second one on the breast. The first child, suddenly switched from nutrient-dense, protein-rich breast milk to a starchy, protein- poor cereal, soon begins to sicken and die. Kwashiorkor typically sets in between 18 months and 2 years Without proteins to maintain fluid balance, the child’s limbs and abdomen become swollen with edema—a distinguishing feature of kwashiorkor.
  46. 46. Health Effects and Recommended Intakes of Protein • PEM –Infections • Lack of antibodies to fight infections • Fever • Fluid imbalances and dysentery • Anemia • Heart failure and possible death –Dysentery, measles worsen condition elevated energy requirement
  47. 47. • Rehabilitation of PEM: – Nutrition intervention must be cautious, slowly increasing protein. • Programs involving local people work better.
  48. 48. Health Effects and Recommended Intakes of Protein • Negative Health Effects of Protein –Limitations –Heart Disease • Foods high in animal protein also tend to be high in saturated fat. • Homocysteine levels increase cardiac risks. • Arginine may protect against cardiac risks. *byproduct of methionine (AA) metabolism * is not incorporated to any prot. factors that increase the levels of Homocysteine: coffee, smoking, alcohol act by decreasing the levels of Homocysteinein the blood, and regulate blood pressure
  49. 49. Health Effects and Recommended Intakes of Protein • Health Effects of Protein –Cancers • High protein intake vs. high fat intake –Adult Bone Loss (Osteoporosis) • High protein intake associated with increased calcium excretion. –Animal vs. vegetable proteins • BUT: Inadequate protein intake affects bone health e.g. red and processed meats are linked to colon cancer animal prots. helps more excretion in comparison to vegetable ones no enough prots. to make collagen, the matrix for building tissues
  50. 50. –Weight Control • High-protein foods are often high-fat foods. • Protein at each meal provides satiety. –Kidney Disease • Does not seem to cause kidney disease but indvs. with compromised kidney function should reduce their consumption of prots.
  51. 51. Recommended Intakes of Protein • Daily protein intake – Supply of essential AAs – Source of N for synthesis of non-essential AAs • Recommended Intakes of Protein – 10-35% energy intake (AMDR) – Protein RDA: 0.8 g/kg/day; athletes: 1.2- 1.7g/kg/day • Assumptions –People are healthy; –Protein is of mixed quality. –The body will use protein efficiently. also can be used to synthesis nucleic acid, glutamic acid KNOW THOSE RANGES, AND IF GIVEN THE WEIGHT DETERMI N THE RECOMON DED INTAKE!!!
  52. 52. p. 194
  53. 53. Health Effects and Recommended Intakes of Protein • Recommended Intakes of Protein –Adequate Energy • Must consider energy intake • Must consider total grams of protein –Protein in abundance is common in the U.S. and Canada.
  54. 54. 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: herpes  Tryptophan: pain and sleep
  55. 55. Nutritional Genomics  Nutrigenomics  Nutrients influence gene activity  Nutrigenetics  Genes influence activity of nutrients  Human genome
  56. 56. Fig. H6-3, p. 201