NUT 1004 Lecture 5 Proteins PDF

1 Proteins Kemar Bundy MSc. MPH, PhD(C) NUT 1004 University of Technology, Jamaica  Learning Outcomes List the primary function of proteins in the body. Classify an amino acid as essential or nonessential. Explain the difference between a high-q...

1 Proteins Kemar Bundy MSc. MPH, PhD(C) NUT 1004 University of Technology, Jamaica  Learning Outcomes List the primary function of proteins in the body. Classify an amino acid as essential or nonessential. Explain the difference between a high-quality protein and a low-quality protein. Identify foods that are rich sources of high-quality proteins.. Explain what happens to proteins as they undergo digestion and absorption in the human digestive tract. Explain the concept of nitrogen balance and identify conditions in which the body is a state of positive or negative nitrogen balance. ©McGraw-Hill Education  What Are Proteins? Proteins are complex organic molecules. Composed of carbon, hydrogen, and oxygen Proteins also contain nitrogen. Specific types include: Structural proteins: collagen and keratin Contractile proteins: Actin & Myosin Blood clotting proteins: Thrombin & Fibrinogen Transport proteins: Haemoglobin and Transferrin Regulatory Proteins: Hormones and Enzymes What are major functions of protein Protein Structure and Functio ©McGraw-Hill Education  What is Acid-Base Balance? Maintaining the proper pH of body fluids involves acid-base balance. Blood and tissue fluid must maintain a pH of 7.35 to 7.45. Acidic - blood has an excess of H+ Too basic - blood has not enough H+ Proteins act as buffers by accepting or releasing H+. Proteins help maintain fluid balance. ©McGraw-Hill Education  Amino Acids Proteins are made of smaller units called amino acids. Human proteins can have 20 different amino acids. Each amino acid is composed of: 1) The amino or nitrogen-containing group 2) R-group — varies with each amino acid 3) Acid group - acid portion ©McGraw-Hill Education  Classifying Amino Acids Essential Amino Acids: Cannot be made by the body Must be supplied by the diet PVT TIM HLL 9 of the 20 amino acids Nonessential Amino Acids: Can be made by the body 11 of the 20 amino acids See Table 7.2 for lists of essential and nonessential amino acids. ©McGraw-Hill Education  CLASSES OF AMINO ACIDS ESSENTIAL NON-ESSENTIAL CONDITIONAL Histidine Arginine Arginine Isoleucine Asparagine Cysteine Leucine Aspartic Acid Glutamine Lysine Glutamic Acid Glycine Methoinine Tyrosine Phenylalanine Ornithine Threonine Proline Tryptophan Serine Valine  Food Sources of Proteins No naturally-occurring food is 100% protein. Foods from animal sources typically have more protein than foods from plants. Seeds, tree nuts, and legumes supply more protein/serving than fruit or the edible leaves, roots, flowers, and stems of vegetables. Legumes are plants that produce seed pods with a single row of seeds, such as soybeans, lentils, beans, peanuts, and peas. See Table 7.3 for a list of commonly eaten foods and their protein contents. ©McGraw-Hill Education monly eaten foods and their protein con ©McGraw-Hill Education  Protein Quality High-quality protein (complete protein): Contains all 9 essential amino acids in amounts that support protein deposition in tissues and child’s growth Most animal products High-quality protein sources (plants): quinoa and processed soy Lacks or has inadequate Low-quality protein amounts of 1 or protein): (incomplete more of the essential amino acids Most plant sources and gelatin (animal connective tissue by- product) Limiting Amino Acids ©McGraw-Hill Education  Amino Acid Composition: Complete and Incomplete Protein Two or more plant proteins can be combined to compensate for deficiencies in essential amino acid: Complementary proteins Who is the best “running-mate” for grains in terms of prot intake recommendation? ©McGraw-Hill Education  COMPLIMENTARY PROTEINS Limiting amino acids in Plant Foods Plant source of Combination in which the proteins Food Limiting AA the AA compliment Legumes (beans) Met Grains, nuts, Red beans and rice seeds Vegetables Met Grains, nuts, Green beans and almonds seeds Grains Lys, Thre, Trp Legumes Rice and red beans; lentils and rice; corn and beans Nuts and Seeds Lys Legumes Soybeans and sesame; peanuts, rice, and black-eyed peas Whitney, Rolfes, Hammond, Piché, Understanding Nutrition First Canadian Edition. Nelson College Indigenous. 2015  What Happens to Proteins in the Body? Learning Outcomes Explain how cells make proteins. Describe what happens to excess amino acids in the body. Explain what happens to proteins as they undergo digestion and absorption in the human digestive tract. Explain the concept of nitrogen balance and identify conditions in which the body is a state of positive or negative nitrogen balance. Calculate a person’s RDA for protein based on his or her body weight. ©McGraw-Hill Education  Protein Synthesis Cells assemble the 20 amino acids in specific sequences and lengths according to information provided in DNA. Amino acids (“beads”) are connected by peptide bonds (“hooks”). Protein is composed of amino acids coded by DNA ©McGraw-Hill Education  DNA Directs Protein Synthesis Figure 7.2 Protein Synthesis Making New Proteins ©McGraw-Hill Education  Protein Denaturation Denaturation involves altering a protein’s natural shape and function by exposing it to various conditions. Examples include: Heat denatures protein in raw eggs. Acidic lemon juice “curdles” protein in milk. Hydrochloric acid denatures food proteins in the stomach, making them easier to digest. Physical agitation (e.g., whipping egg whites) denatures protein. ©McGraw-Hill Education Protein Configuration vs Protein Denaturation ©McGraw-Hill Education  Protein Digestion Chemical digestion of protein begins in the stomach: Hydrochloric acid denatures proteins. The enzyme pepsin digests proteins into smaller polypeptides. The enzymes Polypeptides trypsin enter theand chymotrypsin small intestine: secreted by pancreas break down polypeptides into shorter peptides and individual amino acids. ©McGraw-Hill Education  Protein Absorption Absorption occurs in the small intestine. Absorptive cells release enzymes that digest most small peptides into individual amino acids. Individual amino acids and some di- and tri- peptides enter absorptive cells, where the di- and tripeptides are completely digested to amino acids. Amino acids travel to the liver via hepatic portal vein. ©McGraw-Hill Education Summary: Protein Digestion and Absorption ©McGraw-Hill Education  PROTEIN IN THE HUMAN BODY >40% of body mass is skeletal muscle Collagen is the most abundant protein in the body (25-35%) There is no protein storage site in the body (unlike glucose or fat) Consuming protein regularly is important to ensure there are adequate AAs to replenish pools Urea is the principal vehicle for excreting unused nitrogen Whitney, Rolfes, Hammond, Piché. First Canadian Edition  Protein Turnover Protein turnover Breaking down old or unneeded proteins into their components (amino acids) and recycling the amino acids for new uses Amino acid “pool” A small number of amino acids that have not been incorporated into proteins 1) Endogenous amino acids Those available from the amino acid pool 2) Exogenous proteins Those from dietary sources ©McGraw-Hill Education  Deamination and Transamination Deamination is the removal of nitrogen-containing group from an unneeded amino acid. Transamination is the transfer of nitrogen-containing group from an unneeded amino acid to a carbon skeleton, forming an amino acid. ©McGraw-Hill Education  Deamination Ammonia forms is converted to urea and excreted in urine. Other by-products are incorporated in other biochemical processes. Transamination Synthesis of new nonessential amino acid and other by-products as required. Ammonia and Urea Formation Ammonia (NH3) is converted to urea that the kidneys excrete in urine. ©McGraw-Hill Education  Nitrogen Balance Nitrogen balance (nitrogen equilibrium): Positive nitrogen balance: Body retains more nitrogen than it loses Negative nitrogen balance: Body loses more nitrogen than it retains ©McGraw-Hill Education How Much Protein Do You Need? Daily protein requirement for healthy adults EAR = 0.66 g/kg body weight Daily protein recommendation (RDA) for healthy adults: RDA = 0.8 g/kg body weight Protein needs increase during periods of growth, pregnancy, lactation, and recovery from illness or injury. ©McGraw-Hill Education  Meat Consumption and Health High amounts of red or processed meat is associated with increased risk for CVD and some forms of cancer. Processed meat contain a lot of saturated fat and sodium that increase CVD risk. There is scientific evidence linking red and processed meat intake with colorectal, pancreatic, and stomach cancers. In 2015 to 2016, nearly 25% of meat consumed by Americans was processed. ©McGraw-Hill Education 5 Recommendations for Protein Intak Choose lean or low-fat meat and poultry. Lean cuts of beef include: Round steaks, top round, loin, top sirloin, chuck and arm roasts Lean pork cuts include: Loin, tenderloin, and center loin Choose “extra lean” ground beef (least 95% lean). Trim visible fat from meats. Limit intake of processed meats (“deli meats”). Choose more fish and protein-rich plant protein sources, such as dry beans, seeds, and nuts. ©McGraw-Hill Education Vegetarian Diets ©McGraw-Hill Education ©McGraw-Hill Education  Concerns for Vegetarians Children: May be difficult to consume adequate protein and energy, because plant foods tend to be filling Growth rates of vegan children need close monitoring MayPregnancy: need vitamin B12 supplements, otherwise infant could be deficient in B12. Breastfeeding: Breast milk may be deficient in vitamin B12. Infant can develop severe developmental delays if fed breast milk that lacks vitamin B12. ©McGraw-Hill Education  Excess Protein Intake Excessive red or processed meat intake: May increase risk of heart disease and cancer of the colon/rectum. High-protein diets are generally not recommended for healthy individuals. Excess protein/amino acid intake may lead to dehydration and higher than normal urinary losses of calcium, but this is controversial. Protein-rich foods are high in purines, nitrogen-containing substances that are not proteins. Body makes uric acid from purines. High blood uric acid level can contribute to gout. High uric acid in urine may contribute to kidney stones. ©McGraw-Hill Education  Protein Deficiency Uncommon in the U.S. May occur in: Elderly or low-income people Persons with alcoholism, anorexia nervosa, or intestinal tract disorders Protein-energy malnutrition (PEM) results when the diet lacks energy and high-quality protein. ©McGraw-Hill Education Protein-energy malnutrition (PEM Kwashiorkor Infant is abruptly weaned from breast milk and given low-quality protein diet when younger sibling is born. Adequate energy intake but intake of high-quality protein is low Edema Stunted growth Edema Marasmic kwashiorkor Inadequate energy and protein intake Muscle wasting and edema ©McGraw-Hill Education  Severe PEM Marasmus Starvation—extreme weight loss Extremely inadequate energy and protein intake ©McGraw-Hill Education Source: Centers for Disease Control and Prevention/Dr. Lyle C  What Is a Food Allergy? Allergy: Inflammatory response resulting when body’s immune system reacts inappropriately to a substance that is typically harmless. Allergen — the offending substance Most food allergens are proteins that escape digestion and are absorbed as whole proteins. Allergic reaction -- The body’s immune system responds to defend the body from the proteins. ©McGraw-Hill Education  Signs/Symptoms of Food Allergy Signs occur within a few minutes or couple of hours and typically include: Hives (red raised bumps on skin) Swollen or itchy lips Skin flushing Scaly skin rash (eczema) Difficulty swallowing Wheezing and difficulty breathing Abdominal pain, vomiting, and diarrhea Anaphylaxis is a serious, life-threatening allergic response. ©McGraw-Hill Education  Common Food Allergens Protein-rich foods: Non-proteins: Cow’s milk Food dyes Eggs 8 Most - Naturally present sulfites or Common Food Allergens sulfites added to: Peanuts Wine Tree nuts (walnuts) Potatoes Wheat Shrimp Soy Fish & shellfish ©McGraw-Hill Education Celiac Disease Coeliac disease is a condition where your immune system attacks your own tissues when you eat gluten. This damages your gut (small intestine) so you are unable to take in nutrients. Coeliac disease can cause a range of symptoms, including diarrhoea, abdominal pain and bloating. Coeliac disease is caused by an adverse reaction to gluten, which is a dietary protein found in 3 types of cereal: wheat barley rye  What Is PKU? Phenylketonuria (PKU) Rare genetic disorder Caused by lack of enzyme that converts the essential amino acid phenylalanine to another compound Phenylalanine and its toxic by-products build up in the body and damage tissues. Simple blood test given to newborns detects PKU. Critical to provide low-phenylalanine diet to infant with PKU a few days after birth If undiagnosed, infant will develop intellectual disability by first birthday. ©McGraw-Hill Education  Diet for PKU Infancy: Phenylalanine-free formula and low-phenylalanine foods Allowed: fruits, vegetables, Childhood and adult andyears special: low-phenylalanine foods Avoided: nuts, milk and milk products, eggs, meats and other animal sources of food, as well as foods and beverages containing nonnutritive sweetener aspartame Aspartame contains phenylalanine. Nutricia PKU Foods ©McGraw-Hill Education Thank you ! ©McGraw-Hill Education