Protein: Amino Acids

Objectives After reading Chapter 5, class discussion and activities you will be able to: –Describe the role of proteins –Distinguish between complete and incomplete proteins –Identify sources of quality protein –Calculate calories from protein

Objectives Describe protein digestion/absorption Identify RDA for protein Discuss health related effects of protein

Protein Essential part of all living cells Found in animals and plants; Particularly rich in animal foods – meats, poultry, eggs, etc. Protein is in your skin, hair, nails, muscles, etc. Made of amino acids – amino acids contain nitrogen, which is necessary for life.

Amino Acids p. 182 Fig 6-1

Amino Acids Nonessential amino acids –Body can synthesize –Over half of the 20 AA Essential amino acids –Body cannot synthesize –Nine (9) Conditionally essential amino acids –Phenylalanine  Tyrosine; New Borns

p.182 Tab 6-1

Proteins Peptide bond –Dipeptide –Tripeptide –Polypeptide

Proteins Dipeptide

Proteins Polypeptide (Example: Insulin)

Protein shape and function Amino Acid Sequences

Proteins Protein denaturation –Uncoiling & loss of shape –Therefore, loss of function –Caused by heat, acid, mechanical –Examples: cooked egg, egg whites, curdling of milk, separation of foods with milk or egg (syneresis)

Protein Digestion Mouth –Mixing, moisturizing Stomach –HCl –Pepsinogen  pepsin Proenzyme  Enzyme

Protein Digestion Small intestine –Proteases Intestinal and pancreatic –Peptidases

p. 186 Fig 6-6

Protein Absorption Carriers –Transport AA into intestinal cells –Used for synthesis and energy Capillaries –Carried to liver Absorption misconceptions –Enzyme/amino acid supplements

Protein Synthesis Delivering the instructions –DNA mRNA- attaches to ribosome –Protein-making machine

Protein Synthesis Sequencing errors

Roles of Proteins Building material: Building blocks of muscles, blood, skin, bones, teeth; protein matrix=collagen –Growth –Maintenance

Roles of Proteins Enzymes=catalysts p. 190 Fig 6-9

Roles of Proteins Hormones –Switching Machines

Roles of Proteins Regulation of fluid balance –Edema Acid-base regulation –Acidosis –Alkalosis

Transport proteins

Roles of Proteins Immunity: Molecular Memory –Antibodies: Giant protein molecules designed to combat –Antigens: Invading foreign proteins (virus)

Roles of Proteins Source of energy –Gluconeogenesis –No storage source=muscle wasting –“Amino acid pool” Other roles –Fibrin  blood clotting –Opsin—light-sensitive pigment

Protein Metabolism Protein turnover –Amino acid pool: supply of AA from food/body; collect in cells & blood; ready for use Nitrogen balance –Positive nitrogen balance –Negative nitrogen balance

Protein Metabolism Using amino acids to make proteins=CONDENSATION Using amino acids to make nonessential amino acids

Protein Metabolism Using amino acids to make other compounds –Neurotransmitters Using amino acids for energy and glucose Deamination: AA stripped of N –Ammonia produced

Protein Quality High-quality proteins –All essential AA –Animal proteins=complete –Plant proteins=incomplete Amino acid composition –Limiting amino acid Digestibility –Animal vs. vegetable

Protein Quality PDCAAS –Protein digestibility- corrected amino acid score Reference Protein

Protein Quality Complementary proteins –Two protein foods make up for the lack of certain amino acids in each other when eaten together

Food Labels Quantity of protein Daily Value –50 g protein 10% of a 2000 kcal diet

Nitrogen Balance Determine adequacy of protein intake N 2 In - N 2 Out = Nitrogen Balance –N 2 In = Protein Intake as Nitrogen –N 2 Out = 24 Hour Urine Collection for N 2 + Stool, Insensible Losses Positive Nitrogen Balance –Body excretes less protein than is taken in (Anabolism) Negative Nitrogen Balance –Body excretes more protein than is taken in (Catabolism)

Protein-Energy Malnutrition (PEM) Marasmus –Slow developing, chronic PEM –Muscle wasting; no body fat –Pluckable hair; dry skin Kwashiorkor ?????? Marasmus-kwashiorkor mix

p. 197 Tab 6-3

p. 197 Tab 6-3

Protein-Energy Malnutrition (PEM) Infections not protein intake –Dysentery C-Reactive Protein

Health Effects Conditions Associated with Other Nutrients: –Osteoporosis – Calcium –Heart Disease – Fat –Obesity – Fat/CHO –Cancer - Fat

Health Effects Genetic Associated Diseases –Phenylketonuria –Sickle Cell Anemia Kidney Disease

Recommended Intakes RDA –0.8 g/kg/day –10% - 35% of energy intake

Objectives After reading Chapter 5, class discussion and activities you will be able to: –Describe the role of proteins –Distinguish between complete and incomplete proteins –Identify sources of quality protein –Calculate calories from protein

Objectives Describe protein digestion/absorption Identify RDA for protein Discuss health related effects of protein