Chapter 6 Proteins 1 Large complex molecules found in all living things 2 Synthesis controlled by our DNA genetic material 3 Contains carbon hydrogen oxygen and nitrogen 4 Made from 20 amino acids 9 of which are essential must be obtained from food 5 Nonessential can be synthesized in sufficient quantities We do not need to consume them in the diet 6 Transamination the transfer of an amine froup from an essential amino acid to a different acid group and side chain r group It is used to make nonessential amino acids 7 Conditionally essential amino acide a Nonessential becomes essential b PKU tyrosine becomes a conditionally essential amino acid that must be provided by the diet Phenylalanine tyrosine 8 How are proteins made a Long chains of amino acids connected by peptide bonds b Gene expression when cells use genes to make proteins i Gene segment of DNA that serves as a template for the synthesis expression of a particular protein AT CG c Transcription messenger RNA copies the genetic information from DNA d Translation the genetic information in RNA is converted into the amino acid sequence of a protein e Transcription copy Translation to translate from RNA to ribosome to create a f protein Protein turnover existing proteins are degraded to provide the building blocks for new proteins i Amino acid pool includes amino acids from food and cellular breakdown g Protein organization determines function sequential order of the amino acids i Spiral shape from twist in amino acid chain 9 Hemoglobin red blood cells 10 Protein denaturation proteins uncoil and lose the shape a Damaging substances heat acid base heavy metal alcohol b Protein function is lost i Denatured enzyme high fever blood pH out of normal range during digestion 11 Protein in the diet for protein synthesis all essential amino acids must be available to the cell a Limiting amino acid i Essential amino acid that is missing or in the smallest supply ii Slows down or halts protein synthesis b Inadequate energy consumption i Limits protein synthesis c Incomplete protein low quality insufficient essential amino acids i Derived from animal and soy protein ii Soy protein sufficient for adults not for infants d Mutual Supplementation combine two or more incomplete protein sources to make a complete protein e Complementary proteins two or more foods are combines to supply all nine essential amino acids for a complete protein 12 Protein digestion begins in the stomach and continues in small intestine a Hydrochloric acid denatures protein strands and activates pepsin b Pepsin enzymes breaks down proteins into short polypeptides and amino acids c Gastrin hormone controls hydrochloric acid production and pepsin release d Pancreatic enzymes proteases complete protein digestions e Special sites small intestine transport amino acids dipeptides tripeptides f High doses of individual amino acid supplements can lead to amino acid toxicity and i Chemical score ii Protein digestibility corrected amino acid score PDCAAS b Animal protein and many soy products are highly digestible 90 absorption deficiencies 13 Protein quality a Methods 14 Functions Fluid and electrolyte balance a Cell growth repair maintenance b Enzymes and proteins c d Acid base balance Immune system e Energy source f g Nutrient transport and storage 15 Protein Adequacy a Nitrogen balance determines proteins needs i Positive nitrogen balance negative nitrogen balance in nitrogen balance 16 RDA for protein a RDA 0 8 g per kg of body weight per day b Recommended percentage of energy is 10 35 of total energy intake c Protein needs are higher during growth and development children adolescents and pregnant lactating women 17 Too much protein can be harmful blood cholesterol levels saturated fat b Contributed to bone loss a High cholesterol and heart disease animal protein rich diets are associated with high i High protein diets increase calcium excretion and can lead to bone loss ii However adequate protein intake is associated with decreased risk of osteoporosis c Kidney disease i High protein increased risk among susceptible individuals ii People with diabetes have higher rates of kidney disease and may benefit from iii Max of 2g of protein per kilogram body weight each day is safe for healthy a lower protein diet people 18 Protein Sources 19 Vegetarian Diets a Meats milk based products soy products legumes whole rains nuts quorn a Vegetarianism restricting diet to foods of plant origin b People choose to be for healthy benefits ecological reasons religious reasons ethical reasons and concerns over food safety c Healthy benefits i Lower fat and total energy intake ii Lower blood pressure reduced risk of heart disease fewer digestive problems reduced risk of some cancers reduced risk of kidney disease kidney stones and gallstones d Challenges i Can be low in some nutrients Associated with disordered eating Varied and adequate diet planning Soy and complementary proteins Vegetarian food guide pyramid Special attention to vitamins D B12 and riboflavin b2 and zinc and iron 20 Protein energy malnutrition caused by inadequate protein and energy intake a Common forms marasmus and kwashiorkor 21 Marasmus grossly inadequate energy and nutrition intake a Consequences wasting and weakening of muscle heart stunted brain development and learning depressed metabolism stunted physical growth deterioration of the intestinal lining anemia severely weakened immune system fluid and electrolyte imbalances 22 Kwashiorkor disease resulting from low protein intake a Sympotoms Some weight loss and muscle wasting retarded growth and development edema resulting in distention of the belly fatty degeneration of the liver loss of appetite sadness irritability apathy and skin problems hair loss 23 Genetic disorders caused by defective DNA a Phenylketonuria inherited cannot break down phenylalanine i Phenylalanine and metabolic byproducts build up in tissues and can cause brain damage ii Should consume a diet low in phenylalanine b Sickle cell anemia inherited disorder of the RBCs in people who get the gene from both parents i Cells become crescent shape causing them to become hard and sticky which restricts blood flow and damages organs spleen ii Sickle cells have a shorter life span anemia iii Symptoms impaired vision headaches convulsions bone degeneration c Cystic fibrosis inherited disease affecting the respiratory system and digestive tract i Alteration of chloride transport in cells ii Cells secrete
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