Chapters 6 - 7 Study Guide
Chapters 6 - 7 Study Guide NTR 213-05
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This 6 page Study Guide was uploaded by Elizabeth Weathers on Monday March 7, 2016. The Study Guide belongs to NTR 213-05 at University of North Carolina - Greensboro taught by Laurie H. Allen in Winter 2016. Since its upload, it has received 93 views. For similar materials see Introductory Nutrition in Environmental Science at University of North Carolina - Greensboro.
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Date Created: 03/07/16
Protein Functions Structural proteins Cells Cell Membrane Organelles Cell Fluid (cytoplasm) Body Parts Skin Hair Ligaments Tendons Enzymes Enzymes Assist biochemical reactions Most chemical reactions in the body require enzymes Transport other proteins in blood and across membranes Immunity/safety Skin—barrier from bacteria Blood clotting in case of injury Antibodies protect the body from foreign invaders i.e. vaccines stimulate these to improve immunity against disease Movement Skeletal muscles Smooth muscles Hormones Regulate fluid balance Maintain proper acidity of blood Energy The Structure of Protein: Amino Acids Amino acids are the building blocks of proteins Amino acids contain Carbon, hydrogen, acid group, amino group (nitrogen containing), and a side chain There are hundreds of proteins known, but only 20 amino acids commonly occur naturally Nine are essential The body cannot make and must come from the diet Eleven are nonessential The body can make them by using nitrogen from essential AA and pieces of CHO and fats Protein Denaturation Denaturation—alteration of a protein’s three-dimensional structure due to agitation. Proteins uncoil; after this occurs, the protein no longer functions as it naturally did before The stiffening of egg whites when they are whipped Heat Processing, cooking (hardening of an egg when it is cooked), fever Acidic and basic conditions Stomach; the curdling of milk when acid is added Acidosis and alkalosis (low/high blood pH) Heavy metals (mercury, gold, lead) Alcohol Detergents Protein Digestion & Absorption Mechanical digestion begins in the mouth when chewing breaks down the food Chemical digestion begins in the stomach Hydrochloric acid (HCl) denatures (uncoils) proteins HCl activates pepsinogen to pepsin (enzyme) Pepsin breaks peptide bonds leaving shorter polypeptides Chemical digestion continues in the small intestine Pancreatic enzymes and enzymes in the microvilli of the intestine further break down polypeptides for absorption The majority of protein digestion occurs here Single amino acids, dipeptides and tripeptides can be absorbed into the mucosal cells of the small intestine This uses different transport systems and amino acids can compete for absorption Dipeptides and tripeptides are further broken down into single amino acids Single amino acids then pass into the blood and are brought to the liver Protein Synthesis The process of protein synthesis involves two steps Transcription Translation Transcription—a stretch of DNA (in the nucleus) is used as a template to make a strand of RNA (ribonucleic acid) known as messenger RNA (mRNA) After this, the mRNA strand crosses the nuclear membrane into the cytoplasm of the cell, taking the coding instructions with it Translation—the mRNA attaches itself to one of the ribosomes (protein-making machine) mRNA specifies the sequence in which the amino acids line up for synthesis of a protein Transfer RNA (tRNA) collects amino acids from the cell fluid and brings them to the mRNA Each of the 20 amino acids has a specific tRNA Once the protein is made, tRNA is released to be recycled and used again Protein Quality High-quality, or complete dietary, proteins Contain all amino acids to meet body’s needs More easily digested Animal proteins and soy Incomplete proteins Lower in one or more essential amino acids Most plant proteins Use complementary proteins Types of Vegetarian Diets Semivegetarian: Excludes red meat but may include fish and poultry, as well as dairy products and eggs Pescetarian: Excludes all animal flesh except fish Lacto-ovo vegetarian: Excludes all animal flesh but includes eggs and dairy products Lacto vegetarian: Excludes animal flesh and eggs but includes dairy products Vegan: Excludes all food of animal origin Protein Requirements 0.8 g/kilogram of body weight for adults With more weight, more protein is needed for maintenance and repair 70 kg (154 lb) adult = 56 g of protein/day Average consumption = 70 g of protein/day Higher needs in infants, during pregnancy and lactation (breast feeding), after injury, and in for athletes Pregnant/lactating women: add 25 g of protein/day Protein in Health & Disease Kwashiorkor—pure protein deficiency Marasmus—overall energy deficiency Nitrogen Balance Nitrogen intake equals nitrogen loss Maintaining body protein and weight Negative nitrogen balance: more nitrogen lost than consumed From illness, injury, or decreased consumption Positive nitrogen balance: more nitrogen consumed than lost From growth, pregnancy, or weight training Vitamin Bioavailability Amount of ingested vitamin amount that is absorbed Affected by: Absorption Fat-soluble vitamins: need dietary fat Transport in blood Water-soluble vitamins: blood proteins Fat-soluble vitamins: chylomicrons Conversion of inactive provitamins or vitamin precursors into active vitamins Vitamin Functions promote and regulate body processes necessary for growth, reproduction, and the maintenance of health Ex: making hemoglobin, helping harvest energy, assisting with immunity, promoting bone health, helping remove pollutants (oxidants) from the body Vitamins Water soluble Fat soluble B Vitamins Vitamin C Vitamin A Thiamin Pantothenic acid Riboflavin Vitamin B Vitamin D 6 Vitamin E Niacin Folate Biotin Vitamin B 12 Vitamin K NOTE: fat soluble vitamins are more likely to be toxic vs. water soluble vitamins because the body stores them while excess water soluble vitamins are excreted Vitamin Absorption Water-Soluble Vitamins B vitamins: involved in converting the energy in carbohydrate, fat, and protein into ATP Vitamin C: needed to make connective tissue and as an antioxidant Choline: vitamin? (will not be on our exam) Not stored - need to be consumed regularly Excreted in urine Fat-soluble Vitamins Vitamins A, D, E, & K Found with fats in foods Require special handling for absorption, transport and excretion Excretion limitations increases the risk of toxicity Stored in the liver and fatty tissues Intakes can vary without a risk of deficiency if average intake over weeks/months meets needs
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