Chapter 6 Proteins and Amino Acids 2012 Pearson Education Inc Objectives for Chapter 6 Explain how proteins are different from carbohydrates and lipids Describe the basic structure of an amino acid Explain the difference between essential and nonessential amino acids Identify the key steps in digesting protein Identify the functions of protein in the body Identify sources of lean protein in the diet Create a diet plan that achieves the Recommended Dietary Allowance for protein Calculate the recommended protein intake for an individual based on the Dietary Reference Intakes Explain the health consequences of consuming too little or too much protein Describe the benefits and risks of a vegetarian diet Nutrition and You 2e 2012 Pearson Education Inc What Are Proteins and Why Are They Important Proteins are the predominant structural and functional materials in every cell Contain carbon hydrogen oxygen like carbohydrates and fats In addition also contain nitrogen Each amino acid has Acid group COOH Amine group NH2 Side chain unique All proteins consist of some combination of 20 unique amino acids Nutrition and You 2e 2012 Pearson Education Inc The Structure of an Amino Acid Figure 6 1 Nutrition and You 2e 2012 Pearson Education Inc Essential Nonessential and Conditional Amino Acids Nine essential amino acids Cannot be made by the body It is essential to obtain them from the diet Eleven nonessential amino acids Can be synthesized in the body from other amino acids or by adding nitrogen to carbon containing structures Conditionally essential amino acids Under certain conditions some nonessential amino acids cannot be made in body Nutrition and You 2e 2012 Pearson Education Inc The Making of a Protein Figure 6 2 Nutrition and You 2e 2012 Pearson Education Inc Animation The Building Blocks of Proteins Nutrition and You 2e 2012 Pearson Education Inc Table 6 1 Nutrition and You 2e 2012 Pearson Education Inc Denaturing a Protein Figure 6 3 Nutrition and You 2e 2012 Pearson Education Inc Denaturation of Proteins Changes Their Shape Denaturation the alteration unfolding of a protein s shape which changes the structure and function of the protein Examples cooking meat eggs changing texture Stomach acid untangles proteins to aid in digestion Nutrition and You 2e 2012 Pearson Education Inc What Happens to the Protein You Eat Dietary proteins are digested and absorbed in stomach and small intestine Stomach acids denature protein and Activate pepsin which breaks down protein into shorter polypeptides In the small intestine polypeptides broken down into tripeptides dipeptides and amino acids Amino acids enter blood and travel to liver Nutrition and You 2e 2012 Pearson Education Inc Digesting and Absorbing Proteins Figure 6 4 Nutrition and You 2e 2012 Pearson Education Inc The Fate of Amino Acids in Your Body Figure 6 5 Nutrition and You 2e 2012 Pearson Education Inc Animation Protein Digestion Nutrition and You 2e 2012 Pearson Education Inc Animation Protein Absorption Nutrition and You 2e 2012 Pearson Education Inc Your Body Degrades and Synthesizes Proteins Amino acids come from Diet Breakdown of proteins in the body A limited supply is stored in amino acid pools in blood and cells for needed protein synthesis Protein turnover process of continuous breakdown and synthesis of protein from its amino acids Nutrition and You 2e 2012 Pearson Education Inc Your Body Degrades and Synthesizes Proteins Amino acids can be used to make Body proteins Non protein substances Examples thyroid hormone melanin After amine groups removed converted to urea excreted in urine amino acids can also be Burned for energy Stored as fat Made into glucose Nutrition and You 2e 2012 Pearson Education Inc Protein Synthesis Figure 6 6 Nutrition and You 2e 2012 Pearson Education Inc DNA Directs Synthesis of New Proteins DNA in the cell nucleus contains instructions for protein synthesis Gene DNA segment that codes for specific protein Specialized RNA molecules carry out instructions for protein synthesis Messenger RNA mRNA and transfer RNA tRNA perform very specific roles during protein synthesis When abnormalities occur during protein synthesis serious medical conditions may result Example sickle cell anemia Nutrition and You 2e 2012 Pearson Education Inc How Does Your Body Use Proteins Proteins provide structural and mechanical support and help maintain body tissues Collagen a ropelike fibrous protein that is the most abundant protein in your body Connective tissue the most abundant tissue type in the body made up primarily of collagen it supports and connects body parts as well as provides protection and insulation Proteins build most enzymes and many hormones Proteins help maintain fluid balance Nutrition and You 2e 2012 Pearson Education Inc An Enzyme in Action Figure 6 7 Nutrition and You 2e 2012 Pearson Education Inc Edema Figure 6 8 Nutrition and You 2e 2012 Pearson Education Inc Animation Protein Synthesis Nutrition and You 2e 2012 Pearson Education Inc How Does Your Body Use Proteins Proteins help maintain acid base balance Buffers substances that help maintain the proper pH in a solution by attracting or donating hydrogen ions Proteins transport substances throughout the body Transport proteins shuttle oxygen waste products lipids some vitamins and sodium and potassium through your blood and into and out of cells through cell membranes Proteins contribute to a healthy immune system Specialized protein soldiers called antibodies eliminate potentially harmful substances Proteins can provide energy Protein improves satiety and appetite control Nutrition and You 2e 2012 Pearson Education Inc Proteins as Transport Channels Figure 6 9 Nutrition and You 2e 2012 Pearson Education Inc Table 6 2 Nutrition and You 2e 2012 Pearson Education Inc How Much Protein Do You Need Healthy adults should be in nitrogen balance the state in which an individual is consuming the same amount of nitrogen from protein in the diet as he or she is excreting in the urine Nutrition and You 2e 2012 Pearson Education Inc Animation Nitrogen Balance Nutrition and You 2e 2012 Pearson Education Inc Nitrogen Balance and Imbalance Figure 6 10 Nutrition and You 2e 2012 Pearson Education Inc Not All Protein Is Created Equal Plant proteins upgraded to complete proteins by Consuming modest amounts of soy or animal protein or Being complemented with other plant proteins which provide enough of the limiting amino acid Protein Digestibility Corrected Amino Acid