Download BIOL 103 Ch 6 Proteins for Students

6/17/16 Why is Protein Important? Chapter 6 Proteins and Amino Acids: Func6on Follows Form BIOL 103 A part of every cell Needed in thousands of chemical reac6ons Keep us “together” structurally In short, proteins have many, many func6ons from replacing skin cells, producing an6bodies to assis6ng in nutrient transport and muscle contrac6ons. •  Excess protein intake a greater problem in the U.S. • 
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Amino Acids are Building Blocks of Proteins •  Proteins are sequences of amino acids •  There are _____ amino acids: 1.  Essen6al 2.  Non-­‐essen6al 3.  Condi6onally essen6al • 
Amino acids that are normally dispensable, but become indispensable under certain circumstances such as during cri6cal illness. 1 6/17/16 Amino Acids Iden6fied by Side Chains Protein structure: unique 3D shapes and func6ons •  Amino Acid Sequence – Amino acids are linked to each other by _____________________: •  Dipep3de: 2 amino acids •  Oligopep3de: 3-­‐10 amino acids •  Polypep3de: >10 amino acids •  Protein: a chain with >50 amino acids Protein Structure •  Protein shape – A sequence of AA determines protein shape – Shape of protein determines its func6on. 2 6/17/16 Func6ons of Body Proteins Func6ons of Body Proteins •  Fluid Balance: –  Fluids are found inside and outside cells –  Inside cells: intracellular fluid –  Outside cells: extracellular •  Inters33al fluid •  Intravascular fluid Func6ons of Body Proteins •  Fluid Balance – Blood proteins maintain appropriate fluid levels in vascular system – Edema results when diet lacks enough protein to maintain normal levels of blood proteins •  Edema: Swelling caused by buildup of fluid between cells 3 6/17/16 Func6ons of Body Proteins •  Source of Energy and Glucose – Carbohydrates and fat are protein-­‐sparing •  Body prefers burning them for energy •  Will resort to burning protein for energy if necessary – Body readies protein for use as energy through ___________________________ •  Removal of amino group from an amino acid Protein Diges6on and Absorp6on •  Protein diges6on – In the stomach: •  Proteins are denatured by hydrochloric acid (HCl) •  Cells produce proenzyme pepsinogen, an inac6ve precursor to pepsin •  HCl ac6vates pepsinogen to pepsin •  Pepsin begins diges6on (~10-­‐20%) Protein Denaturaliza6on: Destabilizing a Protein’s Shape •  There are factors that can cause a protein to unfold and lose shape: •  Denatured proteins lose their ability to func6on properly. –  e.g. egg protein, avidin Protein Diges6on and Absorp6on •  In the small intes6ne: –  Proteases from pancreas and intes6nal lining cells break down remaining proteins à small pep6des and/or amino acids –  Depending on the amino acid, uses facilitated diffusion or ac6ve transport during absorp6on –  Q: Why might it be a problem if a person takes amino acid supplementa6on? –  Once amino acids are absorbed into your intes6nal cells à travel via portal vein to liver à released to general circula6on 4 6/17/16 Protein Diges6on and Absorp6on •  If not digested, con6nues down to GI tract as feces •  Diseases of the intes6nal tract cause problems with diges6on by decreasing absorp6on efficiency – Celiac disease: Cannot digest gluten (a protein found in wheat, rye, barley) à presence of gluten trigger autoimmune response against villi – Cys3c fibrosis: s6cky mucus prevents diges6ve enzymes (e.g. proteases) from reaching small intes6ne à poor diges6on à nutrients are not absorbed à malnutri6on Proteins in the Body •  Protein Synthesis: –  Amino Acids (AA) assembled in specific sequence –  If a non-­‐essen6al AA is missing, the cell can either make the AA or obtain it from the liver via bloodstream –  However, if an essen6al AA missing…body may break its own protein down to supply the missing AA –  If essen6al AA unavailable…protein synthesis halts and par6ally completed protein is broken down into individual AA to be used elsewhere in the body Protein in the Body •  Amino Acid Pool and Protein Turnover –  When cells make proteins, they use amino acids from _________________________: available amino acids in body 6ssues and fluids that can be used to make new proteins. –  Cells in your body constantly build and breakdown proteins à ______________________ 5 6/17/16 Proteins in the Body Func6on of Blood Amino Acid Pool •  Synthesis of non-­‐protein molecules –  Proteins are precursors of DNA, RNA, and neurotransmilers •  Protein and Nitrogen Excre6on –  Breakdown of amino acids by removing nitrogen (amino) group/-­‐NH2 –  Amino groups converted to urea –  Urea + water = urine à excre6on (in kidney) Nitrogen Balance •  We can evaluate our nitrogen balance to evaluate what is happening in our body –  Nitrogen intake vs. nitrogen output •  Nitrogen equilibrium –  Nitrogen intake = nitrogen output –  Healthy adults •  Posi6ve nitrogen balance –  Nitrogen intake > Nitrogen output –  Growth; recovery from illness •  Nega6ve nitrogen balance –  Nitrogen intake < Nitrogen output –  Injury and illness 6 6/17/16 Protein in the Diet •  Recommended Intakes of Protein – Adult RDA = 0.8 gram per kilogram of body weight – Severe physical stress can increase body’s need for proteins •  Infec6ons, burns, fevers, surgery increase protein losses •  Diet must replace lost protein •  Protein Consump6on in the United States – Generally higher than recommended range Protein in the Diet •  True or False: “Plant based diet do not contain all the essen6al amino acids human needs. To be healthy, we must either eat animal protein or combine certain plant foods in order to ensure that we get complete proteins.” Vegetarian and Protein •  “Diet for a Small Planet,” 1971 by Frances Moore-­‐Lappe –  Study done 100 years ago on baby rats –  Rats need more proteins to grow than humans Protein given as a percentage of calories •  We need only 2.5-­‐11% of our calories from proteins •  That amount can be supplied by common vegetables. •  Vegetables average around 22% protein by calories, beans 28%, grains 13%. 7 6/17/16 Amino Acid need from WHO Protein Quality is not a problem •  Protein quality is “inferior”: –  Quality measure are mostly based on amounts of AA in foods; plant based foods contain as much or more than you need of each individual AA. •  More is not “beler”: –  Animal foods have more protein, but that does not mean ea6ng more protein than your body needs is beler for your body Proteins and Amino Acids as Addi6ves and Supplements •  Protein and AA addi6ves –  Contribute to structure, texture, taste of foods •  Protein and AA supplements –  Used for a variety of reasons: dieters, athletes, certain diseases. –  Risks are unknown Vegetarian Ea6ng •  Why People Become Vegetarians – Various reasons, including •  Religious beliefs •  Environmental concerns •  Aversion to ea6ng another living creature •  Concerns about animal cruelty concerns 8 6/17/16 Vegetarian Ea6ng •  Health Benefits of Vegetarian Diets – Less fat, saturated fat, and cholesterol intake – More magnesium and folate – More an6oxidants – More fiber and phytochemicals •  Reduces risk for heart disease, obesity, hypertension, and cancer Vegetarian Ea6ng •  Health Risks of Vegetarian Diets –  Vegan diets may be low in some nutrients •  Calcium, iron, zinc, vitamin D, and vitamin B12 –  Higher intake of phytates •  Cooking, fermenta6on, or soaking in acid medium can reduce contents of phy6c acid –  More restric6ve food choices = less nutrients –  Careful planning needed for growth and overall health 9 6/17/16 Health Effects of Too Lille Protein •  Dietary protein = essen6al amino acids •  Protein deficiency: occurs when energy and/
or protein intake is inadequate •  Protein-­‐energy malnutri3on (PEM) –  Kwashiorkor: severe _____________ deficiency •  Symptoms: edema, poor growth, bloated belly •  Affects those between age of 18-­‐24 months old •  Associated with extreme poverty Health Effects of Too Lille Protein Protein-­‐Energy Malnutri6on •  PEM, cont. –  Marasmus: severe _______________ deficiency •  Chronic PEM; “withering” •  Affects Infants and 6-­‐18 months old children •  Usually the children are short and thin for their age •  How to treat? –  Nutri6onal rehabilita6on •  Gradual and careful re-­‐feeding •  Must start with fluid and electrolyte balance, then introduce nutrients 10 6/17/16 Health Effects of Too Much Protein 11