Why is Protein Important?

Transcription

1 Why is Protein Important? Chapter 6 Proteins and Amino Acids: Func6on Follows Form BIOL 103 Spring 2017 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. Amino Acids are Building Blocks of Proteins Proteins are sequences of amino acids There are amino acids: 1. Essen6al (9) 2. Non- essen6al (11) 3. Condi6onally essen6al (6) 1

2 Amino Acids Iden6fied by Side Chains Protein structure: unique 3D shapes and func6ons Amino Acid Sequence Amino acids are linked to each other by bond: Dipep4de: 2 amino acids Oligopep4de: 3-10 amino acids Polypep4de: >10 amino acids Protein: a chain with >50 amino acids Protein shape A of AA determines protein shape Protein Structure Shape of protein determines its. 2

3 2/21/17 Func6ons of Body Proteins Func6ons of Body Proteins Fluid Balance: Fluids are found inside and outside cells Inside cells: intracellular fluid Outside cells: extracellular Inters44al 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

4 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 Denaturaliza6on: Destabilizing a Protein s Shape There are factors that can cause a protein to unfold and lose shape 1. Changes in Acidic or Alkalinity in environment 2. High temperature/heat 3. Alcohol 4. Oxida6on proteins lose their ability to func6on properly. e.g. egg protein, avidin 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 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

5 Review Ques6ons 1. Name a health risk related to high intakes of lipids. 2. Amino acids are linked by what type of bond? 3. What is a protease? 4. Protein diges6on starts at which organ? 5. Name a specific func6on of a protein other than muscles/hair/nails. 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 Cys4c 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 If essen6al AA unavailable 5

6 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 Protein recycling Proteins in the Body Synthesis of non- protein molecules Proteins are precursors of DNA, RNA, and neurotransmimers Protein and Nitrogen Excre6on Breakdown of amino acids by removing nitrogen (amino) group/- NH2 Amino groups converted to Urea + water = à excre6on (in kidney) Func6on of Blood Amino Acid Pool 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

7 Protein in the Diet Recommended Intakes of Protein Adult RDA = 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 7

8 Protein given as a percentage of calories We need only % of our calories from proteins That amount can be supplied by common vegetables. Vegetables average around 22% protein by calories, beans 28%, grains 13%. Protein is one of the easiest nutrient to get 1 medium ear of corn = 2.9 g x 4kcal = 11.6kcal 11.6kcal/77kcal (total cal in corn) = ~15% calories from protein in corn Rest of corn made up of carbs, fiber, and some famy acids fats 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 bemer : Animal foods have more protein, but that does not mean ea6ng more protein than your body needs is bemer for your body 8

9 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 9

10 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 B 12 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 Health Effects of Too Limle Protein Dietary protein = essen6al amino acids Protein deficiency: occurs when energy and/ or protein intake is inadequate Protein- energy malnutri4on (PEM) Kwashiorkor: severe deficiency Symptoms: edema, poor growth, bloated belly Affects those between age of months old Associated with extreme poverty 10

11 Health Effects of Too Limle 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 Health Effects of Too Much Animal Protein Osteoporosis and Protein Consump6on Research shows that consuming high protein diet can Increase calcium absorp6on in intes6ne Increase calcium loss via urina6on à osteoporosis? Consuming phosphorous with calcium appears to decrease the loss of calcium and subsequent loss of bone mass 1990 ar6cle from The Journal of Nutri2on: individuals who consume complex forms of proteins that contain phosphorous experience significantly less bone loss than those who consume simple proteins Simple protein sources: dairy, animal proteins Complex protein sources: soy products, beans, legumes 11