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Lecture 6

Week 6 - Proteins.docx

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Department
Nutrition
Course
NUTR 1010
Professor
Jess Haines
Semester
Fall

Description
Week 6 PROTEINS - Large molecules with many functions - Our bodies contain thousands of different proteins - Contain carbon, hydrogen, oxygen, and nitrogen - Made of long strings of amino acids AMINO ACIDS There are 20 amino acids, 9 of them are essential; our bodies can’t make them and you have to There are 11 non-essential amino acids; they are still important but our body can make them through transamination. • If there aren’t enough of all the essential AA’sIf there aren’t enough of ALL the essential AAs, your body can’t make proteins • Complete proteins have all the essential AAs • Incomplete proteins are missing some AAs • Complementary protein = 2 sources of protein that together contain all the AAs COMPLETE PROTEINS INCOMPLETE PROTEINS COMPLEMENTARY PROTEINS Animal: meat, fish, poultry, eggs, milk. Grains: low in isoleucine and lysine Eating beans with grains Plants: soy, quinoa Beans: low in menthionine and tryptophan provides all the amino acids. HOW PROTEINS ARE MADE Your body keeps a “pool” of amino acids; your DNA tells your body how to string amino acids together to make proteins. Transcription: RNA message, making a copy of your DNA. Translation: creating the protein from the RNA message. During translation, amino acids are attached with peptide bonds. Dipeptide: 2 amino acids Tripeptide: 3 amino acids Ogliopeptide: a few Polypeptide: a lot of amino acids Protein Shape Different AA’s in the chain are attracted to each other; complex folding of the molecule. Folding determines the shape & shape determines the function. One protein may contain several polypeptide chains. Sickle Cell Anemia: genetic mutation that caused proteins that don’t work; one AA difference changes shape, and function of hemoglobin. Protein Digestion Mouth: mechanical digestion Stomach: acid denatures protein; pepsin breaks long proteins into smaller chunks and single AA’s; becomes unfolded; denatured proteins don’t work, so you can’t take hormones/enzymes orally (unless they work before they hit acid, or have special coating). Small intestine: proteases break down remaining proteins into oligopeptides, tripeptides, dipeptides and amino acids; peptidases break ogliopeptides, tripeptides, and dipeptides into amino acids; free amino acids, di- and tripeptides can be absorbed into the intestinal cells; the cells break di- and tripeptides into AA’s. Midterm review: A kilocalorie is the amount of energy it would take to increase the temperature of 1 gram of water by 1 degree Celsius FALSE. Answer: calorie. Aspartame: it is 200 times sweeter than sugar. Review serving sizes! Denatured protein: unfolded protein that doesn’t work anymore; happens in the stomach with the stomach acid; only acid that can do this, and lemon juice. October 12 th WHAT DO PROTEINS DO 1) Cell growth, repair and maintenance: - Many cell structures contain lots of protein; muscle, skin, bones, organs (liver, pancreas), blood cells; all need to be replaced; muscles need the most protein; it allows them to contract (us to move). - We recycle; old cells are broken down and we save the amino acids of the proteins to use again. 2) Act as enzymes and hormones - Enzymes allow chemical reactions to happen; everything our body does involves chemical reactions - Hormones send chemical signals in the body; protein hormones include:  Growth hormone, insulin, prolactin (stimulates breast milk production), gastrin (stimulates the stomach), leptin (role in satiety and weight control). 3) Transport into and out of cells - Facilitated diffusion - Active transport 4) Transport in the blood - Albumin: transports nutrients such as calcium, zinc and vitamin B6 - Lipoproteins 5) Maintain fluid balance – Albumin - Fluids are attracted to protein (diffusion – when you try to dissolve something in water, all particles will distribute equally; in the body, fluids in the cell membrane will try to distribute the atoms evenly but the membranes will not let the atoms move anymore; only water can move them). - Balanced concentrations of protein are needed between the insides and outsides of cells in the blood - If not, edema (swelling of feet); when there is not a lot of protein in the blood and the water moves towards the cells. 6) Maintains electrolyte balance; needed for muscle and nerve function - Main electrolytes: sodium and potassium; cell have sodium/potassium pumps made of protein to keep the balance. 7) Acid base balance - Some proteins are good
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