WH+lecture+5-protein

WH+lecture+5-protein - Protein Structure and Digestion What...

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Protein Structure and Digestion
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What is Protein? One or more folded strands of amino acids Made of C,H,O and Nitrogen Supplies 4 kcal/g Found in animal and plant foods In the body- has structural and regulatory functions
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Sources of Protein One ounce of meat= 7 g One cup of milk= 8 g ½ cup beans= 6-10 g Vegetables/grains= 2-3 g per serving Fruits= 1 g per serving
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Amino Acids Building blocks of protein Folded chains Each protein molecule contains a specific number and sequence of amino acids 20 types- 9 are essential Nonessential can be made by a process called transamination
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20 Amino Acids
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Structure of Amino Acids Alanine
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Conditionally Essential 6 nonessential amino acids are made from essential amino acids Tyrosine/ phenylalanine Cysteine/ methionine Arginine Glutamine Glycine Proline
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Protein Structure Amino acids are linked by peptide bonds Dipeptide Tripeptide Polypeptide Protein- one or more polypeptide chains folded into a 3-D shape
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Protein Structure Sequence determined by DNA
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Denaturation Changes in protein structure due to heat or acid Raw egg vs. cooked egg Acidic marinade can cook raw fish Raw meat vs. cooked meat
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Protein Digestion Begins in Stomach HCL acid Denatures proteins Activates pepsin Small intestine Trypsin and chymotrypsin Brush border enzymes Amino acids, di and tripeptides enter mucosal cell Inside mucosal cell- further breakdown
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Absorption of Amino Acids Amino acids cross mucosal cells by Active Transport – several different transport systems (some are shared) Too much of one amino acid may impair absorption of other amino acids Arginine shares same transport system as lysine- if you take arginine in pill form what will happen to lysine??
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What happens if a protein is not completely digested? Allergic reaction- body thinks the whole protein is a foreign substance Immune system reacts Happens in infants or those with GI disease Benefit to infants
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Protein Metabolism Absorbed amino acids are sent to the liver Can be used to make blood or liver proteins Can be used for energy Can be released to other tissues Can be used to make nonprotein molecules
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Amino Acid Pool Refers to available amino acids in body tissues and fluids Comes from diet and body stores 300 g of protein synthesized a day (only 100g coming from the diet) Protein and energy intake adequate Energy deficient, protein excessive
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Protein Synthesis- process of reading genetic information Amino acid pool is used to make body proteins Instructions on how to make each protein comes from our genes (DNA) Reading the instructions- Process of Transcription and Translation Proteins are made in the ribosomes Gene expression- using genetic information to make proteins
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This note was uploaded on 04/07/2008 for the course NUSC 165 taught by Professor Brownbill during the Spring '08 term at UConn.

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WH+lecture+5-protein - Protein Structure and Digestion What...

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