Week5_6-Proteins

Week5_6-Proteins - Proteins February 11, 2011 Protein...

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Proteins February 11, 2011
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Proteins are made of many Amino Acids (AA) connected together Protein Chemistry
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Amino Acids
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The area in white in each of the boxes above are the side groups referred to previously that makes each amino acid unique. Most proteins are made up of ~20 different amino acids Amino Acids
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Nonessential AAs : Body can synthesize these - Nitrogen, carbon and oxygen from carbohydrates and lipid - Includes glycine, cysteine, serine, etc Essential AAs : Body cannot synthesize these in amounts sufficient to meet physiological needs - Need from diet! - Includes tryptophan, phenylalanine, histidine, etc Conditionally Essential AAs : Normally nonessential, but must be supplied in the diet (essential) in special circumstances - Phenylalanine is a good example Nonessential versus Essential Amino Acids *
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Amino acids in phenylketonuria (PKU) Deficiency in enzyme phenylalanine hydroxylase Can be controlled by diet low in phenylalanine But phenylalanine needed to produce tyrosine Tyrosine essential from diet (conditionally essential AA)
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Amino acid chains are linked by peptide bonds in condensation reactions
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- Side groups with electrical charge are attracted to water (hydrophilic). - Side groups with neutral charge repel water (hydrophobic). Coiled and twisted chains provide stability
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Proteins have specific SHAPES which allow them to have specific FUNCTIONS
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Digestion of Proteins
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In the Stomach: Hydrochloric acid denatures (uncoils) proteins Digestion of Proteins Exposes peptides to the action of enzymes
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In the Stomach: Pepsinogen (inactive) is converted into its active form pepsin by hydrochloric acid Pepsin cleaves large proteins into smaller polypeptides. Digestion of Proteins pepsinogen pepsin HCl
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In the Small Intestine: Pancreatic and intestinal proteases - hydrolyze polypeptides into short peptide chains and single AAs Tripeptides (3 AAs) and dipeptides (2 AAs) Digestion of Proteins proteases
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In the Small Intestine: Peptidases split tripeptides and dipeptides into single amino acids Tripeptidases - cleave tripeptides to dipeptides and single AAs Dipeptidases - cleave dipeptides to AAs Digestion of Proteins Tripeptidases Dipeptidases
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Amino Acids are absorbed into the intestinal cells by Active Transport Some di- and tripeptides are also transported by active transport Some amino acids are kept in the absorptive cells; others are transported into circulation for use by other cells
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Protein Synthesis in the Body DNA mRNA Protein transcription translation
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Nucleus DNA mRNA 1. DNA serves as a template to make strands of (mRNA). Each mRNA strand copies exact instructions for making some protein the cell needs.
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Week5_6-Proteins - Proteins February 11, 2011 Protein...

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