Metab test 2 study guide Proteins Made up of amino acids o Growth and maintenance o Enzymes o Hormones o Fluid balance o Acid Base balance o Transportation o Antibodies o Energy Aliphatic Side chains o Glycine Gly o Alanine Ala o Valine Val BCAA o Leucine Leu BCAA o IsoLeucine iLe BCAA Side chains with alcohol groups o Serine Ser o Threonine Thr Side chains with sulfer o Methionine Met o Cysteine Cys Side chains with Carboxyl or amide groups o Aspartic acid Asp o Glutamic acid Glu o Asparagine Asn o Glutamine Gln Side chains with basic groups o Arginine Arg o Lysine Lys o Histidine His Side chains with aromatic rings o Phenylalanine Phe o Tyrosine Tyr o Tryptophan Trp Imino acid o Proline Pro Dietary protein o Exogenous Protein Quality Digestibility o Animal proteins 90 99 o Plant proteins 70 90 Amino Acid Composition o Complete proteins Contains all essential AA s can t make in body All animal sources Exceptions Gelatin no tryptophan Soy plant complete for adults but not children o Incomplete proteins Low in one or more essential AA s Examples Beans Low in methionine Rice Low in lysine Limiting amino acids o Complementary proteins 2 or more proteins when combined provide all essential amino acids Ex Beans and rice lentil soup with cornbread Requirements o EAR Lowest amount to maintain nitrogen balance of 0 in average healthy adult Based on a reference protein Highly digestible complete 0 66g kg day protein o RDA recommended dietary allowance 0 9g kg day 2 standard deviations Covers 98 healthy US population o Special Needs general guidelines Infants 2 2 5g kg Children 1 5 2g kg Adolescents 0 8 2 g kg Pregnancy 10g day Lactation 15g day Moderate stress injuries 1 1 5g kg Highly stressed burns 1 5 2g kg Renal insufficiency 0 6 0 8g kg Decubitis Ulcers need a lot of protein to heal o Special needs cont Clinical issues BCAA s often used in supplements for those with decreased liver functioning intake synthesis o Metabolized in the muscle so they do not stress the liver HN formulas high nitrogen to promote healing in those with low Arginine to promote wound healing plays a role in collagen Glutamine enteral formulas induced protective responses to gut Can we get too much protein o Amino acids Urea excreted by kidneys o High protein diet should be avoided if Kidney disease Have only 1 kidney or decreased kidney functioning Infants why you shouldn t give them cows milk too much protein o Alpha keto acid Nitrogen off the amino acid from metabolized amino acid Converted to ATP Stored as fat o Amino Acid supplements Transporters on intestinal cells 11 transporters for 20maino acids Competition for transporters Not a problem when consuming ole proteins AA supplements limit absorption of whole proteins Some AA supplements have been found to be contaminated Tryptophan Too little protein o Protein is needed for everything hair skin tendons bones etc o Protein energy Malnutrition Kwashiorker kCal normal low protein Marasmus low in calories and proteins Reversible Acute PEM Edema Fatty liver Older infants children Severe deprivation Chronic PEM Muscle wasting No body fat No edema No fatty liver PROTEIN DIGESTION AND ABSORPTION o Gastric digestion Gastrin Stimulated by food or thought Stimulates HCL production HCL Produced by parietal cells Denatures proteins Converts pepsinogen to pepsin Pepsinogen Zymogen inactive precursor Pepsin Autocatalytic activates itself Pepsin can trigger more pepsin Secreted into the lumen of stomach by gastric chief cells Cleaves proteins at Leo and aromatic residues Partial digestion protein polypeptides Stomach not essential for protein digestion Gastrectomy small or no stomach Achlorydria absence of HCL in gastric juices o Duodenal Digestions Chyme enters duodenum Secretin secreted by intestinal mucosa Stimulates pancreatic acinar cells Trypsinogen secretion CCK secreted by mucosa Stimulates pancreatic bicarbonate Stimulates intestinal production of enterokinase Aka Enteropeptidase Trypsinogen Enterokinase Trypsin o Trypsin Activates pancreatic endopeptidases Trypsinogen trypsin Protelastase elastase Chymotrypsinogen Chymotrypsin Activates pancreatic exopeptidase Procarboxypeptidase A B Carboxypeptidase o Enzyme Specifity Each peptidase has a specific cleavage site Trypsin Basic AA Elastase Aliphatics Chymotrypsin aromatics Carboxy A aromatic and aliphatic Carboxy B basic AA Digestive products Free AAs Some di and tripeptides Oligopeptides Absorption o Proteins from Digested and absorbed dietary protein Protein from sloughed mucosal cells Digested enzymes o Transport systems Amino acid absorption Sodium dependent Sodium independent transport systems Specific for groups of amino acids basic neutral Competition for transport o Hydrocarbon mass o Net electrical charge of amino acid Rate of amino acid absorption BCAA absorbed quicker than smaller aa s Neutral before basic or acidic Essential before nonessention Most slowly are the 2 dicarboxylic Acidic aa s gluc and aspa o Peptides absorption Absorbed more quickly than free AA s After absorption across bursh border o Some aa s stay in intestinal cells and are used for Digestive enzymes Apoproteins for lipoprotein formation Hormones Energy Metabolized into other AA s o Shunted to liver via hepatic portal vein Proteins part 2 In class hand out Functions of Amino acids o Synthesis of non essential amino acids o Protein synthesis o Buffer o Neurotransmitter synthesis o Energy Formation of Nonessential amino acids o Non essential amino acids We can synthesize them o Essential 9 We cannot synthesize them Must be consumed from diet Synthesized by plants bacteria His Leo lys ile Phe val met Trp THr o Conditionally essential Cys Tyr Synthesized from essential aa s o Met Cys o Phe Tyr Protein Formation o DNA Transcription RNA Translation Proteins o DNA Blueprint for all cells Written in code Genetic code is confined to nucleus Only 10 of DNA is copied for RNA If a protein requires an essential AA and the body doesn t have it protein synthesis will halt Remainder used to regulate transcription Promote elements o Promoter elements Binding sites for transcription factors Hormone binding sites Thyroid hormones Glucocorticoid hormones cAMP Increase or decrease transcription o Exons o Introns Coding regions Noncoding regions Removed o Mrna is made from exons RNA o mRNA messenger RNA copy of the blueprint that can leave the nucleus base pairs A C G U o tRNA transfer RNA reads the mRNA and binds to the corresponding amino acid o rRNA
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