Exam 2 Proteins 1 Introduction to Proteins a Made up of amino acids b Functions growth maintenance antibodies transportation acid base balance fluid balance hormones enzymes c Structure of an amino acid in pictures d Structural classification structures on powerpoints in Blackboard do not need to memorize them i Aliphatic 5 1 Open 2 Glycine Alanine Valine Leucine Isoleucine ii Side Chains with OH group 2 1 Serine Threonine iii Side Chains with Sulfur 2 1 Cysteine Methionine iv Side Chains with carboxyl or amide groups 4 1 Aspartic acid glutamic acid glutamine asparagine 2 Acidic v Side Chains with basic groups 3 1 Arginine lysine histidine 2 Positive charges vi Side Chains with Aromatic rings 3 1 Tyrosine phenylalanine tryptophan vii Imino acid 1 Proline 2 Dietary Protein exogenous protein a Quality i Digestibility 1 Animal 90 99 2 Plant 70 90 b c of fiber lower quality ii Amino Acid Composition 1 Complete a All 9 essential amino acids b All animal protein sources c Exceptions i Gelatin no tryptophan ii Soy plant complete for adults a legume 2 Incomplete a Limiting amino acid lowest a a is the limiting one b Low in one or more essential amino acids c E g beans low in methionine rice low in lysine 3 Complementary Proteins a 2 proteins when combined provide all essential amino acids b E g beans and rice lentil soup w cornbread iii Requirements 1 EAR estimated average requirement a 0 66 g kg day to maintain nitrogen balance of 0 for basic functions the minimum amount b Based on a reference protein highly digestible complete 2 RDA recommended dietary allowance a 0 8 g kg day b 2 SD c Covers 98 of healthy U S population for average healthy adult not for growing children infants d No toxicity of protein most people eat more than 0 8 g day 3 Special Needs General Guidelines Infants 0 1 11 9 1 g day 1 2 1 52 g kg day a b Children 4 8 19 g day 0 95 g kg day c Adolescents 14 18 46 52 g day 0 85 g kg day d Pregnancy 25 g day 1 1 g kg day e Lactation same as pregnancy values f g Burns 1 6 2 0 g kg day h Renal Insufficiencies 0 6 0 8 g kg day Surgery 1 2 1 4 g kg day i you want less proteins for them so that they re kidneys do not have to work as hard since they re already not working properly i Pressure Sores Decubitus Ulcers i Stress skin pressured degrades ii Lack of protein in diet causes this iii Starts with redness iv Proteins then degrade open up skin wound moves further down to bone j Clinical Issues v Hard to treat patients are usually sick elderly not eating healthy 1 Usually bound to wheelchair or bed 2 Sometimes in retirement homes very sick disabled people 3 Can be painful or not eats through nerves if wound gets down far enough 4 Usually need to feed patient lots of protein i BCAA s metabolized in muscle not liver often used in supplements for those with low liver function ii HN formulas high nitrogen to promote healing in those with love intake iii Arginine promote wound healing collagen synthesis role iv Glutamine enteral formulas in gut induces protective responses in gut through mouth or feeding tube parenteral formula into blood not gut b c the gut isn t working properly 4 Calculating Protein Requirements a 1 kg 2 2 lb b Protein contributes 10 30 total kcal c 1 g protein 4 kcal d Example A healthy adult female weighing 125 lbs consumes approximately 50g of protein a day i How many g kg is she consuming 125 lbs 2 2 56 82 kg 50 g 56 82 kg 0 88 g kg a little above the RDA ii How many g of nitrogen is she consuming 1 g protein 0 16 g nitrogen 50 g protein x 0 16 g nitrogen 1 g protein 8 g nitrogen consumed iii How many calories does protein contribute 50 g protein x 4kcal 200 kcal iv If she consumes 2000 kcal what percentage of that is protein 2000 kcal 200 kcal 10 iv Can we get too much protein 1 Amino acids urea excreted by kidneys 2 High protein diet should be avoided if a Kidney disease b Only 1 kidney or low kidney function c Infants should only intake mom s milk it has correct ratio of protein 3 Alpha keto acid from metabolized amino acid a Converted to generate ATP b Can be stored as fat 4 Amino acid supplements transporters on intestinal cells a b 11 transporters for 20 a a s c Competition for transporters d Not a problem with with whole proteins e A A supplements limit absorption of whole proteins f Tryptophan a a contaminated i Caused eosimophilia myalgia neuro flulike and death ii Not FDA approved not 100 pure iii Claims jet lag sleep autism pain tolerance chemical addictions appetite control mood enhancement v Too little protein 1 Protein needed for hair skin muscle oncotic pressure acid base balance bones tendons enzymes membranes 2 Protein Energy Malnutrition a Kwashiorkor kcal intake normal low protein i Acute PEM protein energy malnutrition ii Usually in older infants children iii Edema low albumin osmotic imbalance iv Poor lipid absorption v Fatty liver low apoprotein synthesis so there s reduced VLDL transport b Marasmus low kcal intake and protein i Severe deprivation e g starvation ii Chronic PEM iii Adrenal response iv No body fat edema or fatty liver present no fat deposits 3 Protein Digestion and Absorption a Gastric Digestion i Gastrin 1 Stimulated by food or thought 2 Stimulates HCl production ii HCl 1 Produced by parietal cells 2 Denatures protein 3 Converts pepsinogen pepsin inactive active 1 Secreted into lumen of stomach by gastric chief cells 2 Zymogen inactive precursor iii Pepsinogen iv Pepsin 1 Autocatalytic activates itself 2 Cleaves proteins at Leu and aromatic residues 3 Partial digestion protein polypeptides 3 50 b Duodenal Digestion i Chime duodenum ii Secretin intestinal mucosa 1 Stimulates pancreatic acinar cells 2 Trypsinogen secretion iii CCK stimulated by mucosa 1 Stimulates pancreatic bicarbonate neutralizes chime 2 Stimulates intestinal production of enterokinase aka enterpeptidase iv Trypsin 1 Activates pancreatic endopeptidases a Trypsinogen trypsin b Proelastase elastase c Chymotrypsinogen chymotrypsin 2 Activates pancreatic exopeptidases a Procarboxypeptidase A B Carboxypeptidase A B v Enzyme Specificity 1 Each peptidase has specific cleavage site a Trypsin basic A A b Elastase aliphatics c Chymotrypsin aromatics d Carboxy A aromatic aliphatic e Carboxy B basic 2 Digestive Products a Free amino acids b Some di and tripeptides c Oligopeptides 3 10 a a s c Absorption i Proteins from 1 Digested and absorbed dietary protein 2 Protein from sloughed off mucosal cells in 5 10 days these cells slough off and turn over 3 Digestive
View Full Document
Unlocking...