Exam 2 Material
Exam 2 Material HUN3224
Popular in Intermediary Metabolism
Popular in Nutrition and Food Sciences
This 25 page Bundle was uploaded by Channelle Brown on Saturday April 23, 2016. The Bundle belongs to HUN3224 at Florida State University taught by Dr. Farrell in Spring 2016. Since its upload, it has received 25 views. For similar materials see Intermediary Metabolism in Nutrition and Food Sciences at Florida State University.
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Date Created: 04/23/16
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 fiberlower 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 a. Infants (0-1): 11-9.1 g/day; 1.2-1.52 g/kg/day 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. Surgery: 1.2-1.4 g/kg/day g. Burns: 1.6-2.0 g/kg/day h. Renal Insufficiencies: 0.6-0.8 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. Stressskin 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 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 j. Clinical Issues: 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 low 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 formulainto 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 acidsureaexcreted 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 a. transporters on intestinal cells b. 11 transporters for 20 a.a.’s c. Competition for transporters d. Not a problem with whole proteins e. A.A. supplements limit absorption of whole proteins f. Tryptophana.a. contaminated i. Caused eosinophilia 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 pepsinogenpepsin (inactiveactive) iii. Pepsinogen 1. Secreted into lumen of stomach by gastric chief cells 2. Zymogen – inactive precursor 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. Chimeduodenum 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. Trypsinogentrypsin b. Proelastaseelastase c. Chymotrypsinogenchymotrypsin 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 enzymes ii. Transport Systems 1. A.A. absorption a. Na+ dependent b. Na+ independent transport systems c. Specific for groups of a.a.’s (basic, neutral) d. Transport competition i. Hydrocarbon mass ii. Net electric charge of a.a. iii. Rate of A.A. Absorption 1. BCAA, faster than smaller a.a.’s 2. Neutral before basic and acidic 3. Essential before nonessential 4. Most slowly are 2 dicarboxylic (acidic) amino acids Glu and Asp iv. Peptide Absorption – more quickly than free a.a.’s d. After absorption across brush border i. Some amino acids stay in intestinal cells and are used for 1. Digestive enzymes 2. Apoproteins for lipoprotein formation 3. Hormones 4. Metabolizing into other amino acids 5. Energy ii. Shunted to liver via hepatic portal vein Exam 2 Notes – Proteins (Part 2) 1. Functions of Amino Acids a. Synthesis of non-essential amino acids b. Protein synthesis c. Buffer d. Neurotransmitter synthesis e. Energy 2. Formation of non-essential amino acids a. Non-essential amino acids i. We can synthesize them b. Essential i. Cannot synthesize ii. We get them from our diet iii. 9 essential and 1 semi-essential* iv. Synthesized by plants and bacteria v. “PUT TIM HALL” 1. Phe, Val, Thr, Ile, Met, His, Arg*, Leu, Lys vi. Conditionally essential 1. Cys, Tyr 2. Synthesized from essential amino acids a. MetCys b. PheTyr 3. If a protein requires an essential amino acid and the body doesn’t have it, the protein synthesis will halt. 3. Protein Formation a. DNARNAProteins b. DNA i. Blueprint for all cells ii. Written in code 1. A—T (U instead of T in RNA) 2. G—C 3. Purines (“pure as gold”): A, G (have 2 fused rings) 4. Pyrimidines (“CUT the pie”): U (only in RNA), T, C (one ring) 5. Hydrogen bonding iii. Genetic code is confined to nucleus 1. Copy is made that leave nucleus (transcription); copymRNA iv. only 10% DNA is copied for RNA 1. remainder used to regulate transcription 2. promoter elements a. binding sites for transcription factors b. hormone binding sites i. thyroid, glucocorticoid v. exons: coding regions vi. introns: non-coding regions vii. mRNA is made from exons c. RNA i. mRNA (messenger RNA) 1. copy of the blueprint that can leave nucleus ii. tRNA (transfer RNA) 1. reads mRNA and binds to corresponding amino acid 2. 3 codons=1 amino acids (e.g. – 36 nucleotides, 36/3=12 amino acids) iii. rRNA (ribosomal RNA) 1. protein synthesizing machinery 2. forms ribosome iv. DNARNA 1. Transcription v. RNAprotein 1. Translation vi. Proteins undergo post-translational modifications (this is not including rearranging amino acids), including adding nutrients to become active proteins (e.g. – iron in hemoglobin) d. Primary Sequence i. Amino acids linked by peptide bonds (like a necklace) ii. Determined by DNA e. Primary Structure i. Sequencing of amino acids in polypeptide chain ii. Determines final structure 1. R chains affect coiling/folding f. Secondary Structure i. Folding of primary structure (mostly hydrogen bonding) 1. Alpha helix: cylindrical (hair, muscle) 2. Beta-pleated sheets: silk sheets 3. Alpha helix and beta pleated sheet on same strand g. Tertiary Structure i. Looping and binding of amino acids located at considerable distance apart on secondary structure 1. Hydrogen bonds 2. Ionic bonds 3. Hydrophobic interactions 4. Disulfide bonds: Cys, Met a. Hard to break h. Quaternary Structure i. 2 or more polypeptide chains 1. E.g. – hemoglobin (4 subunits), antibodies i. Functional Capacities for Proteins i. Enzymes – all enzymes are proteins, but not all proteins are enzymes ii. Hormones – from 1+ amino acids 1. E.g. – insulin – 2 polypeptide chains, disulfide bridge made in 1 location and transported in blood stream to location of function iii. Structural proteins 1. Contractile proteins – muscle (actin, myosin) 2. Fibrous proteins – collagen, cartilage, hair, bone iv. Cell Membrane Proteins 1. Embedded in membrane 2. Membrane channels/transporters a. Glucose transporters b. Na+ transporters 3. Receptors a. LDL receptors b. Insulin receptors v. Plasma Proteins 1. Albumin a. Synthesized in liver and released in blood b. Transports nutrients (B6, Zn, Ca, fatty acids) c. Maintains oncotic pressure d. Fluid is attracted to albumin, causing higher pressure within vein i. In vein: albumin pressure is about 26 e. Low levels of albumin in bloodfluid retentionedema j. Mutations i. Alterations or changes in the genetic code, usually associated with a disease 1. Point mutation – error in single DNA base (can make no/little difference) a. E.g. – sickle cell b. Seen in African-Americans to prevent mosquitos, the cells can’t carry oxygen the same way and they are shaped differently so they’re stuck in capillaries; survival mechanism) 2. Gene arrangements – gets swapped 3. Frame shift mutations – shift over 4. Gene deletions – deleted 5. Duplications ii. Mutations can happen spontaneously but usually comes from genes/family lines k. Some Nutrient-Related Mutations (Related TopHat Question: “If our DNA improperly codes for a protein, we can consume it to fix the problem” – FALSE. We would just end up digesting the protein. Instead, we need to change our diet.) i. Cystic Fibrosis 1. Defective gene and its protein product 2. Body produces unusually thick, sticky mucus 3. In lungs and pancrease 4. Patients are usually thin ii. Wilson’s Disease 1. Defective for getting copper outside of body 2. Copper found around eyes iii. Acrodermatitis Enteropathica 1. Zinc deficiency, doesn’t let zinc out of enterocyte 2. Zinc – important for skin, diaper rash, creams, skin conditions iv. Hemochromatosis 1. Iron overloading 2. Treatment: donate blood v. Vitamin D Resistant Rickets 1. Problem with the protein 2. Genetic mutation in the VDR alter the function of the receptor 3. Vitamin D: necessary to absorb calcium, maintains Ca2+ that goes in and out of bones 4. Signs/symptoms: soft bones/bowed legs, rickets –children, osteomalaygia – adults, astomelsia 5. Treatment: very high vitamin D doses vi. Maple Syrup Urine Disease 1. Problem with enzyme 2. Metabolized proteins to become toxic (defectivebuild up) 3. Urine smells sweet 4. Deficiency of 1 of the 6 proteins that make up the complex BCKD (branched chain alpha-keto acid dehydrogenase) 5. Defective BCKD protein complex (breaks down leucine, isoleucine, valine) vii. Carbamoyl Phosphate Synthesis 1. Born with this 2. Neonatal hyperammonia viii. Phenylketonuria 1. Inability to break down phenylalanine and tyrosine l. Polymorphisms i. Changes usually not disease-related ii. Responsible for individual differences 1. Differences in metabolism 2. Differences in response to exercise 4. Functions of Amino Acids a. Amino Acid Metabolsim i. Affecting one of the groups from the carbon 1. Decarboxylation a. Remove carboxyl group 2. Side chain cleavage a. Remove side chain 3. Deamination a. Remove NH3+ group 4. Transaminaton a. Move NH3+ group ii. Decarboxylation 1. Removal of carboxyl group 2. Neurotransmitter synthesis a. Affects depression, muscle stimulation, thought processing, etc. b. Tyrosine – dopamine, epinephrine, norepinephrine c. Glutamate – GABA (gamma amino butyric acid) i. Via glutamate decarboxylase ii. GABA is inhibitory; w/o it there would be build-up d. Tryptophan – serotonin stimulation seizures i. Found in turkey iii. Side-Chain Cleavage 1. Removal of R chain 2. Not seen a lot 3. Seen in Serine and Glycine a. Folate metabolism (B9) iv. Deamination 1. Amino acid alpha keto acid + NH3 ammonia a. Ammoniaurea cycle (liver)kidneys b. Ammoniaurine 2. Take off N group 3. E.g. – glutamate <-> (via glutamate dehydrogenase) alpha-ketoglutarate + NH4+ 4. Purpose of Nitrogen group: take out/excrete nitrogen (urine) 5. Usually deals with glutamate or glutamine v. Transamination: 1. Transferring a nitrogen 2. Formation of a non-essential amino acid 3. Catalyzed by aminotransferase enzymes 4. Also requires B6 as a coenzyme (PLP – pyridoxal phosphate) 5. Transferases (transaminases) as an indicator of liver function a. Alanine amino transferase (ALT) b. Aspartate amino transferase (AST) c. Increase in liver dysfunction results in an increase in transamination reactions requiring AST & ALT (increase in enzymes) d. Can test blood levels and LFT (liver functioning tests) e. Mostly happens in liver f. Low albuminproblem with liver functioning g. If at least one of the enzymes is high, it is still worrisome b. Metabolism of alpha-keto acids i. Alpha-keto acid: carbon skeleton left after N-group has been removed (via transamination or deamination) ii. Can be used for production of: 1. Energyglucose, ketone bodies (ketosis), fatty acids 2. Cholesterol iii. Glucogenic vs. Ketogenic 1. Glucogenic: converted to pyruvate and krebs intermediates (OAAPEPgluconeogenesis) - 13 a. Ala, Cys, Gly, Ser, Asp, Asn, Glu, Gln, Arg, Met, Val, His, Pro 2. Ketogenic: converted to acetyl CoA and acetoacetate (the “L” amino acids) a. Lys, Leu 3. Glucogenic and Ketogenic: (5) a. Phe, Ile, Thr, Trp, Tyr iv. A Brief Intro to Nitrogen 1. Protein turnover a. Protein synthesis and degradation 2. Nitrogen Balance a. Intake vs. output b. Indicator of body protein c. Nitrogen balance studies – measure intake and output i. Consumed ii. Excretion: urine, feces, skin (difficult to measure) d. 1 g protein=0.16 g nitrogen e. Positive nitrogen balance: in > out i. Synthesizing new tissues (growth, pregnancy, nursing, building muscle, etc.) f. Negative nitrogen balance: out > in i. Breaking down tissues (starving, sacropenia) g. Equal: in=out i. Average healthy adult is this (e.g. – if you’re not growing) c. Ketone bodies i. Energy made from 1. ketogenic amino acids 2. fatty acids in the absence of glucose (fasting state) a. if glucose is in bloodstream, use fat insteaddiabetic ketoacidosis d. Disposal of Ammonia-Urea Synthesis (Urea synthesis-HAPPENS IN LIVER ONLY) i. Nitrogen Excretion 1. 2500 kcal/day intake a. 300 g CHO b. 100 g fat c. 100 g protein 2. 1 g protein=0.16 g nitrogen a. 16 g nitrogen – excreting (0.16 x 100) 3. Liver damage – impairs ability to rid of nitrogenous waste ii. Regulation 1. CPS 1 (carbamoyl synthetase 1) a. Rate-limiting enzyme b. Forms monomer or dimer (2 forms) c. Monomer in active d. Allosterically regulated by N-acetylglutamate i. Acetyl CoA and glutamine ii. Enhances synthetase affinity for ATP iii. Splits dimer into monomers 2. High Protein Diet a. Increased urea cycling b. Increased production of urea cycle enzymes (CPS 1, arginase, etc.) 3. Carbamoyl Phosphate Synthetase Deficiency a. Rare – 1:62,000 b. Geneticneonatal hyperammonemia i. Effects happen immediately ii. Nitrogen build-upurea removal decreases iii. Symptoms/signs: vomiting, irritability, intermittent ataxia (inability to coordinate motor movement), lethargy, mental retardation c. Treatment: low protein diet, small meals e. Organ Specific Metabolism of Amino Acids i. Liver 1. Amino acids are transported to liver via hepatic portal system 2. From liver, transported to other tissues 3. Major site of gluconeogenesis 4. Urea synthesis (nitrogen excreted via kidneys) 5. Liver specific enzymes a. AST, ALT (indicators of liver function) b. Arginase (urea cycle) c. Phenylalanine Hydroxylase i. Converts phenylalanine to tyrosine d. Methionine Adenosyl Transferase i. MethionineS-adenosyl methionine (SAM) ii. SAM-a methyl donor iii. When SAM donates its methyl group, it then become SAH (S-adenosyl homocysteine) iv. NorepinephrineEpinephrine 6. Tyrosine used for: a. melanin (pigment production) b. neurotransmitter synthesis c. thyroid hormones (T3, T4) d. fumarate, acetoacetate (energy) 7. Phenylketonuria: a. Genetic – happens immediately b. Deficiency of enzyme phenylalanine hydroxylase c. Symptoms: untreated infants are irritable and have an eczema type rash; as they get older w/o treatment, there are tremors, seizures, hyperactivity, severe mental deficiencies, albinism (low melanin production) d. All infants are tested at 3 days in U.S. via blood tests e. Low phenylalanine diet i. Low amounts of meat, fish, poultry ii. No aspartame (made from phenylalanine) 1. Found in artificial sweeteners, diet sodas iii. Tyrosine supplementation ii. Muscle 1. BCAA (branched chain amino acid metabolism) a. These do not put work on the liver i. Valine ii. Leucine iii. Isoleucine 2. BCAA Transferase a. High activity in muscle b. Low activity in liver c. Some activity in kidney, adipose tissue, and brain 3. Once transaminated, the alpha-keto acids: a. Remain in muscle b. Transported to other tissues 4. BCKD Complex a. Branched chain alpha-keto dehydrogenase b. Complex make-up of subunits that carry out a series of dehydrogenase reactions c. Enzyme deficiency: (problems with one or more of the subunits) i. Maple syrup urine disease iii. Kidney 1. Secondary site of gluconeogenesis 2. Excretion of nitrogenous waste a. Urea (main waste product) b. Creatinine c. Uric acid d. Ammonia 3. Deamination a. Can form ammonia and can excrete ammonia b. pH balance c. glutaminedeaminationglutamate + NH3 d. NH3 + HNH4+ (ammonium) i. Ammonium cannot be reabsorbed, so must be excreted in urine e. Loss of H from body brings pH to neutral iv. Brain 1. Neurotransmitter synthesis (decarboxylation reactions) a. GlutamateGABA b. Tyrosinedopamine, epi, norepinephrine c. Tryptophanserotonin 2. Glutamate- removal of ammonia from brain 3. Glucose synthesis a. Brain loves glucose; can use ketones to spare body proteins (gluconeogenesis) b. Glucose – most efficient source of fuel c. Brain uses about 400 kcal/day f. Proteins (other) i. Prions 1. proteinaceous infectious particles which are resistant to inactivation by most procedures that modify nucleic acids 2. convert normal proteins into prions 3. folding – alpha helix to beta sheet different functions 4. primary sequence remains; secondary shape changes 5. diseases caused by prions: a. Creuzfeldt-Jacob: found in native tribes who performed cannibalism, “smiling disease” b. Scrapie: found in sheep c. Mad Cow: (also known as BSE) found in cows d. Can lead to paralysis/seizures 6. clogs brain cells causing misfiring 7. Cannot destroy by cooking, freezing, or any other food processing technique; just avoid the food altogether (e.g. – beef during Mad Cow disease outbreak) ii. Glutathione 1. tripeptide made of gly-cys-glu 2. functions: a. protects cells with antioxidant action b. functions usually with selenium 3. made in body and also found in supplements iii. Carnitine 1. lysineSAM (S-adenosylmethionine)carnitine 2. transports fatty acids across inner mitochondrial membrane 3. no evidence that it burns fat or provides energy iv. Creatine 1. can be synthesized in body or obtained from foods (meat and fish) 2. 95% in muscle 3. phosphorylated to phosphocreatine a. build up in muscle 4. Phosphocreatine: a. If there’s more phosphocreatine, there’s more ATP, which means more work can be done b. Storehouse for high energy phosphate c. Rapidly contracting muscle needs ATP d. Replenishes ATP in muscle e. More muscle, more phosphocreatine f. Doesn’t stay in muscle for an extended period of time i. Spontaneously metabolized into creatinine (nitrogenous waste) ii. Excreted by kidneysdrink enough water/stay hydrated iii. Urinary creatinine: 1. indicator of somatic muscle 2. indicator of renal function (decreased function, too little or too much creatinine in urine) v. Purine & Pyrimidine Bases 1. pyrimidines: U, C, T (asp, gln) 2. purines: A, G (asp, gln, gly) a. from ribose 5-P (HMP shunt from previous exam’s notes) vi. Vitamin Synthesis 1. niacin B3-tryptophan a. NAD, NADP 2. folate metabolism - glycine
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