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FSU / Nutritional Science / HUN 3224 / The body utilizes these, but they are not a primary source of energy.

The body utilizes these, but they are not a primary source of energy.

The body utilizes these, but they are not a primary source of energy.


Exam 2 Study Guide- Proteins  

The body utilizes these, but they are not a primary source of energy.


∙ The body utilizes these but they are not a primary source of ENERGY  o Body cant function if you run out of these  

o They can help with the breakdown of carbs and fats  

o Proteins DO NOT provide a huge amount of ATP

 Functions of proteins  

∙ Growth and maintenance  

∙ Enzymes  

∙ Hormones  

∙ Fluid balance  

∙ Acid-base balance  If you want to learn more check out How does the fed change monetary base?

∙ Transportation

∙ Anitbodies  

∙ Energy (not primary job put possible)  

∙ What are proteins made from?  

What is aliphatic side chains?

o Amino acids  

∙ What is the structure of proteins?  

o Central carbon  

o R group: makes a certain amino acid different from another  o Nitrogen: synthesis of new tissues (makes proteins different from any other nutrient)  If you want to learn more check out wsu unit guide

Side Chains: 

∙ Aliphatic side chains:  

o Glycine  

o Alanine  

o Valine (branched)  

o Leucine (branched)  

o Isoleucine (branched)  

∙ What are the branched chained amino acids?

o Valine  

o Leucine  

o Isoleucine  

 These are all metabolized in the muscle  

∙ Side chains with OH group:  

What are the types of amino acid composition?

o Serine

o Threonine  

∙ Side chains with sulfur:  

o Methionine  

o Cysteine  

∙ Side chains with carboxyl or amide group:  

o Aspartic acid  

o Glutamic acid

o Asparagine  

o Glutamine  

∙ Side chains with basic groups:  

o Arginine  

o Lysine  

o Histidine  

∙ Side chains with aromatic rings  Don't forget about the age old question of ch 1213

o Phenylalanine  

o Tyrosine  

o Tryptophan  

∙ Imino acid:  

o Proline  

 Involved with the structure of collagen  

 Its central carbon is attached to a branch  

Protein Digestibility  

∙ Animal proteins (nothing but fat and protein)  

∙ Plant sources  

o Animal proteins: are superior to plant proteins because plant  protein has a lot of fiber which slows down digestion and  


Amino acid Composition types:  

∙ Amino acids can either be:  

o Complete proteins : have all essential amino acids Ex:  

animal proteins  

o Incomplete proteins : missing one or more essential amino  acids Ex: plant protein sources  


∙ It is important for these people to combine plant proteins to get  the best absorption abilities  

What keeps incomplete proteins from being complete? ∙ Limiting amino acid

∙ This can be fixed by combining incomplete proteins  Don't forget about the age old question of What forces laws and destroys capitalism?

What is the EAR?  

∙ The EAR is based off of meat consumption but doesn’t cover enough  people  

∙ Amount of nitrogen going in the body must meet the amount of  nitrogen going out of the body  

∙ The value is: 0.66g/kg/day of protein is needed to maintain the protein  in the body  

What happens if you have too little protein in the body?  ∙ Protein starts to be used for energy which is not a good thing.  What is the RDA?  

∙ Based off EAR because the EAR value did not cover enough people  ∙ This value gives wiggle room

∙ The value is: 0.8g/kg/day which covers 98% of healthy population who  are disease free  

What are complementary proteins?

Two or more proteins when combined provide all essential amino acids Ex: incomplete + incomplete = complete  

How much protein should Kidney failure patients have? ∙ Should not go above 0.8g of protein a day because of the nitrogen in  the protein which is correlated to urea  

Special needs patients  

∙ Infants (highest protein need)

∙ Children (4-8)

∙ Pregnancy  

∙ Lactation  

∙ Major surgery  

∙ Burns  We also discuss several other topics like mea 150 class notes

o These people have higher protein needs  

What does a burn do to the body?  

∙ A burn puts your body in a hyper-metabolic state  

∙ Protein is needed to grow new skin and collagen  

What is Renal Insufficiency?  

∙ Have lower protein needs because you secrete nitrogen in the form of  urea through the kidneys  

o If the kidneys are not functioning properly then a lower amount  of protein is needed in order to put less stress on the kidneys Decubitus Ulcers:  

∙ Are caused from a decrease in blood flow to the area and a decreased  protein intake causes skin to degrade and go down into the bone  ∙ The body is not able to synthesize proteins properly  

∙ Results also from moderate stress  

∙ Ex: bed sores  

∙ Treatment: zinc and nutrients (proteins are building blocks)  

What are proteins less likely to be stored as?  

∙ Fats because of their other important functions  

Liver Failure Patients:  

∙ Are often given branched chained amino acids because those are  metabolized in the muscle which puts less stress on the liver  HN Formulas:  If you want to learn more check out How do you know if a function is composite?

∙ High nitrogen promotes healing in those with low protein intake  ∙ Makes non essential amino acids from excess nitrogen consumed  What is Arginine?

∙ Is used to promote wound healing and plays a role in collagen  synthesis  

What is Glutamine?  

∙ Enteral formulas which induces the protective responses in the gut  


1kg: 2.22lbs

1gprotein: 4kcal  

1g protein= 0.16g of N  

There are no____in the body?  

∙ Protein Stores  

What happens to Extra Amino Acids?  

∙ The carbon skeleton is kept but the extra nitrogen is excreted in the  kidneys  

High Protein Diet should be avoided if:  

∙ Kidney disease  

∙ Infants  

o Cant take high protein from cows because there kidneys are not  fully developed

o This is the reason why they cant drink cows milk until 1 year A-keto Acid from metabolized protein can be converted into ATP by  what?

∙ Kreb cycle  

∙ Glucose  

∙ Can be stored as fat  

Where are protein transporter located? How many are there?  ∙ Located on intestinal cells  

∙ 11 transporters for 20 amino acids  

o competition for transport but not a problem when consuming  whole proteins  

What can amino acid supplements cause?

∙ Can inhibit absorption of other proteins  

∙ Can displace other amino acids which limits absorption of whole  proteins

Which amino acid is a contaminated amino acid?

∙ Tryptophan  

What happens if you have too much protein?  

∙ Not a big deal if your liver and kidneys are okay  

∙ There is no upper limit  

o Excess amino acids can be stored as fat  

Types of PEM:  

∙ Kwashiorkor:  

o Normal calories but low protein

o Acute PEM (set on quickly)  

o First discovered in Ghana  

o First found in older infants  

o Is an illness that develops in the first child after the second child  is born  

 Symptoms:  

∙ Edema: caused by low albumin which causes fluid to

leak into places in the vascular system such as the  

interstitial space  

o Fluid leaves the blood stream due to low  

protein intake  

∙ Fatty Liver: caused by no lipoproteins to carry carbs

to the adipocytes which is caused by inadequate  

protein so lipids say on the liver because it isn’t  

enough proteins to carry fat off of the liver  

o This can seen in the U.S by:  

 Alcoholics  

o This can bee seen in other countries when the first child is  weined off of breast milk and starts a starchy diet  

∙ Marasmus:  

o Low in calories and protein  

o Severe deprivation (starvation)  

o Chronic PEM  

o No body fat  

o No edema  

o No fatty liver

 This can be seen in developing countries because of

∙ Food shortages  

 This can be seen in the U.S because of  

∙ Anorexia (disordered eating)

∙ Dementia elderly person

∙ Disease state  

What happens in Gastric during protein digestion?

∙ Gastrin is stimulated by food or thought  

∙ Gastrin stimulates the production of HCL  

∙ HCL is secreted by parietal cells which is involved in denaturing  proteins and turning pepsinogen into pepsin  

What is Pepsinogen?

∙ Is a zymogen (inactive enzyme that is involved in protein digestion and is secreted into the stomach as a precursor for pepsin  

What is every enzyme involved in protein digestion?  

∙ A zymogen because if it was not a zymogen it would auto-digest the  body which leads to pancreatitis

o Is anything ending in “gen” and beginning in “pro”

What is pepsin?  

∙ Autocatalytic which means it can activate itself  

∙ It is secreted into the lumen of the stomach by the gastric chief cells  ∙ Once activated by HCL it can then go and find another pepsinogen and activate itself  

o Function of Pepsin  

 Cleaves proteins at the leu and aromatic residues  

 Partially digests proteins into polypeptides  

What is Achlorhydia?  

∙ Absence of HCL in gastric juices  

What occurs in the Duodenum in protein digestion?

∙ Chyme enters the duodenum  

∙ Secretin is secreted by the intestinal mucosa which stimulates the  pancreatic acinar cells and trypsinogen secretion

∙ CCK is secreted by mucosa  

o Stimulates pancreatic bicarbonate  

o Stimulates intestinal production of enterokinase/enteropeptidase   Enterokinase is secreted by the enterocytes  

What is needed for full protein digestion in small intestine? ∙ Enterocytes and a fully functioning pancreas  

Pancreatic Zymogens:  

∙ All activated by trypsin  

o Endopeptidases:

 Trypsinogen to trypsin  

 Protelastase to elastase  

 Chymotrypsinogen to chymotrypsin  

∙ All of these cleave towards the middle line of the  


o Exopeptidases:  

 Propcarbodypeptidase (A or B) goes to carboxypeptidase (A or B)  

∙ These cleave toward the exterior of polypeptide  

particularly at the carboxyl ends  

Enzyme Specificity  

∙ Each peptidase has a specific cleavage site  

o Trypsin: basic amino acids  

o Elastase: alphatics  

o Chymotrypsin: aromatics  

o Carboxy A: aromatic and aliphatic  

o Carboxy B: basic  

What are digestive products of proteins:  

∙ Free amino acids

∙ Some di and tripeptides  

∙ Oligopeptides  

Describe Protein Absorption.

∙ Digested and absorbed dietary proteins  

∙ Protein from sloughed mucosal cells  

∙ Digestive enzymes  

∙ Anything that enters the gut can be reabsorbed  

Protein Transport System:  

∙ Amino acid absorption is  

o Sodium dependent  

o Sodium independent transport systems  

o Specific for groups of amino acids-basic/neutral  

o Supplements will throw this off  

∙ Rate of absorption:  

o Branched chains are absorbed quicker than  

smaller amino acids  

o Neutral amino acids are absorbed before basic  

or acidic  

o Essential amino acids are absorbed before non

essential amino acids  

o 2-dicarboxylic-acidic amino acid such as glu  

and asp are absorbed the slowest  

o peptides are absorbed more quickly than free  

amino acids  

∙ Factors for Protein Transport Competition:

o Hydrocarbon mass  

o Net electrical charge of amino acid  

o Essential vs. nonessential  

What does di/tripeptides moving in between the cells cause? ∙ Immune inflammatory response  

∙ They are recognized as intruders  

What happens after absorption across the brush border?

A. Some amino acids stay in the intestinal cells and are used for:  a. Digestive enzymes  

b. Apoproteins for lipoprotein formation  

c. Hormones  

d. Metabolized into other amino acids  

e. Energy (not primary source

B. Can be shunted to the liver via hepatic portal vein once the cell has  everything it needs  

What are some functions of amino acids?

∙ Synthesis of non essential amino acids  

∙ Protein synthesis  

∙ Buffer

∙ Neurotransmitter synthesis  

∙ Energy  

Describe Nonessential amino acids.

∙ Can be synthesized in the body  

Describe Essential Amino Acids  

∙ Need to eat them must be takin in by the diet  

∙ Cant be synthesized in the body  

∙ Only synthesized by plants and bacteria  

o His  

o Leu  

o Lys  

o Ile  

o Phe  

o Val  

o Met  

o Thr  

o Try  

 Conditional essential amino acids:  

∙ Can be synthesized from essential amino acids  

o Cys and tyr  

What happens when a protein requires an essential amino acid that the body doesn’t have?

∙ Protein synthesis halts  

Describe Chromosomes.  

∙ Contain DNA  

Describe DNA.  

∙ Contain base pairs which are split and then transcribed into RNA in the  nucleus  

∙ DNA is the blueprint for all cells  

o Written in code (nucleotide bases)  

o Genetic code is confined to the nucleus  

o Only 10% of DNA is copied for RNA  

 The remaining percentage that is not copied is used to  regulate transcription  

o Ex: promoter elements  

 Promotor elements are binding sites for  

transcription factors  

 Copied DNA (mRNA) goes to the ribosome to make  


Describe Hormones.  

∙ Bind to very specific places  

∙ Are derived from one or more amino acid  

o Ex:

 Thyroid hormone  

 Glucocorticoid hormes  

 cAMP  

∙ can increase or decrease transcription  

o Insulin:  

 2 polypeptide chains with disulfide bridges made in one  location and transported in the blood stream to another  

location to function  

What is within the coding region?

∙ Exons (coding region)  

∙ Introns (non coding region)  

o Introns are spliced out  

What is mRNA made from?

∙ Exons  

Name the Types of RNA.  

∙ mRNA-messenger RNA is sent to the ribosome for polypeptide  synthesis  

o copy of the blueprint that can leave the nucleus  

o made of exons  

o base pairs ACGU instead of T

∙ tRNA-transfer RNA-reads the mRNA and binds to corresponding amino  acid  

o if t-RNA reads the code wrong then it can code for a different  amino acid or put it in the wrong order which can cause  


∙ rRNA-ribosomal RNA-protein synthesizing machinery (proteins are  made in the ribosome).  

Where does translation occur?  

∙ In the ribosome  

What is Post Translation modification?

∙ Anything that happens after translation which includes adding  nutrients to become active proteins  

Levels of Structure of Proteins:  

Primary Sequence:  

∙ Amino acids are linked by peptide bonds  

∙ This is determined by the DNA

∙ Sequencing of amino acids in polypeptide chains  

∙ These are formed in the ribosome through translation  

∙ Determines the final structure of protein molecule (side chains  and affects coiling and folding)  

∙ The primary sequence is held together by carbon-nitrogen bonds

∙ This sequence is important because if it is not correct it can  throw the whole protein off  

Secondary Structure:  

∙ Folding of primary structure  

∙ Hydrogen bonding  

∙ Can either be alpha helix or beta pleated sheet or can be both  ∙ R chains are to the outside  

o Alpha helix:  

 Coiling to form cylindrical shape  

∙ Ex: hair, muscle, myosin  

o Beta Pleated Sheet:  

 Ex: silk proteins  

∙ A proteins can have both an alpha helix and a Beta pleated sheet  Tertiary Structure:  

∙ Looping and binding of amino acids located at considerable distance  apart on 2 degree structure  

o Have disulfide bonds ex: cys, met  

o Can have ionic bonding  

Quaternary Structure

∙ Involves two or more polypeptide chains  

o An addition for example of a heme or oxygen occurs here   Ex: hemoglobin, myoglobin, antibodies  

What are peptides made up of?  

∙ Carbon-nitrogen bonds  

What does the R-chain of proteins do?

∙ Makes an amino acid different from every other amino acid  ∙ Gives the amino acid its name  

What does a protein have to have in order to function?  

∙ Shape  

What are all enzymes?  

∙ Proteins but not all proteins are enzymes  

Describe Structural Protein Types.  

∙ Contractile –are in the muscle  

o Ex: actin, myosin  

∙ Fibrous – are collagen, cartilage, hair, bone  

What are cell membrane proteins?

∙ Embedded in the cell membrane  

o Membrane channels/ transporters (glucose transporters, Na+  transporter, transport proteins)  

o Receptors (insulin receptor, LDL receptor)  

Describe Albumin.

∙ Plasma proteins that maintains osmotic pressure in the vascular  system  

∙ Is synthesized in the liver and released into the blood  

∙ Transports nutrients such as B6, Zn, Ca, and fatty acids  o Albumin is not specific it transports any nutrient  

∙ When there is LOW albumin:  

o Fluid leaks into the interstitial space which then gets taken over  by gravity and pools down into the arms and legs which causes  edema  

 Low albumin is NOT caused by dietary problem unless it is  a severe protein deficiency such as PEM  

∙ Low albumin is usually caused by DISEASE and by  

the liver not being able to synthesize it  

What is fluid attracted to?  

∙ High albumin which causes high pressure in the veins  

Genetic Disorders : 

∙ Deals with genes  

Types of Mutations :  

∙ Point Mutation: error in a single base pair read wrong  

o Causes difference in protein formed  

 Ex: sickle cell anemia  

∙ Frame Shift: whole code is read wrong  

∙ Gene rearrangements  

∙ Gene deletions  

∙ Duplications  

Polymorphisms: are mutations that are not associated with disease  ∙ Responsible for individual differences  

Types of Mutation Defeciencies:  

∙ Cystic Fibrosis: mutation in the sodium chloride transporter which affects the mucus that coats the inside of the lungs

o Causes the mucus to remain thick which inhibits gas  


 Symptoms:  

∙ Coughing  

∙ Lungs affected  

∙ Pancreas affected  

o You can STOP the symptoms by:  

 Salt supplement  

∙ Wilsons Disease: mutation in the copper transporter that doesn’t  allow copper to leave the body  

o Copper builds up in the body which causes copper to  

appear on the lungs

o This is causes by a genetic mutation at the DNA level  

 You can stop the symptoms of this by:  

∙ Staying away from copper  

∙ Acrodermatitis: cant keep zinc in the body  

o Causes skin to degrade  

 Ex: really bad diaper rash that wont heal  

∙ You can stop the symptoms by:  

o Zinc supplements  

∙ Vitamin D resistant rickets: mutation in the vitamin D receptor  which causes the bones to bend because they cant calcify  o Bone start to bow either in or out  

∙ Maple Syrup Urine Disease  

o Body doesn’t have all of the enzymes to metabolize BCAA   Partially digested BCAA  

 Urine starts to smell like maple syrup  

∙ The branched chained amino acids are  

secreted into the kidneys through urine giving  

all maple syrup smell  

o Can stop the symptoms by:  

 Not eating BCAA

What are the four types of Amino Acid Metabolism?

∙ Decarboxylation: removal of carboxyl group  

o This is done for neurotransmitter synthesis  

o Ex: DOPA to Dopamine (tyrosin to dopamine to norepinephrine to epinephrine  

 Glutamate to GABA  

 Trypotophan to serotonin  

∙ Side Chain Cleavage : removal of R Chain  

o Ex: folate metabolism the only place youll see this  

 Serine to glycine  

∙ Deamination: removal of nitrogen for excretion (first step in urea  synthesis)  

o Disposal of ammonia-urea synthesis  

o Nitrogen excretion –majority of excreted nitrogen goes through  the urea cycle  

∙ Transamination: transfer of nitrogen and makes new non essential  amino acid

o Catalyzed by aminotransferase enzymes  

o Also require B6-PLP

o These reactions are reversible  

 Ex: glutamate -- transfers nitrogen to pyruvate  

∙ Glutamate becomes alpha keto glutarate and  

pyruvate after accepting the nitrogen becomes  

alanine aminotransferase

What ways can you manipulate an amino acid?

∙ Remove side chain  

∙ Remove nitrogen  

∙ Remove carboxyl group  

o All changes the amino acids function  

When you eat proteins what are they digested and absorbed into? ∙ Enterocyte  

How are amino acids turned into proteins?

∙ Through transcription and translation  

o Proteins can turn back into amino acids from:  

 Lysozymes  

 Ubiquitin  

What are some protein products?  

∙ Glucthathione  

∙ Carnitine: moves fats into the mitochondrial membrane  ∙ Creatine: donatates phosphates  

What happens to extra amino acids?

∙ Excreted by the kidneys through nitrogenous waste  o Types of nitrogenous waste:  

 Four types  

∙ Two main:  

o Ammonia and urea  

What can amino acids also be turned into?

∙ Nucleotides  

What happens when a nitrogen is taken of an amino acid when the cell  doesn’t need proteins?

∙ Forms an alpha keto acid and the nitrogen is excreted through  nitrogenous waste by kidneys  

What can alpha keto acid be used for?

∙ Energy and go into other pathways  

How can you make a non essential amino acid?  

∙ Put nitrogen back on the alpha keto acid  

What does SAM do?  

∙ Donates methyl groups  

Describe excitatory neurotransmitters.

∙ Allow for reactions to happen and signals to occur  


∙ Stops neuronal transmission  

∙ If you don’t have GABA then that causes seizures from too much  neuronal firing  

Which transferases are indicators of liver function?  

o AST and ALT  

o These show up in liver functioning test

o Increases in liver dys-functioning increases AST and ALT  presence in the blood  

How does the alpha keto skeleton used to produce energy? ∙ Can be turned into either  

o Glucose  

o Ketones  

o Fatty acids (not likely but possible)

 Cholesterol can be made from alpha keto acids  

∙ Glucogenic amino acids:  

o Are converted to pyruvate and kreb intermediates  

 Ala  

 Gly  

 Cys  

 Ser  

 Asp  

 Asn  

 Glu  

 Gln  

 Arg

 Met

 Val  

 His  

 Pro  

∙ Ketogenic amino acids :  

o Are converted to acetyl CoA and acetoacetone  

 Leu  

 Lys  

∙ Ketone bodies: are energy made from  

o Ketogenic amino acids  

o Fatty acids in the absence of glucose  

∙ Both gluco and keto genic amino acids:  

o Phe  

o Ile  

o Thr  

o Trp  

o Tyr  

When does amino acids make energy?

∙ During fasting state  

What does the shape of the R chain allow for?

∙ For the amino acid to either be keto or glucogenic or both  Describe protein turnover.  

∙ Indicator of protein synthesis and degradation  

o As you make you break

 Ex: bone  

Describe Nitrogen balance.

∙ Tells intake vs output  

∙ An indicator of body protein  

∙ Nitrogen balance studies are based on nitrogen consumed vs. nitrogen  excreted via urine, feces ,and skin  

o Positive:  

 More protein in than out  

 Cant put your body in this state  

 Synthesizing new tissues  

 Proteins are high  

∙ Ex:  

o Pregnant women, children, anabolism, adding  

more lean mass, lactation, growth  

o Negative:  

 Amino acids being used for energy  

 Breakdown of muscle  

 You can put yourself in this stage by starving  

 More out than in  

∙ Ex: eating disorder, starvation, PEM

o Equal:  

 In=out  

 Not making new tissues  

 Most adults  

Where does urea synthesis occur?  

∙ Liver  

Urea Cycle Pathway: 

∙ Not an energy producing pathway (happens whether fed or unfed)  ∙ Cycle occurs in the liver  

∙ This cycle is regulated by the CPS1 enzyme (rate limiting enzyme)  o Forms monomer or dimer  

o Monomer is active form  

o Allosterically regulated by N-acetylglutamate  

∙ Common substances that nitrogen being excreted during deamination  in the urea cycle is  

o Glutamine and glutamate  

o Carbamoyl phosphate combines with ornithine via ornithine  transcarbamoylase enzyme to make citrulline  

o Aspartate is added to citrulline to go to arginiosuccinate by the  argininosuccinate synthetase enzyme  

∙ What enzyme during the urea cycle cleaves off urea from arginine? o Arginase  

∙ What is cleaved off of arginosuccinate during the urea cycle when it  goes to arginine?

o Fumarate  

∙ By what enzyme during the argininosuccinate during the urea cycle  does it go to arginine?  

o Argininosuccinase  

∙ What is cleaved off of arginine during the urea cycle before it goes to  ornithine?

o Urea via arginase enzyme  

∙ The Kreb bicycle: kreb cycle feeding the urea cycle  

What enzymes are liver specific during the urea cycle?  

∙ CPS1 and arginase  

What amino acid is needed to keep the urea cycle going?

∙ Aspartate  

What are the transaminate reactions of urea synthesis?  

∙ Alanine transfers its nitrogen to pyruvate  

∙ Pyruvate transfers its nitrogen to glutamate  

∙ Glutamate transfers its nitrogen to OAA  

∙ OAA goes to aspartate and that keeps the urea cycle going  o Whoever doesn’t have the nitrogen is turned into alpha keto  acids  

What are the functions of N-acetylglutamate?

∙ Is composed of acetyl CoA + glutamine  

∙ Enhances synthetase  

∙ Affinity for ATP  

∙ Splits dimers into monomers  

What is the inactive/active forms of CPS1?

∙ Inactive: dimer  

∙ Active: monomer  

o CPS1 needs energy and N-acetylglutamate to turn into the active monomer  

 If CPS1 cant be broken down into a monomer then the urea cycle cant happen  

Describe a High protein diet.

∙ Regulates urea cycle  

∙ Increases urea cycling  

∙ Increases production of urea cycle enzymes (CPS1 and arginase)  Describe Carbamoyl Phosphate Synthetase Deficiency.  

∙ Rare  

∙ Symptoms show immediately  

∙ Nitrogen becomes ammonia and you cant produce CPS1 which causes  build up in the blood stream  

∙ Causes neonatal hyperammonemia  

o Symptoms:  

 Vomiting

 Irritability  

 Intermittent ataxia (no reflexes  

 Lethargy  

 Mental retardation  

∙ The symptoms can be stopped by  

o Low protein diet, small meals  

o Only fed the exact amount of nitrogen they  

need for growth during infancy/ childhood  

o As adult eats the EAR value of 0.6g/kg/day of  


Describe the Liver.  

∙ Urea cycle occurs here  

∙ Amino acids are transported to the liver via hepatic portal system  ∙ From liver transported to other tissues  

∙ Liver is major site of gluconeogenesis and can raise the blood glucose  levels through this  

o Is the only tissue for urea synthesis  

 Liver specific enzymes:  

∙ AST and ALT (indicate liver function)  

∙ Arginase (urea cycle)

∙ Phenylalanine hydroxylase  

What does the phenylalanine hydroxylase enzyme do?

∙ Converts phenylalanine to tyrosine  

What is tyrosine used for?

∙ Melanin (pigmentation)

∙ Neurotransmitter synthesis  

∙ Fumarate and acetoacetate synthesis  

∙ Thyroid hormone  

∙ Turns DOPA into Dopamine  

∙ Is both gluco and ketogenic  

What does the loss of phenylalanine hydroxylase enzyme cause? ∙ Phenyl ketone (build up of ketones can become neurotoxic) What is Phenylketonuria?

∙ Deficiency of enzyme phenylalanine hydroxylase  

∙ Causes build up of phenyl ketone bodies and a deficiency in tyrosine  o Symptoms in infants:  

 Irritable  

 Have eczema like rash  

o Symptoms in older babies  

 Tremors  

 Hyperactivity  

 Seizures  

o Infants are tested for this at 3 days

∙ What is the treatment of the build up of phenyl ketone bodies in pku  patients?

o Low phenylalanine diet with small amounts of fish, poultry, and  meat  

o Vegetarian based diet  


∙ What is the treatment of tyrosine deficiency caused by pku?  o Tyrosine supplements  

What makes the liver specific enzyme SAM?  

∙ Methionine  

∙ SAM donates methyl groups  

o Once it has donated its methyl group it becomes SAH

∙ Norepinephrine to epinephrine reaction uses SAM

What enzyme does methionine use to make SAM?

∙ Methionine adenosyl transferase  

What creates carnitine?

∙ Lysine-trimethylysine-carnitine  

Where is BCAA transferase found?

∙ In the muscle  

What are the Functions of BCAAs  

∙ Carries out transamination reactions  

∙ High activity in skeletal muscle  

∙ Low activity in liver  

∙ Some activity in kidney, adipose tissue, brain but majority is in the  muscle  

Once the Transamination of BCAAs occur what happens to the alpha keto  acids?

∙ They either:  

o Remain in the muscle  

o Transported to other tissues  

 Through the BCAA transferase enzyme BCAAs become  ∙ Alpha keto acids  

o Go on to be gluco or ketogenic intermediates

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