Chapter 6 Amino Acids

If that same adult then consumes a meal containing ~300 mg cholesterol, what would their circulating cholesterol concentration be assuming all of it was absorbed?

156mg/dl

newborns are screened within

24-48 hours of age

If an average adult has ~5 liters of blood and a circulating cholesterol level of 150 mg/dL, how much total cholesterol do they have circulating in their blood?

7500mg

what dietary recommendation would you provide to someone trying to increase their lean muscle mass?

eat more amino acids / protein adequate amount of protein and decreasing fat positive nitrogen balance CHO consumption has to be adequate as well.

Intestinal cells use AAs for

energy production as well as for synthesis of proteins and nitrogen containing compounds

alanine and the liver and muscle

in a fasted or catabolic state glutamate will transfer its amino group to pyruvate to fomr a -ketoglutarate alanine is released into the blood for travel to the liver within the liver alanine undergoes transamination back to pyruate which is then used to remake glucose

glutamine and the muscle

in extrahepatic tissues, glutamine is used for ammonia transport..like skeletal muscle. glutamine formed in the muscle is released into the blood for transport and use by other tissues glutamine use by cells increases dramatically with hypercatabolic conditions such as infection or trauma in these conditions muscle glutamine release cannot meet other cellular demands----supplementation of 20-25 g/day can improve patient outcomes

what is the primary function of the urea cycle?

to remove nitrogen from the body.

what type of reaction is important for the synthesis for nonessential amino acids?

transamination

(T/F)Muscles preferentially catabolize leucine, isoleucine, and valine.

true

Organ specific AA metabolism can create dependence between organs

tue

heel prick test

uses mass spectrometry to detect over 30 metabolic disorders 99 percent for amino acid and fatty acid disorders all infants get this done

primary storage form of amino acids in the body?

they're not stored in the body.

Disposal of ammonia in the urea cycle

- NH3 combines with CO2 or HCO3- to form carbamoyl phosphate - Crabamoyl phosphate reacts with ornithine transcarbamoylase (OTC) to form citruline - Aspartate reacts with citruline to form argininosuccinate - Arginosuccinate is cleaved to form fumarate and arginine - Urea is formed and ornithine is reformed from cleavage of arginine

What are the 9 essential amino acids?

1. Histidine 2. Isoleucine 3. Leucine 4. Lysine 5. Methionine 6. Phenylalanine 7. Threonine 8. Tryptophan 9. Valine

Carbon skeleton/a-keto acid uses

AA carbon skeletons can then by used for multiple cellular processes: energy production - AA can be used as an energy source with dietary cHO and lipid intake is inadequate glucose production- several amino acids are gluconeogenic to be gluconeogenic the catabolism of the AA msut yield pyruvate or intermidiates of the TCA cycle ketone body production - to be ketogenic the catabolism of the AA must generate acetyl coA or acetoaceteate cholesterol production fatty acid synthesis - occurs in times of excess energy needs requires consumption of adequate CHO as well

AA catabolism generates a significant amount of ___ which must be disposed of by the body.

Ammonia.

Sources of Amino Acids

Animal products-meat, poultry, fish, eggs, dairy Plant products- grains, legumes, nuts, seeds Endogenous proteins- desquamated mucosal cells and digestive enzymes

Conditionally Essential Amino Acid

Become essential if an essential amino acid is limiting or if the metabolism of an essential amino acid is impaired Tyrosine, cysteine, proline, arginine, glutamine<-- KNOW BY MEMORY

Amino Acid Protein Digestion

Begins in stomach via action of HCL. In small intestine the acidic chyme stimulates release of secretin and cholecystokinin.

Amino Acid Classification

Essential Conditionally Essential

the ___ is the primary site for most AA uptake following a protein containing meal.

Liver liver derives 50% of its energy from oxidation

Peptide absorption

Majority of amino acids are absorbed at PEPTIDES peptide absorption requires a transport system (PEPT1) peptide transport is more rapid than AA transport peptides are hydrolyzed to individual AAs within enterocyte and released into blood as FREE AAs intact peptides can be found in blood and can be hydrolyzed within the plasma or more commonly at the cell surface of tissues(especially liver kidneys, and muscle).

Are amino acids stored in the body?

No. a daily supply is needed.

amino acid absorption

Occurs primarily in the duodenum and jejunum requires carriers which are sodium-dependent BCAAs and essential AAs are absorbed fastest Competition among AAs for carriers can lead to imbalanced AA absorption transport across the basolateral side of the membrane and into blood use the same carrier systems.

Which amino acid becomes conditionally essential in patients with PKU

Tyrosine

rare findings

abnormal smell abnormal hair blood in urine dysmorphic features

skeletal muscle use of AAs

after eating skeletal muscles exhibit net protein synthesis muscle preferentially catabolize aspartate, aspargine, glutamate, leucine, isoleucine, adn valine following transamination the a keto acids of the BCAAs either remain within the muscle or transported for use in other tissues catabolism of branched chain a keto acids is catalyzed by branched chain a-keto acid dehydrogenase (BCKAD)

what are the two most active aminotransferases?

alanine aminotransferase(ALT) found in liver aspartate aminotransferase(AST) found in heart

respiratory signs

hyperpnea respiratory failure tachynpea apnea

amino acids as biogenic amines

biogenic amines are synthesized via AA catabolism and function as neurotransmitters -serotonin -catecholamines -histamines

Why is both too much and too little protein a major concern with urea cycle disorders?

both would result in increased nitrogen accumulation

brain and accessory tissues and AAs

brain has high capacity for active transport of AAs competition for common carriers can become problematic elevatons of certain AAs in the breain will cause a variety of neurologic problems...impaired brain development; altered behavior and mental function altering dietary carbohydrate and protein intake in a healthy individual does not elicit similiar neurologic consequences

amino acid disorders

can affect metabolism of single amino acids treatment is based on restriction of dietary protein needs must be met using synthetic formula treatment requires a balance of meeting nutritional needs and preventing nutritional deficiencies

inborn errors of metabolism

can lead to an accumulation of compounds with harmful effects can lead to deficiencies of substances that are essential for normal growth and development over 200 types of genetic metabolic disorders have been reported dietary interventions involve rigid restrictions of protein fat or CHO

Essential Amino Acid

cannot be synthesized by the body must be acquired in the diet phenylalanine, valine, threonine, methionine, tryptophan, histidine, isoleucine, leucine, lysine <-- KNOW BY MEMORY

Within the first 3 hours after consuming a cholesterol containing meal, which lipoprotein will be transporting the majority of the dietary cholesterol?

chylomicrons

Glucose-6-phosphatase

converts glucose-6-phosphate to glucose

maple syrup urine disease

defect in one of the proteins in the branched chain ketoacid decarboxylase complex inability to catabolize isoleucine, leucine, and valine clinical manifestations include seizures, acidosis, coma, and death

Phenylketonuria (PKU)

defect in phenylalanine hydroxylase that leads to the inability to convert phenylalanine to tyrosine untreated PKU leads to neurologic abnormalities, seizures, and mental retardation nutrition therapy involves a low phenylalanine diet throughout the patients life

disposal of ammonia - glutamate and glutamine synthesis

excess ammonium ions can be used to make non essential amino acids glutamate dehydrogenase can use an ammonium ion and a-ketoglutarate to make the amino acid glutamate glutamine syntetase can use an ammonium ion and glutamate to make the amino acid glutamine.

(T/F)Dietary amino acid intake has absolutely no influence on neurotransmission and brain function.

false

(T/F)Glutamate supplementation can significantly improve critically ill patient outcomes

false, Glutamine

(T/F)alanine is oxidized for energy within the skeletal muscle when dietary energy consumption is inadequate.

false, alanine is released from skeletal muscle then transferred to liver and converted to pyruvate then glucose for energy.

(T/F)Skeletal muscle is the predominant user of dietary amino acids.

false, in the gut

intestinal glutamine metabolism

glutamine is primary energy source of energy for intestinal cells glutamine stimulates mucosal cell proliferation glutamine can help prevent atrophy of gut mucosa and bacterial translocation glutamine is used for mucin synthesis

increased nitrogen levels in the blood can lead to:

hepatic encephalopathy treated by GI tract to promote ammonia diffusion and by promoting the colonic bacteria to decrease ammonia production

organ dysfunction

hepatomegaly hepatic dysfunction cardiomegaly cardiomyopathy

To maximize AA uptake would administration of individual amino acids or intact proteins be more effective?

intact proteins --

AA interdependence begins with the

intestinal cells because they are the first cells in the body to receive dietary AAs.

deamination of amino acids

involves the removal of an amino group with no transfer to another the amino group is released as ammonia and converted to an ammonium ion deamination also produces an a=keto acid the ammonium ions generated by deamination must then be disposed of, typically in urine as urea. can get these foods from processed meats and cheeses

Transamination of Amino Acids

involves the transfer of an amino group from one amino acid to an alpha keto acid amino acid + a-keto acid <--> aketo acid +amino acid transamination reactions are important for non-essential AA synthesis transamination reactions are catalyzed by enzymes called aminotransferases which typically require vitamin b6 alanine aminotransferase and aspartate aminotransferase are two of the most active aminotransferases.

urea is formed in the __ and removed by the ___.

liver ; kidneys

BCAAs tend to be utilized by:

muscle

Amino Acids as neurotransmitters

neurotransmitters are compounds generated in the body that transmit signals from a neuron to a target cell across a synapse. AAs that act as neurotransmitter: -glycine: acts primarily as an inhibitory nuerotransmitter in the spinal cord -taurine: functions as an inhibitory neurotransmitter -glutamate: acts primarily as an excitatory neurotransmitter in the brain and the spinal cord -aspartate: acts as an excitatory neurotransmitter in the CNS

amino acids consumed in excess of needs are:

oxidized or catabolized

gastrointestinal signs

poor feeding vomiting diarrhea reflux

Neurological signs

poor suck lethargy abnormalties of tone seizures

in what clinical scenarios might the urea cycle be impaired?

renal failure liver damage kidney failure

What is the primary therapeutic treatment for an individual with an amino acid disorder?

restrict intake of the problematic amino acid

urea cycle disorder

result in an impaired capacity of the body to excrete nitrogen in the form of urea ranges of severity and onset vary dramatically can initially be treated with dialysis and nitrogen binding medications extreme dietary protein restriction is required which makes supporting grwoth very difficult it is incredibly important to ensure that essential amino acids needs are being met micronutrient deficiency is also of signigicant concern

Clinical Manifestations

signs and symptoms

Protein digestion begins in the -------- via the action of ----------?

stomach; HCl

histamine

synthesized from histidine mediates attention and alertness

serotonin

synthesized from tryptophan an excitatory neurotransmitter and prtent vasoconstrictors affects sleep, mood, appetite, and cognitive functions

catecholamines

synthesized from tyrosine dopamine helps coordinate movement norepinephrine is important for sleep and alertness epineprine functions as a hormone with effects on nutrient metabolism

disposal of ammonia - the urea cycle MAJOR ROUTE

the urea cycle functions in the liver requires energy fluctuates with diet adn hormone concentrations once formed, urea travels through the blood to the kidneys for excretion in urine blood urea nitrogen (BUN) is used clinically to assess nitrogen balance BUN is decreased with liver failure bc they're not making urea, positive nitrogen balance, and in females who are pregnant BUN is increased with renal disease and excessive protein catabolism bc urea will stay in blood and you wont pee it out.