Protein and Amino Acid Metabolism Flashcards Preview

MCM Exam 1 > Protein and Amino Acid Metabolism > Flashcards

Flashcards in Protein and Amino Acid Metabolism Deck (29):

Because of the fact that the Liver cant deaminate BCAAs cause of their hydrophobic side chains, what happens to them?

Used as fuel in muscle.


What is ammonia toxicity?
Where are the disorders that cause this condition?
What is the toxic agent?
What is the main effect of this agent?
What are the most at risk organs?

Excessive ammonia
Disorders of urea cycle or liver failiure
NH3 cause it can slip in membranes (not NH4+)
pH imbalance and swelling
Brain and CNS (swelling of astrocytes)


How does Phenylalanine enter TCA cycle?
What enzyme catalyzes the first step in this and what does it do?
What is Phenylketonuria?
What is phenylalanine converted to instead?
What smell does this cause in urine?
What are the physiological effects?
How do you treat?

Phenylalanine ---> Tyrosine ---> Fumarate
Phenylalanine Hydroxylase, puts oh on phenylalanine converting it to tyrosine
Disease where above enzyme has defects
Phenyl pyruvate then phenyllactate and phenylacetate
Musty smell
Severe brain impairment
Limit Phe in diet, supplement with Tyrosine.


What is proteasomal degradation and what signal do they see? Is this selective or non-selective for proteins?

Proteosomes in cytoplasm that cleave polyubiquitin proteins. Ubuiquitin is the marker. This is selective.


In the metabolism of Methionine, what is the enzyme at which Homocystinuria can occur?
What coenzyme does this need?
What substrate does this enzyme use?
What kind of dimer can this substrate form?
What is the disease associated with this enzyme?
What are the causes of this disease?
Most affected organ systems?
How do you treat this?

Cystathionine B- Synthase
PLP (Pyridoxal Phosphate)
Homocystinuria, buildup of homocystine cause homocysteine not metabolized correctly
Vitamin B deficiencies or genetic defects in the enzyme
Eye, skeletal, CNS, Vascular
Vitamin supplementation in some cases


What amino acids enter at Succinyl CoA?

Met, Thr, Ile, Leu, and Val


What is transamination?
What enzyme does this?
What is Oxidative deamination?
What system does this waste product then enter?

Putting an ammonia onto a substrate
Aminotransferase (PLP)
Removing the ammonia
Urea cycle


What is Albinism?
What is the defect reason for this?
What are the visual effects?

Severe lack of melanin
Defects in enzyme Tyrosinase that converts Tyrosine to Melanin
Complete absence of pigmentation (skin, hair, eyes)


What is proteolysis?
What is an exopeptidase?
What is an endopeptidase?

Degradation of proteins for reabsorption
Cleaves at C or N ends
Cleaves within the protein at specific site


For the secreted proteolytic enzymes Trypsinogen, chymotrypsinogen, and enterokinase, what is the relationship between them and which are zymogens?

Enterokinase activates zymogen trypsinogen in SI Lumen. Trypsin then activates chymotrypsinogen other molecules of trypsin.


What is a transamination? What are the enzymes called?

Amino group transferred to an alpha keto acid, shuffling of amine groups. Enzymes are called Transaminases/aminotransferases


In what form is ammonia removed from the brain?
In what form is ammonia removed from other tissues?
In what pathway is urea generated and by what mechanisms?

Gln and Glu (alpha keto glutarate aminated to these)
Gln and Ala
AA metabolic pathways, by deamination


What three AAs form creatine?
What is phosphocreatine?
What is Creatinine?
What are elevated levels in serum indicative of?
What can be used as a diagnostic for myocardial infarction?

Arg, Gly, Met
energy storage in muscle and brain, quick ATP
Muscle degeneration, kidney disfunction
Cardioselective isoform of Creatine Kinase (CK-MB)


Why is TCA cycle anaplerotic? What are the two major anaplerotic reactions

Means "fill up". Different reactions provide intermediates to replenish TCA cycle.
Degradation of AAs
Carboxylation of Pyruvate


What ph are the lysosomal proteolytic enzmes active and inactive? What are three types? Are these selective or non-selective for proteins?

Active at ph 5 in lysosome, inactive at 7 in cytosol
Macoautophagy, microautophagy, chaperone mediated autophagy. These are non-selective


What is deficient in maple syrup urine disease?
What does this cause?
How do you treat?

Branched- chain a-keto acid dehydrogenase complex (BCKD)
Branched-chain ketoaciduria
Branch chained AAS in urine, also in blood causing toxic effects on brain and retardation
Diet limiting BCAA (Val, Leu, Ile


What are some Tryptophan derivatives? (made from Tryptophan)

Melatonin, Serotonin


What are some Tyrosine Derivatives?

Thyroid hormones T3 (Triiodothyronine) and T4 (Thyroxine)


What is Thyroglobulin?
What is Hyperthyroidism?
How is this treated?

Large protein made by thyroid that produces T3, T4, has 120 Tyrosine residues that when iodinated create these hormones
Very active Thyroid
Treated with agents which block iodination of thyrogloblin to decrease T3, T4


What is protein turnover?

Protein Breakdown ---> Free AA ---> Protein Synthesis


How are free amino acids supplied? (3)
How are they depleted? (3)

Protein turnover, Digested food, De novo synthesis of essentials
Making proteins, nitrogen compounds, and AA degradation


What Amino acids enter the TCA cycle at alpha-Ketoglutarate? What is lost in this reaction?

Gln, His, Arg, Pro, all converted to Glu then a-Ketoglutarate.
NH4+ is lost.


How is NH4+ removed from the muscle?

Pyruvate + NH4+ ---> Alanine, can diffuse to liver where converted back into pyruvate and ammonia enters urea cycle. Pyruvate back to muscle if needed


What is the required co-enzyme of transaminases? What is it a derivative of?
What is Alanine transaminase abbreviation?
What is aspartate transaminase abbreviation?

Pyridoxyl-5' phosphate (PLP)
Vitamin B6


What kind of diet increases urea cycle?
What kind of diet decreases it?
What hormones play a role in urea production? (2)
Where is 20-30% of urea hydrolyzed? What is the purpose of this?

High nitrogen diet.
High Carbohydrate diet.
Insulin, glucagon
GI tract by bacteria, source of nitrogen for them


What are the essential AA's?

FML HWK I TV (he says under certain conditions also Arg and one other that doesnt show up on his slide)


Muscle uses branch chain amino acids as fuel during prolonged ____ and _____.

Exercise, fasting


What is the purpose of the Urea cyle? (Ornithine cycle)
Where does it occur?
Where is the product sent for excretion?

Create urea (double nitrogen waste product)
Liver mitochondrion and cytosol


Which are the two ketogenic AAs?
Which AAs are Ketogenic and GLucogenic?
What does Ketogenic mean?
What does Glucogenic mean?
What is ratio of ketogenic to both to glucogenic?

Lysine, Leucine
Phenylalanine, Isoleucine, Tryptophan, Tyrosine
Acetyl CoA or acetoacetate
Pyruvate or TCA cycle intermediates