Quiz 1 (Protein/AA Metabolism) Flashcards
Defective transport of nonpolar/neutral amino acids, especially ____, can lead to ____ Disease.
Tryptophan / Hartnup
*key characteristic = photosensitivity
Defective transport of dimer is cystine and dibasic amino acids can lead to ___.
(What are theses amino acids?)
Cystinuria
*key characteristic = cystine crystals in the kidneys causing abdominal pain
(“COLA” - Cystine / Ornithine / Lysine / Arginine)
Essential Amino Acids
“TIM HRKL VolsWagon Ferrari”
Or
“My Tall Handsome Vegan Friend Is Reliably Watering Kale Leaves”
Methionine (M) / Threonine (T) / Histidine (H) / Valine (V)/ Phenolalanine (F) / Isoleucine (I) / Arginine (R) / Tryptophan (W) / Lysine (K) / Leucine (L)
Alpha-ketoglutarate can act as a precursor for the synthesis of which amino acid(s)?
Glutamate
*Glutamate —> Glutamine / Histidine / Proline / Arginine
Pyruvate can act as a precursor for the synthesis of which amino acid(s)?
Valine / Alanine* / Leucine
*directly
OAA can act as a precursor for the synthesis of which amino acid(s)?
Aspartate* / Asparagine / Lysine / Methionine / Threonine / Isoleucine
*directly
3-Phosphoglycerate can act as a precursor for the synthesis of which amino acid(s)?
Serine* / Cysteine / Glycine
*directly
Exopeptidases attack the ____ of a protein.
Endopeptidases attack the ____ of a protein.
Exo- = C- and N- terminus ends
Endo- = digestive (specific) sites within the protein
Lysosomes sequester Intracellular proteolytic enzymes that are active when ___.
pH = 5
*because the lysosome creates a low pH environment, these enzymes are active within the lysosomes, but not outside them (where pH =7)
The catalytic core of a proteosome is termed as the ___ subunit.
20S
Ubiquitin receptors in the ___ regulatory unit of a proteosome target multi-Ubiquitin chains.
19S
Cleaving of peptide bonds in a proteosome is made possible by ____ which acts as a nucleophile.
-OH of Threonine
Trypsinogen, an inactive zymogen, is activated by an ___ that is embedded in the intestinal mucosa.
Enterokinase
What role do enteropeptidases play in protein digestion?
They convert the zymogen trypsinogen to active trypsin
Ketogenic / Glucogenic Amino Acids
Ketogenic (only) = Lysine / Leucine
*form precursor for ketone bodies or fatty acids (Acetyl-CoA or Acetoacetate)
Both = Phenolalanine / Tryptophan / Tyrosine / Isoleucine / Threonine
*”FWY IT”
Glucogenic = all others
*form precursors for glucose metabolism
What are the 3 main steps in amino acid metabolism?
- Aminotransferase / Transaminase = shuffling of amine groups
- Glutamate Dehydrogenase
- Urea Cycle = repackaging and excretion of amine group as ammonium
___ is the ketoacid of aspartate.
OAA (Oxaloacetate)
Transaminase reaction require the use of the coenzyme ___ which is a derivative of ___.
PLP (pyridoxyl-5’-phosphate)
Vitamin B6
Transamination reaction transfer amino groups to ___.
Alpha-keto acids.
Glutamine Synthetase converters Glutamate to Glutamine in order to trap ___.
Nitrogen
*for later excretion in the Urea Cycle
Met, Thr, Ile, and Val can be metabolized to form ___ which can be converted to ___ (an intermediate of the TCA cycle).
Propionyl CoA
Succinyl CoA
Mutations in ___ are the most common cause of homocystinuria.
CBS (cystathione beta-synthase)
*enzyme used in the metabolism of Methionine
Deficiencies in pathways for metabolizing branched chain amino acids results in ___.
What are these amino acids?
Maple Syrup Urine Disease
*usually caused by deficient activity of BCKD complex
Val / Ile / Leu
Phenylalanine metabolizes into ___ by the enzyme ___.
Tyrosine
Phenylalanine Hydroxylase
*if defective, leads to Phenylketonuria (neurological problems / musty urine)
Hypothyroidism vs. Hyperthyroidism
Hypo- = low T4 / high TSH
Hyper- = high T4 and T3 / low TSH
*T3 and T4 (thyroxine) are made by Thyroglobulin which consists of Tyrosine resides
Key amino acid derivative:
Tyrosine —> ?
Serine —> ?
Glutamate —> ?
Tryptophan —> ?
Tyrosine —> thyroid hormones (T3/T4); endocrine hormones (dopamine); melanin
Serine —> Acetylcholine (involved in neurotransmission)
Glutamate —> GABA
Tryptophan —> Serotonin (which is converted to Melatonin); NAD+ and NADP+ (requires Vitamin B6)
Grave’s Disease results from defective metabolism of ___.
Tyrosine
Albinism is a result of the inability of ____ to be converted to melanin, resulting in a lack of pigmentation.
Tyrosine
Ammonia is removed as ___ and ___ in the brain.
Glutamate / Glutamine
*other tissues: Alanine / Glutamine
What occurs when there is excess ammonium?
Glutamate Dehydrogenase will continue to generate glutamate from alpha-ketoglutarate to use up the NH4+
This lowers the pool of alpha-ketoglutarate, which lowers TCA cycle activity, learning to unconsciousness
Pyruvate is the alpha-keto acid of ___.
Alanine
The urea cycle primarily takes place in the ___.
Liver
An Alanine Aminotransferase (ALT) is used in the removal of excess NH4+ from the ___.
Muscle
Reactions of ALT and GLDH
ALT - transamination
*transfer of NH3 onto Glutamine
GLDH - oxidative deamination
*generation of NH4+
What is the rate limiting enzyme of the Urea Cycle?
Carbamoyl Phosphate Synthetase
Urea production is ___ by a high protein diet and ___ by a high carb diet.
Increased / decreased
*proteins tend to bring in amino acids with Nitrogen
A defect in ___ can cause hyperammonemia since ammonium ions cannot enter the Urea Cycle.
CPS-1 (Carbamoyl Phosphate Synthetase)
Ammonia (NH3) is a toxic agent while ammonium (NH4+) is not because…
As an uncharged molecule, ammonia can permeate/cross membranes and cause pH imbalances leading to swelling of cells
Creatine is made from which 3 amino acids?
Arg / Gly / Met
___ serves as a diagnostic for myocardial infarction.
CK-MB (creatine kinase)
Basic essential amino acids:
His / Lys
Branched chain amino acids are initially metabolized in the ___ because the enzyme ____ is in higher concentration there.
Muscles / branched-chain amino acid transferase
Urea is synthesized in the liver from ___ and ___.
Aspartate / Carbamoyl Phosphate
