Molecular Biology Flashcards
Parietal Cells
Found in stomach. Produce HCL and Intrinsic Factor
HCL
Degrades protein, activates pepsinogen
Chief Cells
Found in stomach. Produce pepsin
Endopeptidase
Degrades protein to peptide
G Cell
Found in stomach. Produces gastrin (blood stream)
Mucus Cell
Found in stomach. Secretes Mucus and HCO3 to protect the stomach lining
Enteropeptidase/Enterokinase (brush border)
Found in duodenum. Activates trypsinogen -> trypsin, which in turn activate proteases to hydrolyze protein.
Hyperchlorhydria
Zollinger Ellison syndrome. Gastrin secreting tumor
HYPOchlorhydria
Pernicious Anemia. Autoimmune destruction of parietal cells. B12 deficiency
Cystic Fibrosis
Decrease pancreatic enzymes. Mutation in CFTR
Hartnup disease
Defect absorbing neutral AA. Decrease in Tryptophan and Niacin (Pellagra like manifestations) Photosensitivity.
Cystinuria
Defect in dibasic AA absorption (Cysteine). Cysteine stones - Kidney stones
H2 Blocker
Treats HYPOchlorydria
Glucogenic AA Degradation
Alanine -> Pyruvate -> Glucose
TCA Intermediates
Ketogenic Degradation of AAs
Lysine -> Acetyl CoA -> Ketone Bodies
Purely Ketogenic Amino Acids
Leucine & Lysine
Glucogenic & Ketogenic Amino Acids
Isoleucine, Phenylalanine, Threonine, Tryptophan & Tyrosine
Transamination
Catalyzed by aminotransferases/transaminases. Pyridoxal Phosphate (B6) - cofactor. Transfers alpha amino group from one carbon skeleton (amino acid) to another (α-keto acid, which becomes an amino acid). Can not be done to lysine or threonine.
Trans-deamination
Transaminate L-amino acids to generate glutamate, which can then be oxidatively de-animated to to form α-ketoglutarate and ammonia.
Excretion from Intestines
NH3 -> directly to Portal system (Liver) (Periportal)
Excretion from Liver
Urea / Protein (synthesis) to transport nitrogen
Excretion from Muscle
Breaks down branched chain amino acids (BCAAs)
Form Alanine -> transport NH3 to liver
Form Glutamine -> transport NH3 to kidneys
Urea Cycle Rate Limiting Step
Carbamoyl Phosphate Synthase 1
Source of Nitrogen in Urea
N1 -> Free NH3
N2 -> Aspartate
In essence, both come (indirectly) from glutamate, which gathers nitrogen from other amino acids to repeat the process.
Non Oxidative deamination
Serine and threonine can be directly de animated to NH4+. Catalyzed by serine dehydratase or threonine dehydratase.
Oxidative deamination
Occurs in liver and kidneys. Catalyzed by glutamate dehydrogenase (GLDH). Located in mitochondria.
Urea Cycle step 1 (Rate Limiting)
Ammonia + Bicarbonate + ATP -> Carbamoyl Phosphate via CPS-1
Urea cycle step 2
Carbamoyl Phosphate -> citrulline via Ornithine transcarbomylase
Urea cycle step 3
Citrulline is taken out of mitochondria, converted to arginosuccinate via arginosuccinate synthase
Urea cycle step 4
Arginosuccinate -> Arginine via arginosuccinate lyase
Urea cycle step 5
Arginine -> Urea via arginase. (Conversely, arginine could be converted back to ornithine and then citrulline to redo the cycle)
Pyridoxine (B6) - Pyridoxal Phosphate
Co-factor required for transamination
Folate
Co-factor required for one carbon transfer
Tetrahydrobiopterin
Co-factor required for hydroxylation
Serine Hydroxy-methyltransferase
Converts serine to glycine and vice versa
Cystathionine β synthase
Creates cystathionine from serine and methionine, which can be converted to cysteine.
AAs derived from glycolysis intermediates
Serine and glycine from 3-phosphoglycerate, Cysteine from methionine and serine, alanine from Pyruvate (via transamination with B6)
AAs derived from TCA cycle (α-ketoglutarate)
Glutamate (directly), Glutamine (from glutamate), Proline (from glutamate semialdehyde) and Arginine (from ornithine)
AAs derived from TCA cycle (Oxaloacetate)
Aspartate (Transamination of oxaloacetate) and Asparagine (from Aspartate via asparagine synthetase)
Tyrosine synthesis/catecholamine synthesis step 1
From Phenylalanine via phenylalanine hydroxylase. Requires THB as a co-factor.
Catecholamine synthesis step 2
Tyrosine -> Dopa via tyrosine hydroxylase. Rate Limiting Step. Requires THB as a co-factor.
Catecholamine synthesis step 3
DOPA -> Dopamine via DOPA decarboxylase. B6 as a co-factor
Catecholamine synthesis step 4
Dopamine -> Nor-epinephrine. Uses Ascorbate as a co-factor
Catecholamine synthesis step 5
Nor-epinephrine -> Epinephrine. Requires SAM as a co-factor. Uses cortisol.
Schizophrenia cause
Overproduction of dopamine
Parkinson’s disease cause
Underproduction of dopamine
Pheochromocytoma
Benign tumor that produces excessive catecholamine secretion. Can cause life-threatening hypertension or cardiac arrhythmias.
MAO
Mono amino oxidase. Enzyme that breaks down catecholamines.
COMT
Catecholamine O-methyl transferase. Enzyme that breaks down catecholamines
Formation of melanin
DOPA -> Dopaquinone via tyrosinase, copper as a cofactor. Melanin is then produced.
Thyroglobulin
Used by thyroid to produce T3 and T4 hormones. Made up primarily of tyrosine residues.
Melatonin
Hormone derived from Serotonin (5-hydroxytryptamine) which is synethesized from tryptophan
5-Hydroxy indole acetic acid
Product of serotonin breakdown by MAO
MAO-A
Can catabolize Epinephrine, Norepinephrine, serotonin, melatonin, Dopamine, Tyramine, and tryptamine
MAO-B
Can catabolize dopamine, tyramine, and tryptamine
