Eicosanoids, Amino Acid Metabolism, and One-Carbon Metabolism Review

Comprehensive vocabulary flashcards covering eicosanoid signaling, amino acid biosynthesis and degradation pathways, nitrogen disposal via the urea cycle, and one-carbon metabolism featuring THF, B12, and SAM.

Eicosanoids

Signaling molecules derived from arachidonic acid or other polyunsaturated fatty acids that regulate processes such as inflammation and immunity.

Phospholipase $A_2$ ($PLA_2$)

The enzyme responsible for hydrolyzing membrane phospholipids to release arachidonic acid.

Cyclooxygenase ($COX$) Pathways

The metabolic pathways involving enzymes ($COX-1$ and $COX-2$) that convert arachidonate into prostaglandin $H_2$ ($PGH_2$), the precursor for prostaglandins and thromboxanes.

Thromboxane $A_2$ ($TXA_2$)

An eicosanoid that facilitates platelet aggregation and vasoconstriction, essential for the formation of blood clots.

Lipoxins ($LXs$)

Anti-inflammatory eicosanoids that assist in the resolution of inflammation, unlike most eicosanoids that promote inflammatory responses.

NSAIDs (Nonsteroidal Anti-inflammatory Drugs)

Pharmacological agents that inhibit cyclooxygenase enzymes to reduce the synthesis of prostaglandins and thromboxanes, thereby alleviating pain and inflammation.

Corticosteroids

Hormones or drugs that inhibit phospholipase $A_2$ ($PLA_2$), preventing the initial release of arachidonic acid and suppressing the production of all eicosanoids.

Leukotriene $D_4$ ($LTD_4$)

A lipid mediator and potent bronchoconstrictor that plays a central role in the pathophysiology of asthma.

Essential vs. Non-Essential Amino Acids

Classification of amino acids based on whether the human body can synthesize them (Non-Essential) or if they must be obtained through dietary intake (Essential).

Ketogenic Amino Acids

Amino acids like leucine and lysine that are metabolized into ketone bodies or acetyl-$CoA$ rather than glucose.

Branched-Chain $\alpha$-Ketoacid Dehydrogenase ($BCKDH$)

An enzyme complex whose deficiency leads to the accumulation of branched-chain amino acids, causing Maple Syrup Urine Disease ($MSUD$).

Phenylalanine Hydroxylase

The enzyme that converts phenylalanine to tyrosine; its deficiency results in the metabolic disorder Phenylketonuria ($PKU$).

Urea Cycle

A liver-based metabolic pathway that detoxifies ammonia by converting it into urea for excretion by the kidneys.

Carbamoyl Phosphate Synthetase I ($CPS-I$)

The mitochondrial enzyme that catalyzes the first committed step of the urea cycle; it is activated by $N$-acetylglutamate ($NAG$).

Alkaptonuria

A genetic disorder caused by a deficiency in homogentisate oxidase, leading to the excretion of black urine due to homogentisic acid buildup.

Tetrahydrofolate ($THF$)

The biologically active form of Folate (Vitamin $B_9$) that functions as a coenzyme for the transfer of one-carbon units in nucleotide and amino acid synthesis.

Intrinsic Factor ($IF$)

A glycoprotein produced by gastric parietal cells that is required for the absorption of Vitamin $B_{12}$ in the ileum.

S-Adenosyl Methionine ($SAM$)

A universal methyl donor synthesized from methionine and $ATP$ that is essential for $DNA$, $RNA$, and neurotransmitter methylation.

Methyl Trap

A functional folate deficiency caused by Vitamin $B_{12}$ deficiency, where folate remains stuck as $5$-methyl-$THF$ and cannot be used for $DNA$ synthesis.

Megaloblastic Anemia

A blood disorder characterized by large, immature red blood cells, typically resulting from deficiencies in folate or Vitamin $B_{12}$, which impairs $DNA$ synthesis.