BMS131 – Introduction to Medical Biochemistry & Amino Acids

Vocabulary flashcards covering key terms, classifications, and biochemical roles of amino acids from Lecture 1.

Biochemistry

The science that studies biomolecules, their reactions, metabolic pathways, regulation, and role in health and disease.

Biomolecule

Any molecule present in living organisms, including carbohydrates, lipids, proteins, nucleic acids, vitamins, minerals, gases, and water.

Organic Biomolecules

Carbon-containing biomolecules such as carbohydrates, lipids, proteins, nucleic acids, and vitamins.

Inorganic Biomolecules

Non-carbon biomolecules including minerals, electrolytes, gases, and water.

Amino Acid

Building block of proteins composed of an α-carbon linked to an amino group, carboxyl group, hydrogen, and distinctive R-side chain.

Peptide Bond

The covalent bond formed between the α-carboxyl group of one amino acid and the α-amino group of another with loss of water.

Chemical Classification of Amino Acids

Grouping of amino acids based on R-group structure: aliphatic, aromatic, or heterocyclic.

Aliphatic Amino Acids

Amino acids whose side chains contain no ring (e.g., Gly, Ala, Val, Leu, Ile, Met).

Aromatic Amino Acids

Amino acids with benzene rings in the side chain (Phe, Tyr, Trp).

Heterocyclic Amino Acids

Amino acids whose side chains include non-benzene rings (Pro, Hydroxyproline, Histidine, Tryptophan).

Branched-Chain Amino Acids (BCAA)

Valine, leucine, and isoleucine—aliphatic amino acids with branched side chains.

Hydroxy Amino Acids

Amino acids containing –OH groups: serine, threonine, tyrosine, hydroxyproline.

Sulfur-Containing Amino Acids

Cysteine and methionine, characterized by sulfur atoms in the R-group.

Amide Amino Acids

Asparagine and glutamine—amides of aspartic and glutamic acids, respectively.

Essential Amino Acids

Amino acids not synthesized by humans and must be obtained from diet: Val, Leu, Ile, Thr, Met, Lys, Phe, Trp, His.

Semi-essential (Half-essential) Amino Acid

Arginine—synthesized insufficiently during growth; required partly from diet.

Non-essential Amino Acids

Amino acids synthesized endogenously in adequate amounts.

Metabolic Classification of Amino Acids

Grouping into glucogenic, ketogenic, or mixed based on degradation products entering glucose or ketone pathways.

Glucogenic Amino Acids

Amino acids whose catabolism yields precursors for gluconeogenesis.

Ketogenic Amino Acids

Amino acids degraded solely to acetyl-CoA or acetoacetate, forming ketone bodies.

Mixed Amino Acids

Amino acids that are both glucogenic and ketogenic.

Non-polar Amino Acids

Amino acids with hydrophobic R-groups lacking charge or polarity (e.g., Gly, Ala, Val, Leu, Ile, Met, Phe, Trp, Pro).

Polar Uncharged Amino Acids

Amino acids with polar but uncharged side chains (Ser, Thr, Tyr, Cys, Asn, Gln, Hydroxyproline).

Polar Charged Amino Acids

Amino acids whose side chains carry positive or negative charge at physiological pH.

Basic (Positively Charged) Amino Acids

Lysine, hydroxylysine, arginine, histidine—contain extra amino groups and positive charge.

Acidic (Negatively Charged) Amino Acids

Aspartic acid and glutamic acid—contain a second carboxyl group giving negative charge.

S-adenosyl Methionine (SAM)

Active form of methionine that serves as a universal methyl-group donor in transmethylation reactions.

Glutathione

Tripeptide (Glu-Cys-Gly) acting as a major cellular antioxidant and detoxifier.

Catecholamines

Neurotransmitters and hormones (dopamine, norepinephrine, epinephrine) synthesized from tyrosine.

Melanin

Pigment polymer synthesized from tyrosine, responsible for skin, hair, and eye coloration.

Thyroid Hormones

Iodinated tyrosine derivatives (T3 and T4) regulating metabolism.

Nicotinic Acid (Niacin)

Vitamin B3 derived partly from tryptophan; precursor for NAD⁺/NADP⁺.

Serotonin

Tryptophan-derived neurotransmitter involved in mood, sleep, and gut motility.

Melatonin

Neurohormone synthesized from serotonin; regulates circadian rhythms.

γ-Aminobutyric Acid (GABA)

Inhibitory neurotransmitter produced by decarboxylation of glutamate.

Neurolathyrism

Neurodegenerative disorder linked to ingestion of certain Lathyrus legumes containing toxic amino acids.

Homoarginine

Plant non-protein amino acid implicated in neurolathyrism; cleaved to L-lysine and urea.

Diaminopropionic Acid

Non-protein neurotoxic amino acid found in Lathyrus species associated with neurolathyrism.