Biomolecules: Amino Acids and Carbohydrates

Vocabulary flashcards covering amino acid structures and classification, monosaccharides, disaccharides, polysaccharides, reducing sugars, and sugar isomerism from lecture notes.

Glycine

The simplest amino acid in which the R-group is hydrogen ($R = \text{H}$), making it non-chiral.

Alanine

A neutral amino acid with a methyl group as its R-group ($R = \text{CH}_3$).

Aspartic Acid

An acidic amino acid (also called aspartate) with the side chain structure $R = \text{CH}_2\text{COOH}$.

Glutamic Acid

An acidic amino acid (also called glutamate) with the side chain structure $R = \text{CH}_2\text{CH}_2\text{COOH}$.

Lysine

A basic amino acid containing an amino-terminated side chain with the structure $R = \text{(CH}_2\text{)}_4\text{NH}_2$.

Cystine

A sulfur-containing amino acid derivative formed when two cysteine molecules are connected by a disulfide bond.

Substituted Methane

A chemical representation of an $\alpha$-amino acid, where four different functional groups are attached to a central $\alpha$-carbon (chiral carbon).

Peptidoglycan

A structural heteropolysaccharide (also known as murein) consisting of alternating monomers of NAG (N-acetylglucosamine) and NAM (N-acetylmuramic acid).

Agar-Agar

A polysaccharide derived from red algae species Gelidium and Gracilaria.

Cellulose

The most abundant organic compound in the biosphere; an unbranched homopolysaccharide joined by $\beta\,1\rightarrow4$ glycosidic bonds that cannot be digested by humans due to the absence of $\beta$-amylase.

Glycogen

Animal starch; a branched and coiled storage homopolysaccharide composed of approximately 30,000 glucose units with $\alpha\,1\rightarrow4$ and $\alpha\,1\rightarrow6$ glycosidic bonds (branching every 10–12 units) that turns red with iodine.

Inulin

A storage homopolysaccharide composed of 60 fructose units found in Dahlia roots; used to test glomerular filtration rate (GFR) for kidney function because it is excreted unchanged in urine.

Amylose

The unbranched, coiled component of starch (20%) consisting of 200–1,000 glucose units with $\alpha\,1\rightarrow4$ glycosidic bonds that turns blue with iodine.

Amylopectin

The branched component of starch (80%) consisting of 2,000–2,00,000 glucose units with $\alpha\,1\rightarrow4$ linear bonds and $\alpha\,1\rightarrow6$ branch points every 20–25 units, turning red with iodine.

Homopolysaccharide

A polysaccharide composed of repeating units of a single type of monosaccharide monomer (e.g., starch, glycogen, cellulose, chitin, inulin).

Heteropolysaccharide

A polysaccharide composed of more than one type of monosaccharide monomer unit (e.g., peptidoglycan, hyaluronic acid).

Reducing Sugars

Carbohydrates with free functional groups that reduce $\text{Cu}^{2+}$ (blue) in Fehling's or Benedict's solution to $\text{Cu}^+$ (red cuprous oxide); includes all monosaccharides, lactose, and maltose.

Trehalose

Insect blood sugar; a non-reducing disaccharide composed of two $\alpha$-glucose units connected by an $\alpha\,1\rightarrow1$ glycosidic bond.

Sucrose

A non-reducing disaccharide composed of $\alpha$-glucose and $\beta$-fructose linked via an $\alpha\,1\rightarrow\beta\,2$ glycosidic bond.

Maltose

A reducing disaccharide formed by two $\alpha$-glucose units connected by an $\alpha\,1\rightarrow4$ glycosidic bond.

Lactose

Milk sugar; a reducing disaccharide composed of $\beta$-galactose and $\beta$-glucose connected by a $\beta\,1\rightarrow4$ glycosidic bond.

Stachyose

A tetrasaccharide composed of glucose, two galactose units, and fructose.

Epimers

Isomers that differ in spatial configuration around only a single specific chiral carbon atom.

Mannose

A hexose monosaccharide and $\text{C}_2$ epimer of glucose.

Galactose

A hexose monosaccharide and $\text{C}_4$ epimer of glucose.

Glucose

A hexose aldose sugar ($\text{C}_6\text{H}_{12}\text{O}_6$) also known as corn sugar, grape sugar, or dextrose, having 4 chiral carbons and 16 ($2^4$) possible stereoisomers.

Fructose

A hexose ketose sugar ($\text{C}_6\text{H}_{12}\text{O}_6$) known as levulose or fruit sugar, which forms a furanose ring and is the sweetest natural sugar.