Monomers, Polymers, Carbohydrates, and Biochemical Tests

Vocabulary flashcards defining key biological molecules, reaction types, carbohydrate structures, and testing procedures covered in the lecture notes.

Monomer

Smaller units that join together to form larger molecules (e.g., monosaccharides such as glucose, fructose, and galactose; amino acids; nucleotides).

Polymer

Molecules formed when many monomers join together (e.g., polysaccharides, proteins, and DNA/RNA).

Condensation reaction

A chemical reaction in which a chemical bond forms between $2$ molecules and a molecule of water is produced.

Hydrolysis reaction

A chemical reaction in which a water molecule is used to break a chemical bond between $2$ molecules.

Glycosidic bond

The type of chemical bond formed when monosaccharides react in a condensation reaction (e.g., $1,4$ or $1,6$ glycosidic bonds).

Disaccharide

A carbohydrate formed when $2$ monosaccharide monomers are joined by a single glycosidic bond via a condensation reaction, with the general molecular formula $C_{12}H_{22}O_{11}$.

Maltose

A disaccharide formed by a condensation reaction between $2$ glucose monosaccharides ($\text{glucose} + \text{glucose}$).

Sucrose

A disaccharide formed by a condensation reaction between glucose and fructose ($\text{glucose} + \text{fructose}$).

Lactose

A disaccharide formed by a condensation reaction between glucose and galactose ($\text{glucose} + \text{galactose}$).

Starch

An insoluble, large storage polymer of $\text{α-glucose}$ in plant cells made of amylose ($1,4$ glycosidic bonds, compact helix) and amylopectin ($1,4$ and $1,6$ glycosidic bonds, branched).

Amylose

A component of starch composed of $\text{α-glucose}$ with $1,4$ glycosidic bonds that forms a compact helix stabilized by intermolecular hydrogen bonds.

Amylopectin

A component of starch composed of $\text{α-glucose}$ with $1,4$ and $1,6$ glycosidic bonds, creating a branched structure with many terminal ends for rapid hydrolysis into glucose.

Glycogen

The main storage polymer of $\text{α-glucose}$ in animal cells (also found in plant cells) featuring $1,4$ and $1,6$ glycosidic bonds, a highly branched structure for rapid hydrolysis, and high compactness and insolubility.

Cellulose

An unbranched, straight-chain polymer of $\text{β-glucose}$ with $1,4$ glycosidic bonds where alternate glucose molecules are rotated $180^\text{∘}$, allowing crosslinking hydrogen bonds to form microfibrils that provide high tensile strength to plant cell walls.

Benedict's test for reducing sugars

A test where an equal volume of Benedict's reagent is added to a sample and heated at $100\text{ }^\text{∘}\text{C}$ for $5\text{ }\text{mins}$, with a positive result showing a colour change from blue to orange and forming a brick-red precipitate.

Benedict's test for non-reducing sugars

A test where non-reducing sugars (e.g., sucrose) are hydrolysed by adding $1\text{ }\text{cm}^3$ of $\text{HCl}$ and heating in a boiling water bath for $5\text{ }\text{mins}$, neutralised with sodium carbonate solution, and then tested with Benedict's reagent as usual.

Colorimetry (for sugars and starch)

A method used to determine concentration by measuring absorbance or \text{%} transmission of standard solutions, plotting a calibration curve, and reading off the concentration of unknown samples.