A-Level Biology: Biological Molecules, Enzymes, and Genetics

Vocabulary practice flashcards covering biological molecules (starch, cellulose, triglycerides), enzyme action and inhibition, cattle selective breeding, and protein structures based on exam lecture materials.

Extracellular enzyme

An enzyme, such as amylase, that is secreted by cells to catalyse chemical reactions outside of the cell, such as in the digestive system.

Amylase

An extracellular enzyme that catalyses the hydrolysis of the polysaccharide starch (amylose) into the reducing sugar maltose.

Amylose

An unbranched, helical polymer of $\alpha$-glucose units linked together in starch, with its coiled shape maintained by internal hydrogen bonding.

Cellulose

A structural polysaccharide made of uncoiled, straight polymer chains that provides high tensile strength to support plant cell walls.

Selective breeding

The artificial selection and mating of organisms exhibiting desirable features over multiple generations to increase specific productivity traits.

Balanced diet

A diet that provides all essential nutrients and energy in the correct proportions necessary to maintain metabolic health and prevent deficiency or malnutrition.

Triglyceride molecule (components A, C, and D)

A lipid molecule composed of a glycerol backbone (A) joined to three fatty acid hydrocarbon chains (C, showing an unsaturated bend) via covalent ester bonds (D).

Ester bond

The covalent chemical bond formed between a hydroxyl group of glycerol and the carboxyl group of a fatty acid during the condensation synthesis of a triglyceride.

Amylose-iodine complex

A helical molecular structure formed when an iodine molecule lodges inside the coil of an amylose polymer, producing a distinct colour change.

Maltose

A reducing disaccharide produced by the enzymatic hydrolysis of starch or amylose by the action of amylase.

Chloride ions ($\text{Cl}^-$)

Inorganic ions that act as inorganic enzyme activators (cofactors) to accelerate the rate of maltose formation by amylase.

Gene

A specific sequence of DNA nucleotides that carries the code to synthesize a polypeptide or protein molecule.

Ribosome

The intracellular organelle where mRNA binds to allow the translation of genetic code into a polypeptide chain.

Non-competitive enzyme inhibition (by $\alpha$-amanitin)

Inhibition in which an inhibitor ($\alpha$-amanitin from the death cap fungus) binds away from the active site, inducing a conformational change in the active site so that the substrate cannot bind to form an enzyme-substrate complex.

Primary structure

The specific linear sequence of amino acids joined together by peptide bonds in a polypeptide chain.

Tertiary structure bonds (A, B, and C)

Bonds that stabilize a protein's 3D folding: A represents an ionic bond (between $R^-$ and $R^+$), B represents a hydrogen bond (between $O$ and $H$), and C represents a covalent disulfide bond (between $S$ and $S$).

Disulfide bond

A strong covalent bond formed between the sulfur atoms of two cysteine amino acid R-groups ($S-S$), helping maintain the tertiary structure of proteins.

Ionic bond (in tertiary protein structure)

An electrostatic attraction formed between oppositely charged acidic and basic R-groups ($R^-$ and $R^+$) within a folded protein.

Hydrogen bond

A weak interaction between a partially positive hydrogen atom and an electronegative atom (such as oxygen), stabilizing amylose helices and protein structures.

Protein denaturation

The loss of a protein's native three-dimensional conformation caused by high temperatures that increase kinetic energy, breaking weak hydrogen and ionic bonds.