⚗️ Biomolecules &amp; Biochemistry

Water Properties

A polar molecule that forms hydrogen bonds, giving cohesion, high specific heat and excellent solvent ability essential for life.

Carbon Chemistry

Carbon forms four covalent bonds, allowing chains, rings and the huge variety of organic molecules in living things.

Carbohydrates

Sugars and starches built from carbon, hydrogen and oxygen that serve as fuel and structural material.

Monosaccharides

The simplest sugars, such as glucose, fructose and galactose, with the formula near CH2O per carbon.

Disaccharides

Two monosaccharides joined by a glycosidic bond, for example sucrose, lactose and maltose.

Polysaccharides

Long chains of sugar units, including starch, glycogen, cellulose and chitin, used for storage and structure.

Lipids

Hydrophobic molecules including fats, oils, waxes and steroids used for energy storage, insulation and membranes.

Triglycerides

Fats formed from glycerol joined to three fatty acids, the main long-term energy store in animals.

Proteins

Polymers of amino acids that act as enzymes, structural parts, transporters, hormones and antibodies.

Amino Acids

Twenty building blocks, each with an amino group, a carboxyl group and a variable side chain.

Nucleic Acids

DNA and RNA, polymers of nucleotides that store and transmit genetic information.

Nucleotides

Monomers made of a sugar, a phosphate group and a nitrogenous base that link to form nucleic acids.

Enzymes

Biological catalysts, mostly proteins, that speed up reactions by lowering the activation energy.

Vitamins

Organic micronutrients needed in small amounts, often serving as coenzymes in metabolic reactions.

Minerals in Biology

Inorganic ions such as calcium, iron and magnesium needed for bones, blood, nerves and enzymes.

pH and Buffers

The pH scale measures hydrogen ion concentration; buffers resist pH change to keep conditions stable in cells.

Macromolecules

Large polymers formed by condensation reactions and broken down by hydrolysis, including carbohydrates, proteins and nucleic acids.

Intermediate topics (20)

Condensation and Hydrolysis

Dehydration synthesis joins monomers by removing water, while hydrolysis splits polymers by adding water.

Glycosidic Bond

The covalent link between sugar units formed by condensation, alpha in starch and beta in cellulose.

Starch vs Cellulose

Starch has alpha-glucose helices for storage; cellulose has straight beta-glucose chains forming strong fibres.

Saturated and Unsaturated Fats

Saturated fatty acids have no double bonds and pack tightly; unsaturated ones have kinks that keep them liquid.

Phospholipids

Lipids with a hydrophilic phosphate head and two hydrophobic tails that self-assemble into membranes.

Steroids

Lipids built on four fused carbon rings, including cholesterol and hormones like oestrogen and testosterone.

Peptide Bond

The covalent amide link between the carboxyl group of one amino acid and the amino group of the next.

Primary Structure

The linear order of amino acids in a polypeptide, which determines all higher levels of folding.

Secondary Structure

Local folding of the backbone into alpha helices and beta sheets stabilised by hydrogen bonds.

Tertiary Structure

The overall three-dimensional shape of one polypeptide, held by side-chain interactions and disulfide bridges.

Quaternary Structure

The arrangement of multiple polypeptide subunits into one functional protein, such as haemoglobin.

Denaturation

Loss of a protein's native shape from heat, pH or chemicals, which destroys its function.

Active Site

The specific pocket on an enzyme where the substrate binds and the reaction takes place.

Induced Fit Model

Suggests the enzyme's active site changes shape slightly as the substrate binds, improving the fit.

Activation Energy

The minimum energy needed to start a reaction, lowered by enzymes without changing the overall energy change.

Factors Affecting Enzymes

Temperature, pH, substrate and enzyme concentration, and inhibitors all alter the rate of enzyme-catalysed reactions.

Competitive Inhibition

An inhibitor resembling the substrate binds the active site and can be overcome by more substrate.

Cofactors and Coenzymes

Non-protein helpers such as metal ions or vitamin-derived molecules that many enzymes require to function.

DNA Structure

Two antiparallel strands of nucleotides wound into a double helix, held together by base pairing.

RNA Types

Messenger, transfer and ribosomal RNA, each with a distinct role in protein synthesis.

Advanced topics (14)

Michaelis-Menten Kinetics

Models reaction velocity as Vmax times substrate over Km plus substrate, describing enzyme saturation.

Allosteric Regulation

Binding of a molecule at a site other than the active site changes enzyme shape and activity.

Feedback Inhibition

The end product of a pathway inhibits an early enzyme, preventing overproduction.

Noncompetitive Inhibition

An inhibitor binds elsewhere on the enzyme, lowering Vmax without changing Km.

Cooperativity

Binding of a ligand to one subunit alters affinity at others, giving haemoglobin its sigmoidal oxygen curve.

Protein Folding and Chaperones

Chaperone proteins such as Hsp70 help nascent polypeptides reach their native fold and prevent aggregation.

Prions

Misfolded infectious proteins that convert normal proteins into the abnormal form, causing diseases like scrapie.

Free Energy in Biology

Reactions proceed spontaneously when the change in Gibbs free energy is negative; ATP hydrolysis drives unfavourable ones.

ATP Structure and Function

Adenosine triphosphate stores energy in its phosphate bonds and acts as the universal energy currency of cells.

Glycoproteins and Glycolipids

Carbohydrate-tagged molecules on cell surfaces that mediate recognition, adhesion and blood group identity.

Lipid Rafts

Cholesterol and sphingolipid-rich membrane microdomains that cluster signalling proteins.

Ribozymes

RNA molecules with catalytic activity, supporting the RNA world hypothesis for life's origin.

Protein Post-Translational Modification

Chemical changes such as phosphorylation, glycosylation and ubiquitination that regulate protein activity and fate.

Isoenzymes

Different molecular forms of an enzyme that catalyse the same reaction but vary in kinetic properties or tissue location.