Enzymes, biological molecules, metabolism, and the processes that supply cells with energy.
Glycolysis converts one glucose molecule into two pyruvate molecules, producing a net gain of 2 ATP and 2 NADH while conserving the carbon skeleton of glucose. Understanding the precise inputs and outputs clarifies how carbon and energy flow through this central metabolic pathway.
The active site is the specialised region of an enzyme where substrate molecules bind and chemical reactions are accelerated. It combines a binding pocket that holds the substrate in the right orientation with catalytic residues that lower the activation energy, enabling the reaction to proceed rapidly.
DNA and RNA are both nucleic acids, but they differ in sugar chemistry, strand number, base composition, and cellular roles. DNA stores genetic information in a stable double helix, while RNA performs diverse tasks such as coding, regulation, and catalysis in a typically single‑stranded form.
The Krebs cycle (citric‑acid cycle) oxidizes each acetyl‑CoA in the mitochondrial matrix, releasing two CO₂ molecules and transferring energy to three NADH, one FADH₂ and one GTP per turn. Because one glucose provides two acetyl‑CoA, the cycle runs twice, delivering the bulk of the electron carriers that power oxidative phosphorylation.
Enzyme activity rises with temperature and approaches an optimum, then sharply falls as the protein denatures. Each enzyme also has a characteristic optimal pH; deviations alter ionisation of active‑site residues, changing shape and reducing catalytic efficiency.
Pyruvate oxidation, also called the link or transition reaction, converts each pyruvate molecule into acetyl‑CoA, producing NADH and CO₂ in the mitochondrial matrix. This single step bridges glycolysis and the Krebs (citric‑acid) cycle, allowing the carbon skeletons from glucose to enter aerobic respiration.
Chemiosmosis is the process by which the energy of an electron‑transport chain creates a proton gradient across a membrane. The resulting proton motive force drives ATP synthase, a rotary enzyme that converts ADP + Pi into ATP. This article explains where the gradient forms, how it is maintained, and how ATP synthase harnesses it.
DNA replication relies on a coordinated set of enzymes—helicase, topoisomerase (gyrase), primase, DNA polymerases, ligase, and telomerase—each performing a distinct chemical job at the replication fork. Understanding what each enzyme does explains how a cell copies its genome quickly and accurately.
Competitive inhibition raises the apparent Km without changing Vmax, while non‑competitive inhibition lowers Vmax while leaving Km unchanged. On a Lineweaver‑Burk plot the two patterns appear as intersecting lines on the y‑axis or x‑axis respectively, allowing quick visual identification.
Sucrose is split into glucose and fructose by the enzyme invertase (also called sucrase) through a hydrolysis reaction. This guide explains the biochemical mechanism, the conditions that affect the reaction, and a simple laboratory demonstration using yeast.