Chemical synapses transmit signals by releasing neurotransmitter molecules from the presynaptic terminal, which then bind to receptors on the postsynaptic cell to generate an electrical or biochemical response. This article walks through each step of that process, the key molecular players, and how the response is shaped.
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.
An action potential is a rapid, transient reversal of a neuron’s membrane voltage that proceeds through three main phases: depolarization, repolarization, and recovery (hyperpolarization). This article explains what drives each phase, the ion channels involved, and how the neuron returns to its resting state.
Binary fission is the asexual reproduction method by which most bacteria duplicate. A single circular chromosome is copied, the cell elongates, and a protein‑based Z‑ring constricts the middle, producing two genetically identical daughter cells.
The sliding filament theory explains how the thin actin filaments and thick myosin filaments within a sarcomere slide past each other, shortening the muscle fiber. This process requires calcium, ATP, and a coordinated cycle of cross‑bridge attachment and release.
Antibodies are Y‑shaped glycoproteins composed of two identical heavy chains and two identical light chains. Each antibody has a variable Fab region that binds a specific epitope and a constant Fc region that mediates immune effector functions. This article breaks down each part, labels the diagram, and shows how the structure enables antigen recognition.
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.
A cell’s resting membrane potential is the voltage difference across its plasma membrane when it is not actively sending signals. It arises from unequal ion concentrations, selective membrane permeability, and the activity of ion pumps, most notably the Na⁺/K⁺‑ATPase. This electrical gradient is essential for nerve signaling, muscle contraction, and many other cellular processes.
Physical and chemical barriers form the first line of innate immune defense, preventing pathogens from entering the body. These constitutive defenses include intact skin, mucosal surfaces, antimicrobial peptides, low pH, and the resident microbiota, all of which act together to reduce the workload of the adaptive immune system.
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.