Cytology – Condensed Review Notes

Cell: smallest autonomous unit of living matter.
Protoplasm: living colloidal matrix; roughly three-quarters water in bound and free forms.
Major intracellular ions: potassium (cation), phosphate, bicarbonate, sulfate (anions); extracellular: sodium, chloride.
Principal biomolecules: nucleic acids, proteins, carbohydrates, lipids.

Metabolism: anabolism (synthesis) and catabolism (degradation/energy release).
Irritability: ability to respond to stimuli.
Contractility & Conductivity: shortening or impulse transmission (muscle, nerve).
Secretion & Excretion: production and disposal of substances.
Endo/Exocytosis: uptake or release via membrane vesicles.
Growth & Reproduction: chiefly via mitotic division.

Archive of genetic information; source of rRNA, mRNA, tRNA.
Morphology: usually single, shape mirrors cell, variable position.
Interphase components: nuclear envelope (double membrane with pores, continuous with rough ER), karyolymph, chromatin (heterochromatin = condensed/inactive; euchromatin = dispersed/active; Barr body = inactive X), nucleolus (RNA synthesis & ribosome assembly).

Cytosol: protein-rich aqueous matrix, site of intermediary metabolism & cytosolic protein synthesis.
Inclusions: non-living deposits (glycogen, lipids, pigments, crystals).
Organelles.
Cytoskeleton.

Phospholipid bilayer with embedded proteins; fluid-mosaic.
Protein classes: transport (carriers/channels), receptors, recognition/glycoproteins.
Functions: isolation, selective transport, cell communication, self-identification.
Glycocalyx: carbohydrate-rich coat for recognition, adhesion, selective uptake, protection.

Rough ER: continuous with nuclear envelope, ribosome-studded; synthesises secretory proteins, glycogen, degradative enzymes.
Smooth ER: ribosome-free; lipid & steroid synthesis, glycogen and ion metabolism, detoxification.

Stacked cisternae with cis (forming) and trans (maturing) faces.
Concentrates, modifies (e.g., glycosylation), sorts, and packages proteins; forms lysosomes.

Double-membrane organelles with cristae and matrix granules.
Sites of citric acid cycle, oxidative phosphorylation, β-oxidation; contain own DNA/RNA.

Membrane vesicles rich in acid hydrolases.
Primary lysosome: newly formed, enzyme-only.
Secondary lysosome/phagolysosome: fused with substrate; residual body remains post-digestion.
Roles: heterophagy, autophagy, post-mortem autolysis.

Early (near membrane) and late (near Golgi) compartments that route pinocytosed material to lysosomes.

Small oxidase/catalase-containing vesicles; abundant in liver/kidney; detoxification and fatty-acid β-oxidation to acetyl-CoA.

Stacks of pore-bearing cisternae continuous with rough ER; typical in rapidly dividing cells.

Ribosomes: free (cytosolic protein synthesis) or bound (secretory/membrane proteins).
Proteasomes: degrade ubiquitin-tagged or abnormal proteins.

Microfilaments (actin ± troponin/tropomyosin): cell movement, core of microvilli/stereocilia.
Myosin: motor protein in muscle; interacts with actin for contraction & cytokinesis.
Intermediate filaments (e.g., keratin, vimentin, neurofilaments): structural support, desmosomal attachment.
Microtubules (tubulin): cilia/flagella, spindle, organelle transport, axon growth.
Centrioles: nine triplet microtubule cylinders in centrosome; organise spindle.
Basal bodies: centriole-like origins of cilia/flagella.

Cell shape varies with function, contacts, and motility (e.g., round, columnar, spindle).
Organelle positioning is stereotyped (nucleus central in round cells, elongated along long axis, Golgi juxtanuclear).
Typical mammalian cell diameter: roughly one to two-dozen micrometres; nuclear size independent of organism size.