Osmosis is the passive movement of water molecules across a partially permeable membrane from a region of higher water potential to lower water potential. In plant cells, if placed in hypotonic solution, water enters via aquaporins, causing incipient plasmolysis reversal; in hypertonic, water exits leading to plasmolysis. Cytoplasm shrinks first, then vacuole. (Diagram: turgid vs flaccid cell). Key: water potential gradient (ψ = ψs + ψp).

Occurs in thylakoid membranes of grana. Light energy excites chlorophyll in PSII (P680), electrons passed via ETC to PSI (P700), generating ATP via chemiosmosis (proton gradient through ATP synthase) and photolysis of water (2H2O → 4H+ + 4e- + O2). NADP+ reduced to NADPH. Cyclic photophosphorylation in PSI for extra ATP. Limiting factors: light intensity, CO2.

Human insulin gene isolated via restriction enzymes (e.g. EcoRI), inserted into plasmid vector (e.g. pBR322), ligated with DNA ligase. Transformed into E. coli via heat shock/electroporation. Selected via antibiotic resistance (ampR). Expressed in fermenter, purified via chromatography. Advantages: mass production, no animal allergens.

After meal, high blood glucose detected by beta cells in pancreas → secrete insulin. Insulin binds to receptors on liver/muscle, activates GLUT4 translocation for uptake, promotes glycogenesis & glycolysis. Blood glucose falls → alpha cells detect low glucose → secrete glucagon → glycogenolysis & gluconeogenesis. Homeostasis restored. (Graph: curve showing regulation).

Primary succession: bare rock → pioneer species (lichens) → soil formation → herbaceous → shrubs → climax community (deciduous forest). Pond: phytoplankton → zooplankton → submerged plants → floating plants → marginal reeds → terrestrial. Changes: increased species diversity, biomass; nutrient cycling via detritivores. Human impact: eutrophication accelerates.