Chlorella sorokiniana TEM micrographs: control (a), Pb-treated (b, c) and Cd-treated (d, e) culture. a. A cell with a cup-shaped chloroplast containing thylakoids, a central pyrenoid, and electron clear starch grains. b. A colony of algal cells with misshaped chloroplasts, a nucleus, and cytoplasm lipid droplets. c. The typical appearance of a Pb-treated culture with cells organized as colonies. d. A cell with a shape-altered chloroplast still containing thylakoids and starch grains. e. A multivesicular body. Scale bars: 2 μ (c); 500 nm (b, d); 300 nm (a, e).