Protein
Videos
Proteins are large biomolecules and macromolecules that comprise one or more long chains of amino acid residues. Proteins perform a vast array of functions within organisms, including catalysing metab
Polypeptide
John Kendrew with model of myoglobin in progress
Proteins in various cellular compartments and structures tagged with green fluorescent protein (here, white)
Constituent amino-acids can be analyzed to predict secondary, tertiary and quaternary protein structure, in this case hemoglobin containing heme units.
Cell nucleus
Videos
The cell nucleus is a membrane-bound organelle found in eukaryotic cells. Eukaryotic cells usually have a single nucleus, but a few cell types, such as mammalian red blood cells, have no nuclei, and a
HeLa cells stained for nuclear DNA with the blue fluorescent Hoechst dye. The central and rightmost cells are in interphase, thus their entire nuclei are labeled. On the left, a cell is going through mitosis and its DNA has condensed.
An image of a newt lung cell stained with fluorescent dyes during metaphase. The mitotic spindle can be seen, stained green, attached to the two sets of chromosomes, stained light blue. All chromosomes but one are already at the metaphase plate.
Oldest known depiction of cells and their nuclei by Antonie van Leeuwenhoek, 1719
Drawing of a Chironomus salivary gland cell published by Walther Flemming in 1882. The nucleus contains polytene chromosomes.