Sample Lesson Plant and Animal Cell Organelles The cells of eukaryotes (protozoa, plants and animals) are highly structured. These cells tend to be larger than the cells of bacteria, and have developed specialized packaging and transport mechanisms that may be necessary to support their larger size. Use the following interactive animation of plant and animal cells to learn about their respective organelles. Nucleus: The nucleus is the most obvious organelle in any eukaryotic cell. It is enclosed in a double membrane and communicates with the surrounding cytosol via numerous nuclear pores. Within each nucleus is nuclear chromatin that contains the organism’s genome. The chromatin is efficiently packaged within the small nuclear space. Genes within the chromatin are made of deoxyribonucleic acid (DNA). The DNA stores the organism’s entire encoded genetic information. The DNA is similar in every cell of the body, but depending on the specific cell type, some genes may be turned on or off - that's why a liver cell is different from a muscle cell, and a muscle cell is different from a fat cell. When a cell is dividing, the nuclear chromatin (DNA and surrounding protein) condenses into chromosomes that are easily seen by microscopy.