Cells ReviewOnline version Comprehensive Review of all things cells! by Morgan Ball 1 The Cell Theory 2 Research contributions to the Cell Theory. 3 Features Unique to Prokaryotic Cells 4 Features Unique to Eukaryotic Cells 5 Features Unique to Plant Cells 6 Features Unique to Animal Cells 7 Features that All Cells have in Common All living things are composed of cells Cells are the basic units of structure and function in living things New cells come from pre-existing cells. Robert Hooke discovered and named cells by observing slices of cork Anton van Leeuwenhoek discovered microscopic organisms by observing pond water. Matthias Schleiden determined that all plants are made of cells. Theodor Schwann determined that all animals are made of cells. Rudolf Virchow determined all new cells are produced from pre-existing cells. The invention of the microscope allows scientists to see cells for the first time. DNA in the form of circular chromosomes DNA floats freely in a region called the nucleoid DNA in the form of linear chromosomes. DNA is kept safe in a membrane-bound nucleus. Contains Membrane-bound Organelles. A rigid cell wall made of cellulose. Chloroplasts are present, turning sunlight into energy. A large, central vacuole full of water. Centrioles are present to aid in cell division. Small, numerous vacuoles spread throughout the cytoplasm. Some form of DNA is present, although it may be in different shapes. Ribosomes build proteins out of DNA code. A cell membrane creates a boundary between the inside of a cell and it's environment. Cytoskeleton fibers shape and organize the layout of the cell. Cells structures "float" in the cytoplasm.