Inside a plant cell. The top half of the cell is removed to show internal structures. Much of the interior of the cell is taken up by a fluid-filled vacuole (grey-blue), which stores water and enzymes, and helps the cell maintain its shape. The view then takes in the central nucleus (dark blue) that contains the cell's genetic material, which is surrounded by endoplasmic reticulum (brown), studded with protein-making ribosomes (flashing white). Proteins are packaged by the Golgi apparatus (pink). The view moves to the cell wall (green) and the cell membrane (blue). The wall contains cellulose and is very tough, and along with the vacuole plays the main role in keeping the cell, and the plant, rigid. The inner cell membrane is a flexible phospholipid bilayer. Inside the cell, there is a cytoskeleton of microtubules (blue) and thin actin filaments (grey). Mitochondria (gold) are organelles that provide energy for the cell. The view then moves to a chloroplast, which is the site of photosynthesis in a plant cell. The chloroplast contains stacks of discs called thylakoids, which contain the photosynthetic pigment chlorophyll, arranged in stacks called grana. The chloroplast uses light energy to manufacture sugars from carbon dioxide, releasing oxygen as a waste product.