Unlike animals, most plants do not need to find food,
because they can make it for themselves. Plants use energy from sunlight to
turn water and carbon dioxide into an energy-rich sugar called glucose. This
process is called photosynthesis, which means “making things with
light”. Photosynthesis takes place inside capsules in the leaf cells,
called CHLOROPLASTS.
Plants use their leaves to make food. Oxygen is created as a
by-product. During photosynthesis, plant leaves take in carbon dioxide from the
atmosphere. Using the energy from sunlight, this is combined with water drawn
up from the roots to make glucose. Oxygen is also produced in this chemical
reaction and exits the leaves into the surrounding air.
Different plant cells perform different tasks. Palisade cells and
spongy cells are located just below the epidermis and are a plant’s main
food-producers. The tall palisade cells are packed with green chloroplasts,
which carry out photosynthesis. The irregularly shaped spongy cells also have
chloroplasts. Air spaces between the cells are filled with carbon dioxide,
water vapour and other gases.
Many leaf cells contain tiny, lens-shaped organelles
called chloroplasts. These can move around the cell towards the direction of
sunlight. Chloroplasts contain a green, light-capturing pigment called
chlorophyll. This chemical helps the chloroplasts to act like minute solar
panels.
Chloroplasts are made up of stacks of tiny disclike membranes
called grana, held in a dense mass of material known as the stroma. The grana
are where water is split into hydrogen and oxygen, using some of the light
energy captured by the chlorophyll. The rest of the light energy is used in the
stroma to combine the hydrogen with the carbon dioxide to make glucose.
