What Is Photosynthesis?

Photosynthesis is a chemical reaction occurring in plants to create Glucose. The reactants of the reaction are Carbon dioxide and water to produce oxygen and glucose. The reactants and products are opposite in respiration, which is a chemical reaction that takes place in the cells of all living organisms, this reaction is used to release energy used by the cell to carry out its function. The respiration equation is glucose and oxygen reacting together to produce carbon dioxide, water and energy.

Both these reactions are biochemical meaning they are naturally occurring chemical reactions in living organisms.

What makes photosynthesis different from other reactions is that is uses light energy to power the chemical reaction. The reason is that the cells in the leaves of plants contain green pigment called chlorophyll found in chloroplast. Chlorophyll absorbs energy from light and this energy is the used to activate the chemical reaction photosynthesis. Photosynthesis takes place in the leaves as this the the part of the plant that receives the most amount of sunlight. Root cells have no chloroplasts containing chlorophyll, as they are underground and receive no sunlight. The reason why chlorophyll is green as it absorbs mostly blue and red wavelengths and reflects green. We know that white light can be split into the colours of the rainbow and this is call dispersion.

Chloroplast are found at the top of the leaf, to absorb maximum amount of sunlight, stomata are found under the leaf. Stomata are holes, used for gas exchange in the plant and are surrounded by guard cells. The gases exchanged are carbon dioxide and oxygen. The guard cells are open when full of water and close when they are not, preventing water loss through transpiration. Water is absorbed up the roots to the leaves through the xylem vessel, the phloem transports dissolved nutrients. Photosynthesis occurs in plants ONLY in the presence of sunlight or light, plants respire all the time, so their cells can carry out their function.

Examples of cells and their function are root hair cells which absorb water, xylem cells transport water, guard cells open and close the stomata are just few.

Examples of cells and function in humans are red blood cells transport oxygen, nerve cells transmit electrical signals and sperm cells fertilise eggs cells.

Photosynthesis is a good way of understanding that although we learn biology, chemistry and physics separately, in real life they work together. Photosynthesis occurs in plants, and is a chemical reaction using light energy.