This video is about the reaction of photosynthesis. Plants have the unique ability to produce their own organic nutrients such as glucose, and for this reason, they are also known as producers or autotrophs. Animals are not able to produce their own food and must therefore consume other organisms, which could be plants or other animals. Plants are usually the first organisms in a food chain because they can convert light energy from the Sun into chemical energy that can be used by other organisms in the food chain. The chemical energy is stored in the nutrient molecules that the plants produce during photosynthesis. Photosynthesis can therefore be defined as the process by which plants manufacture carbohydrates, such as glucose, from raw materials using light energy. The raw materials required for photosynthesis include carbon dioxide and water. The plant obtains carbon dioxide from the air when it diffuses into the leaf through stomata, while water is absorbed by the roots and travels up the steam to the leaves in xylem vessels. Along with these raw materials, light energy from the Sun and chlorophyll found in the chloroplasts of plant cells are also requirements for photosynthesis. Remember that light energy is not a substance and therefore not considered a raw material. The plant uses the requirements for photosynthesis to produce carbohydrates such as glucose. The glucose can be used in respiration to release energy for cellular functions or be converted into other useful substances for plants such as starch, cellulose, lipids and amino acids. Oxygen is released as a byproduct of photosynthesis and can either be used in respiration to break down glucose or diffuse out into the atmosphere through the stomata. Most of the oxygen that is produced during photosynthesis is actually not used by the plant, but released into the atmosphere, which is why some consider oxygen a waste product of photosynthesis. The word equation for photosynthesis is as follows: Carbon dioxide and water in the presence of light and chlorophyll will produce glucose and oxygen. The balanced chemical equation for the process shows that six molecules of carbon dioxide and six molecules of water react to produce one molecule of glucose and six molecules of oxygen. Note that light energy is written above the arrow and chlorophyll below the arrow to show that chlorophyll traps light energy to facilitate the process of photosynthesis. This means that photosynthesis is an endothermic reaction since energy is absorbed from the surroundings to form products. Neither light nor chlorophyll contributes any chemical elements to the equation so they are not written on the reactant side of the equation. It is important to know where the carbon dioxide and water comes from, as well as what happens to the glucose and oxygen that is produced during the reaction. Now let's take a look at an example of the type of questions you could expect to find in an exam paper. The first question asks us to state two reactants needed for photosynthesis. Remember that the reactants of photosynthesis are written on the left side of the equation for the process, so that would be carbon dioxide and water. The second question asks us to describe how the plant would obtain these reactants mentioned at the previous question. When constructing your answer, think about where these substances occur. Carbon dioxide is a gas which occurs in the air, so it will therefore diffuse from the air into the leaf. Be sure to mention that it enters the leaf through stomata. Water is found in the soil, so it will be absorbed from the soil into the root hair cells of the roots. In summary, plants are known as producers or autotrophs because they produce organic nutrients through the process of photosynthesis. Photosynthesis is an endothermic reaction during which light energy is converted into chemical energy that can be used by other organisms in food chains. Carbon dioxide, water, light, and chlorophyll are all needed for photosynthesis to occur in order to produce glucose and oxygen. The process can be represented by a word or balanced chemical equation. Don't forget to check out all our other fantastic revision resources here at Save My Exams.