Respiration of plants and animals

Respiration in Plants: All living things need energy to carry out their life processes such as body movements, cell division, chemical changes in the cell and plant germination. The set of major energy releasing reactions that occur in all living organisms is termed as respiration. It may involve the breakdown of various substrates and nutrients that are ingested or utilised by the organism as food. The by-products and amount of energy released during respiration depend on the involvement of oxygen and the metabolic route followed. There are mainly two types of respiration; aerobic respiration and anaerobic respiration. Oxygen is required for aerobic respirati ion and it takes place in the mitochondria. Aerobic respiration gives more energy. Oxygen is not required for anaerobic respiration and it takes place in the cytoplasm. Anaerobic respiration gives less energy. Plants generally follow the aerobic mode of respiration. Respiration in plants is a composite process involving breathing or gaseous exchange and cellular respiration. If oxygen is not available, plants can also respire anaerobically, but only for a few days at the most. Gaseous exchange takes place in plants through stomata by simple diffusion. Root cells of plants also need oxygen to obtain energy like other living cells of the plants. Roots take up air from the air spaces present between the soil particles. Due to their unique ability to synthesise their own food, green plants are also referred to as autotrophs. Plants synthesise their food by photosynthesis and the synthesised food is stored mainly in the form of glucose. The process of respiration takes place in specialised organelles called mitochondria, present in each cell of a plant. The glucose is oxidised to carbon dioxide and water to produce energy. The process of respiration in plants follows absorption of oxygen from the atmosphere, oxidation of stored food by the absorbed oxygen and release of energy as a result of oxidation. Carbon-dioxide and water are the end products of respiration which are released from the plant. Energy released by respiration cannot be directly used by the cell. The energy is used to make molecule called ATP or Adenosine Triphosphate, which is stored in the cell until it is needed by any life process. ATP is also called the energy currency of the cell. Respiration uses the product of photosynthesis, while photosynthesis uses the products of respiration. Plants make glucose during photosynthesis, whereas animals obtain glucose through feeding.
Respiration in Animals: Respiration is a catabolic process that can be divided into external, internal and cellular respiration. In external respiration, organisms take in oxygen from atmosphere and release carbon dioxide. In internal respiration, gaseous exchange takes placein cells within the bodies of organisms. And, in cellular respiration, chemical reaction takes place within cells by using oxygen. Different organisms carry out the process of respiration in different ways. In single-celled and microscopic animals such as protozoa, the Special respiratory organs or transport system is absent. Respiratory gases diffuse across thin cell membrane and rapid intak ke and release of gases take place from body surface. Earthworm show cutaneous respiration. The thick skin of earthworm does not allow passage of gases by simple diffusion. It is richly supplied with thin walled blood capillaries that facilitate gaseous exchange through the body surface.