Respiration is the process of releasing energy from glucose, which goes on in every cell. It’s a process that occurs continuously in the cells of organisms using oxygen to produce energy and giving off carbon dioxide as a waste product, changing stored chemical energy in food to a form that organisms can use. So in terms of the gas taken in and the gas given out, respiration is the opposite of photosynthesis. All living organisms respire; it is how they release energy from food. It is not just breathing in and out. Respiration is needed in plants to build sugars, nitrates and other nutrients in to amino acids, which are then built up into proteins.
The result is that during the day when the plant is both respiring and photosynthesising there is a two-way traffic of oxygen and carbon dioxide both into and out of the plant. During the night when the plant is respiring but not photosynthesising, oxygen is being taken in but not given out - and carbon dioxide is being given out but not taken in.
Fortunately, plants use up more carbon dioxide in photosynthesis than they produce in respiration, and produce more oxygen while photosynthesising than they use up while respiring - otherwise there would not be enough oxygen in the atmosphere for humans and animals to breathe.
Respiration occurs in the cellular organelle, Mitochondria. (Organelle is a membrane-bound structure that is specialised to perform a specific process within a cell.) Mitochondria are structures that come about in large numbers inside muscle cells, where great amounts of energy are needed. The mitochondria hold a large number of different enzymes, which are responsible for different stages of respiration.
One similarity in Photosynthesis and respiration is that they both need an electron transport chain, which is a process where energy is produced through oxidative (photo)phosphorylation. To summarise the process; it starts with a molecule transferring its electrons to an enzyme embedded in a membrane. Through a series of reactions, electrons move from one enzyme to another. At each stop, a small amount of energy is released - this is used to make energy. As the electrons progress through the chain, free energy is included into the ATP as usable chemical energy.
A difference between the two life processes is that respiration breaks down carbohydrates whereas photosynthesis makes them. One important similarity is that both respiration and photosynthesis are needed in order to keep a plant alive.
Both photosynthesis and respiration use enzymes; Enzymes are biological catalysts that are produced by our body to speed up chemical reactions. An active site on an enzyme has a shape that fits one or more specific substrates, which fit like a lock and key. Once the substrate(s) fit in to the enzyme, either an anabolic or catabolic reaction occurs. After this reaction has taken place, the new product leaves the enzyme to be used up again.
Another difference between the processes is that photosynthesis only occurs in Autotrophs while respiration takes place in all organisms.
The energy transfer in photosynthesis is opposite to that in respiration.
As in photosynthesis, the energy transfer is endothermic which means that the reactions that take place take in energy from the surroundings. Where as in respiration, the energy transfer is exothermic; which means the reactions transfer energy to the surroundings, not from.
To conclude, respiration is an exothermic reaction, while photosynthesis is an endothermic reaction. Both processes use enzymes and they both require an electron transport chain. One processes’ products are the other’s reactants. Respiration breaks down carbohydrates whereas photosynthesis makes them. And last but not least, both life processes are needed in order to keep a plant alive. So even though both processes are similar regarding what they are needed for and their reactants plus products, there are many differences between them.
If light is required to photosynthesise, and photosynthesis is required in
order for plants to live… Then what about habitats where there is no light? Have a think.
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