the inisial step in respiration where plant cells break down glucose into an acid
Answers
“Plant respiration is the chemical reaction by which plants cells stay alive.” The process of respiration is expressed as:
Glucose + Oxygen → Carbon Dioxide + Water (+ Energy)
Do Plants Breathe?
The answer to this question is not direct. Yes, plants need oxygen for respiration but at the same time they also give out carbon dioxide. Thus, plants have proper system to ensure the availability of oxygen. Unlike animals, plants do not possess any specialized organs for exchange of gases but they have lenticels and stomata (present in stems and leaves respectively) that carry out the function of gaseous exchange.
Plants do not have any specialized organ to respire and exchange gases because each part of the plant takes care of the need of gases themselves. The parts of the plant do not display any great demand for exchange of gases. Added to this, stems, leaves and roots respire at very lower rate as compared to animals. But during the process of photosynthesis, large exchange of gases takes place and each part of the plant is well adapted to fulfill its need of gases. Availability of oxygen is not a problem during photosynthesis because the cells release oxygen within cells. It is important to note that each living cell in a plant is located quite close to the surface of the plant and in case of stems, the living cells are arranged in the form of thin layers beneath and inside the bark and have openings which are referred as lenticels. Thereby, the respiration and translocation takes place at every part of the plant.
The complete combustion of glucose produces H2O and CO2 as end products and release energy in the form of heat. In case, this energy is required by the cell, it will utilize accordingly. Following reaction explains the entire process:
C6H12O6 + 6O2 → 6CO2 + 6H2O + Energy
During the process of respiration, O2 is utilized and carbon dioxide, energy and water are released as products. There is also a situation when then the oxygen is not available. For instance, the first cell on this planet must have carried out reaction in the absence of oxygen and even in the current living world we are aware of several living organisms adapted to anaerobic conditions. Some of these organisms are facultative and some are obligate. In any of these cases, all living organisms retain enzymatic machinery to partially oxidize glucose in the absence of oxygen. This process is also called as Glycolysis which includes breaking down of glucose to Pyruvic Acid.
Respiration In Roots
The process of respiration in roots is carried out in the following manner:
Air occurs in several interspaces of soil. The hairs of the roots are in direct contact with them.
Oxygen of the soil gets diffused via root hairs and reaches all internal cells of the root for respiration.
Carbon dioxide produced during the diffusion is released in the opposite direction.
In the condition of water logging, air gets deficient in soil and in this case, metabolic activity of the roots declines.
Respiration In Stems
The stems of herbaceous plants possess stomata and the air gets diffused via it and reaches the cells for respiration.
The carbon dioxide produced during the process gets diffused in the air via stomata.
When the stems are woody, this gaseous exchange is carried out by lenticels.
Respiration In Leaves
Leaves of the plants have tiny pores which are referred as stomata. The exchange of gases takes place by the process of diffusion via stomata. The stomata are present in large number on lower surface of leaves of plant. Each stoma is surrounded and controlled by Guard Cells (two kidney shaped cells). Then the stoma, open gaseous exchange takes place between Atmosphere and Interior of Leaves.
Types of Respiration
Respiration is of two types:
Aerobic Respiration: In this type of respiration, the food substances are completely oxidized into H2O and CO2 with the release of energy. It requires atmospheric oxygen and all higher organisms respire aerobically. Following figure shows the steps included in Aerobic Respiration.
Aerobic Respiration
Anaerobic Respiration: In this type of respiration, partial oxidation of food takes place and energy is released in the absence of oxygen. This type of respiration occurs in prokaryotic organisms like bacteria and yeast. Ethyl alcohol and carbon dioxide are formed in this process.