how do plants recycle hydrogen during cellular respiration
During cellular respiration in plants, hydrogen is not directly recycled. Instead, hydrogen is used as an electron carrier in metabolic reactions within the cells.
1. Glycolysis: The process of cellular respiration begins with glycolysis, which occurs in the cytoplasm of plant cells. During glycolysis, glucose is broken down into two molecules of pyruvate. During this process, some hydrogen atoms are transferred to NAD+ (nicotinamide adenine dinucleotide), forming NADH.
2. Citric Acid Cycle (Krebs Cycle): Pyruvate molecules from glycolysis are transported into the mitochondria, where they undergo further breakdown in the citric acid cycle. In this cycle, hydrogen atoms are transferred to coenzymes such as NAD+ and FAD (flavin adenine dinucleotide), producing NADH and FADH2.
3. Electron Transport Chain (ETC): The NADH and FADH2 generated from glycolysis and the citric acid cycle donate their high-energy electrons to the electron transport chain, which is located in the inner mitochondrial membrane. As electrons pass through the ETC, they release energy, which is used to produce ATP (adenosine triphosphate).
4. Oxygen as the Final Electron Acceptor: At the end of the electron transport chain, oxygen serves as the final electron acceptor. It combines with hydrogen ions (H+) to form water (H2O), completing the process of cellular respiration.
So, although hydrogen is not recycled in the sense that it is reused within the plant, it is used as an intermediary in the transfer of electrons during cellular respiration.
During cellular respiration in plants, the process by which they convert glucose and oxygen into carbon dioxide, water, and energy, the recycling of hydrogen occurs through several steps. Here's a step-by-step explanation:
1. Glycolysis: The first step of cellular respiration is glycolysis, which occurs in the cytoplasm. During this process, one molecule of glucose is broken down into two molecules of pyruvate. As glucose is broken down, hydrogen atoms carried by NADH (nicotinamide adenine dinucleotide) are produced.
2. Transition Reaction: In the transition reaction, pyruvate molecules from glycolysis move into the mitochondria. In this step, each pyruvate loses a carbon dioxide molecule and a hydrogen atom. The released hydrogen atom combines with NAD+ (nicotinamide adenine dinucleotide) to form NADH.
3. Citric Acid Cycle (or Krebs Cycle): The next step takes place in the mitochondria. The two-carbon compound, acetyl CoA, produced in the transition reaction enters the citric acid cycle. Here, acetyl CoA combines with oxaloacetate to form citric acid. During the cycle, citric acid is gradually broken down, releasing carbon dioxide and hydrogen atoms (or electrons). Hydrogen atoms are picked up by NAD+ and FAD (flavin adenine dinucleotide) to form NADH and FADH2.
4. Electron Transport Chain: The final step in cellular respiration is the electron transport chain, which occurs in the inner mitochondrial membrane. Here, NADH and FADH2 generated in the previous steps release their hydrogen atoms. The hydrogen atoms are split into protons (H+) and electrons (e^-). The electrons move through a series of protein complexes, creating a flow of electrons. As the electrons pass through these complexes, protons are pumped across the inner mitochondrial membrane into the intermembrane space. This creates an electrochemical gradient.
5. ATP Generation: As protons accumulate in the intermembrane space, they create a higher concentration than in the mitochondrial matrix. Protons flow back into the matrix through an ATP synthase enzyme embedded in the inner membrane. This movement of protons generates ATP (adenosine triphosphate), which is the energy molecule used by cells.
In essence, hydrogen atoms from glucose are carried by NADH and FADH2 during cellular respiration. These hydrogen atoms are then released in the electron transport chain, where they generate ATP and combine with oxygen to form water. The released energy is used by the cell for various physiological processes, and water is a byproduct of this whole process.
Plants do not recycle hydrogen during cellular respiration. Instead, they obtain their hydrogen atoms from water molecules during photosynthesis, and then release them as byproducts when glucose is broken down through cellular respiration. To understand this process better, let's break it down step by step:
1. During photosynthesis, plants absorb water (H2O) through their roots and carbon dioxide (CO2) from the atmosphere through their leaves.
2. Inside the chloroplasts of plant cells, sunlight energy is captured and used to convert water and carbon dioxide into glucose (C6H12O6) and oxygen (O2). This process is known as photosynthesis.
3. The chemical equation for photosynthesis is: 6CO2 + 6H2O + sunlight → C6H12O6 + 6O2.
4. The glucose produced during photosynthesis is utilized as an energy source for the plant.
5. When the plant needs energy, it undergoes cellular respiration to break down glucose and release energy in the form of ATP (adenosine triphosphate).
6. The overall chemical equation for cellular respiration is: C6H12O6 + 6O2 → 6CO2 + 6H2O + energy (ATP).
7. During cellular respiration, the glucose molecule is gradually oxidized, and the hydrogen atoms it contains are stripped off.
8. The hydrogen atoms from glucose combine with oxygen to produce water (H2O).
9. The released energy is captured and used to power various cellular processes.
Therefore, rather than recycling hydrogen like some other organisms, plants obtain hydrogen from water molecules during photosynthesis and release it as water again during cellular respiration.