Summary of Plant Respiration
Plants, unlike animals, lack specialized respiratory organs; instead, they use stomata and lenticels for gas exchange, allowing O2 uptake and CO2 release. Cellular respiration, which involves breaking C-C bonds in complex organic molecules, is the process by which plants release energy. The main substrate for respiration is glucose, although fats and proteins can also serve as substrates, undergoing breakdown in the cytoplasm.
Key Processes:
- Glycolysis: The initial step of respiration occurs in the cytoplasm where glucose is converted into two molecules of pyruvic acid through a series of enzyme-catalyzed reactions.
- Fermentation: In the absence of oxygen, pyruvic acid can be converted into lactic acid or ethanol, depending on the organism, through fermentation pathways.
- Aerobic Respiration: Under aerobic conditions, pyruvic acid enters the mitochondria to be converted into acetyl CoA, which then enters the Krebs cycle. This cycle generates NADH and FADH2, which are utilized in the electron transport chain to produce ATP through oxidative phosphorylation, with oxygen being the final electron acceptor.
The respiratory pathway is classified as amphibolic since it is involved in both catabolic and anabolic processes, illustrating the interconnection between breakdown and synthesis of substrates in plant metabolism. The respiratory quotient (RQ) provides insight into substrate utilization during respiration.