When it comes to anaerobic respiration, the correct statement is a) every pathway in anaerobic respiration must start with glycolysis. This is because glycolysis is the initial step in both aerobic and anaerobic cellular respiration, where glucose is broken down into pyruvate, generating a small amount of ATP in the process.
In anaerobic conditions, the pyruvate produced from glycolysis can then be further processed through different fermentation pathways, such as lactic acid fermentation or alcoholic fermentation, depending on the organism and environmental conditions. This means that all pathways in anaerobic respiration begin with glycolysis to produce the substrates needed for further energy extraction.
On the other hand, statement b) anaerobic respiration uses electron transport chain to generate a proton motive force is misleading. While some anaerobic organisms utilize a form of electron transport chain, they do not rely on oxygen as the terminal electron acceptor, which is what typically generates a proton motive force in aerobic respiration. Instead, they might use other molecules like nitrate or sulfate. Thus, while it is somewhat true that some anaerobic processes can involve electron transport, it is not universally applicable to all anaerobic respiration processes.