What are the different ways in which glucose is oxidised to provide energy in various organisms?
Glucose is oxidised to provide energy through different pathways depending on the availability of oxygen. In all cases, the first step is the break-down of glucose, a six-carbon molecule, into a three-carbon molecule called pyruvate in the cytoplasm.
In aerobic respiration, organisms use oxygen to break-down pyruvate completely into carbon dioxide and water. This process takes place in the mitochondria and releases a large amount of energy.
In anaerobic respiration, the break-down occurs without oxygen. In yeast, pyruvate is converted into ethanol and carbon dioxide. In our muscle cells, when there is a lack of oxygen, pyruvate is converted into lactic acid, which causes cramps. This process releases much less energy than aerobic respiration.
Explanation
The answer is derived directly from the 'Break-down of glucose by various pathways' section in the provided text. It covers the initial common step (glucose to pyruvate), the aerobic pathway (using oxygen in mitochondria), and the two anaerobic pathways mentioned (yeast fermentation producing ethanol, and muscle cells producing lactic acid). The distinction in energy release is also highlighted as per the context.
Solution Steps
Step 1: Identify the initial common step: Glucose (6-carbon) breaks down into Pyruvate (3-carbon) in the cytoplasm.
Step 2: Describe Aerobic Respiration: Pyruvate breaks down in mitochondria using oxygen into Carbon Dioxide and Water, releasing high energy.
Step 3: Describe Anaerobic Respiration in Yeast: Pyruvate converts to Ethanol and Carbon Dioxide without oxygen.
Step 4: Describe Anaerobic Respiration in Muscles: Pyruvate converts to Lactic Acid due to lack of oxygen, causing cramps.