Question

Why do we need oxygen?

Select one:

a. It is the final electron acceptor in the electron transport chain

b. It is needed to change the blood's pH

c. It activates pepsinogen into pepsin

d. Bacteria require it to break down plant products in large intestine

e. It is needed for glycolysis to occur

Answer 1

Answer - a. It is the final electron acceptor in Electron Transport Chain

In the ELECTRON Transport Chain, that occurs in the mitochondria, an electron gradient is generated, electron moves from high potential to low potential collecting H+ ions in the intermembranous space. The hydronium ions move out bringing conformational changes in the ATPase pump, generating ATP. The electron reaches the Complex V, from where it is accepted by oxygen. After accepting electron, oxygen combines with hydronium ions to form water as the by product.

Hence, option A is the correct answer.

For a change in blood pH, buffer molecules are required. The basic buffers in blood involve the CO2 and bicarbonate system and other charged proteins. There is no role of oxygen in changing pH. For converting pepsinogen to pepsin, acidic environment is required, which is present in the stomach by acid produced. Requirement of oxygen is not mandatory, bacteria present are facultative anaerobes and can work in an anaerobic environment as well. For glycolysis to occur, the basic products required are ATP and NADH molecules. No oxygen molecules are required.

Hence, option B,C,D and E are incorrect.