NEET Practice Questions (MCQs) with Answers & Solutions

The summary section explicitly states that in competition, 'both species suffer'.

The text defines interference competition: 'in interference competition, the feeding efficiency of one species might be reduced due to the interfering and inhibitory presence of the other species, even if resources (food and space) are abundant.'

According to the NCERT text, 'For aerobic respiration to take place within the mitochondria, the final product of glycolysis, pyruvate is transported from the cytoplasm into the mitochondria.' Specifically, Pyruvate, after it enters the mitochondrial matrix, undergoes oxidative decarboxylation.

The NCERT states, 'Pyruvate, which is formed by the glycolytic catabolism of carbohydrates in the cytosol, after it enters mitochondrial matrix undergoes oxidative decarboxylation.' This process involves both oxidation (reduction of NAD+) and decarboxylation (release of CO2).

The NCERT states, 'The reactions catalysed by pyruvic dehydrogenase require the participation of several coenzymes, including NAD+ and Coenzyme A.' FAD+ is involved later in the TCA cycle, and ATP/GTP are products or used in other steps, not coenzymes for this specific reaction.

The NCERT states, 'The acetyl CoA then enters a cyclic pathway, tricarboxylic acid cycle, more commonly called as Krebs’ cycle'.

The NCERT clearly states, 'Pyruvate... undergoes oxidative decarboxylation by a complex set of reactions catalysed by pyruvic dehydrogenase.'

The reaction shows: Pyruvic acid + CoA + NAD+ $\xrightarrow{\text{Pyruvate dehydrogenase}}$ Acetyl CoA + CO2 + NADH + H+. ATP is not directly produced in this step; it is generated later through oxidative phosphorylation using the NADH. The question specifically asks for DIRECT product for one molecule of pyruvic acid. So, ATP is not a direct product.

In the reaction, NAD+ is converted to NADH + H+, indicating that NAD+ acts as an electron and hydrogen ion acceptor, undergoing reduction. This is an oxidative step for pyruvate.

The Second Law of Thermodynamics states that many conceivable processes that are perfectly allowed by the First Law are never observed. The example given in the NCERT text is: 'A book lying on a table jumping to a height by itself. But such a thing would be possible if the principle of conservation of energy were the only restriction. The table could cool spontaneously, converting some of its internal energy into an equal amount of mechanical energy of the book... But this never happens.' This illustrates that while energy conservation allows it, the Second Law forbids such spontaneous, ordered energy conversion from a colder object to mechanical work.