NEET Practice Questions (MCQs) with Answers & Solutions

The NCERT states, 'First, each plant part takes care of its own gas-exchange needs. There is very little transport of gases from one plant part to another.' This localized gas exchange minimizes the requirement for extensive transport systems.

The NCERT states that 'Only during photosynthesis are large volumes of gases exchanged and, each leaf is well adapted to take care of its own needs during these periods. When cells photosynthesise, availability of O2 is not a problem in these cells since O2 is released within the cell.' However, not all cells, tissues, and organs photosynthesise, meaning that other parts still require oxygen which is not internally produced.

The NCERT text mentions, 'When cells photosynthesise, availability of O2 is not a problem in these cells since O2 is released within the cell.'

The chapter highlights that 'the energy released by oxidation in respiration is not (or rather cannot be) used directly but is used to synthesise ATP, which is broken down whenever (and wherever) energy needs to be utilised. Hence, ATP acts as the energy currency of the cell.'

The text states, 'In stems, the ‘living’ cells are organised in thin layers inside and beneath the bark. They also have openings called lenticels.'

The NCERT provides the example of tripalmitin (a fat) as a substrate: '$2(C_{51}H_{98}O_6) + 145O_2 \rightarrow 102CO_2 + 98H_2O + energy$'. Calculating the RQ ($CO_2/O_2$) would be $102/145 \approx 0.7$, which is less than 1. For carbohydrates, RQ is 1.

The NCERT explains that the 'strategy that the plant cell uses is to catabolise the glucose molecule in such a way that not all the liberated energy goes out as heat. The key is to oxidise glucose not in one step but in several small steps enabling some steps to be just large enough such that the energy released can be coupled to ATP synthesis.' This contrasts with combustion where most energy is released as heat in a single step.

The text states, 'Usually carbohydrates are oxidised to release energy, but proteins, fats and even organic acids can be used as respiratory substances in some plants, under certain conditions.' Nucleic acids are primarily involved in genetic information storage and transfer, not typically as direct respiratory substrates.

The NCERT text emphasizes that 'What is important to recognise is that ultimately all the food that is respired for life processes comes from photosynthesis.' Animals are heterotrophic, obtaining food from plants directly or indirectly.

The NCERT states, 'This energy trapped in ATP is utilised in various energy-requiring processes of the organisms, and the carbon skeleton produced during respiration is used as precursors for biosynthesis of other molecules in the cell.'