Question

Photorespiration a. is the process in which plants use sunlight to make ATP. b. is an inefficient way that plants can produce organic molecules by using \(\mathrm{O}_{2}\) and releasing \(\mathrm{CO}_{2}\) c. is a process that plants use to convert light energy to NADPH. d. occurs in the thylakoid lumen. e. is the normal process of carbohydrate production in cool, moist environments.

Short answer

Option b is correct. Photorespiration is an inefficient way that plants can produce organic molecules by using \(\mathrm{O}_{2}\) and releasing \(\mathrm{CO}_{2}\).

Step-by-step solution

Understanding Photorespiration

Photorespiration is a process in plant metabolism where the enzyme RuBisCO oxygenates RuBP, wasting some of the energy produced by photosynthesis. The process is considered 'inefficient' because it can lead to the loss of carbons to CO2. It occurs in conditions of high oxygen and light intensity.

Evaluate the options

Option a is incorrect, as ATP production using sunlight is a part of photosynthesis, not photorespiration. Similarly, option c is also incorrect as converting light energy to NADPH is again a part of photosynthesis, not photorespiration. Option d is incorrect because photorespiration does not take place in the thylakoid lumen, but in chloroplasts, peroxisomes and mitochondria in the cell. Option e isn't correct either because photorespiration isn't the normal process of carbohydrate production in any environment. If anything, it counteracts efficient carbohydrate production especially under hot, dry conditions when plants close their stomata. This leaves us with option b.

Final Answer

After evaluating each option, option b is the only one left. It states photorespiration is an inefficient way that plants produce organic molecules by using O2 and releasing CO2. This accurately describes photorespiration.

Key concepts

Plant Metabolism

Plant metabolism encompasses all the biochemical processes that allow plants to grow, reproduce, and respond to their environment. One key aspect of plant metabolism is photosynthesis, through which plants convert light energy into chemical energy stored in glucose. However, not all metabolic processes contribute positively to a plant's energy balance. An example of an inefficient metabolic pathway is photorespiration.

During photorespiration, the enzyme RuBisCO adds oxygen instead of carbon dioxide to ribulose-1,5-bisphosphate (RuBP), which leads to the consumption of energy and reducing power without producing sugar. This process is seen as a wasteful detour in the energy-efficient pathway of photosynthesis, especially under conditions where oxygen levels are high and carbon dioxide levels are low, such as hot and dry climates where plant stomata are closed to prevent water loss.

RuBisCO Enzyme

The RuBisCO enzyme, or Ribulose-1,5-bisphosphate carboxylase/oxygenase, is one of the most abundant enzymes on Earth and a pivotal component in the process of carbon fixation during photosynthesis. RuBisCO catalyzes the first major step of the Calvin cycle, which is the addition of carbon dioxide to RuBP. However, RuBisCO is not always efficient because it can also react with oxygen in a process called photorespiration.

In the context of photorespiration, RuBisCO's affinity for oxygen increases, leading to a less productive pathway where no sugar is generated, and carbon is lost in the form of carbon dioxide. There is an evolutionary trade-off at play: while RuBisCO's ability to initiate photosynthesis is vital, its propensity to initiate photorespiration can diminish the plant's energy gains.

Photosynthesis Efficiency

The efficiency of photosynthesis is crucial for the growth and survival of plants, directly affecting their ability to produce biomass and yield. In ideal conditions, photosynthesis is an incredibly efficient process as it converts solar energy into chemical energy. However, environmental factors, such as temperature, light intensity, and availability of water and carbon dioxide, can influence the efficiency of photosynthesis.

Photorespiration is a process that occurs when the enzyme RuBisCO reacts with oxygen instead of carbon dioxide, leading to decreased photosynthesis efficiency. As photorespiration consumes energy and releases previously fixed carbon dioxide, it is seen as a hindrance to a plant's productivity. Researchers are continually searching for ways to reduce photorespiration, with the aim to improve crop yields, especially in the face of climate change where efficiency in plant metabolism could be increasingly compromised.