A fully illuminated plant was placed in an atmosphere containing CO2 composed of radioactive carbon. Then the atmosphere surrounding the plant was exchanged for air containing no radioactive carbon, and the plant was placed in total darkness. When the atmosphere surrounding the plant was sampled for radioactive carbon dioxide at various times after the plant was placed in total darkness, the following data were obtained.

Time (hr.) 1 2 3 4
CPM (counts/min.) 40 86 126 159

Which one of the following is the most likely interpretation?

1 Plants cannot respire in the dark.

2 Respiration was occurring in the dark.

3 Respiration, but not anaerobic glucose breakdown occurs in the dark.

4 Fermentation and glucose breakdown were occurring in the dark.

5 The interpretation provided in choices 2 and 4 are equally valid.

How many 14C atomsareincorporated in to laminate whenever fatty acid synthesis is carried out with the following labelled substrate?why?

The answer is 3, I know that for sure

To determine the most likely interpretation of the provided data, we need to analyze the changes in radioactive carbon dioxide (CO2) levels over time after the plant was placed in total darkness.

First, let's understand the process:

1. Illuminated plant in radioactive CO2 atmosphere: The plant was placed in an atmosphere containing radioactive carbon (CO2). During photosynthesis, plants absorb CO2, and the radioactive carbon gets incorporated into organic molecules produced by photosynthesis.

2. Atmosphere exchange and darkness: The atmosphere surrounding the plant was exchanged for air containing no radioactive carbon, and the plant was placed in total darkness. In this condition, the plant cannot perform photosynthesis, which requires light.

3. Sampling of radioactive CO2 at various times: The atmosphere surrounding the plant was sampled at different times after the plant was placed in total darkness.

Now, let's examine the data obtained:

Time (hr.) | CPM (counts/min.)
1 | 40
2 | 86
3 | 126
4 | 159

Based on the data, we can observe that the counts per minute (CPM) of radioactive carbon dioxide increase over time. This increase indicates that carbon dioxide is being released, suggesting that some metabolic processes are occurring in the plant.

The most likely interpretation is option 2: Respiration was occurring in the dark. Respiration is a metabolic process that occurs in all living cells, including the cells of plants, and it involves the breakdown of organic molecules (such as glucose) to release energy. Respiration can occur in the absence of light, unlike photosynthesis.

Options 3 and 4 can be ruled out because respiration includes anaerobic glucose breakdown. Fermentation, mentioned in option 4, is a type of anaerobic glucose breakdown, but it is not the only process occurring in the dark. Respiration is a broader term that includes both aerobic and anaerobic processes.

Option 1, which states that plants cannot respire in the dark, is incorrect based on the observation of increasing CPM over time. Option 5 is also incorrect because option 2, respiration, is the most likely interpretation based on the provided data.