Question

1. what roles do photosynthesis & cellular respiration play in the carbon & oxygen cycles?
2. why are bacteria so important for the nitrogen cycle?
3. what is the name of the process where nitrogen is converted into nitrates?

Explanation:

Question 4

Photosynthesis takes in carbon dioxide ($\ce{CO_2}$) from the atmosphere and converts it into glucose ($\ce{C6H12O6}$) and oxygen ($\ce{O2}$) (using light energy, in plants/algae/cyanobacteria). This removes $\ce{CO_2}$ from the carbon cycle's atmospheric pool and adds $\ce{O2}$ to the oxygen cycle. Cellular respiration (by plants, animals, fungi, etc.) breaks down glucose, releasing $\ce{CO_2}$ back into the atmosphere (and using $\ce{O2}$), thus returning carbon to the carbon cycle and consuming $\ce{O2}$ from the oxygen cycle.

Bacteria drive key nitrogen cycle processes:

• Nitrogen fixation: Symbiotic (e.g., rhizobia in legume roots) or free - living bacteria convert atmospheric $\ce{N2}$ into ammonia ($\ce{NH3}$) or ammonium ($\ce{NH4^+}$), making nitrogen available to plants.
• Nitrification: Nitrifying bacteria (e.g., Nitrosomonas, Nitrobacter) convert ammonia to nitrites ($\ce{NO2^-}$) and then to nitrates ($\ce{NO3^-}$), which plants can absorb.
• Denitrification: Denitrifying bacteria (e.g., Pseudomonas) convert nitrates back to $\ce{N2}$, returning it to the atmosphere and completing the cycle.
• Decomposition/Ammonification: Bacteria (and fungi) break down dead organisms/waste, releasing nitrogen as ammonia, which re - enters the cycle.

The process where nitrogen (specifically atmospheric $\ce{N2}$ or ammonia) is converted into nitrates ($\ce{NO3^-}$) is called nitrification (a two - step process: first, ammonia is converted to nitrites by bacteria like Nitrosomonas; then nitrites are converted to nitrates by bacteria like Nitrobacter). If referring to converting atmospheric $\ce{N2}$ to nitrates via a multi - step process including fixation and nitrification, but the direct conversion of ammonia (or ammonium) to nitrates is part of nitrification. However, sometimes “nitrogen fixation” is confused, but fixation makes ammonia, while nitrification makes nitrates. The specific process of converting ammonia/ammonium to nitrates is nitrification, and if starting from $\ce{N2}$, it's a combination of fixation and nitrification. But the process of forming nitrates from ammonia - derived forms is nitrification.

Answer:

In the carbon cycle: Photosynthesis removes atmospheric $\boldsymbol{\ce{CO_2}}$ (fixes it into organic compounds like glucose). Cellular respiration releases $\boldsymbol{\ce{CO_2}}$ back to the atmosphere (breaks down organic carbon).

In the oxygen cycle: Photosynthesis produces $\boldsymbol{\ce{O2}}$ (releases it into the atmosphere). Cellular respiration consumes $\boldsymbol{\ce{O2}}$ (uses it to break down organic matter).

Question 5