Question

1. what roles do photosynthesis & cellular respiration play in the carbon & oxygen cycles?

Explanation:

Role in Carbon Cycle:

• Photosynthesis: Plants (and some other organisms) use carbon dioxide ($\ce{CO_2}$) from the atmosphere, along with water and sunlight, to produce glucose ($\ce{C_6H_{12}O_6}$) and oxygen ($\ce{O_2}$) through the reaction: $\ce{6CO_2 + 6H_2O \xrightarrow[\text{Chlorophyll}]{\text{Light Energy}} C_6H_{12}O_6 + 6O_2}$. This process removes $\ce{CO_2}$ from the atmosphere and incorporates carbon into organic compounds (like glucose) in living organisms. These organic compounds can be used for growth, stored as biomass, or transferred through the food chain. When organisms die and decompose (or are fossilized over long periods), the carbon can be stored in the soil, sediment, or as fossil fuels (like coal, oil, and natural gas).
• Cellular Respiration: All living organisms (plants, animals, fungi, etc.) perform cellular respiration. In this process, glucose (or other organic compounds) is broken down in the presence of oxygen to release energy, producing carbon dioxide and water as byproducts: $\ce{C_6H_{12}O_6 + 6O_2

ightarrow 6CO_2 + 6H_2O + Energy (ATP)}$. This releases $\ce{CO_2}$ back into the atmosphere (or aquatic environments, for aquatic organisms), completing the cycle of carbon moving from the biotic (living) to the abiotic (non - living) part of the ecosystem.

Role in Oxygen Cycle:

• Photosynthesis: As seen in the photosynthesis equation above, oxygen is a byproduct. This oxygen is released into the atmosphere (or dissolved in water for aquatic photosynthetic organisms). It replenishes the atmospheric oxygen that is used up by organisms during respiration and by processes like combustion (burning of fossil fuels or organic matter).
• Cellular Respiration: While respiration consumes oxygen (as seen in the respiration equation), it is part of the cycle because the oxygen consumed is the same oxygen that was produced by photosynthesis. The continuous process of photosynthesis producing oxygen and respiration (along with other processes like combustion) consuming it maintains the balance of oxygen in the atmosphere. For example, during the day, photosynthetic organisms produce more oxygen than they consume through their own respiration, leading to a net increase in atmospheric oxygen. At night, when photosynthesis stops, organisms still respire, consuming oxygen, but the overall cycle is balanced over time due to the large - scale photosynthetic activity of plants (and other photosynthetic organisms) on Earth.

Answer:

Carbon Cycle:

• Photosynthesis: Removes $\ce{CO_2}$ from the atmosphere, incorporates carbon into organic compounds (e.g., glucose) in organisms. Carbon is then transferred through food chains, stored in biomass, soil, sediment, or as fossil fuels.
• Cellular Respiration: Releases $\ce{CO_2}$ back into the atmosphere (or aquatic environments) by breaking down organic carbon - containing compounds (e.g., glucose) to release energy.

Oxygen Cycle:

• Photosynthesis: Produces $\ce{O_2}$ as a by - product, releasing it into the atmosphere (or water), replenishing oxygen used by respiration and combustion.
• Cellular Respiration: Consumes $\ce{O_2}$ to break down organic compounds for energy, using the oxygen produced by photosynthesis, maintaining the oxygen balance over time.