Cell respiration and photosynthesis

Question

1.Why is much needed in substrate linked reactions molecules such as NAD and FAD?

2.In the electron transport chain to what is useful that the oxygen acts as a final electron acceptor?

3.And how oxygen prevents blockages on the system?

4.What is a self cell and a non self cell?

5.How to identify if a bacteria is heterotrophic or aurotrophic?

Answer 1

Let’s tackle your questions on cell respiration, photosynthesis, and cellular biology step by step!

1. Why are molecules such as NAD and FAD needed in substrate-linked reactions?

NAD (Nicotinamide adenine dinucleotide) and FAD (Flavin adenine dinucleotide) are essential coenzymes that play critical roles in cellular metabolism, particularly in substrate-level phosphorylation and the oxidation-reduction reactions (redox reactions) during cellular respiration. Here’s why they are needed:

1. Electron Carriers: Both NAD and FAD function as electron carriers. In metabolic pathways, they accept electrons during oxidation reactions. For example, during glycolysis and the citric acid cycle, NAD and FAD capture electrons from substrates being oxidized.
2. Energy Transfer: When NAD and FAD are reduced (i.e., gain electrons), they become NADH and FADH22​, which carry high-energy electrons to the electron transport chain (ETC). This transfer is crucial for the subsequent generation of ATP through oxidative phosphorylation.
3. Regeneration: By participating in redox reactions, NAD and FAD are regenerated for continued cycles of metabolism, enabling ongoing energy production within the cell.

2. In the electron transport chain, why is it useful that oxygen acts as the final electron acceptor?

Oxygen serves as the final electron acceptor in the electron transport chain during aerobic respiration, and this role is critical for several reasons:

1. Energy Production: Oxygen’s high electronegativity allows it to efficiently accept electrons from the electron transport chain. This process helps maintain a proton gradient across the inner mitochondrial membrane, which is essential for ATP synthesis via ATP synthase.
2. Water Formation: When oxygen accepts electrons, it combines with protons (H++ ions) to form water. This not only removes electrons from the chain but also prevents the buildup of electrons, promoting the continuous flow of electrons through the chain.
3. Sustaining Cellular Respiration: By acting as the final electron acceptor, oxygen prevents the blockage of the electron transport chain. If oxygen were absent, the chain would become saturated with electrons, halting the entire electron transport process and leading to cell death.

3. How does oxygen prevent blockages in the system?

Oxygen prevents blockages in the electron transport chain in the following ways:

1. Continuous Electron Flow: As the ultimate electron acceptor, oxygen facilitates the continual flow of electrons through the chain. This process is crucial for keeping the components of the electron transport chain active and functioning properly.
2. Reduction of Noxious Compounds: By accepting electrons, oxygen prevents the accumulation of reactive oxygen species (ROS) that can result from unpaired electrons. This reduces oxidative stress and damage within the cell.
3. Enabling ATP Production: The removal of electrons allows the proton gradient to be maintained, which is necessary for ATP production. If oxygen is not present, the gradient cannot sustain itself, leading to a halt in ATP synthesis.

Answer 2

Hello Patricia,

I would first like to mention that these are all great questions pertaining to photosynthesis and cellular respiration. While this topic can be a challenge to understand, I will attempt to provide you some insight as I answer your questions.

1. NAD and FAD are needed in substrate-linked reactions because they act as electron carriers. During these reactions, they accept electrons and hydrogen atoms, which are later used to generate ATP through oxidative phosphorylation.
2. In the electron transport chain, it is useful that oxygen acts as the final electron acceptor because oxygen has a high affinity for electrons. By accepting the electrons at the end of the chain, oxygen helps maintain the proton gradient that drives the synthesis of ATP. Oxygen is the most electronegative element, so it can effectively accept the electrons, preventing a buildup of electrons and the subsequent disruption of the electron transport chain.
3. Oxygen prevents blockages in the electron transport system by acting as the final electron acceptor. If oxygen was not present, the electron transport chain would become blocked, as the electrons would have nowhere to go. This would lead to a breakdown in the proton gradient and a disruption in ATP synthesis. By accepting the electrons, oxygen keeps the system flowing and prevents the buildup of electrons that could cause damage.
4. A self cell is a cell that is recognized by the body's immune system as belonging to the organism. A non-self cell is a cell that is not recognized by the body's immune system and is perceived as foreign, potentially triggering an immune response.
5. To identify if bacteria is heterotrophic or autotrophic, you can look at the bacteria's nutritional requirements.

Heterotrophic bacteria will require organic compounds as a source of carbon and energy. They cannot synthesize their own organic compounds from inorganic precursors. One example include bacteria that feed on dead organic matter, such as decomposers.

On the other hand, autotrophic bacteria can synthesize their own organic compounds from inorganic precursors, such as carbon dioxide. They use energy from sunlight (phototrophs) or inorganic chemical reactions (chemotrophs) to power this process. Some examples include cyanobacteria among other types of bacteria that use hydrogen or sulfur compounds as energy sources.

The key distinction is that heterotrophic bacteria rely on organic compounds from their environment, while autotrophic bacteria can produce their own organic compounds from inorganic sources.

I hope this answered your questions. Please do not hesitate to reach out if you have further questions!

Kind regards,

Dr. Malcolm