(a) Name the type of nutrition exhibited by organisms that carry out photosynthesis - Leaving Cert Biology - Question 11 - 2020

The balanced chemical equation for photosynthesis is:

This equation indicates that six molecules of carbon dioxide and six molecules of water, in the presence of light energy, are converted into one molecule of glucose and six molecules of oxygen.

The stomata are small pores located on the surface of leaves that play a crucial role in gas exchange during photosynthesis. They allow the entry of carbon dioxide, which is essential for the synthesis of glucose, and facilitate the release of oxygen as a byproduct of photosynthesis.

Part B of the diagram would contain the most chloroplasts. This is typically where active photosynthesis occurs, as this area is generally rich in chlorophyll — enhancing the plant's ability to capture sunlight.

Chlorophyll molecules absorb light energy, mainly from the blue and red wavelengths of sunlight. This absorbed energy is essential for converting carbon dioxide and water into glucose and oxygen during the photosynthetic process.

The particles released from chlorophyll during the light dependent stage are electrons (e⁻). These electrons are crucial for creating energy carriers like ATP and NADPH.

In pathway 2, the electrons that are released from chlorophyll are captured by the electron transport chain. Electrons are transported through a series of proteins embedded in the thylakoid membrane. As they move through the chain, they lose energy, which is used to pump hydrogen ions (H⁺) into the thylakoid lumen, creating a proton gradient. This gradient drives ATP synthase to produce ATP from ADP and inorganic phosphate. At the end of the chain, the electrons reduce NADP⁺ to NADPH. Thus, the pathway results in the formation of ATP and NADPH, which are vital energy carriers for the Calvin cycle.

The 3-carbon molecule which enters the mitochondrion is pyruvate (or pyruvic acid).

When pyruvate is broken down, the two products formed are carbon dioxide (CO₂) and acetyl CoA (Acetyl Coenzyme A).

The series of reactions that take place after pyruvate enters the mitochondrion is known as the Krebs Cycle (or Citric Acid Cycle).

In the electron transport chain, high energy electrons are passed along a series of carriers (electrons lose energy as they are transferred). This energy is used to pump protons (H⁺) from the mitochondrial matrix into the intermembrane space, creating a proton gradient. Protons flow back into the matrix through ATP synthase, synthesizing ATP from ADP and inorganic phosphate. Finally, electrons combine with oxygen (the final electron acceptor) and hydrogen ions (H⁺) to form water.