Although photosynthesis is often summarised by a single equation, in fact the process occurs in two distinct phases; the light phase and another phase called the carbon fixation phase or the light independent phase - VCE - SSCE Biology - Question 3 - 2005 - Paper 1

Output X (oxygen) is produced during the light-dependent reactions of photosynthesis. When light is absorbed by chlorophyll, water molecules (H₂O) are split in a process called photolysis. This yields oxygen, protons, and electrons.

The general equation for the process is:

$2H_2O \rightarrow 4H^+ + 4e^- + O_2$

Here, two water molecules produce four protons and electrons, leading to the release of oxygen as a byproduct.

Output Y is glucose or carbohydrates. It is generated as a result of the light-independent reactions (Calvin cycle) in the process of photosynthesis.

Aerobic respiration in both plants and animals depends on photosynthesis because it requires glucose and oxygen, which are products of photosynthesis. In the presence of oxygen, glucose is broken down to produce ATP, the energy currency of cells. The relationship is cyclical: photosynthesis produces glucose and oxygen, which are then utilized in aerobic respiration to release energy.

An advantage of aerobic respiration is its efficiency in energy production. Aerobic respiration generates significantly more ATP per molecule of glucose compared to anaerobic respiration. Specifically, aerobic respiration can yield approximately 36 to 38 ATP molecules, whereas anaerobic respiration yields only 2 ATP molecules. This makes aerobic respiration a more efficient pathway for energy retrieval.

Conclusion 1: The apical meristem is crucial for the growth of lateral buds.

Explanation: In the experiment, group 2, where the apical meristem was removed, showed growth in lateral buds. This indicates that the presence of the apical meristem inhibits lateral bud growth in untreated plants.

Conclusion 2: Auxin plays a role in promoting the growth of lateral buds.

Explanation: Group 3 had the apical meristem removed with auxin applied, and this group showed significant growth of lateral buds. This suggests that the application of auxin can stimulate lateral bud growth in the absence of the apical meristem.

Conclusion 3: A barrier can affect the growth of lateral buds.

Explanation: In group 4, where the apical meristem was intact but a barrier was placed, there was growth of lateral buds. This indicates that while the apical meristem contributes to inhibiting lateral bud growth, the barrier also influences growth patterns by preventing competing hormonal influences from the apical meristem.