Question

extension questions
model 4 – the study of photosynthesis

1. when algae are undergoing photosynthesis, the concentrations of various molecules change with in the cells. these concentrations can be monitored and graphed. in complete sentences, explain the shape of each line on the graph in model 4.

carbon dioxide—
oxygen—
rubp—

1. photosynthesis is typically represented by a simple equation:

$6co_2 + 6h_2o + \text{light} \longrightarrow c_6h_{12}o_6 + 6o_2$

a. compare and contrast this simplified equation with the one presented in model 1.

b. using the information from this activity explain why the equation above is a vastly oversimplified representation of the actual process.

Explanation:

The problem is about photosynthesis, which falls under Biology (a subfield of Natural Science). For question 31 (explaining the graph lines):

• Carbon dioxide: In photosynthesis, algae use \( CO_2 \) as a reactant. So its concentration should decrease over time (the line for \( CO_2 \) in the graph likely shows a downward trend as it’s consumed).
• Oxygen: Photosynthesis produces \( O_2 \) as a by - product. Thus, its concentration should increase over time (the \( O_2 \) line in the graph should show an upward trend as it’s generated).
• RuBP (Ribulose - 1,5 - bisphosphate): RuBP is involved in the Calvin cycle (carbon fixation). It is regenerated and its concentration should remain relatively stable or have a small, steady - state - like change (the RuBP line in the graph should be relatively flat or have minor fluctuations as it’s recycled in the cycle).

For question 32 (about the photosynthesis equation):

• Part a: The simplified equation \( 6CO_2 + 6H_2O+\text{light}

ightarrow C_6H_{12}O_6 + 6O_2 \) is a summary. Model 1 (not shown here, but typically in photosynthesis models) likely shows the detailed steps (like light - dependent and light - independent reactions, involvement of enzymes, ATP, NADPH, etc.). The simplified equation omits these detailed molecular processes and intermediate compounds, while a more detailed model would include them.

• Part b: The simplified equation is a gross oversimplification because photosynthesis is a complex process with two main stages (light - dependent and light - independent reactions). It involves many enzymes, electron transport chains, ATP synthesis, NADPH production, and the Calvin cycle with intermediate molecules (like RuBP, 3 - PGA, etc.). The simplified equation just shows the overall reactants and products, not the intricate biochemical steps and intermediate compounds involved in converting \( CO_2 \) and \( H_2O \) into glucose and \( O_2 \).

Answer:

Question 31 Explanations:

• Carbon dioxide: The concentration of carbon dioxide decreases over time because algae use \( CO_2 \) as a reactant in photosynthesis to produce glucose and other organic compounds.
• Oxygen: The concentration of oxygen increases over time as it is a by - product of photosynthesis (produced when water is split during the light - dependent reactions).
• RuBP: The concentration of RuBP remains relatively constant (or has small fluctuations) because it is regenerated in the Calvin cycle (carbon fixation cycle) and is continuously reused to fix carbon dioxide.

Question 32 Explanations:

• Part a: The simplified photosynthesis equation is a general summary of the overall reactants and products. A more detailed model (like Model 1) would show the two main stages (light - dependent and light - independent reactions), the role of ATP, NADPH, enzymes, and intermediate compounds. The simplified equation omits these detailed biochemical processes and intermediate molecules.
• Part b: The equation is a gross oversimplification because photosynthesis is a complex, multi - step process. It involves the light - dependent reactions (where water is split, ATP and NADPH are made, and oxygen is released) and the light - independent reactions (Calvin cycle, where carbon dioxide is fixed using RuBP, and glucose is synthesized with the help of ATP and NADPH). The simplified equation does not show the intermediate compounds, the role of energy carriers (ATP, NADPH), enzymes, and the detailed steps of the two - stage process.