Techniques for varying concentrations of carbon dioxide, light intensity or temperature experimentally to investigate the effects of limiting factors on the rate of photosynthesis
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All 12 Flashcards — Techniques for varying concentrations of carbon dioxide, light intensity or temperature experimentally to investigate the effects of limiting factors on the rate of photosynthesis
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Question
What is a limiting factor?
Answer
The factor in **shortest supply** that holds back the rate of a process. Only raising it can increase the rate.
Question
Name the three limiting factors of photosynthesis.
Answer
**Light intensity**, **carbon dioxide concentration** and **temperature**.
Question
Why does only the limiting factor change the rate?
Answer
Because it is the one in shortest supply; the others are already plentiful, so adding more of them does nothing.
Question
On a rate-vs-light graph, what is limiting on the rising part?
Answer
**Light intensity** — while the curve climbs, increasing light increases the rate.
Question
On a rate-vs-light graph, what is limiting on the plateau?
Answer
**CO₂ concentration** (or **temperature**) — light is no longer limiting once the rate goes flat.
Question
Why does a rate-vs-light curve plateau?
Answer
Because **light is no longer the limiting factor**; another factor (CO₂ or temperature) now limits the rate.
Question
On a graph with two CO₂ levels, what does the higher-CO₂ curve do?
Answer
It **plateaus higher up** — more CO₂ lets light keep raising the rate for longer.
Question
How does increasing CO₂ affect the rate while CO₂ is limiting?
Answer
It **increases** the rate, because CO₂ is a raw material that was in short supply.
Question
What happens to the rate if temperature rises too far above the optimum?
Answer
The rate **falls** (and can drop to zero) because the **enzymes denature**.
Question
Why does very high temperature lower the rate of photosynthesis?
Answer
Photosynthesis uses **enzymes**, and high temperature **denatures** them, destroying their shape so they stop working.
Question
How do you spot the limiting factor from a curve's shape?
Answer
If the curve is **sloping**, the factor on the axis is limiting; if it is **flat**, something else is limiting.
Question
Define the 'rate of photosynthesis'.
Answer
How fast photosynthesis happens — e.g. the volume of oxygen released or CO₂ taken up per minute.
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Photosynthesis
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