BIO Unit 3 AoS 2 DP 6

Limiting Factor Definitino

Any factor that slows down the rate of photosynthesis when there is not enough of it, e.g. carbon dioxide, water, chlorophyll, and light energy.

Rate Definition

The speed at which a process occurs, or how quickly reactants are used of or products created.

Possible limiting factors for photosynthesis

Light availability, temperature, water availability, and carbon dioxide concentration.

How does light availability affect the rate of photosynthesis?

As light intensity increases, rate of photosynthesis does, until a plateau is reached in the rate, meaning light is no longer the limiting factor.

What is the limiting factor when light intensity is high and all other inputs are in abundance?

The enzymes involved in the reaction/number of chloroplasts as all are working at capacity, limiting reaction.

How does temperature affect the rate of photosynthesis?

As temperature increases, rate of photosynthesis increases, since increased temperature leads to more kinetic energy, and successful collisions between substrates and active sites of enzymes.

How does light availability affect the rate of photosynthesis? (Hint: Taken too far).

If temperature increases above optimal temperature, enzymes begin to denature, meaning enzyme loses its functional 3D shape causes the active site to change shape.

How does light availability affect the rate of photosynthesis? (Hint: Taken too far part 2).

If 3D shape is lost, active site is no longer complementary to the substrate, meaning no enzyme-substrate complexes can form, meaning rate of photosynthesis quickly decreases.

How does water availability affect the rate of photosynthesis?

Water is only needed in small amounts in photosynthesis compared to the water stored in a plant. If there isn’t enough, the plant will close its stomata to conserve water, reducing CO₂ that can enter, slowing down photosynthesis.

How does carbon dioxide concentration affect the rate of photosynthesis?

Increasing carbon dioxide will increase the rate of photosynthesis, until a saturation point is reached when all active sites of the enzymes responsible for carbon fixation are occupied.

How does carbon dioxide concentration affect the rate of photosynthesis? (Hint: Further increase).

Any further increases in concentration level will not increase the rate of reaction (plateau) as carbon dioxide is no longer the limiting factor. At high levels, the plant’s internal environment can become too acidic, slowing photosynthesis rate as optimal pH is lost.