Check and Challenge

Topics: Photosynthesis, C4 carbon fixation, Calvin cycle Pages: 2 (362 words) Published: April 9, 2013
Check and Challenge

1. Why is metabolic activity most accurately expressed as a rate?

Rate as a measure means that minimum and maximum of the stimulus is required to maintain a living organism. High light suggests great growth and low light suggests minimum or no growth.

2. How does increasing light intensity affect the rate of photosynthesis?

Light intensity is a factor which can limit the rate of photosynthesis because if the light intensity is increased the rate of photosynthesis increases. However, at higher light intensities, the rate of photosynthesis will level off.

3. Describe the process of photorespiration. What is its effect on the rate of photosynthesis?

Photorespiration is the process of combining PGA and glycolate to make one molecule. This is done by binding Rubisco with three carbon oxygen molecules because of the similar structures of CO2 and O2

4. Describe the location and function of two system of carbon dioxide fixation in C4 plants.

The location of the two systems in C4 plants is in the bundle sheath cells. The mesophyll cells that surround the bundle sheath cells do not contain Rubisco. They fix carbon dioxide by combing a 3 carbon molecule, which results in a 4 carbon acid and is transported to bundle sheath cells. The carbon molecule that is released by the 4 carbon molecule is fixed again by Rubisco, forming PGA.

5. Which reaction in photosynthesis is inhibited by oxygen? Construct a graph that compares the effect of oxygen on C3 and C4 photosynthesis?

The fixation of carbon by the enzyme Rubisco is inhibited by the presence of oxygen.

6. Explain the following statement: The C4 pathway separates carbon fixation from the Calvin cycle in space, and the CAM pathway separates in time.

C4 plants have structural changes in their leaf anatomy so that their C4 and C3 pathways are separated in different parts of the leaf. Rubisco is where the CO2 level is high and the O2 level is low. CAM...
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