Essential Idea: Photosynthesis uses the energy in sunlight to produce the chemical energy needed for life

  
1. Which of the following summarises the process of photosynthesis?
  • A. carbohydrate + oxygen → carbon dioxide + water
  • B. Carbohydrate + water → carbon dioxide + oxygen
  • C. carbon dioxide + water → carbohydrate + water
  • D. carbon dioxide + water → carbohydrate + oxygen
2. The pigments in leaves that absorb light energy may be separated by the process of ...
  • A. distillation
  • B. chromatography
  • C. filtration
  • D. PCR

Q3 & 4. The image shows the pigments present in a plant such as spinach, identified using chromotography:

 

chromatography of plant pigments

 

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3. Which of the pigments is the most soluble in the given solvent?
  • A. Lutein
  • B. Chlorophyll b
  • C. Chlorophyll a
  • D. Phaeophytin

4. The table below gives the Rf values of some of the pigments.

  Rf value
I 0.98
II 0.81
III 0.59
IV 0.28
 

Which of the pigments would be found at position X?

  • A. IV
  • B. II
  • C. III
  • D. I
5. The diagram shows an absorption spectrum for plant pigments.

absorbance graph for chlorophyll

  

What is the colour of light that is maximally absorbed at approx. 675 nm?

  • A. Red
  • B. Yellow
  • C. Green
  • D. Blue

Q6-8. A student investigated how light intensity affected the rate of photosynthesis using algae trapped in small alginate balls as shown in the image. Trapping the algae does not alter their rate of photosynthesis.

A bright light was placed near the boiling tube. The rate was measured by timing how long it took the algal balls to rise from the bottom of the test tube to the surface of the water.

Algal Balls in boiling tube

6. Name the gas produced by the algae and the process that produces the gas.

  Name of gas Name of process
A Carbon dioxide photolysis
B air photosynthesis
C oxygen photolysis
D oxygen respiration
7. Which of the following should the student control in order to obtain reliable data?
  • A. Temperature of the air
  • B. Number of algal balls in each test tube
  • C. Wavelength of the light
  • D. All of the above.

8. The student moved the lamp different distances from the algal balls and recorded the time taken for the balls to rise from the bottom of the test tube to the surface of the water. The rate of photosynthesis was calculated.

rate of photosynthesis graph

  

As the light intensity is increased above 4 arbitrary units, the rate of photosynthesis does not increase significantly. Why?

  • A. The light intensity is not high enough
  • B. The wavelength of the light changes with intensity
  • C. Another factor becomes limiting
  • D. Oxygen production stops at this point
9. In which of the following conditions might carbon dioxide be the limiting factor?
  • A. Humid, warm tropical rainforest at night
  • B. Mid-day on a hot sunny savannah grassland
  • C. Damp, cool night in a temperate forest
  • D. Just after sunrise in a sunny tropical forest
10. Oxygen production in photosynthesis involves this reaction:

4H2O → O2 + 2H2O + 4H+ + 4e-

If one photon of light yields 0.125 molecules of oxygen, how many photons are needed to produce one molecule of oxygen?

  • A. 2
  • B. 8
  • C. 10
  • D. 16