7. Students’ solutions will vary and should be a basic diagram showing inputs and outputs of
photosynthesis in language that a grade 4 student would understand. Sample answer: carbon
dioxide (what we breathe out) + water + light energy (from the Sun) → glucose (sugar for
energy) + oxygen (what we breath in), perhaps with the inputs and outputs drawn on the
leaves of a green plant.
CHAPTER 6 SUMMARY
Make a Summary
(Page 199)
1. Students’ answers should be similar to Figure 2 on page 187 of the Student Book.
2. Students’ responses to the Starting Point questions should show greater understanding of the
concepts than at the start of the chapter, and they should be able to describe any
misconceptions that they have since revised.
1. (a) 6CO2(g) + 6H2O(1) + light energy Æ C6H12O6(s) + 6O2(g)
(b) The O2 molecules produced by photosynthesis come from H2O molecules.
(c) Water is used as both a reactant and a product in photosynthesis. It provides the
protons and electrons required for the dark reaction of photosynthesis.
2. Deciduous leaves are green in the summer due to the high levels of chlorophyll pigments
in them and are yellow, orange, or red in the fall because chlorophyll pigments are
degraded at low temperatures, whereas the carotenoid and xanthophyll pigments are not.
3. Carbon fixation means the incorporation of carbon from carbon dioxide into
carbohydrates such as the glucose molecule (C6H12O6).
4. ATP is produced during the first stage of photosynthesis (light reaction) and by the plant
cells’ own mitochondria, which are able to perform cellular respiration.
5. Photosynthesis requires CO2, which is produced by cellular respiration. Photosynthesis
produces O2 and glucose, which are the reactants in cellular respiration.
CHAPTER 6 REVIEW
(Pages 200–201)
Part 1
1. B
2. B
3. D
4. A
5. A
6. D
7. C
8. B
9. C (99 %), A (48 %), B (37 %), D (15 %)
10. 4, 3, 1, 2
Part 2
11. (a) The shorter the wavelength, the greater the energy; therefore, a shorter wavelength has
more energy.
(b) Plants can use wavelengths from 380 to 480 nm and from 620 to 680 nm in
photosynthesis.
12. (a) Old textbooks often referred to the Calvin cycle as “the dark reaction” because it did not
appear to require light to occur.
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(b) The term “dark reaction” is misleading because although the Calvin cycle does not
require light energy directly, it does require light to activate and produce certain Calvin
cycle enzymes.
14. Purple, blue, orange, and red are least visible in spinach leaves. This is because these colours
are most absorbed by the pigments in spinach.
15. Green and yellow wavelengths are the least absorbed in the pigment extract. Chlorophyll
reflects the green light rather than absorbing it.
16. The pigment most responsible for the peak at 670 nm is chlorophyll a.
17. There are no peaks between 500 and 620 nm because chlorophyll does not absorb green light;
it reflects it.
18. Chlorophyll a and chlorophyll b are responsible for absorption in the range of 400 to 480 nm.
19. The H+ ion concentration in the pH 4 solution does not favour the transport of H+ ions and
thus does not allow for the creation of ATP. Once placed in the pH 8 solution, the H+ ions
have dropped, resulting in an environment that will allow for the movement of H+ and the
formation of ATP.
20. She did not want the light reactions to create additional H+.
21. The products of the Calvin cycle would appear due to the abundance of H+ ions that would
create NADPH that could be used in the Calvin cycle.
22. Hydrogen fuel is clean burning (water is the product of its combustion), whereas methane
produces carbon dioxide.
23. Both of these products are extremely flammable.
24. The plants would be removing CO2 from their environment to produce the methane. This
would result in an equilibrium between the CO2 added to the environment and the CO2
removed.
25. To generate electricity from biofuel, the raw biomass is converted into a variety of gaseous,
liquid, or solid fuels before it is used to generate electricity. The conversion process can be
chemical (e.g., conversion of plant oils into diesel fuel), thermochemical (e.g., heating plant
matter may convert it into solids, liquids, or gases such as methane), or biochemical (e.g.,
using bacteria and yeast, plant carbohydrates may be converted into ethanol that is used as a
fuel). The heat generated by combusting the various fuels is used to convert liquid water into
steam, which then turns the turbines of a generator in a thermal generating plant.
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Approximately 5.9 % of Canada’s electricity is produced using biomass. The
potential to increase this proportion is very large.
The cost of this process is that it is more difficult to convert biomass to fuel.
However, the production of these fuels is more environmentally friendly, and it is a
renewable energy source. Of the 1.1 billion acres of farmland in North America (Canada and
the United States), approximately 150 million acres could be dedicated to energy farming
without appreciably affecting food production. For example, using hay pellets as a biofuel,
● A total biomass production capacity of 480 million tonnes could be achieved.
● About 8.9 billion GJ (an energy equivalent of 1.5 billion barrels of oil) could be produced
each year.
● Heat costs are lowered by approximately $8 to 12/GJ USD compared to natural gas, oil,
and electricity.
● Would provide lower and more stable heating costs while dramatically cutting
greenhouse gas emissions.
CHAPTER 7 Cellular Respiration
Starting Points
(Page 202)
See the Teacher’s Resource, pages 264–265, for examples of answers that show common
misconceptions.
1. (a) Organisms use the oxygen they absorb in cellular respiration to accept two electrons from
the electron transport chain to produce water.
(b) The carbon in carbon dioxide is from the carbon atoms found in the glucose molecule
(C6H12O6).
(c) Carbon dioxide is excreted by the body because it is fully oxidized and cannot provide
any further energy. Carbon dioxide reacts with water to form carbonic acid. The buildup
of carbonic acid may lower pH to toxic levels, which will denature proteins.
2. (a) Bakers add yeast to flour to produce carbon dioxide gas, which causes the baked product
to rise.
(b) The gas produced in fermentation is carbon dioxide.
(c) The bubbling will stop when the glucose is used up. A high concentration of ethanol (a
product of alcoholic fermentation) kills the remaining yeast cells.
(d) Wine is produced.
(e) The name of this process is alcoholic fermentation.
3. (a) The reasons your muscles feel stiff after a long, hard run is because of the accumulation
of lactic acid in the cells of your muscle tissues.
(b) Panting at the end of a run increases your oxygen uptake, and this helps your body to
convert the lactic acid back into pyruvate.
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