Thinq questions:
1) The algae beads provide a convenient experimental system because they are uniform in size and
contain roughly the same number of algal cells per bead. Why are these advantages for the
experiments you will perform?
a) We will be measuring photosynthesis and cellular respiration rates, and the amount of
organelles we use will impact these rates. It's easy to see, manipulate, and count the algae
beads. A fixed number of beads corresponds to a set amount of alga cells.
2) Under the light, which process(es) will be taking place: photosynthesis, cellular respiration, or
both?
a) Both will occur at the same time, but photosynthesis will be the main factor in bright
light.
3) Why are you measuring the absorbance of the solution at 550 nm?
a) The optimal wavelength of light to shine on the samples is the green spectrum, because
the spectrophotometer counts the quantity of light absorbed by a sample and the samples
will be yellow or purple due to the CO2 indicator. The wavelength of light at 550 nm
corresponds to green wavelengths and will be absorbed.
Focus questions:
1) As the algae photosynthesize, how will the pH of the CO2 indicator change? Why? How will the
pH change if the cells begin to respire?
a) When the rate of photosynthesis exceeds that of cellular respiration in intense light, the
pH of the CO2 indicator rises, rendering the CO2 purple. Cellular respiration will take
precedence in the absence of light, and the pH of the CO2 indicator will drop, making it
yellow.
2) Imagine that the algae are experiencing the light conditions that would result in the graph from
page 7. Predict what color changes will happen in the CO2 indicator between compensation
points 1 and 2, and explain why. What about after compensation point 2?
a) Between points 1 and 2, enough light is present to allow photosynthesis to outpace
cellular respiration. This indicates that more CO2 is consumed than created, resulting in a
more basic solution. The indicator will shift from yellow to purple as a result of this.
After point 2, light levels are low enough that cellular respiration outpaces
photosynthesis, resulting in more CO2 being created than consumed, causing the solution
to turn acidic. The indication will shift from purple to yellow as a result of this.
1) The algae beads provide a convenient experimental system because they are uniform in size and
contain roughly the same number of algal cells per bead. Why are these advantages for the
experiments you will perform?
a) We will be measuring photosynthesis and cellular respiration rates, and the amount of
organelles we use will impact these rates. It's easy to see, manipulate, and count the algae
beads. A fixed number of beads corresponds to a set amount of alga cells.
2) Under the light, which process(es) will be taking place: photosynthesis, cellular respiration, or
both?
a) Both will occur at the same time, but photosynthesis will be the main factor in bright
light.
3) Why are you measuring the absorbance of the solution at 550 nm?
a) The optimal wavelength of light to shine on the samples is the green spectrum, because
the spectrophotometer counts the quantity of light absorbed by a sample and the samples
will be yellow or purple due to the CO2 indicator. The wavelength of light at 550 nm
corresponds to green wavelengths and will be absorbed.
Focus questions:
1) As the algae photosynthesize, how will the pH of the CO2 indicator change? Why? How will the
pH change if the cells begin to respire?
a) When the rate of photosynthesis exceeds that of cellular respiration in intense light, the
pH of the CO2 indicator rises, rendering the CO2 purple. Cellular respiration will take
precedence in the absence of light, and the pH of the CO2 indicator will drop, making it
yellow.
2) Imagine that the algae are experiencing the light conditions that would result in the graph from
page 7. Predict what color changes will happen in the CO2 indicator between compensation
points 1 and 2, and explain why. What about after compensation point 2?
a) Between points 1 and 2, enough light is present to allow photosynthesis to outpace
cellular respiration. This indicates that more CO2 is consumed than created, resulting in a
more basic solution. The indicator will shift from yellow to purple as a result of this.
After point 2, light levels are low enough that cellular respiration outpaces
photosynthesis, resulting in more CO2 being created than consumed, causing the solution
to turn acidic. The indication will shift from purple to yellow as a result of this.
