Biology Lab 8 Photosynthesis Concept Questions

Based on your knowledge of photosynthesis, explain why planting trees might help counteract global warming.

Global warming can be attributued to the increase in greenhouse gas emissions. Photosynthesis uses CO2 to create oxygen. So not only do trees reduce the amount of CO2 but they also produce O2.

Explain why a few degrees increase in the Earth's temperature might increase rates of photosynthesis in plants significantly. Hint: The biochemical reactions of photosynthesis require enzymes.

A slight increase in temperature will increase the rate of an enzyme-catalyzed reaction.

Based on the properties of visible light, why do green plants appear green to us? (Hint: How do we recognize an object's color?)

We recognize an object's color based on the wavelengths of light that are transmitted or reflected. Plants appear green because all wavelengths besides green are absorbed by the plant.

In which set of reactions, the Light Reactions or the Calvin Cycle, does the absorption of light by chlorophyll and accessory pigments occur?

The Light Reactions. Light is absorbed by chlorophyll molecules located in the thylakoids of the chloroplasts.

If you were to design the lighting in a greenhouse, what color of bulbs would you most likely use for illumination? Why?

Red bulbs (630-730 nm). The rate of photosynthesis is greatest when plants are exposed to red lights.

A student obtained a negative photosynthetic rate (ppm O2/min/cm2) when the spinach leaf was illuminated with green light for ten minutes. The student concluded that the spinach leaf does not photosynthesize in green light. Is this a valid conclusion? Exp

It is NOT a valid conclusion. Just because the student obtained a negative photosynthetic rate does not mean that the spinach leaf does not photosynthesize in green light. In order to find out how much the spinach leaf photosynthesized you have to take in

Explain why chlorophyll b and the carotenoid pigments (e.g., carotene and xanthophyll) are termed accessory pigments based on their function in the process of photosynthesis, (see the discussion of chloroplast pigments in this lab outline).

Chlorophyll b, carotene, and xanthophyll are termed accessory pigments because they absorb different wavelengths than chlorophyll a and transmit the energy to chlorophyll a. If a photon of sunlight strikes an accessory pigment molecule, energy is conveyed

Since carotenoid pigments (carotenes and xanthophyll) are yellow-orange in color, what wavelengths of light would you expect carotenoids
a. to reflect?

Carotenoids reflect the longer yellow, red, and orange wavelengths

Since carotenoid pigments (carotenes and xanthophyll) are yellow-orange in color, what wavelengths of light would you expect carotenoids
b. to absorb?

Carotenoids absorb light in the blue-green and violet region

Why do spinach leaf cells appear green in color even though the chloroplasts in these leaves contain yellow and yellow-orange pigments?

During the summer the yellow and yellow-orange pigments were masked by the chlorophyll which makes the leaf appear green.

In autumn, many of the leaves of deciduous trees change color, from green to some shade of yellow, orange, or red. This change is triggered by such environmental factors as decreasing day length and freezing temperatures. Based on your knowledge of the pi

As summer fades into fall, the days start getting shorter and there is less sunlight. This is a signal for the leaf to prepare for winter and to stop making chlorophyll. Once this happens, the green color starts to fade and the reds, oranges, and yellows

List the gases which pass through the stomata and the metabolic processes (respiration or photosynthesis) which consume or produce each gas.

When the stomata are open, CO2 enters a leaf (used for photosynthesis) and H2O (product of both photosynthesis and respiration) and O2 exit (product of photosynthesis).

The portion of the cell wall of the guard cells which faces the pore is much thicker than the outer cell wall. How is this difference in cell wall thickness partially responsible for the opening and closing of the pore?

The thickened inner wall of the guard cells facilitates the opening of the stomata when water moves into the guard cells.

The loss of water vapor from plant parts (primarily through the stomata) is called what?

Transpiration