Question

final exam review homework #1 - due monday
you are doing an experiment. you have 3 plants growing in normal soil and identical pots. each plant is watered consistently. plant #1 is placed under grow lights, plant #2 is placed in a box with only a little light, and plant #3 is placed under a box with no light. each plant is growing on top of a scale and their masses are measured every day at 12 noon. after 30 days, plant #1 has steadily gained mass every day, plant #2 has stayed about the same as it was when it started, and plant #3 has lost mass!
reminder: mass means nearly the same thing as weight
word bank - these are all words that could be helpful to include for the following questions:
photosynthesis, cellular respiration, carbon dioxide, oxygen, glucose, sunlight, water

a. explain why plant #1 increased in mass: what is the source of mass and what process is involved?

b. plant #3 decreased in mass because it was only doing cellular respiration. explain why this would decrease the mass. where did the mass go?

Explanation:

Part a

Plant #1 increased in mass because it performed photosynthesis. Photosynthesis uses sunlight (from grow lights), carbon dioxide (from air), and water (from soil) to produce glucose (a sugar) and oxygen. The glucose is used to build plant structures (like cellulose) or stored, adding to the plant's mass. The process of photosynthesis converts light energy into chemical energy stored in glucose, which contributes to the plant's mass gain.

Plant #3 was in no light, so it couldn’t photosynthesize—only do cellular respiration. Cellular respiration breaks down glucose (and other organic molecules) to release energy, producing carbon dioxide and water. The glucose (and stored energy - rich molecules) are broken down, so the plant loses the mass of these molecules. The mass (in the form of carbon dioxide and water vapor) is released into the air as by - products of cellular respiration.

Answer:

Plant #1 increased in mass due to photosynthesis. The source of mass is carbon dioxide (from air) and water (from soil), which are used in photosynthesis (powered by sunlight from grow lights) to produce glucose. This glucose is used to build plant materials, increasing mass.

Part b