Question

Aerobic vs. Anaerobic Respiration

A group of students perform two investigations to demonstrate the cycling of matter and the flow of energy in aerobic and anaerobic conditions. In the first investigation, the students observe respiration in yeast, a single-celled organism. The students design apparatus shown in Figure 1. They fill a test tube with a glucose, yeast, and water solution. The layer of oil in the test tube functions to prevent the solution from coming in contact with the air. Lime water is alkaline and clear, but turns milky in color when in the presence of carbon dioxide. The students connect the test tube to the lime water with a glass tube. After 5 minutes, the students observe that the beaker of lime water contains bubbles and is milky in color. The yeast in the test tube produce 2 ATP of energy for each molecule of glucose they consume.

In the second investigation, the students observe respiration in snails and in an aquatic plant called Elodea. Snails will feed on Elodea when given the opportunity. The students use test tubes containing water and bromothymol blue, an indicator that changes color with pH. The table lists information about bromothymol blue.

pH Color of Solution in the Test Tube
Acidic (carbon dioxide is dissolved) Yellow
Neutral Green
Basic (Oxygen is dissolved) Blue

The students observe test tubes with different contents. They measure the levels of respiration and energy production of each test tube. The table shows the data obtained after 24 hours.

Test Tube Contents: Elodea only, Snails only, Elodea and snails, Elodea and snails

Light Present: Yes, Yes, Yes, No

CO2 Level (ppm): 0.0, 10.2, 6.2, 11.1

O2 Level (ppm): 12.0, 1.8, 5.8, 0.9

Water Color: Blue, yellow, green, yellow

Observations: Elodea is green, Snails fall to the bottom of the tube, Elodea is green and snails are active, Elodea turns brown and snails fall to the bottom of the tube

ATP Produced per glucose molecule: 36-38, 0, 36-38, 0

Use the drop-down menus to complete the sentences.

Investigation 1 demonstrates (Aerobic, Anaerobic) conditions where (oxygen, no oxygen) is present. Investigation 2 demonstrates (Aerobic, Anaerobic) conditions where (oxygen, no oxygen) is present.

Answer 1

Investigation 1 demonstrates anaerobic conditions where no oxygen is present.
Investigation 2 demonstrates aerobic conditions where oxygen is present.