Question

Ms. Snyder's students were studying living things and energy. They emptied a package of yeast into a cup of warm water. Next, they added 5 grams of sugar. After 15 minutes, the students noticed bubbles forming on the surface of the water. Using a dropper, they put a sample of the liquid on a glass slide and looked at the sample with a microscope. The yeast cells were growing and reproducing. The bubbles were a by-product of the yeast using the sugar for energy.

What were the bubbles made of?

A) Water
B) Oxygen
C) Hydrogen
D) Carbon dioxide"

Answer 1

The bubbles observed in the yeast experiment are made of carbon dioxide, produced by yeast cells during the process of alcoholic fermentation as they metabolize sugar.

Step-by-step explanation:

The bubbles that formed on the surface of the water after the yeast was mixed with sugar and warm water are made of carbon dioxide gas. This is a result of the process of alcoholic fermentation, which occurs when the yeast cells metabolize sugar in the absence of oxygen. The sugar is broken down to produce energy for the yeast cells, and during this biochemical reaction, carbon dioxide and ethanol are produced as by-products. In the context of the student's experiment, as well as in baking, this production of carbon dioxide gas is what causes bubbles and makes bread dough rise, leaving behind small holes after the bread is baked.