Budding Bakers
Sometimes there is a piece of bread provided with school lunch. The bread in a school lunch is a combination of yeast, wheat flour, and other ingredients. Did you know that there was once a living organism in that roll? Yeast is a type of fungus that makes dough rise or increase in size to become soft.
The drawing below shows dry yeast from a container.
![]()
Yeast cells have organelles like those found in humans. The table below shows how yeast appears under a microscope and describes how it appears at two magnifications.

Yeast uses cellular respiration for energy. Yeast cells are able to get the materials they need through their semi-permeable membranes. Depending on the size of the molecule, some molecules may pass through freely while others may not.
Yeast uses cellular respiration to fulfill its energy needs. Write a label or draw an arrow in each box to create a model showing how two substances move across a yeast cell membrane, allowing cellular respiration to occur.

In ➡️
Out ⬅️
The drawing below shows a classroom investigation using yeast.

Explain how the result of the investigation indicates that yeast cells use sugar for survival.
After learning about how yeast obtains energy, a group of students made a chart to compare how yeast and trees obtain energy.
Carbon Dioxide
Oxygen
Cellular Respiration (Input Gas)
Photosynthesis (Input Gas)
After learning about how yeast obtains energy, a group of students made a chart to compare how yeast and trees obtain energy.
Sugar
Sunlight
Cellular Respiration (Energy Source)
Photosynthesis (Energy Source)
A group of students decided to investigate further whether the yeast was alive or not. They observed yeast under a microscope and made the following claims. Which student’s claim is best supported?
Based on the passage, which three characteristics can best be used to identify yeast cells as living organisms?