Fungi – Yeast

Yeast is a single-celled microorganism that belongs to the fungi family. It is an oval-shaped, eukaryotic organism that helps in making bread and can also cause bread to spoil.

Structure of a yeast cell

• The outer cell wall protects the oval cell and gives it shape, and it is made of chitin.
• Inside the wall lies the cytoplasm, a jelly-like substance where the cell organelles are found.
• Glycogen stores the energy needed by the cell in the form of oil globules.
• A large vacuole occupies about 20% of the cell space, breaking down proteins into smaller pieces and storing nutrients.
• A true nucleus is present inside the cell, classifying yeast as a eukaryotic organism.

How yeast reproduces

Yeast reproduces through a process called budding. A single yeast cell begins by growing an outward bump called a bud. The nucleus inside the cell stretches and splits into two parts. After the nucleus splits, a new yeast cell forms from the original one, starting out smaller than the parent cell.

How fermentation works

Yeast carries out a chemical process known as fermentation. During fermentation, the yeast consumes available glucose and releases carbon dioxide gas. When making bread, yeast is mixed into the dough, where it eats the glucose molecules and releases carbon dioxide to make the bread soft and fluffy. That same yeast can also grow on neglected bread, giving it a brown, powdery look when it spoils.

Facts about fungi and yeast

• Fungi are microorganisms found in water, on land, and especially in large numbers on dead plants and animals.
• There are about 70,000 different types of fungi, divided into single-celled unicellular types and multicellular types.
• Yeast cells are extremely tiny, so a single spoonful can hold almost 10 billion of them.
• The field of science that studies yeast and other fungi is called mycology.