Site author Richard Steane
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Yeast cell structure

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Yeast comes in strange forms ...

This is a cake of yeast as used by breadmakers

Dried yeast as used in the kitchen and for home-brewing
Yeast is a living organism. It can be used to make bread and alcoholic drinks such as beer and wine. Different species of yeast may cause infections such as thrush.

Yeast consists of single cells. They are smaller than animal and plant cells, but slightly larger than bacteria.

These cells also have several similarities with cells of (green) plants and animals, but lots of differences, which is why they are put into a kingdom of their own.

On the outside of the cell is a cell wall, but it is not made of cellulose.

Inside this is a membrane enclosing the cytoplasm.

A yeast cell contains a nucleus, like those in plant and animal cells

There are mitochondria in yeast cells.

There are no chloroplasts in yeast cells.

Yeast cells do contain ribosomes, the same size as ribosomes in animal and plant cells.

Some of these yeast cells have small outgrowths - buds - so they are about to reproduce.

Yeast cell (sectional view)
- click to label

Approximate sizes:

in micrometres (µm) also known as microns
[1µm = 0.001mm = 0.000001m (10-6m)]
cell/component size / µm note
yeast cell 3-4 much variation between strains and growing conditions

What you should know

Yeast is a single-celled organism.

Yeast cells have a nucleus, cytoplasm and a membrane surrounded by a cell wall.

Notes on words:

The word yeast can be both singular and plural, but some people use the term yeasts for different but closely related species.

Saccharomyces cereviseae is the scientific name of (baker's or brewer's) yeast.

Saccharomyces means 'sugar fungus': yeast grows in fruit juice, especially grape juice, and sugar is usually added to bread dough.

cerevisiae means 'of beer'.

This topic has connections with other units on this site:
Cell biology
Eukaryotes and prokaryotes
Animal cells
Plant cells
Bacterial cells

A little more detail
Cell structure and specialisation
Higher level
Prokaryotic cells
Eukaryotic cells
Virus particles

Web references

[Youtube videos]

Budding of Yeast Cells - time lapse photography - (skip to 55secs-3:30)

Yeast cells (stained with methylene blue?) bobbling about for 22 seconds, not dividing, but showing some interesting internal structure

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