Fungal cell
Before you start
Mushrooms grow out of soil and some have stems, so for a long time fungi were classified with plants. Yet the yeast that makes bread rise cannot make its own food from light at all; like us, it must take in food from its surroundings. On the plant cell and animal cell pages, we meet the structures that set those two groups apart. If you have not read them, that is fine, because this page explains the parts it uses. A yeast cell lets us test which features really belong together. Its bud is also a cell division in progress, and the cell division page shows how the genetic material is shared out when a cell divides.
Seeing a cell wall and deciding “plant” leaves something unchecked: can this cell make food using light? Yeast has a firm cell wall, but no chloroplasts to do that job, so it must obtain nutrients from its surroundings. Its nucleus holds DNA, and the bud at its side shows it producing another cell. Compare these features with plant and animal cells one at a time. Is there a nucleus? A wall? Chloroplasts? Combining those answers keeps one familiar shape from making the whole decision for us.
The setupThis is an enlarged budding yeast cell, cut open and coloured so that each kind of structure can be told apart. Select a structure in the model or from the list to read its name, its job and how to recognise it; Look closer moves in to its detail. The cutaway switch closes the cell to show its outside, including the scars left by earlier buds.
What to do and noticeStart at the boundary: select the wall, then the plasma membrane inside it. Next, look for what is missing compared with the plant cell: there are no chloroplasts, so yeast cannot make food from light. Then follow the bud: find the narrow neck that joins it to the mother cell, and the small nucleus that has already moved into the bud.
Predict firstDoes having a cell wall make a cell a plant cell?
Plasma membrane
A cell must take in materials without letting everything enter or leave freely, so it needs a selective boundary. The membrane mainly contains phospholipids and proteins. A phospholipid has a water-friendly end and a water-avoiding part. In water, the water-avoiding parts turn inward and pair up, so the water-friendly ends face the water on both sides. The two layers belong to one membrane, not two separate membranes. Proteins in the membrane can provide passages or help particular substances cross.
The thin membrane surrounding the cell contents. In cells that have a wall, the wall lies outside this membrane. Animal cells have no cell wall.
Follow one set of protein instructions
The cell model shows where structures are. This separate construction shows what “DNA information is used to make protein” means. DNA stores the instructions, and the working copy is made of messenger RNA. Advance one step at a time; nothing moves on by itself.
Each numbered square stands for the information specifying one amino-acid unit, and each circle stands for the unit itself. An amino acid is one small bead in the chain of a protein. Matching colours let us follow the order from the information to the chain. These are instruction markers, not pictures of DNA or RNA molecules. Distances and the number of units are chosen to make each step visible.
Now follow a bud becoming a separate cell
Locate the boundary, follow one set of instructions for a protein, then examine the structures that distinguish this cell.
Prerequisites: A cell is a basic unit that carries out life processes. It must take in materials, build its parts and keep information for making them. We will start with these needs and introduce the structures one at a time.A wall does not make it a plant
Predict firstDoes having a cell wall make a cell a plant cell?
Not necessarily. This yeast cell has a wall but no chloroplasts, so it cannot make food from light; it absorbs nutrients from its surroundings. Its wall is also made of different materials from a plant wall. Select the plasma membrane to see the selective boundary, then the wall outside it: the two are not the same layer.
How to observe
- Start with the boundaries, then explore inside; distinguish a wall from a membrane.
- Select a structure, read what it does, then use Focus to inspect its detail.
- Inspect the bud and bud neck; a fungal wall is not a plant wall.
What this model simplifies
Sizes, counts and colours are adjusted for teaching; this is not a raw microscope image. Cellular organization is dynamic. Each model represents one example, not every member of its group; bacterial accessory structures, plant chloroplasts and fungal forms particularly vary.
