Site author Richard Steane
The BioTopics website gives access to interactive resource material, developed to support the learning and teaching of Biology at a variety of levels.


Plant Cell Structure

This unit also contains some information to assist you in relation to other units, and some supplementary details - pass your mouse cursor over the green text and any gaps you can see, especially after a prompt like this: >
You should be able to draw an average animal cell with 3 labels
In this way you can test your knowledge.

Plant cells have the three main components found in most animal cells:
> nucleus
> cytoplasm
> cell membrane
Inside the cell there are the same smaller structures (organelles) which are found in animal cells:
the site of respiration: > mitochondria
the site of protein synthesis: > ribosomes

Extra features found in plant cells

Parts of the diagrams will be highlighted as the cursor passes over the text below (or all parts if you tap/mouseover the images)
A group of epidermis cells taken from
the inside of an onion
- stained with iodine
onion epidermis cells

The nucleus can be clearly seen inside each of these cells.

The cell walls (which are actually double as two cells are touching) give each cell a clear outline.

The cytoplasm forms a very thin layer, only seen in some of the cells (near the nuclei).

What cannot be easily seen is the cell membrane - pushed against the cell wall - although it is peeling away in some places, leaving a small gap.
I usually introduce my classes to plant cell structure using these specimens

The main extra feature that plant cells have is a cell wall on the outside. This is mostly made of cellulose, and it gives a tough covering on the outside of the cell membrane. It therefore gives plant cells a distinctive polygonal outline.
The cell wall also prevents the plant cell from swelling or shrinking as much as an animal cell would if placed in different liquids.
Surprisingly, the cell wall does not usually prevent much passing through it. Water can usually pass through the cell wall, as it is actually made of a mesh of cellulose fibres running in different directions, rather like a basket.
Cellulose is actually a polysaccharide carbohydrate, but it is difficult to break down. It forms most of the fibre in our diets.

Most plant cells also have a vacuole, filled with a liquid called cell sap, which is mostly water with some substances dissolved in it. It forms a relatively large space within the cytoplasm, which is usually pushed up against the cell wall in a thin layer. The cell membrane is held closely against the cell wall and often cannot be easily seen. The nucleus is also usually fairly to the edge of the cell. Although it is said that plant cells have permanent vacuoles, they may vary in size or disappear altogether if water is removed from the cell.

Some (but not all) plant cells - mostly those in the middle of leaves - have chloroplasts - green structures which contain the pigment chlorophyll. This absorbs light energy which is then used in photosynthesis to make sugars. These sugars are used by the plant as food for several purposes: to provide energy from respiration within plant cells and for growth.
A group of leaf cells from the pondweed Elodea
- not stained
elodea leaf cells

The cell walls are quite noticeable in this image - and they do not have the green colouration.

The green dots are chloroplasts.

Notice the colourless space - the vacuole - in the middle of the cells.

The nucleus appears to be hidden (between the chloroplasts?).

Approximate sizes:

in micrometres (µm) also known as microns
[1µm = 0.001mm = 0.000001m (10-6m)]

cell/component size / µm
onion cell length 300
onion cell width 70
Elodea cell length 50
chloroplast length 3

What you should know

In addition to nucleus, cytoplasm, cell membrane, mitochondria and ribosomes, plant cells often have: Plant and algal cells also have a cell wall made of cellulose, which strengthens the cell.

Notes on words:

Cellulose is based on (little) cells and -ose which is a link to sugars (glucose) from which it is built up.

Polysaccharide: poly- means many and -saccharide means sugars. Cellulose consists of many glucose molecules joined together in strands. Starch is another polysaccharide built up from glucose, but put together in a different way.

Carbohydrate is a class of chemical compounds containing the elements carbon hydrogen and oxygen.
Their simplest chemical formula is sometimes written as CH2O which partly explains the -hydrate part; H2O is the formula for water.

Chloroplast: chloro- means green , and -plast means formation; a fixed shape.

Chlorophyll: again chloro- means > green , and - phyll means leaf.

An organelle is a structure with a special function within a cell - like an organ within a body.

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