It is important that you know the meanings of all the key scientific words as this will make it easier for you to understand what quesitons are asking and you may be tested on the meanings of some of these.

Look at the words below. Do you know a meaning for each? Click/Tap on the definition to check that you know the correct keyword.


The name given to the membrane around the nucleus. It has pores in it large enough to allow the two halves of the ribosome out.

Nuclear envelope

The name given to the membrane around the vacuole.


A dark staining region of the nucleus where the ribosomes start to be formed.


The site of synthesis for lipids. It is made up of fluid filled cavities that join continuously to the nuclear envelope.

Smooth endoplasmic reticulum

The organelle in the cell responsible for packaging and processing the substances produced by the cell. Under the microscope these appear as membrane bound flattened sacs.

Golgi apparatus

A small sac of cytoplasm in the cell surrounded by a membrane. These can break off from the golgi apparatus.


Linked to the nuclear membrane it contains ribosomes and is the site of production for most extracellular proteins.

Rough endoplasmic reticulum

These are permanent in plant cells and temporary in animal cells. They are used to store excess water and ions.


These are smaller in prokaryotic cells than eukaryotic. They may or may not be attached to the endoplasmic reticulum. They are the site of protein production.


In a plant cell this is made of cellulose, in a prokaryotic cell it is made of peptidoglycans. These are not found in animal cells.

Cell wall

These can be found surrounding the cell wall in a prokaryotic cell.


A process of using chemicals to highlight key structures in the cell.


A stain that binds to DNA and therefore shows up the nucleus within a cell.

Methylene Blue

A network of proteins within the cell which are used to move organelles and plasma proteins around the cell and the membrane.


Literally means good nucleus. It is a type of cell which contains membrane bound organelles. Animal, plant, fungal and protocist cells are examples of these.


This is a small cell which contains a loose chromosome and no membrane bound organelles.


A small vesicle in the cell which contains powerful enzymes.


Also called cytosol. This is the contents of the cell outside the nucleus mainly made up of water, amino acids and ions.


Found inside the chloroplast, it is where some of the chemical reactions for photosynthesis takes place.


Found inside the mitochondria, it is where some of the chemical reactions of respiration take place.


Made up of two bundles of microtubules at right angles to each other. Thought to be involved in cell division.


The protein microfilaments within a cell. Used to make up the cytoskeleton.


How much bigger an image appears compared to the original.


The clarity of an image sometimes referred to as the distance that two points can be seen as two separate points.


A microscope which uses light. These are relatively cheap, can use live or dead specimens and produce colour images. They produce lower magnification and resolution that electron microscopes.

Optical microscope

A microscope which uses electrons. These produce images with higher magnification and resolution but can only produce black and white images with non-living specimens.

Electron microscope

A microscope which uses high powered beams of light. The image produced is high resolution and contrast compared to a light microscope.

Laser microscope

An electron microscope which produces a 3D image.

Scanning electron microscope

An electron microscope which produces a 2D image.

Transmission electron microscope

A scale that can be added to the eyepiece of a microscope.

Eyepiece Graticule

The main structure of a eukaryotic cell. Contains chromatin as well as the nucleolus.


Site of ATP production inside the cell. These are between 2-5 micrometers long.


Large organelles between 4 and 10 micrometers long in the cell. The site of photosynthesis.


Small protrusions form the cell which are surrounded by the cell surface membrane. They contain microtubules and are involved in movement – eg the lining of the airways.


Small loop of DNA.


A tail like structure which allows microscopic organisms to swim.


Small hair like structures which allow bacteria to adhere to each other or to host cells.


A small ruler on a slide which is used to calibrate the eyepiece graticule.

Stage Micrometer

A stain that interacts with cell walls of plant cells to stain them yellow and starch granules in the cell to stain them blue-black.

Key words   Unit 2.5 - Biuological Membranes