Cells

A cell is the basic unit of life and they can be studied using electron microscopes. When we use an electron microscope we see many more features than with a typical light microscope because of more powerful magnification and also due to higher resolution.

cell_labeled This is a fairly typical cell and there are many features. I will guide you through the features of this cell.

©Alila Medical Media

See more images of cells at Alila Medical media.

 

 

 

 

Cell surface membrane/plasma membrane: If you are on OCR you need to call this the cell surface membrane, do not abbreviate it to Cell membrane. The cell surface membrane is about 7nm wide and controls the entry and exit of substances to and from the cell.

Structure of plasma membrane

Image supplied by Alila Medical media. Click on the link to see more images of cells.

 

Mitochondrion/Mitochondria: If you are on AQA you to be specific when you use singles and plurals. If you are talking about a single then its mitochondrion, if its more than one then its mitochondria. The mitochondria carry out the process of aerobic respiration releasing energy. At A level you must always write releasing energy, and not producing energy. This is because energy cannot be produced. You can produce ATP though as its a chemical substance.

Mitochondrion structure

Image supplied by Alila Medical media. Click on the link to see more images of cells.

 

Ribosomes: These have two subunits and carry out protein synthesis. They are also found embedded in the rough endoplasmic reticulum or free within the cytoplasm. The image below shows a ribsome with a mRNA molecule and tRNA being used for protein synthesis.

Ribosome and translation

Image supplied by Alila Medical media. Click on the link to see more images of cells,

 

Smooth endoplasmic reticulum: This carries out lipid synthesis. Lipids are fats at A level.

Lysozymes: These are vesicles that contain powerful hydrolytic enzymes. They can be used to break down old organelles or to destroy the cell when it is no longer needed.

Nucleus contain chromatin, nucleolus and around the nucleus is a double membrane called the nuclear envelope. There are holes in the nuclear envelope called nuclear pores.

Centrioles form spindle fibres during cell division. Cell division at A level can either be mitosis or meiosis. Below is an image of centrioles.

Structure of the centrioles

Image supplied by Alila Medical media. Click on the link to see more images of cells,

 

 

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