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The mitochondria is an organelle found in most cells of eukaryotic organisms, excluding some specific cells such as red blood cells. It has a double membrane and is variable in size (but usually betwee...

A mutation is a random change in the amount of DNA or sequence of DNA nucleotides within a cell. DNA is a double helix with two polynucl...

A gene is a section of DNA coding for a specific protein. This protein will perform a certain function within the organism. You interit two forms of each gene, one from each parent. These are ...

A pathogen is a microorganism that causes a disease. Pathogens spread communicable diseases meaning that they are transmitted person to person and are infectious.
Types of pathogens include bacteria,...

The cell membrane separates the intracellular and extracellular environments. The lipid bilayer only allows small polar molecules (such as O2 or CO2), small hydrophobic molecules (fatty acids, steroid hor...