Your cells require oxygen for respiration, so you need to get it from the air into your bloodstream. You must also expel carbon dioxide from your bloodstream. All of this occurs in your lungs. Your lungs are forced to take in and expel air when you breathe.
There are trillions of cells in multicellular organisms like humans. Those cells have to work together to keep the organism going, which requires organisation.
You need to know about a few examples of exchange surfaces. Mammals exchange gases in their lungs and absorb nutrients in their small intestines. In plants, gas exchange occurs in the leaves. In fish, gas exchange occurs in the gills.
Substances dissolved in water are called soluble. In order to survive, living organisms must be able to exchange dissolved substances with their environment. Surface area and size affect the pace at which this can occur.
The most common way microorganisms are grown (cultured) is in a "culture medium", a combination of carbohydrates, minerals, proteins and vitamins. A nutrient broth solution or solid agar jelly can be used as the culture medium.
Bacteria and other prokaryotic cells replicate by a process known as binary fission. Cells that undergo binary fission make copies of their genetic material, then split into two daughter cells.
Stem cells are cells that have NOT yet been differentiated. They are not yet specialised. Some cells do not become specialised yet, but are called undifferentiated.
Download AQA GCSE Mathematics past exam papers to practice so that you prepare yourself for your final exam.
Download AQA GCSE Science past exam papers to practice so that you prepare yourself for your final exam.
