What's in a cell?

All animals and plants are made of cells. Animal and plant cells have features in common, such as a nucleus, cytoplasm, cell membrane, mitochondria and ribosomes. Plant cells also have a cell wall, and often have chloroplasts and a permanent vacuole. Note that cells may be specialised to carry out a particular function.We use microscopes to see very tiny structures such as cells. Bacterial cell structure Bacterial cells are much smaller than plant or animal cells. They were first seen under a microscope by Anton van Leeuwenhoek in 1676. As microscopes have improved, scientists have come to understand bacterial cell structure better.Using electron microscopes we now know that bacteria have a cell wall. This is similar to a plant cell wall but is more flexible. Bacteria do not have a nucleus. They do have two types of DNA – plasmid and chromosomal. The chromosomal DNA carries most of the genetic information. Plasmid DNA forms small loops and carries extra information. Some bacteria have a flagellum – a whip like tail. This helps the bacteria to move itself along. When we talk about these flagellum tails in multiple bacteria, we call them flagella. Structure of a salmonella bacterium cell Structure of a bacteria cell

Plant and animal cells Function of cells which animal and plant cells have in common PartFunctionNucleusContains genetic material, which controls the activities of the cellCytoplasmMost chemical processes take place here, controlled by enzymesCell membraneControls the movement of substances into and out of the cellMitochondriaMost energy is released by respiration hereRibosomesProtein synthesis happens herePlant cells also have extra parts: Extra parts of plant cells PartFunctionCell wallStrengthens the cellChloroplastsContain chlorophyll, which absorbs light energy for photosynthesisPermanent vacuoleFilled with cell sap to help keep the cell turgidMake sure you can label diagrams of animal and plant cells, like these: Generalised animal and plant cell

Microscopes Microscopes have been in use for approximately 350 years. Hans and Zaccharias Janssen are credited with constructing the first usable one in the 1590s. Microscope from the end of the nineteenth century Modern microscope Early microscopes did not magnify to a great extent and scientists have worked hard to improve this. We now have modern light microscopes that can magnify 1,500 times and electron microscopes that can magnify up to two million times. This has allowed scientists to see things such as cells in much greater detail. As a result our understanding of their structure and function has improved. Magnification calculations We can calculate the length of a magnified object by using the magnification of the lens.Length of object = length of magnified object ÷ magnificationFor example, if a specimen appeared 10mm in length under a microscope with a magnification of 1,000 times, the calculation of the actual length would be:Length of object = 10 ÷ 1000 = 0.01 mm

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