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  • A cell is the basic unit of life. Some living

  • organisms such as animals and plants are made of hundreds of trillions of these basic units

  • of life called cells. Animal Cells -- A typical animal cell will

  • include the nucleus, a cell membrane and a cell cytoplasm. The nucleus is the structure

  • that contains the genetic information, otherwise known as DNA and it controls the actions and

  • the reactions of the cell. The cell membrane, which is the border of the cell, acts as the

  • gatekeeper and its controls what enters and exits the cell. As well as enabling neighbouring

  • cells to stick to one another. The cell cytoplasm is the site of the cell's chemical reactions.

  • Lots of chemical reactions occur here such as respiration. Respiration takes place in

  • specialised structures called mitochondria. Plant Cells -- Plant cells contain the structures

  • that animal cells contain, that we've just discussed, the nucleus, the cytoplasm and

  • the cell membrane, but they also include lots of extra structures. For example, they contain

  • a cell wall. A cell wall is made of cellulose and this structure provides support for shape

  • of the cell. Plant cells also contain chloroplasts which are filled with a chemical called chlorophyll.

  • Chlorophyll enables plant cells to absorb light so it can be used in photosynthesis.

  • Chlorophyll is also the substance that gives plants its green colour. Finally, plant cells

  • also contain structures known as vacuoles; these are filled with a watery substance which

  • contains dissolved sugars called cell sap. The role of the vacuole is to provide support

  • for the cell shape and to store sugars. Specialised Cells -- Some cells are specialised;

  • they are able to carry out particular jobs. The specialised cells we will look at are

  • red blood cells, nerve cells and white blood cells. Red blood cells do not possess a nucleus.

  • This is so that they have got enough space to be able to absorb and transport as much

  • oxygen as possible. Nerve cells are specialised in that they have branched endings called

  • dendrites. This is so they can communicate with lots of other nerve cells. You will also

  • notice they have long axons along which the electrical message can travel. Finally, white

  • blood cells enable us to fight infections. They can be identified by the characteristic

  • lobed nucleus. White blood cells have a flexible cytoplasm so that they can engulf pathogens

  • in a process called phagocytosis. Some other white blood cells are specialised to produce

  • antibodies and it's these antibodies that fight pathogens.

A cell is the basic unit of life. Some living

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B2 US specialised nucleus cytoplasm white blood chlorophyll cell membrane

Intro to Cells | Cells and Molecules | The Fuse School

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    Licia Chou posted on 2015/05/29
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