Eukaryotic Organelles

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The nucleus is the largest organelle found in animal and plant cells, at around 7-10 micrometres. Its main function is to control the cell.

  • Contains chromatin
  • Surounds the nucleolous and is surrounded by two membranes with a small gap between, called the nuclear envelope.
  • Nuclear envelope contains nuclear pores that allow molecules through.
  • It is found in almost all cells, apart from red blood cells and phloem sieve tubes in plants.
  • Houses genetic material

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  • Creates ribonucleic acid and ribosomes.
  • These travel out of the nucleus, through the nuclear pores, to the cytoplasm where they are involved in protein synthesis.
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Endoplasmic Rectilium:

They are found near the nucleus and are made of flattened sacs called cisternae, which are continuous with the nuclear envelope.

Rough ER:

  • Studded with ribosomes.
  • Transports proteins which are made on the attached ribosomes.
  • Some of these proteins may be secreted.
  • Some of these proteins may be placed on the cell surface membrane.

Smooth ER:

  • Involved in making lipids and the production of steroids.
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Golgi Apparatus:

The golgi apparatus is found in both plant and animal cells and the main function is to 'package and process' proteins.

  • Variable in size.
  • A stack of membrane bound, fluid filled sacs, often found near the nucleus.
  • Receives proteins from the ER and modifies them, eg- it may add a sugar molecule.
  • Packages modified proteins into vesicles for transport.
  • Some proteins may be secreted.
  • Some proteins may go to the cell surface membrane.


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Lysosomes are only found in animal cells.  Their main function is to break down worn out components of cells.

  • Contain extremely powerful digestive enzymes.
  • Break down foreign substances like pathogens.
  • Specialised lysosomes (acrosomes) in the head of a sperm cell contain enzymes to help penetrate the egg by breaking down the material surrounding it.
  • Variable in size.
  • Spherical sacs surrounded by a single membrane.


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Mitochondria are found in animal and plant cells and are the site of respiration where ATP is produced.

  • 2-5 micrometers.
  • Called the universal energy carrier because ATP provides energy for almost all cellular activities.
  • Has a sausage shape structure and 2 membranes.
  • Inner membrane folded inside to form cristae, which are folded in the matrix (central part of mitochondrion).

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Chloroplasts are only found in plant cells and are the largest organelle in plant cells, besides the nucleus.

  • 5 micrometers.
  • Used for photosynthesis.
  • Contains chlorophyll.
  • Membrane bound disk shaped organelle containing stacks of membranes.
  • This forms the surface for reactions of photosynthesis.
  • Contain 2 fluid separated membranes.
  • Inner membrane folded into a netwrk of flattened sacs called Thylakoids, that are stacked into grana (one granum, two grana).


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Vesicles are found in animal cells and are used to transport many different substances around the cell.

  • The size is variable but usually around a few micrometers.
  • Regulates pressure and water in cells.
  • membrane bound sacs.
  • Various functions and are common in secretory cells.
  • Hydrophilic head and hydrophobic tail.
  • Consists of fluid enclosed by a lipid bilayer membrane.
  • Can form naturally.

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  • Large vesicles formed by smaller vesicles joining.
  • Membrane bound.
  • Have no specific shape.
  • Contain water with many compounds in it.
  • Function depends on cell- eg turgor pressure in plants.


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Ribosomes are found in animal cells and provide a surface for                   protein synthesis.

  • Act as an assembly line where coded information (mRNA) from the nucleus is used to assemble protens from amino acids.
  • Small spherical organelle composed of 2 subunits which can be found on the rough ER, cytoplasm and other places. 
  • Translate genetic information in the form of mRNA into proteins.
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Centrioles are small tubes of protein fibres that are usually 500 nm long.

  • Small hollow cylinders containing a ring of microtubules.
  • Take part in cell division and move chromosomes around.
  • Tubular structure containing 9 microtubules.
  • When two are next to eachother, they are usually at right angles.
  • Absence of centrioles causes divisional errors.
  • Usually in pairs next to the nucleus.

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Flagellae/ Cilia:

Flagellae/ cilia are found in animal cells, and are used for movement in cells such as sperm and aquatic bacteria.

  • Nine micotubules surrounding.
  • Called undulipodia in eukaryotes.
  • Clilia are short versions and are less than 10 micrometres long.


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Cell Wall:

The cell wall is found in plant cells and can be anywhere from 5-100 nm thick.

  • permeable, tough, flexible and sometimes rigid layer that surrounds plant and bacterial cells.
  • Located outside the cell membrane and provides support and protection, as well as acting as a filtering mechanism.
  • Made of cellulose (in plants).
  • Only present in plants and prokaryotes like bacterial cells.

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The cytoskeleton provides a stable internal framework for the cell.

  • Made up of microtubules.
  • The microtubules have a diameter of 25nm but join tgether to make the size of a cell.


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extremely helpful- thank you! :)

Pete Langley - Get Revising founder


Great resource - thanks.

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