AS Biology Unit 2 - Organelles

Summay of Organlles 

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Golgi Apparatus

What is it?

  • A series of curved sacs enclosed by a membrane, each sac smaller than the last.

Where is it:

  • Found In the cytoplasm of most eukaryotic cells

Recognising an Electron Microscope:

  • Stacks of  curved and flattened Cisternae present, each one smaller than the previous 
  • Smooth membrane with no ribosomes
  • Vesicles Present

Role:

  • Vesicles formed in the rER fuse to the Golgi Apparatus
  • It modifies protein by adding carbohydrates
  • Removes water from concentrated proteins
  • Produces lysosomes/secretory vesicles
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Mitochondria

Where is it?

  • Found in the cytoplasm of most eukaryotic cells

What does one look like?

  • Shaped like a peanut
  • Surrounded by a double membrane
  • Inner membrane folded into finger like projections called CRISTAE
  • Central area contains a jelly called the MATRIX
  • Floating in the matrix are: Ribosomes and Circular DNA 

Role:

  • To create ATP energy from a series of complicated biochemical reactions
  • The energy created is used to drive other functions of the cell
  • They are the site of the later stages of aerobic respiration
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Ribosomes

What is it?

  • A small organelle made of RNA and protein

Where is it?

  • It is found in the cytoplasm or atached to endoplasmic reticulum

Role:

  • They are the site of protein systhesis
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Nucleus

What is it?

  • It is a organelle encolsed by a double membrane perforated by pores

Where is it?

  • It is found in the cytoplasm of eukaryotic cells 

Role:

  • Contains chromosomes
  • Contains the nucleolus 
  • The DNA in the chromosomes contain genes that control the synthesis of proteins
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Nucleolus

What is it?

  • It is a dense body

Where is it?

  • It is found within the nucleus 

Role:

  • It is where ribosome are made

Under an Electron Microscope:

  • It shows up as a dark staining area.
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Rough Endoplasmic Reticulum

What is it?

  • It is a series of single flattened sacs enclosed by a membrane
  • Ribosomes are found on the surface

Where is it?

  • It spreads throughout the ctyoplasm stretching from the cell membrane forming continious connections with the nuclear envelope.  

Roles:

  • It makes up a large part of the transport system
  • It is the site of synthesis for many important chemical reactions
  • Proteins are produced by the ribosomes attached to the rER
  • The proteins are them stored and transported within the rER
  • Proteins are folded in the lumen of the rER into 3D Tertiary strucutres
  • The rER produce vesicles and package the proteins
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Smooth Endoplasmic Reticulum

What is it?

  • A series of single tubular sacs made of membrane
  • Does not have any attached ribosomes

Where is it?

  • It is found in the cytoplasm of many animal and plant cells

Role:

  • Makes lipids and steroids
  • e.g. Reproducive Hormone
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Centrioles

What is it?

  • Two hollow cylinders made up of a ring of nine protein microtubles.
  • They are arranged at right angles to eachother

Where is it?

  • They are found in the cytoplam near the nucleus

Roles:

  • They are involved in the formation of spindle during nuclear division.
    • When the cell divides they pull apart and produce a spindle of microtubles which are involved in the movement of chromosomes.
  • They are involved in transport within the cell cytoplasm.
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Lysosomes

What is it?

  • Spherical Sacs containing digestive enzymes bound by a single membrane.

Where is it?

  • Found in the cytoplasm of eukaryotic cells

Role:

  • Involved in the break down of unwanted strucutres within the cell.
  • Involved in the destruction of whole cells when old cells are replaced or during development.
  • The acrosome is a specalised lysosome
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Plasma Cell Surface Membrane

What is it?

  • A phospholipid bilayer containing proteins and other molecules forming a partially permeable barrier. 

Where is it?

  • It is surrounds animal and plant cells

Role:

  • It gives the cell shape and protection
  • It regulates the movements of substances into and out of the cell
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Chloroplasts

What is it?

  • An organelle found in plant cells with a double outer memberane
  • Within the stroma there are other membrane structures e.g. thylakoids

Where is it?

  • Found in green parts of the plant

Roles:

  • They contain chlorophyll which is responsible for the plants green colour and ability to absorb energy from the sunlight.
  • They create sugars which they use for food.
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