Organelles

Organelles Revision

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  • Created by: kudzi.c
  • Created on: 10-10-14 22:05

Nucleus

Structure 

  • Largest organelle;
  • Surrounded by nuclear envelope (composed of two membranes, seperated by fluid) with nuclear pores (allow relatively large molecules through);
  • Nucleolus is densest part, and spherical.

Function

  • House nearly all genetic material
  • Chromatin consists of DNA and proteins (and instructions for making more proteins)
  • Nucleolus - creates ribosomes & RNA which go through the pores into the cytoplasm where they synthesise protein;
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Endoplasmic Reticulum

Rough & Smooth Endoplasmic Reticulum.

Structure

  • Flattened membrane bound sacs (cisternae)
  • Continuous with outer nuclear envelope
  • Studded with Ribosomes

Function

  • Transports proteins synthesised by the attached ribosomes (for secretion or placement on the plasma membrane)
  • Lipid synthesis
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Golgi Apparatus

Structure

  • Stack of membrane boud, flattened sacs;
  • Transport vesicles can bud off from the end.

Function

  • Processes material as it passes through
  • Recieves proteins from RER and modifies them - e.g. create gylcoproteins and hormones or haemoglobin;
  • Packages modified proteins into vesicles so they can be transported
    • Vesicles can then go to plasma membrane and 'exocytosis' their contents through fusing with plasma membrane.
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Mitochondria

Structure

  • Spherical or sausage shaped;
  • Double membraned (because they orignated from bacteria), inner membrane (cristae) is highly folded (increase surface area)
  • Central part - matrix, contains enzymes for Krebs Cycle.
  • Contains circular loop of DNA and tiny ribosomes

Function

  • Create ATP (Adenosine Triphosphate) during aerobic respiration on inner membrane
    • Therefore provide energy for the rest of the cell's activities;
    • ATP - universal energy carrier.
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Chloroplasts

Structure

  • Double membrane, 'chloroplast envelope'
    • Inner membrane is continuous, with 'eleborarte network' of flattened membrane sacs (thylakoids).
  • Thylakoids - look like pile of plates,
    • Stack called a granum (pl. grana)
    • Have chlorophyll on them
  • Contain ribosomes, starch grains and circular loop DNA (also originated outside plants like mitochondria)
  • Stroma contains enzymes for Calvin cycle 

Function

  • Site of photosynthesis.

Exta info... *irregular white blob is often starch whilst black ones are likely are oil/lipids

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Lysosomes

Structure

  • Spherical sacs
  • Single membrane
  • Use cytoskeleton move

Function

  • Contain (powerful) hydolytic enzymes 
    • The type that digest invading microorganisms or penetrate egg cell
  • Break waste down into smaller simple compunds that can be recycled in the cell

***A Type Of Vesicles***

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Ribosomes

Structure

  • Consists of two subunits
  • Some bound to RER & others loose in cytoplasm.
  • Cleft where mRNA runs (so they can translate the instructions)

Function

  • Protein synthesis 
  • Assembly line where mRNA is used to assemble proteins from amino acids
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Centrioles

Structure

  • Small tubes of protein fibres (microtubules);
  • Triplets of microtubules form a ring;
  • Pair next to nucleus in animal cells and some protocists at right angles.

Function

  • Form spindles which move chromosomes during nuclear division.
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Cillia & Flagella

Cillia & Undulipodium

Structure

  • 9+2 structure - 9 pairs of microtubules around periphery and one pair in the centre
  • Longer and normally one per cell
  • Smaller and lots of them covering speific surface of cell. No larger than 10micrometres

Function 

  • Move fluid outside the cell
  • Move the whole cell.
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Cytoskeleton

Structure

  • Microtubules cylinders (c. 25nm diameter);
  • Made of tubulin

Function

  • Supports cell structure
  • Movement of organelles (comme vesicles) inside the cell using microtubule motors and ATP
  • Movement of an mcroorganism through a liquid or waft liquid past cell.

+ Fun Fact - Undulipodium contain microtubules

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Cell Wall

Structure

  • Made of cellulose fibres 
    • Primary layer: Random arrangement
    • Secondary layer: Fibres are parallel to one another then next layers are perpendicular to the previous layer.

Function

  • Withstand water/turgor pressure (donc stop the cell from bursting because of the permanent vacuole)
  • Support whole plant structure.
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Vacuoles

Structure

  • Surrounded by tonoplast (membrane)
  • Filled with water and solutes

Function

  • Large cell vacuoles maintain cell stability.
  • Pushes cytoplasm against cell wall making it turgid. Opposing pressures.
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