Cell Organelles: their function+appearance



  • Contains DNA: acts a template for RNA
  • Controls all cellular activities
  • During cell divison: DNA condenses=chromosomes
  • No during cell division: DNA spread loosely= chromatin
  • Nucleolous= construction of ribosomes
  • Nuclear pores allow ribosomes to reach cytoplasm

Image result for nucleus diagram a level

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Rough Endoplasmic Reticulum (RER)

  • 1) Ribosomes in RER: make proteins to be transported+seceted
  • 2) These proteins enter lumen of RER: combine with carbs
  • 3) Transported to Golgi for further processing
  • Cells that produce a lot of proteins (pancreas) have more RER. 

Image result for rough endoplasmic reticulum a level

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Smooth Endoplasmic Reticulum (SER)

  • Continuoes from RER but has not ribosomes.
  • SER makes lipids=phospholipids for membranes= more SER in cells that produce a lot of lipids: liver cells
  • SER contains enzymes to detoxify toxic products of metabolism.

Image result for smooth endoplasmic reticulum diagram a level

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Golgi Apparatus

  • Golgi= series of interconnected cisternae
  • Function=modify proteins+lipids= prepare them for secretion
  • 1) Vesicles from RER join the apparatus at the cis face
  • 2) Vesicles are modified, then passed to trans network
  • 3) Vesicles made in trans network leave golgi via trans face
  • 4) Vesicles move to cell membrane=fuse with it= releasing contents

Image result for golgi apparatus diagram a level

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  • Function: manufacture proteins
  • Consists of two types of molecule: rRNA+protein
  • Two subunits come together by attaching to mRNA before protein synthesis begins
  • 80s ribosomes=eukaryotes
  • 70s ribosomes-prokaryotes

Image result for ribosome diagram a level

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  • Function:absorb light energy for photosynthesis
  • Cholorophyll pigments for absorbing light= in thylakoid
  • Space between grana= thick fluid= stroma
  • Stages of photosnythesis take place in the stroma and grana

Image result for chloroplast diagram a level (http://ib.bioninja.com.au/_Media/chloroplast-functions_med.jpeg)

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  • Function: digest cellular material
  • Contains 40 to 50 varities of enzymes
  • Enzymes used to break down carbs, proteins, lipids
  • Enzymes escape=little damage: cytoplasm has neutral pH, enzymes work best at an acidic pH

Image result for lysosome diagram a level

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Centrioles: constructed of microtubules arranged in 9 triplets forming a cylinder.

Microtubules: small tubular structue in the cytoplasm composed of tubulin (protein) that is arranged in spindles.

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  • structure composed of microtubules found on surface of cells
  • Moves to create currents, propels cell along

Cilia:Same structure as flagella but are shorter (only difference)

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  • Function: carry out aerobic respiration
  • Most numerous in very active cells (muscle, nerve).
  • Double membrane: inner membrane, folded into series of cristae
  • Have their own DNA+possess 70s ribosomes=evidence that mitochondria may have evolved from prokaryotic organisms

Image result for mitochondria diagram

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Cell wall

  • Cell walls of plants+algae=made of cellulose
  • Cell walls of fungi+made of chitin
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Organelles working together:production+secretion o

1) Nucleolus manufactures ribosomes for protein synthesis in RER.

2) Nucleus manufactures mRNA=needed by ribosomes for making proteins.

3) Ribosomes in RER make proteins.

4) RER processes proteins which are then sent to Golgi body in vesicles.

5) Golgi body further processes proteins and sends them to plasma membrane in vesicles.

6) Vesicles fuse with plasma membrane to secrete finished protein product.

Related image (http://1.bp.blogspot.com/-zfZpIndhYUw/Ui-D7SkNYUI/AAAAAAAAABM/NauJKc_cAiU/s640/543439_595120710529744_12682743_n.jpg)

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Difference between Prokaryotic and Eukaryotic cell

Feature                  Eukaryotic                    Prokaryotic

Nucleus                 present                         absent

DNA                      In nucleus                     free in cytoplasm

Cell wall                cellulose or chitin         murein

Membrane-bound   present                       absent


Ribosomes           large (80S)                   small (70S)

Capsule               absent                           present

Pili                       absent                          sometimes present

Size                    larger (2-200um)          smaller (less than 2um)

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