Cell Structure & Organisation


Nucleus & Mitochondria

  • control the cells activities and retain the chromosomes
  • most prominant feature in the cell
  • bound by double membrane called nuclear membrane/envelope
  • outer membrane is continuous with endoplasmic reticulum
  • pores allow passage of large molecules out of nucleus
  • granular nucleoplasm contains genetic material chromatin- coils of DNA bound to protein
  • nucleolus manufactures RNA to make ribosomes


  • sites of aerobic respiration, produces energy carrier molecule ATP
  • double membrane separated by fluid filled intermembrane space
  • inner membrane folded inwards forming cristae
  • organic matrix contains chemical compounds including DNA to control its own protein production
  • cristae provide large surface area
  • muscle cells have large numbers of mitochondria
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Endoplasmic Reticulum

  • elaborate system of parallel double membranes forming flattened sacs
  • fluid spaces inbetween are cisternae
  • connected to nuclear membrane
  • interconnection allows for transport of materials throughout cell

rough ER

  • ribosomes on outer surface
  • transports proteins made by the ribosomes
  • present in cells that make enzymes

smooth ER

  • membranes lack ribosomes
  • syntheisises and transports lipids

liver cells and secretory cells have many ER

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Ribosomes & Centrioles

  • found in both prokaryote and eukaryote cells
  • smaller in prokaryotes
  • occur singly in the cytoplasm or associated with rough ER
  • one large and one small sub unit
  • manufactured in the nucleus from ribosomal RNA and protein
  • synthesise proteins


  • found in all animal cells and most protoctists
  • located just outside nucleus in the centrosome
  • hollow cylinders at right angles to eachother
  • centrioles divide during cell division
  • syntheisise microtubules of a spindle
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Golgi Body & Lysosomes

  • compacter version of the ER
  • formed by rough ER being pinched into vesicles which fuse into the golgi body
  • proteins in the vesicles can then be modified and packaged 
  • golgi body can be pinched off into vesicles again and the products secreted 
  • other functions are: producing secretory enzymes, secreting carbs, producing glycoprotein, transporting and storing lipids, forming lysosomes.


  • small vacuoles formed when vesicles are pinched off the golgi body
  • contain and isolate potentially harmful digestive enzymes
  • can also release these to destroy old organelles
  • lysosomes discharge their contents into vacuoles
  • can also digest material brought into the cell
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Organelle Interrelation

  • functions of organelles within the cell are often linked
    • ribosomes produced in nucleolus take up position on the rough ER
    • pores in nuclear membrane allow mRNA molecules to leave nucleus and attach to ribosomes on rough ER
    • protein synthesis occurs on the ribosomes making proteins in primary form
    • these polypeptides are then modified in the golgi apparatus into their tertiary structure
    • these enzymes are packaged into secretory vesicles and transported to the membrane to be secreted
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Chloroplasts & Vacuole

  • chloroplasts are found in the cells of photosynthesising tissue
  • surrounded by double membrane
  • stroma- fluid filled with ribosomes, lipid, circular DNA and starch grains
  • thylakoids- flattened sacs stacked to form granum
  • chlorophyll is found in the thylakoids
  • the arrangement provides a large surface area for trapping light


  • in plants this is large and permanent
  • fluid filled sac with a single membrane called he tonoplast
  • storage site made of cell sap to store chemicals e.g glucose
  • provides an osmotic system to support young tissues
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Cellulose Cell Wall

  • consists of cellulose microfbrils embedded in a polysaccaride matrix
    • fully permeable to water and substances in solution
    • cell wall can withstand the vacuole pushing against it, reaching a state of turgor
    • cellulose microfibrils are very strong providing mechanical strength
    • cells can connect through pores where plasmodesmata can pass, enabling exchange of materials
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Differences Between Plant & Animal Cells

Plant     Animal

  • cell wall surrounds membrane 
    • no cell wall, membrane only
  • chloroplasts present
    • no chloroplasts
  • single large permanent central vacuole filled with cell sap
    • small temporary scattered vacuoles
  • no centrioles
    • centrioles
  • plasmodesmata
    • no plasmodesmata
  • starch grains used for storage 
    • glycogen granules used for storage
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Differentiation & Specialisation

  • single celled organisms carry all life functions out within a single cell
  • multicellular organisms need specialised cells to carry out particular functions
  • each cell becomes specialised in structure to suit its role
  • some cells remain undiffereniated as 'packing' cells
  • other cells can differentiate in a number of ways:
    • shape- nerve cells elongate
    • numbers of organelles- cells carrying out photosynthesis need more chloroplasts
    • contents of cell- red blood cells are packed with haemoglobin
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  • Cells that differentiate in the same way
  • a collection of specialised cells of the same type working together to carry out a particular function


  • a part of the body that carries out a structural and functional unit made from more than one tissue


  • a collection of organs that carry out a particular function


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  • Cells that differentiate in the same way
  • a collection of specialised cells of the same type working together to carry out a particular function


  • a part of the body that carries out a structural and functional unit made from more than one tissue


  • a collection of organs that carry out a particular function


  • all of the systems of the body working together
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Differences Between Prokaryote & Eukaryote Cells

Prokaryote    Eukaryote

  • found in bacteria and blue/green algae
    • found in plants, animals, fungi and protoctists
  • no membrane bound organelles
    • membrane bound organelles
  • ribosomes are smaller
    • ribosomes are larger
  • DNA lies free in cytoplasm
    • DNA located on chromosomes
  • no nuclear membrane or ER
    • distinct membrane bound nucleus
  • cell wall containing murein
    • cell wall in plants of cellulose
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  • unusual life form
  • extremel small
  • 'non cells'- no cytoplasm, organelles or chromosomes
  • outside a living cell they are a virion
  • when inside a host they take over the cells metabolism and multipy within it
  • each virus particle has a core of nucleic acid surrounded by a capsid protein coat
  • most viruses are found in animal cells
  • those attacking bacteria have DNA
  • animal and pant viruses have RNA
  • they cause a variety of diseases
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