Cells and Miocroscopy - B1

  • Created by: mevan
  • Created on: 23-05-21 16:14

The Structure of a Cell

an organism is a living thing. unicellular organisms are made of only one cell, where multicellular organisms are made of many cells.

  • nucleus - controls the activities of a cell and contains DNA
  • cytoplasm - site of most chemical reactions
  • cell membrane - controls the movement of substances in and out of a cell
  • mitochondria - where energy is released in respiration (the site of respiration)
  • ribosomes - site of protein synthesis
  • cell wall - strengthens the cell
  • chloroplasts - absorbs light to make food in photosynthesis
  • vacuole - a store of cell sap

in eukaryotic cells, the DNA is inside a nucleus

in prokaryotic cells, the DNA is not inside a nucleus, and instead, there is a single loop of DNA. there may also be plasmids, which are rings of DNA.

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Specialised Animal Cells

each specialised cell has adaptations, which are features that enable the cell to perform a particular job.

  • sperm cell - 
    • streamlined shape and tail allows it to swim
    • many mitochondria release a lot of energy for respiration
  • nerve cell / neurone - 
    • long body allows info to be passed for long distances
    • branches allow info to be passed to many cells at a time
  • muscle cell - 
    • many mitochondria release energy through respiration very quickly 
    • filaments allow contraction and relaxation
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Specialised Plant Cells

each specialised cell has adaptations, which are features that enable the cell to perform a particular job.

  • root hair cells
    • hair like projection increases surface area which leads to faster absorption 
    • many mitochondria releases energy for transport of water and mineral ions
  • xylem - 
    • lignin strengthens the walls, and is waterproof to prevent leaks
    • hollow tube allows water to travel through without nucleus or vacuole in the way
  • phloem - 
    • tubes formed from living cells joined end to end
    • pores allow sugar to move through in either direction
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Differentiation and Stem Cells

as an organism develops, cells differentiate and their structures change to enable them to carry out different functions. they become specialised.

  • in animals, most cells differentiate at a very early stage in development
  • in plants, cells can differentiate throughout the life of the plant

some cells do not differentiate and remain unspecialised. these cells are called stem cells. a stem cell has the possibility to differentiate into any type of cell, or to reproduce to form new stem cells.

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Light and Electron Microscopes

light microscope:

  • low magnification
  • low resolution
  • readily available and cheaper
  • cannot see some organisms or microorganisms

electron microscope:

  • high magnification
  • high resolution
  • expensive
  • enables cells to be studied in more detail 
  • allows bacteria and subcellular structures to be seen
  • has improved the scientific understanding of cells because of this
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Magnification Calculations

image size = magnification * real size

micrometres are 1000* bigger than nanometres

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