Cell structure: Summary notes

Summary notes on cell structure

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  • Created on: 17-10-15 14:26
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Chapter 1
Cell Structure ­ Summary Notes
Microscopes
Light microscopes:
Glass lenses refract light produce magnified image
Must have thin
and transparent specimens
Specimens must be stained structures visible
Resolution = 200nm
Magnification = image size / object size
mm (÷1000) m (÷1000) nm
Resolution ­ degree of detail that can be seen in an image
Electron microscope:
Beam of electrons instead of light
Transmission electron (TEM) or s canning electron (SEM)
TEM:
Passes electrons through thin specimen
Specimen ­ stained with heavy metals (e.g. lead)
Ions of metals taken up more by certain parts of cell
Structures with more stain = darker
SEM:
Bounce electron beams o ff surface of object
3D image
Can be magnified almost as much as TEM
Greyscale
Cell structure
Ultrastructure ­ inner structure of cell seen with electron microscope
Organelles ­ structures within cell
Nucleus:
Usually largest organelle
Surrounded by 2 membranes ­ nuclear envelope with nuclear pores
Contains chromosomes ­ long molecules of DNA ­ tangles of c hromatin in
nondividing cells
DNA ­ carries instructions for protein synthesis
Nucleolus ­ contains DNA to make ribosomes
Endoplasmic reticulum (ER):
Rough ER ­ ribosomes attached
Smooth ER ­ no ribosomes
Cisternae ­ enclosed spaces formed by membranes , isolated from cytoplasm
RER:
Protein synthesis on ribosomes
Protein molecules c ollect in cisternae before transport
SER:
Different roles in different cells

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Chapter 1
E.g.…read more

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Chapter 1
Cilia/flagella:
Long, thin extensions from cell surface
Some animal cells, rarely plant cells
Cilia ­ shorter, large numbers
Flagella ­ longer, one or two
Contain microtubules in 9+2 arrangement
Move by microtubules sliding against each other
Cilia ­ move fluids over cell surface
Flagella ­ make cell swim through liquid
Cytoskeleton:
Network of microfilaments (protein filaments) and microtubules
Support cell and determine s hape
Provide tracks along which o rganelles are moved
Microtubules act as motors ­ use energy from ATP to pull…read more

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