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24 Cards in this Set

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The electron microscope 3.
Ü The limitation of the electron microscope is the fact that in preparing tissues fro use in an electron microscope the cells are preserved (dead); cell function therefore cannot be observed.
The electron microscope
Ü The electron microscope uses a beam of electrons, rather than light, to magnify x25,000 (scanning electron microscope) or greater than x100,000 (transmitted electron microscope).
Describe the cell membrane
Ü The hydrochloric ends of the phospholipid face into the cytoplasm and outwards into the extra cellular fluid (watery fluid). The hydrophobic ends face each other in the center of the membrane.
Diffusion
Ü Diffusion is the general term that refers to the spreading out of particles.
Ü Particles of gases diffuse easily and move randomly to arrange themselves equally within the limits of the space they occupy.
A comparison between diffusion and osmosis 2.
Ü Osmosis differs from diffusion as osmosis is the diffusion (passive movement) of water, and diffusion is the passive movement of substances other than water.
Ü Osmosis involves a semi-permeable membrane and diffusion does not necessarily involve a membrane.
Surface area 1.
Ü The surface area of the cell is the outside area of the cell.
The cell theory states that:
Ü All living organisms are composed of cells.
Ü All cells are produced from pre-existing cells.
Ü The cell is a unit of structure.
Ü The cell is a unit of function.
Ü The cell is a unit of differentiation.
Ü The cell is a unit of reproduction.
There is movement of molecules into and out of cells
Ü Membranes move cells provided separation from and link the cell to the external environment.
The light microscope
Ü Developments in the light microscope have allowed living cells and organelles to be observed.
The current model of membrane structure and how it accounts for the movement of some substances into and out of cells 3.
Ü A semi-permeable membrane is a membrane that will let through water (the solvent) but stops any dissolved particles (the solute), which are too big from passing through.
The light microscope 3.
Ü Special staining techniques, where parts of the cell or cell organelles are coloured, can be used to improve cell examination with the light microscope.
What is osmosis?
Ü Osmosis is the flow of water through a semi-permeable membrane.
Ü Water will move from a weak solution (low concentration of solute, lots of water) to a strong solution (high concentration of solute, less water).
The current model of membrane structure and how it accounts for the movement of some substances into and out of cells 4.
Ü The cell membranes of the roots and root hairs, for example, are semi-permeable.
The current model of membrane structure and how it accounts for the movement of some substances into and out of cells 2.
Ü Cell membranes have tiny pores (holes) that vary in size. The sizes of the pores changes permeability of the membranes.
The light microscope 2.
Ü The light microscope can magnify x50, x100, x400, or even x1000 (with an oil immersion lens)
The electron microscope 2.
Ü A beam of electrons allows biologists to resolve much smaller shapes and patterns and therefore see the detail of structure within the cell (cellular organelles). Things within the cell are referred to as intracellular.
Surface area 6.
Ü That is, surface area divided by volume or as a ratio (SA:V).
A comparison between diffusion and osmosis 1.
Ü Diffusion and osmosis are both examples of passive transport processes that occur with a concentration gradient. (Particles tend to move from where there are many to where there are few particles.)
Surface area 2.
Ü The volume of the cell is the inside capacity or amount of substance or space inside the cell or organism
The current model of membrane structure and how it accounts for the movement of some substances into and out of cells
Ü The current model of membrane structure shows us that cell membranes are selective permeable or semi-permeable.
Surface area 5.
Ü The relationship between surface area and volume can be expressed as a fraction:

Surface area SA
Volume V
Surface area 3.
Ü The volume of the cell determines its metabolic needs and waste products.
Surface area 4.
Ü The function of the cell surface is to control the rate of removal of wastes and absorption of nutrients.
The light microscope 4.
Ü At light microscope level you can see only the structures indicated in the diagrams below.