MICROSCOPE IN CELL STUDIES, Eukaryotic Cell structures, Role of ATP, Prokaryotic cells, Viruses.
This is an extensive summary with the information needed with the syllabus 9700 of CIE As Level biology. This got me an A in my exam for paper 1 and paper 2.
CHAPTER 1: CELL STRUCTURE
MICROSCOPE IN CELL STUDIES
Magnification calculations:
- Magnification is how many times bigger the image is observed than the
actual.
magnification = image / actual
Eyepiece Graticules & Stage micrometres:
- Eyepiece graticule and stage micrometre used to measure size of the object.
- Stage micrometres are in micrometres and it is usually 1omicrometres
divisions.
- Eyepiece graticule has 100 divisions with no scale.
Magnification:
- How many times bigger the image of a specimen observed is in comparison
to the actual size of the specimen.
- To calculate you multiply the eyepiece lens magnification and the objective
lens magnification
Resolution:
- Ability to distinguish between two separate points. Limited by the wavelength
of light.
- Longer the wavelength of light, the more the light is diffracted.
- Electron microscopes have higher resolution and magnification as electrons
have smaller wavelengths than visible light.
Light microscopes:
- Used for specimens above 200 nm
- Specimens can be living or dead, used to look at whole cells, organisms,
tissues.
, Electron microscopes:
- Used for specimens above 0.5 nm
- Fire a beam of electrons, the electrons are picked by electromagnetic lensa
which shows the image.
- Due to higher frequency of electron waves the magnification and resolution
are better.
- Transmission electron: specimen covered in resin, thin slices made stained
with heavy metals.
- Scanning electron: specimens coated with a thin layer of metal, electrons
reflected making a 3D image.
Eukaryotic Cell structures:
Cell surface membrane:
- All cells are surrounded by a cell surface membrane which controls the
exchange of materials between the internal cell environment and the external
environment.
- Membrane is described as partially permeable
- Cell membrane is formed from a phospholipid bilayer of phospholipids
spanning a diameter of around 10 nm
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