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Infection and response
Organisation
Cell biology
Biological molecules
Homeostasis and response
Responding to change (a2 only)
Energy transfers (a2 only)
The control of gene expression (a-level only)
Substance exchange
Bioenergetics
Genetic information & variation
Inheritance, variation and evolution
Genetics & ecosystems (a2 only)
Ecology
Cells
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1f industrialisation and the people: britain, c1783-1885
1c the tudors: england, 1485-1603
Britain & the wider world: 1745 -1901
Inter-war germany
World war one
2n revolution and dictatorship: russia, 1917-1953
World war two & the holocaust
1l the quest for political stability: germany, 1871-1991
The cold war
2j america: a nation divided, c1845-1877
Medieval period: 1066 -1509
The fight for female suffrage
2m wars and welfare: britain in transition, 1906-1957
2d religious conflict and the church in england, c1529-c1570
Britain: 1509 -1745
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25/10/2023
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And most scientists would agree that anything that is not made of a cell or cells -for example, a virus- cannot be a living organism. MICROSCOPES KEY DEFINITIONS electron micrograph: photograph of an image seen using an electron microscope magnification : how much bigger the image is than the specimen (the sample you're looking at). Resolution: It is how detailed the image is. The ability to distinguishes between two points that are close together. The higher the resolution, the clear the image • organelles : small structures within the cells, each of which has a specific function. • Photomicrograph: photograph of an image seen using an optical microscope. • artefacts : False images created by the staining process or the conditions. inside the electron microscope. It can be a variety of things such as: - dust -air bubbls. O 。 O CELL STRUCTURE, • Cells are the basic units of living things O All living organisms are made of cells -fingerprints OPTICAL (LIGHT) MICROSCOPES Relatively cheap Easy to use. Portable and able to be used in the field as well as laboratories. Able to be used to study whole living specimens. Uses light to form an image Poor resolution due to the long wavelength of light • Living_samples can be examined and a colour 。 0 O O O O rage is obtained LASER SCANNING CONFOCAL MICROSCOPES O • A special type of light microscope that use laser beams...
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to scan a specimen that 's usually tagged with fluorescent dyes. • When the laser hits the dyes it causes them to give off fluorescent light. These microscopes can be used to look at different depths in thick Specimens. O It can be used to observe whole living specimens, as well as cells. The images are high resolution and show high contrast. Multiple images produced by the microscope can be combined by the computer to generate 3D images of a specimen. O 9 TYPES OF ELECTRON MICROSCOPES There are two types: TRANSMISSION ELECTRON MICROSCOPE (TEM) 。 O • Use electromagnets to focus a beam of electrons, which is then transmitted through the specimen to produce 20 images. Denser parts of the specimen absorb more electrons, which makes them look darker on the electron micrograph. 。 。 •The electrons form a 2D black-and-white image • The specimen has to be chemically fixed by being dehydrated and stained. • The specimens to be viewed need to be very thin, and stained with heavy metals. High magnification and resolution SCANNING ELECTRON MICROSCOPES (SEM) • High resolution and 3D imaging SEMS scan a beam of electrons across the specimen O Electrons bounce off the surface of the specimen to create an n image. The images produced show the surface of the specimen and can be 3D but they give lower resolution images than TEMS.. The images are black and white. 0 · O ELECTRON MICROSCOPE Advantages ♥ Electron microscopes can have a 2000x better resolution. than light microscope. • Higher magnification D than light microscopes. Disadvantages • The interior of an election. microscope is a vocuum. We cannot view living specimens... Electron microscopy requires very. careful staining and the specimen. often has to be very thin. Electron microscopy can lead to artefacts (false images). Large, not portable and very expensive Specimens, even whole ones for use in SEMS, have to be dead, as they are viewed while in a vacuum. The metallic salt stains. used for staining specimens may be potentially hazardous to the user.