2.1 CELL STRUCTURE Flashcards
what is magnification?
the number of times larger an image appears, compared with the size of the object
what is resolution?
the clarity of an image; the higher the resolution, the clearer the image
what are some key feature of optical microscopes?
Relatively cheap and easy to use, portable and can study whole living specimens, use visible light that has a wavelength of between 400 and 700 nm
what are some key feature of laser scanning microscopes?
Uses laser beams to scan something which is usually tagged with fluorescent dye
The laser causes the dye to give off light, the light is focused through a pinhole onto a detector which is connected to a computer, generating an image (3D)
what are some key feature of Transmission electron microscopes?
Use electromagnets to focus a beam of electrons which is transmitted through the specimen
Denser parts absorb more electrons so they look darker
They can only be used on thin specimens which have been chemically fixed ((dehydrated and stained))
2D image produced
what are some key feature of Scanning electron microscopes?
Scans a beam of electrons across the specimen
This knocks off electrons from the specimen which are gathered in a cathode ray tube to form an image, it shows the surface but they are lower resolution
what is the maximum resolution for an optical, Transmission electron and scanning electron microscope?
- 2 um
- 0002um
- 002 um
what stains are used for light and electron microscopes?
For Light Microscopes a dye is used like methylene blue or eosin, it is taken up by some parts high contrasts the different structures (multiple stains can be used at once)
For Electron Microscopes objects are dipped in heavy metals (like lead, the metal ions scatter the electrons creating a contrast as some show up darker
what is a cytoplasm?
contains a network of protein threads running through it
what are the four functions of the cytoskeleton?
- The microtubules and micro filaments support the organelles keep them in position
- They help to strengthen the cell and maintain its shape
- They’re responsible for movement of materials within the cell
- The proteins of the cytoskeleton can also cause the cell to move (whole cell)
what is the plasma membrane?
The membrane found on the surface of animal cells and just inside the cell wall of plant cells and prokaryotic cells. It’s made of many lipids and proteins
what is the function of the plasma membrane?
Regulates the movement of substances into and out of the cell. It also has receptor molecules on it, which allow it to respond to chemicals like hormones
what is the cell wall?
A rigid structure that surrounds plant cells. It is made mainly of the carbohydrate cellulose
what is the nucleus?
A large organelle surrounded by a nuclear envelope which contains many pores. The nucleus contains chromatin(which is made from DNA and proteins) and a structure called the nucleolus
what if the function of the nucleus?
The nucleus controls the cells activities (by controlling the transcription of DNA) DNA contains instructions to make proteins. The pores allow substances to move between the nucleus and the cytoplasm. The nucleolus makes ribosomes