2.1 eukaryotic cells Flashcards
what is the difference between magnification and resolution
magnification is a measure of how much bigger the image is in comparison to the real object, whilst resolution is a measure of how close two objects can be together before we can see them as one
what is the magnification and resolution of:
- a light microscope
- an electron microscope
light
-mag: 1500X, res: 200 nano meters
electron
-mag: 500 000, res: 0.1-1 nano meter
why do people stain things before viewing them under the microscope
-it is used particular types, or different parts of the cell under the microscope, the cell absorbs this stain and enhances the visualisation
name 3 advantages and two disadvantages of using a light microscope
ADVANTAGES
-can see living plants and animals and their parts directly, so you can compare slides with living tissue
-relatively cheap, which makes them more available for schools and universities ect.
-they’re light and portable so can be used anywhere
DISADVANTAGES
-limited resolution and magnification
-preservation and staining tissue can produce artefacts in the tissue being observed which will affect the image
how does an electron microscope work
the electrons form an image by being scattered by the specimen. The electromagnetic or electrostatic lenses focus the electron beam to form an image.
what are the conditions needed for an electron microscope to work
- the specimen must be in a vacuum
- could involve chemical preservation, freeze drying, dehydration etc.
- stained using heavy metal ions
why are specimens going under an electron microscope stained with heavy metal ions
to improve the scattering of the electrons to make greater contrast in the image, ultimately making it easier to interpret
name and explain the two types of electron micrographs
transmission electron micrographs, 2D images
scanning electron micrographs, lower magnification but 3D
give an advantage and four disadvantages of using an electron microscope
ADVANTAGE
-huge powers of magnification and resolution, can see cell structure and tissues in much more detail
DISADVANTAGE
-all specimens are examined in a vacuum
-specimens undergo severe preparation treatment which is likely to result in artefacts
-extremely expensive
-large, and must be kept at constant temperature and pressure
what is the job if the cell surface membrane
to control what goes in and out of the cell
describe the structure of the phospholipid bilayer
the phospholipids in the membrane form a bilayer or a unit membrane. The lipids are polar lipids and phospholipids
with water on each side
hydrophilic heads pointing towards the water, shielding their hydrophobic tails
what are the two main function of the membrane proteins
- they move channels across the membrane, form pores that allow specific molecules to move through that open and shut based on the conditions of the cell (gated channels)
- they can act as receptor molecules, making cells sensitive to a particular hormone e.g enzymes
what is the function of membranes of the cell and membranes in the cell
They control the movement of substances
localise enzyme reaction pathways
whats the name of cytoplasm + nucleus
protoplasm
describe the nucleus and its function
surrounded by a nuclear membrane and contains nuclear pores, the nuclear envelope. so chemicals can pass in and out which allows the nucleus to control the events in the cytoplasm