Microscopy and Cells Flashcards
Advantages of light microscope
- can see parts of living plants/animals directly - allows you to compare slides with living tissue
- relatively cheap so available
- quite light and portable so can be used in the FIELD
Disadvantages of light microscope
- preservation and staining tissue can make artefacts so it may not be a true representation
- limited powers of resolution and magnification
Why are TEM samples stained with heavy metal ions?
To improve scattering of electrons and make greater contrast in image.
TEM and SEM difference in picture?
TEM have 2D, SEM have 3D
Advantages of electron microscope
- huge powers of magnification and resolution, showing many details of cell structure
Disadvantages of electron microscope
- Impossible to look at living material as specimens examined in vacuum, as air would scatter electrons,
- Specimens undergo severe treatment likely to result in artefacts.
- Hard to prepare specimens
- Very expensive
- Large, have to be kept at constant temp and pressure and need to maintain an internal vacuum.
What does the cell membrane generally do? (4)
- controls what passes into and out of the cell
- allowing the fluids either side of it to have different compositions
- flexible to allow cell to change shape slightly
- secretions are packed into vesicles, so some must be able to break and fuse together
What type of lipids are found in the cell membrane? Explain.
Polar lipids, mainly phospholipids. Lipids with phosphate group. With water or aqueous solutions on each side, the molecules forma bilayer with hydrophilic heads pointing into water while hydrophobic tails stay protected int he middle.
What are polar lipids and where are they found?
Lipid molecules with one end joined to a polar group
What happens in SER? (2)
Lipids and carbs made
Properties of molecules that enable them to enter cell by diffusion (3)
Small, lipid-soluble, non-polar
What are the different epithelial tissues?
Squamous epithelium, cuboidal, columnar, ciliated, glandular, compound stratified.
Where is squamous epithelium found?
Lining surfaces of blood vessels, forms walls of capillaries, and forms lining of alveoli.
Where are cuboidal and columnar found?
Lining many other tubes
What do ciliated epithelia have and where are they found?
Goblet cells that produce mucus.
Form surfaces of tubes in gas exchange system and oviducts.
