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.
Where is compound epithelium found and what’s its purpose?
Found where surface is continually scratched and abraded, eg skin.
Thickness of tissue protects cells underneath that are growing.
Name some types of tissue that aren’t epithelial
Muscle tissue, nervous, collagen, elastin, glandular
What is connective tissue, and what types does it include?
Main supporting tissue.
Bone tissue, cartilage tissue, packing tissue.
How can a capsule or slime layer make it more dangerous?
Because it protects the bacterium from phagocytosis, and covers cell markers on the cell membrane that identify the cell, so immune system doesn’t recognise.
What is the bacterial cell wall made of?
Peptidoglycan
What components do bacteria have?
Glycogen granules, cell surface membrane, 70S ribosomes, cell wall, nucleoid. Some have flagellum, capsule/slime layer, photosynthetic membranes, plasmids.
How can pili make the bacteria more vulnerable?
Bacteriophage can use them as an entry point.
What do pilli do?
Help attachment to host cell, and helps sexual reproduction.
What’s in a bacteria cell membrane that isn’t in a eukaryotic one?
Respiratory enzymes
How can plasmids be transferred to other bacteria?
Pilli
What is the structure of the nucleoid?
Single length of DNA folded and coiled.
What are different ways antibiotics work against bacteria?
- Some inhibit formation of peptidoglycan layer of cell wall - effective against gram positive
- Some interact with phospholipids of outer membrane, good for gram negative
- Some target prokaryote ribosomes etc
What are the bacterial types by shape (4) ?
Sphere - cocci
rod - bacilli
twisted -spirilla
comma - vibrios
What are the bacterial types by respiratory requirements?
Obligate areobes need oxygen.
Facultative anaerables use when availabe
Obligate anaerobes can’t have oxygen.
