ESSENTIAL CELL BIOLOGY EXAM
QUESTIONS WITH VERIFIED ANSWERS
Events in evolution of eukaryotes from prokaryotes: - ANSWER-Eukaryotes cells may
have originated as predators
Eukaryotic cells may have formed when ancient archaeal cell engulfed an ancient
bacterium
Phagocytosis
Modern eukaryotic cells evolved from a symbiosis
Eukaryotes - ANSWER-DNA im membrane bounded nucleus
Ex: plants, animals, fungi
Mostly multicellular
More complex, bigger genomes
Elaborate cytoskeleton
Have mitochondria
Prokaryotes: - ANSWER-DNA in no distinct nuclear compartment
Ex: Archaea. Bacteria
Small and simple in outward appearance
Live mostly as independents or in loosely organized communities
Not in multicellular organisms
Far more varied than eukaryotes
Usually have cell wall
Carry very little, so are smaller
Major factor affecting quality of microscope image: - ANSWER-Resolution
Amphiphilic molecule - ANSWER-Hydrophobic (water hating) and hydrophilic (water
loving) on the same molecule
Why important?
For phospholipid bilayers
Helps form plasma membrane
Keeps water enclosed
Basic preparation for microscopy: - ANSWER-1. Fixation
Chemical:
Glutaraldehyde
Formaldehyde
Osmium tetraoxide
Cryo:
Freeze fast, then fix
2. Dehydration:
Chemical substitution
, Compatible with embedding media
3. Embedding:
Plastic, wax
4. Solid block is readily sectioned with a microtome
5. Section is placed on a slide
6. Stain
Why fix? - ANSWER-To preserve the cells within the tissue they must be treated with a
fixative
Why embed - ANSWER-They are usually soft or fragile after fixation so need to be
embedded or frozen before being sectioned
Fixed tissue is hardened
Why stain? - ANSWER-There is little in contents of most cells to impede the passage of
light rays
Almost invisible in an ordinary light microscope
Stain dyes have certain affinity for charged molecules and will show up
Resolution: - ANSWER-Minimum distance between 2 objects where they can be
distinguished as separate entities
Resolution of each type of microscope: - ANSWER-Light microscope:
0.2 um
Electron microscope:
0.002 nm
1,000 times that of light microscope
0.05nm
1 nm
Main tenets of cell theory - ANSWER-All living cells organisms are composed of one or
more cells
Cell is the basic unit of structure and organization in organisms
Cells arise from existing cells
Two general groups of prokaryotes: - ANSWER-Bacteria
Archaea
Model organisms: - ANSWER-1.) Yeast
2.) Arabidopsis
3.) Caenorhabditis elegans (worm)
4.) Drosophila (fly)
5.) Frog
6.) Zebrafish
7.) Mouse
8.) Humans
QUESTIONS WITH VERIFIED ANSWERS
Events in evolution of eukaryotes from prokaryotes: - ANSWER-Eukaryotes cells may
have originated as predators
Eukaryotic cells may have formed when ancient archaeal cell engulfed an ancient
bacterium
Phagocytosis
Modern eukaryotic cells evolved from a symbiosis
Eukaryotes - ANSWER-DNA im membrane bounded nucleus
Ex: plants, animals, fungi
Mostly multicellular
More complex, bigger genomes
Elaborate cytoskeleton
Have mitochondria
Prokaryotes: - ANSWER-DNA in no distinct nuclear compartment
Ex: Archaea. Bacteria
Small and simple in outward appearance
Live mostly as independents or in loosely organized communities
Not in multicellular organisms
Far more varied than eukaryotes
Usually have cell wall
Carry very little, so are smaller
Major factor affecting quality of microscope image: - ANSWER-Resolution
Amphiphilic molecule - ANSWER-Hydrophobic (water hating) and hydrophilic (water
loving) on the same molecule
Why important?
For phospholipid bilayers
Helps form plasma membrane
Keeps water enclosed
Basic preparation for microscopy: - ANSWER-1. Fixation
Chemical:
Glutaraldehyde
Formaldehyde
Osmium tetraoxide
Cryo:
Freeze fast, then fix
2. Dehydration:
Chemical substitution
, Compatible with embedding media
3. Embedding:
Plastic, wax
4. Solid block is readily sectioned with a microtome
5. Section is placed on a slide
6. Stain
Why fix? - ANSWER-To preserve the cells within the tissue they must be treated with a
fixative
Why embed - ANSWER-They are usually soft or fragile after fixation so need to be
embedded or frozen before being sectioned
Fixed tissue is hardened
Why stain? - ANSWER-There is little in contents of most cells to impede the passage of
light rays
Almost invisible in an ordinary light microscope
Stain dyes have certain affinity for charged molecules and will show up
Resolution: - ANSWER-Minimum distance between 2 objects where they can be
distinguished as separate entities
Resolution of each type of microscope: - ANSWER-Light microscope:
0.2 um
Electron microscope:
0.002 nm
1,000 times that of light microscope
0.05nm
1 nm
Main tenets of cell theory - ANSWER-All living cells organisms are composed of one or
more cells
Cell is the basic unit of structure and organization in organisms
Cells arise from existing cells
Two general groups of prokaryotes: - ANSWER-Bacteria
Archaea
Model organisms: - ANSWER-1.) Yeast
2.) Arabidopsis
3.) Caenorhabditis elegans (worm)
4.) Drosophila (fly)
5.) Frog
6.) Zebrafish
7.) Mouse
8.) Humans
