MBLS - 101
CELL BIOLOGY MIDTERM QUESTIONS
CH-1
1. Endoplasmic reticulum is not part of a prokaryotic cell.
1.1 Cell theory
1.2.b Contrast light microscopy, super-resolution fluorescence light microscopy, and electron
microscopy in terms of the cell components that can generally be distinguished using each.
- Light microscopy: It reveals some of a cell’s components. One can classify some of the specific
components in the cytoplasm, but structures smaller than 2 um cannot normally be resolved. (Size of a
mitochondria)
- Super-resolution fluorescence light microscopy: Its resolution is up to 20 nm (0.02 um.)
We can see some small molecules with this. Cytoskeleton elements, organelles, etc.
- Electron microscopy
- Transmission electron microscopy (TEM): We use it for studying structures too small for light microscopy
such as cell organelles or proteins. It still has limitations.
- Scanning electron microscopy: Used for studying the topography of the specimen in 3D. (El relieve).
Worse resolution than TEM.
1.2.c Compare how samples are prepared for light versus electron microscopy and explain how
these preparations affect whether the technique can be used for viewing living cells or tissues.
Light microscopy: A tissue often must be fixed/ preserved, supported by embedding, cut, and stained before
it’s viewed.
Electron microscopy
- Transmission electron microscopy: Specimen is fixed on a support grid, and either embedded in
resin or stained with a particular compound. It must be dehydrated and cut into very thin pieces by
a diamond knife. Because of this, you cannot study live specimens or 3D structures.
- Scanning electron microscopy: It produces 3D images. Cannot visualize live specimens.
,Answer: A ribosome because it is too small. The smaller component that can be seen with a
conventional light microscope is a mitochondrion.
1.3.a Describe the structural differences between prokaryotes and eukaryotes. (Exam question!)
PROKARYOTES EUKARYOTES
Unicellular organisms that exist in various forms and
shapes
They don’t form multicellular organisms, they form They are either unicellular or MULTICELLULAR.
colonies
They do not have a nucleus. They have a nucleus and organelles.
They do not have compartmentalization Yeast is a very famous eukaryote. You can see its
organelles.
Prokaryotes do not have mitochondrias
They are also small, usually just a few micrometers Eukaryotes are bigger in size
long
Their population can evolve fast due to their rapid
proliferation
1.3.b Analyze how eukaryotic cells and organisms rely on the function of prokaryotic cells and their
descendants.
- Mitochondria and Chloroplasts: These organelles, which are found in eukaryotic cells, are believed to have
originated from ancient prokaryotic cells through a process called endosymbiosis. Mitochondria likely
evolved from aerobic bacteria, while chloroplasts originated from photosynthetic cyanobacteria. They are
essential for energy production (mitochondria) and photosynthesis (chloroplasts), which are fundamental
processes for eukaryotic life.
- Digestive System and Gut Microbiota: Many animals, including humans, have complex digestive systems
that rely on a variety of prokaryotic organisms in their gut. These microorganisms assist in the breakdown of
complex molecules and the absorption of nutrients.
1.3.c Compare prokaryotes and eukaryotes in terms of their relative preponderance on Earth, their
range of habitat, and their tendency toward multicellularity. (Exam question!)
PROKARYOTES EUKARYOTES
,They are the most diverse and numerous cells on Outnumbered by prokaryotes.
earth.
They exploit a vast range of habitats, from hot puddles They are either unicellular or MULTICELLULAR.
of volcanic muds to the interior of other living cells.
They don’t form multicellular organisms, they form versatile in their habitat range. They are found in
colonies nearly all environments,
THE EUKARYOTIC CELL - this was asked last year.
1.4.b Explain how the structure of the mitochondrion supports its function.
The inner membrane contains most of the proteins responsible for
energy production in eukaryotic cells; it is highly folded to provide a
large surface area for this activity.
1.4.c Outline the evolution of mitochondria and chloroplasts and cite the evidence for these origins.
These organelles, which are found in eukaryotic cells, are believed to have originated from ancient
prokaryotic cells through a process called endosymbiosis. This means they became dependent on each
other, these organelles cannot function by themselves, and the cell cannot function without them.
Mitochondria likely evolved from aerobic bacteria, while chloroplasts originated from photosynthetic
cyanobacteria.
This is believed because eukaryotic cells may have originated as predators engulfing other cells. Both
mitochondria and chloroplasts have their own DNA. Which indicates these organelles have retained some
genetic autonomy, like their prokaryotic ancestors.
, 1.5.a Review why scientists study model organisms. This was asked last year.
We cannot study every cell in the world, this is why we have model organisms, to understand that family of
that species. If you want to learn the basics of cell biology, you shall not dive into the complicated human
cell, but a simple yeast.
· Fruit flies to study insects.
· Arabidopsis to understand plants.
· Mice -> mammals
They’re easy to maintain, cheap, and we know the whole sequence of their genome.
CH-2
Answer: Ionic bonds, salts. Salts consists of ions that are kept together exclusively by ionic
bonds
Answer: Cysteine and methionine
