1. All living cells, both prokaryotic and eukaryotic, have the following cell structures:
plasma membrane, cytosol, ribosomes, and at least one chromosome. Choose any one
of these. Describe its basic structure (including molecular composition) as well as the
function. Explain why a cell could not exist without the function(s) performed by this
cell structure.
Ribosomes are critical to the survival of the prokaryotic cell. They are found both free
and bound to the rough endoplasmic reticulum (RER) in the cytoplasm of the cell.
Ribosomes are responsible for making proteins in the cell. The messenger RNA (mRNA)
incorporates a series of codons that tell the ribosome the sequence of the amino acids that
are needed to make the protein. Using the mRNA as a template, the ribosome reads and
translates each codon of the mRNA, pairing it with the appropriate amino acid provided by
a tRNA. Molecules of transfer RNA (tRNA) contain a complementary anticodon on one end
and the appropriate amino acid on the other. The small ribosomal subunit, typically bound
to a tRNA containing the amino acid methionine, binds to an AUG codon on the mRNA and
recruits the large ribosomal subunit. Therefore, almost every protein made in prokaryotic
cells start with the codon AUG.
If the cell were not able to make the proteins as dictated by the mRNA with the help of
the ribosomes, the cell would unfortunately die. The cell needs specific proteins for all of its
life processes, including metabolism, replication, and defense. All of these proteins would
cease to exist without the ribosome.
2. Cells can be categorized as either prokaryotic or eukaryotic. Only bacterial cells are
prokaryotic. For question two, answer any one of the following comparison questions. Be
sure to compare both molecular (physical) structure and function in each answer.
a.Compare the nucleoid area (prokaryotic) to a nucleus (eukaryotic)? How do they differ; how
are they similar?
b.Compare the bacterial flagellum (prokaryotic) to an animal cell flagellum (eukaryotic)? How
do they differ; how are they similar?
c.Compare a bacterial cell wall (prokaryotic) to a plant cell wall (eukaryotic)? How do they
differ; how are they similar?
Both prokaryotic and eukaryotic cells have fragments of genetic material within their structure.
Prokaryotic cells house their genetic material within the nucleoid area of the cell, in contrast to
the nucleus seen in eukaryotes. Eukaryotic cells cover their nucleus with a membrane; the
nucleoid area in the prokaryote does not have this nuclear membrane. Furthermore, the
genetic material seen in eukaryotes is housed within chromosomes inside that nucleus
described above. The prokaryotic cell only contains one or two small chromosomes in its
nucleoid area. Moreover, eukaryotic cells package their nucleic material around specialized
proteins known as histones. These proteins serve to make the information compact enough to
fit in a small space. Prokaryotic cells do not have histones, and as such, must use only a few
chromosomes to house their genomes.
3. Eukaryotic cells (in plants, animals, fungi, and algae) are bigger than prokaryotic (bacterial)
cells. This bigger size allows eukaryotic cells to have more structural complexity.
Choose any one of the following eukaryotic cell structures for a short essay:
•Mitochondrion
•Cytoskeleton
•Golgi apparatus
•Endoplasmic reticulum
•Lysosome
•Chloroplast (found only in photosynthetic cells)
In your answer, describe its basic structure (including molecular composition) as well as the
function. Why is the function important to keeping the cell alive?
Provide references in APA format. This includes a reference list and in-text citations for
references used throughout the assignment.
The Golgi apparatus (GA) is an organelle found in most eukaryotic cells. This is one of
the membrane bound organelles found in these advanced cells. It processes and packages
macromolecules, such as proteins and lipids, after their synthesis and before they make their
way to their destination; it is particularly important in the processing of proteins for secretion
out of the cell. The GA looks a lot like a stack of plates, each known as a cisterna. A mammalian
cell typically contains 40 to 100 stacks (Duran, 2008). Each cisterna includes Golgi enzymes
which modify proteins that travel through the GA.
The GA may be thought of as distributions center that sorts and packages material for
shipping out throughout the cell. The cell may also rid itself of wastes by packaging substances
to expel through the cell membrane. The GA transports the precursors of proteins, lipids,
secretory molecules, and other substances to various areas of the cell for use in cellular
functions. Proteins and lipids built in the smooth and rough endoplasmic reticulum bud off in
tiny bubble-like vesicles that move through the cytoplasm until they reach the Golgi complex.
The vesicles fuse with the Golgi membranes and release their stored material into the
organelle. Once inside, the compounds are further processed by the GA, which modifies the
final structure. When completed, the product is extruded from the GA in a vesicle and directed
to its final destination inside or outside the cell.
References
Duran J. (2008). "The role of GRASP55 in Golgi fragmentation and entry of cells into
mitosis". Mol. Biol. Cell 19 (6): 2579–87.