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Tamia Johnson & Wells Powell
Nucleolus
******Definition: A small, typically round granular
body composed of protein and RNA in the nucleus of a
cell.
It is usually associated with a specific chromosomal
site and involved in ribosomal RNA synthesis and the
formation of ribosomes.
**Locations: The location
of the nucleolus takes place within the nucleus (Pretty self
explanatory). Understand that it does not contain a
nucleus and is composed of Nucleic acids and proteins.
Peroxisomes
Peroxisomes: A small organelle that is present in the cytoplasm of many cells
and that contains the reducing enzyme catalases and usually some oxidases.
Location: Peroxisomes are membrane bound organelles found in eukaryotic
cells (nucleated cells). They would be found distributed throughout the cell.
Plant & Animal cell locations
In Depth...
***** The nucleolus builds ribosomes.
● Ribosomes are made up of rRNA and a protein. They may
be found dispersed in the cytoplasm or attached to rough
endoplasmic reticulum.
● Ribosomes are essential to cell function because they
build many different types of proteins through the process
of DNA transcription.
Important
●
For instance if it were not for transport proteins the cell
could not receive essential nutrients.
1.)The nucleolus disassembles at the beginning of mitosis, its components
disperse in various parts of the cell and reassembly occurs during
telophase and early G1 phase.
2.) Ribosome assembly begins with transcription of pre‐rRNA.
3.) During transcription ribosomal and nonribosomal proteins attach to the
RNA. ***The nucleolus also contains proteins and RNAs that are not
related to ribosome assembly and a number of new functions for the
nucleolus have been identified.
These include assembly of signal recognition particles, sensing cellular
stress and transport of HUMAN IMMUNODEFICIENCY VIRUS 1 (HIV‐1)
messenger RNA.
***The nucleus has a primary function and that
is to assemble ribosomes its the largest
structure in the nucleus.
Function of Peroxisomes
***A major function of the peroxisome is the breakdown of FATTY ACID molecules, in a process
called beta-oxidation.
In this process, the FATTY ACIDS are broken down two carbons at a time, converted to AcetylCoA, which is then transported back to the cytosol for further use.
In animal cells, beta-oxidation can also occur in the mitochondria. In yeast and plant cells, this
process is exclusive for the peroxisome.
***The nucleolus is responsible for producing RNA nucleotides which are
important in the construction process of transcription in protein synthesis,
the nucleolus is also the site of rRNA production which is a major component
of ribosomes (also involved in protein synthesis).
***Nucleolus contains the genes for three of the four classes or ribosomal RNA.
***Without these RNA, ribosomes cannot be formed and this will make the cell
devoid of the platform for the formation of proteins.
Why is the Peroxisome
Important?
**** Peroxisomes are important for lipid metabolism.
****Peroxisomes contain the first two enzymes required for the synthesis of
plasmalogens.
**** Peroxisomes also play important roles in cholesterol and bile acid
synthesis, purine and polyamine catabolism, and prostaglandin metabolism. In
plants, peroxisomes are required for photorespiration.
Size and Shape of the nucleolus
The nucleolus is a small round granular cell
Size and shape of the
peroxisomes?
The peroxisome is a small round cell that
hides within the nucleus Accordingly, they
are remarkably fluid and can change
dramatically in abundance, size, shape and
content in response to numerous cues.
These dynamics are controlled by multiple
aspects of peroxisome biogenesis that are
coordinately regulated with each other and
with other cellular processes.
No ribosomes would be made and from that
no proteins would be made. This is where
diseases come into play
● When peroxisomes don't work diseases
can start to occur because the reduction
of catalases and oxidases aren't reducing
fast enough so it causes a build up in the
cell.
Diseases/ and or health
problems in the nucleolus
The nucleolus is a multifunctional organelle with multiple roles involving cell proliferation, growth,
survival, ribosome biogenesis and stress response signaling.
Alteration of nucleolar morphology and architecture signifies an early response to increased cellular
stress.
This review briefly summarizes nucleolar response to cardiac stress signals and details the role
played by nucleolar proteins in cardiovascular pathophysiology.
Other diseases with
peroxisomes
**A peroxisome is an important part of a normal body cell like the nucleus or mitochondria.
***Two of the most common peroxisomal diseases are called Zellweger [zel´weg-er] Disease and
Neonatal Adrenoleukodystrophy. (uh-dree-noh-loo-koh-dis-truh-fee)
In these two diseases, the patient has defects in the process of making bile acids because some of the
steps occur within the peroxisome part of the cell. These diseases affect many organs in the body.
This is because peroxisomes occur in cells throughout the body. In peroxisomal diseases, the liver
disease can vary in severity. These diseases can also include problems in the brain, including mental
retardation, convulsions, deafness, blindness, and muscle weakness.
Research and studying of
Nucleolus
****Recent
studies suggest that the mammalian nucleolus may also play roles in tumorigenesis, viral
replication and cellular stress sensing. However, the pathway and the identities of the molecular
machineries involved in these mechanisms within this nuclear organelle remain largely unknown.
***In addition to its major role in ribosome production, the nucleolus may also be involved in
messenger RNA (mRNA) export or degradation
Mammalian nucleolus
Research and Studying of
Peroxisomes
● More than half a century of research on peroxisomes has revealed unique features
of this ubiquitous subcellular organelle, which have often been in disagreement
with existing dogmas in cell biology.
● About 50 peroxisomal enzymes have so far been identified, which contribute to
several crucial metabolic processes such as β-oxidation of fatty acids, biosynthesis
of ether phospholipids and metabolism of reactive oxygen species, and render
peroxisomes indispensable for human health and development.
Work Cited
●
Wanders, R. J.; Waterham, HR. R. (2006). "Biochemistry of Mammalian Peroxisomes Revisited". Annual Review of
Biochemistry 75: 295–332.doi:10.1146/annurev.biochem.74.082803.133329. PMID 16756494. edit
●
Jump up^ Wanders, R.; Waterham, H. (2006). "Peroxisomal disorders: the single peroxisomal enzyme deficiencies".
Biochimica et Biophysica Acta (BBA) - Molecular Cell Research 1763: 1707. doi:10.1016/j.bbamcr.2006.08.010. edit
●
Jump up^ Weller, S.; Gould, S. J.; Valle, D. (2003). "Peroxisome Biogenesis Disorders". Annual Review of Genomics and
Human Genetics 4: 165–211.doi:10.1146/annurev.genom.4.070802.110424. PMID 14527301. edit
●
Alberts B, Johnson A, Lewis J, et al. Molecular Biology of the Cell. 4th edition. New York: Garland Science;
2002. Peroxisomes. Available from: http://www.ncbi.nlm.nih.gov/books/NBK26858/