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HL&WL BIOLOGY BLOG


Saturday, February 24, 2007

QUESTION ONE





Diagram of a cell nucleus



Cell nucleus (a cell's information center)
The cell nucleus is the most conspicuous organelle found in a eukaryotic cell. It houses the cell's chromosomes, and is the place where almost all DNA replication and RNA synthesis occur. The nucleus is spheroid in shape and separated from the cytoplasm by a double membrane called the nuclear envelope. The nuclear envelope isolates and protects a cell's DNA from various molecules that could accidentally damage its structure or interfere with its processing. During processing, DNA is transcribed, or copied into a special RNA, called mRNA. This mRNA is then transported out of the nucleus, where it is translated into a specific protein molecule. In prokaryotes, DNA processing takes place in the cytoplasm.

Mitochondria and Chloroplasts (the power generators)
Mitochondria are self-replicating organelles that occur in various numbers, shapes, and sizes in the cytoplasm of all eukaryotic cells. As mitochondria contain their own genome that is separate and distinct from the nuclear genome of a cell, they play a critical role in generating energy in the eukaryotic cell, organelles that are modified chloroplasts; they are broadly called plastids, and are often involved in storage.
Diagram of an endomembrane system
Endoplasmic reticulum and Golgi apparatus (macromolecule managers)
The endoplasmic reticulum (ER) is the transport network for molecules targeted for certain modifications and specific destinations, as compared to molecules that will float freely in the cytoplasm. The ER has two forms: the rough ER, which has ribosomes on its surface, and the smooth ER, which lacks them.

The ER contains many Ribosomes (the protein production machine)
The ribosome is a large complex composed of many molecules, only exist floating freely in the cytosol, whereas in eukaryotes they can be either free or bound to membranes.
Lysosomes and Peroxisomes (of the eukaryotic cell)
The cell could not house such destructive enzymes if they were not contained in a membrane-bound system.
Centrosome (the cytoskeleton organiser)
The centrosome produces the microtubules of a cell - a key component of the cytoskeleton. It directs the transport through the ER and the Golgi apparatus. Centrosomes are composed of two centrioles, which separate during cell division and help in the formation of the mitotic spindle. A single centrosome is present in the animal cells. They are also found in some fungi and algae cells.
Vacuoles
Vacuoles store food and waste. Some vacuoles store extra water. They are often described as liquid filled space and are surrounded by a membrane. Some cells, most notably Amoeba have contractile vacuoles, which are able to pump water out of the cell if there is too much water.

My cell annology ; School

Nucleus (a cell's information center) would be the school's general office where all information about the student , school etc are.
Nucleolus would be the principal who is "located" inside the nucleus controlling the running of the school

Like how important the nucleus & the nucleolus is to the cell , the principal & the school's general office are very important to the school too .
& they both control the running of the cell & school

Cell membrane (regulates the movement of water, nutrients and wastes into and out of the cell.) would be like the school's security guard .

Like the cell membrane , the school's security guard prevents students from leaving the school during school hours & prevents strangers from entering the school

Mitochondria (the power generators) would be the school's canteen where all types of food are & where all students and teachers get their food .

Like the mitochondria , the school canteen provides food for the students & teachers giving them energy to last for the day .

Rough Endoplasmic reticulum (moves materials around the cell) would be like the teachers in the school .

Like the rough endoplasmic reticulum , the teachers teaches the students thus providing them with information , circulating their knowledge around the school.

Ribosomes (makes proteins) would be like the students in the school.

Like the ribosomes , we students would produce good results for the school like how ribosomes makes proteins for the cell .

Lysosomes (chemicals used to digest waste) would be like the cleaners we have in the school.

Like the lysosomes , the cleaners in the school helps to clear all rubbish and help clean the school in turn making the school a clean enviroment to study in . Like the importance of the lysosomes , the cleaners are important in a school too.

Golgi apparatus (packing & secreting of energy) would be like the like the HOD of each department.

Like the golgi apparatus , the HOD of each department decides in what way should the teachers be teaching the students . Like how the golgi apparatus and the rough enndoplasmic reticulum work closely together , the HOD of each department works closely with the teachers too.

TATA! My cell anology of a school(:


Credits:
http://www.fortbend.k12.tx.us/mastersonline/Ft_Bend_ISD/6306/qvms/johnson/cell_part.htm
http://en.wikipedia.org/wiki/Cell_(biology)
http://web.jjay.cuny.edu/~acarpi/NSC/13-cells.htm

DONE BY YEOHUILING :D

4:49 PM

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