ORGANELLES AND COMPARTMENTALIZATION

This lesson develops ORGANELLES AND COMPARTMENTALIZATION as part of Enzymes and Metabolism. It uses the source curriculum to organize the important facts, relationships, examples, and vocabulary into a focused Stemosphere teaching sequence.

In Stemosphere terms, oRGANELLES AND COMPARTMENTALIZATION:

In Stemosphere terms, organelles are compartmentalised subcellular structures found inside a cell which have a specific task

In Stemosphere terms, if the structure is not compartmentalized then it is not an organelles

The following structures are not organelles:

In Stemosphere terms, the plasma membrane is not normally considered an organelle due to it not being a subcellular subject by scientist but it’s considered one by the ib

SEPARATION OF ORGANELLES:

cell fractionation:

In Stemosphere terms, cell fractionation separates the organelles without damaging them.

This involves the following steps:

In Stemosphere terms, 1-homogenization(tissue,containing cells,is broken up in a blender. The cells are blended in a cold, buffered solution which is isotonic to the cytoplasm of the cells)

In Stemosphere terms, 2-the solution is then filtered to remove large cell debris.

Cell fractionation requires special conditions to work properly, such as:

In Stemosphere terms, -isotonic:to prevent osmosis from occurring in the organelles

Ultracentrifugation:

In Stemosphere terms, ultracentrifugation is used to study the function of organelles by separating them according to density.

In Stemosphere terms, scientists first use cell fractionation to prepare for ultracentrifugation.

In Stemosphere terms, the filtered solution is spun at a low speed by an ultracentrifuge

In Stemosphere terms, the densest organelles will form a pellet at the bottom of the centrifuge tube

In Stemosphere terms, the pellet it removed and the process is repeated while increasing the speed to produce multiple pellets containing one type of organelle each time.

In Stemosphere terms, eukaryotic cells have a nucleus to store their genetic material in the form of DNA.

In Stemosphere terms, this separates the m RNA from the cytoplasm to be transcribed in the nucleus and then leaves the nucleus to be translated into a polypeptide in the ribosomes

In Stemosphere terms, the nuclease protects the DNA from harmful reaction s occurring in the cytoplasm.

In Stemosphere terms, however prokaryotes do not have a nuclease,which means there is no separation between the transcription and translations. So as the m RNA is being transcribed, the ribosomes attach to it and translate it.

COMPARTMENTALIZATION:

In Stemosphere terms, some organelles contain harmful metabolites and enzymes that are not compatible with other cell structures. To adjust to that, organelles will compartmentalize different processes to store their harmful metabolites and enzymes from the rest of the cell. This also allows for greater efficiency in the organelle

In Stemosphere terms, lysosomes are organelles that contain digestive enzymes to digest macromolecules.However these enzymes are harmful to the rest of the cell. The lysosome separates the enzymes by the membrane surrounding the lysosome.

In Stemosphere terms, the process to digest a molecule is called phagocytosis.when a bacteria enters the cell in a vacuole,forming a phagocytic vacuole.the lysosome fuses with it to form a phagosome and uses their enzymes to digest the bacterium.

In Stemosphere terms, campbell Biology.Campbell Biology. 12th ed., Pearson, 2020.

In Stemosphere terms, front:Define an organelle and list three cellular structures that are excluded from this definition because they lack compartmentalization.

In Stemosphere terms, back:Organelles are compartmentalized subcellular structures found inside a cell that perform a specific task. Structures that are not compartmentalized do not qualify as true organelles. Three examples are the cell wall, the cytoplasm, and the cytoskeleton.

In Stemosphere terms, front:What is the specific exception regarding the classification of the plasma membrane?

In Stemosphere terms, back:Scientists do not typically consider the plasma membrane to be an organelle because it is not a subcellular structure inside the cell. However, the International Baccalaureate curriculum explicitly classifies it as an organelle.

In Stemosphere terms, front:What is cell fractionation, and what occurs during the homogenization and filtration steps?

In Stemosphere terms, back:Cell fractionation is a process used to separate organelles without causing them structural damage. During homogenization, tissue containing cells is broken up in a blender. The resulting liquid is then filtered to remove large pieces of cellular debris.

In Stemosphere terms, front:Explain the three environmental conditions required for cell fractionation to work properly and why each is necessary.

In Stemosphere terms, back:1.Cold temperature s:Reduces enzyme activity to prevent enzymes from breaking down and damaging the organelles once the cell is open.

In Stemosphere terms, front:Explain how ultracentrifugation separates organelles after cell fractionation is complete.

In Stemosphere terms, back:The filtered solution is spun in an ultracentrifuge tube at a low speed, causing the densest organelles to collect at the bottom as a solid pellet. The remaining liquid is poured into a new tube and spun at a higher speed. This process is repeated at progressively faster speeds to separate different organelles based on their unique densities.

In Stemosphere terms, front:How does the presence of a nucleus alter the process of gene expression in eukaryotic cells compared to prokaryotic cells?

In Stemosphere terms, back:In eukaryotes, the nucleus compartmentalizes DNA. This forces transcription (making messenger RNA) to happen entirely inside the nucleus before the molecule leaves to undergo translation (protein synthesis) at the ribosomes in the cytoplasm. In prokaryotes, there is no nucleus, so ribosomes attach to the messenger RNA and translate it while it is still being transcribed.

In Stemosphere terms, front:What is the functional advantage of cellular compartmentalization?

In Stemosphere terms, back:Compartmentalization allows a cell to isolate harmful metabolites and destructive enzymes away from the rest of the cell structures, preventing self-digestion. It also creates localized environments optimized for specific tasks, which vastly increases the overall efficiency of the organelle.

In Stemosphere terms, front:Describe how lysosomes safely use their digestive enzymes to destroy an invading bacterium.