B2.2 Compartmentalisation Flashcards
What are some parts of the cell which are not organelles? Why?
The cell wall, cytoplasm and cytoskeleton are not organelles. The cell wall and cytoskeleton are not surrounded by a membrane and are not involved in metabolic processes. The cytoplasm is not a discrete structure with a specific function.
Explain how the structure of the nuclear envelope facilitates translation
Translation is the process by which ribosome reads mRNA by codons to make specific proteins.
The structure of the nuclear envelope is advantageous for translation as the mRNA can be modified within the nucleus post-translation before it meets with the ribosome in the cytoplasm. As a result, variants of the same proteins can be produced from the gene splicing process. Secondly, the nuclear membrane’s phospholipid bilayer is permeable only to non-polar and small molecules. Hence, the nuclear pores in the nucleus control the exit of proteins and entry and exit of mRNA. This establishes internal composition of the nucleus, but plays an essential role in regulating eukaryotic gene expression.
Describe the process of phagcytosis
Firstly, the phagocyte recognises the foreign particle through membrane receptors. The foreign particle is ingested through the phagocytic vacuole. Then, the phagocytic vacuole fuses with the lysosome forming a phgolysosome. Lastly, there is a final destruction of the ingested particle.
What are some advantages of conpartmentalization in the cytoplasm of cells
Compartmentalization creates discrete structures. This reduces comeptition for different metabolic processes occuring inside of cells. For instance, the lysosome in animal cells contains metabolites such as hydrolytic enzymes that operate in acidic environments. However compartmentalization allows for the lysosome to be of a neutral to slightly alkaline pH such that self-digestion does not occur.
Describe how ultracentrifugation is used to study organelles?
For cell fractionation, it separates cells into their different components, isolating organelles. Hence organelles are separated based on size and density. The heaviest cell components sink to the bottom and are called pellets and the lightest are called supernatants. Cell lysis is carried out to release cellular components, homogenization occurs through lysis of plasma membrane.
Explain how compartmentalization is beneficial during phagocytosis
Phagocytosis is a type of endocytosis process where foreign particles/pathogens are engulfed within a membrane. There is an endocytosis of the pathogen and forms a vesicle using the plasma membrane. The phagosome isolates materials from the rest of the cell’s interior and hence prevents the spread of the pathogen. The membrane of the lysosome additionally prevents self digestion as the pH of the lysosome is neutral but the enzymes inside are hydrolytic and operate in acidic environments. The phagolysosome is hence operating in an isolated environment. This allows processing and presentation of antigens, allowing for elimination of waste of phagocytosis.
ERQ: Outline the advantages of a compartmentalized structure in eukaryotes.
Enzymes and substrates involved in an enzymatic process can be in close proximity to one another. The optimal pH can also be maintained in areas of the cell. Reactions can also happen faster and more efficiently. Substances that can cause damage to the cell can be stored safely. Organelles can be moved around the cell and there is a lower chance of non-specific interactions.
