Is exocytosis an active or passive process?
It is an active process.The process in which the cell releases materials to the outside by discharging them as membrane-bounded vesicles passing through the cell membrane.
The formation of the membrane by GA+ movement of the vesicles and fusion with the cell membrane need energy.
Also, exocytosis includes movement of a substance against its concentration gradient (from low to high concentration) e.g. secretory granules or waste products.
So, exocytosis is an active process.
How is the cell protected from enzymes of lysosomes?
The membrane that surround the lysosomes and the PH of the lysosomes is not optimum for their function.
Why peroxisomes are not like lysosomes?
Peroxisomes are organelles that contain oxidative enzymes, such as D-amino acid oxidase, ureate oxidase, and catalase. They may resemble a lysosome, however, they are not formed in the Golgi complex. Peroxisomes are distinguished by a crystalline structure inside a sac which also contains amorphous gray material. They are self replicating, like the mitochondria. Components accumulate at a given site and they can be assembled into a peroxisome. They may look like storage granules, however, they are not formed in the same way as storage granules. They also enlarge and bud to produce new peroxisomes.
Peroxisomes function to rid the body of toxic substances like hydrogen peroxide, or other metabolites. They are a major site of oxygen utilization and are numerous in the liver where toxic byproducts are going to accumulate.
How can determination of type of intermediate filaments help to diagnose cell of origin in tumors?
The tumour cells sometimes are not possible to identify their tissue of origin under the microscope because the cells are not normal "different in shaped from the normal cells" but they contain the intermediate filaments of their origin, so we can detect the type by immunohistochemical techniques.