First I think it is important to understand how scientists "see" small
cellular organelles. One way they see these organelles is through staining, when you
stain a organelle or a cell, you will see different characteristics based on the stain.
Another way to 'see' what is there is by separating the cell by the size and
weight of the organelles (through centrification, basically spinning the contents of
the cell around VERY fast in a substance that allows different layers of
'stuff' depending on its density).
The lysosome is about the same, the lysosome tends to stain more granular than the peroxisome. A peroxisome will often have a crystalline structure inside. (like a crystalline shape inside a sphere).
The structures vary in size from 0.2 to 2 micrometers in diameter. The staining reveals a crystal like matrix in spherical vesicles. The crystalloid matrix is urate oxidase. These are small organelles containing around 40 enzymes for intercellular digestion. The lysosome membrane helps to protect the enzymes as much as it helps protect the cell. This is because the optimal pH for these enzymes is around a pH of 5. The membrane of the lysosome is again a lipid bilayer and is thought to have a ATP hydrolysis to pump H+ into the lysosome to maintain the pH. This also has another affect, that is free protons. Other small molecules can pass through the lysosome membrane, but will then become charged by picking up a free proton, then they are less likely to be able to leave the lysososome.
It used to be thought that peroxisomes are formed by the budding of smooth Endoplasmic Reticulum (ER). However, now it is thought that they form through self-assembly. (I will get more information references as I do some more thorough literature searches). The peroxisome is another major source of Oxygen utilization (along with the mitochondrion). There are specific proteins associated with the peroxisomes membrane, also there are 3 oxidation enzymes associated with peroxisomes:
The enzyme contents vary with various types of cells. One of the main functions of peroxisomes in liver cells is detoxification. This is done by the oxidation of substances like:
Why peroxisomes are not like lysosomes.
Peroxisomes are organelles that contain oxidative enzymes, such as D-amino acid oxidase, urate 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.
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.
The peroxisome is made as a phospholipid bilayer, encapsulating oxidative materials. They would be 'sphere-ish' in shape, not necessarily a perfect sphere, and sometimes, they may take other shapes. But most electron micrographs I have seen (2 dimensions) show them as circles. (As you may be aware, the Cell membrane is also a phospholipid bilayer.) Peroxisomes have membrane proteins that are critical for peroxisomal function, to import proteins into their interiors, proliferate or segregate to daughter cells (This update, thanks to Babich Temps). The main differences would be:
- 1. Types of phospholipids used.
- 2. Size of the membrane (i.e. peroxisomes are MUCH smaller than the cell).
Please send questions/comments/suggestions to: Mark Dalton at
markwdalton@gmail.com.