To show that lines are parallel, we draw small arrow marks on them. In the figure above, note the arrows on the lines PQ and RS. When we write about parallel lines there is a shorthand we can use. We can write which is read as the line segment PQ is parallel to the segment RS.
Lysosome[edit] Lysosomes are spherical bodies, or vacuoles that are enclosed by a single membrane. The membrane serves as a protectorate to the cell, since lysosomes contain harsh digestive enzymes, which would cause significant damage if exposed to cell content.
About 40 different digestive enzymes reside inside a lysosome. These enzymes are made by organelles called ribosomes that are attached to the endoplasmic reticulum and put into packages by the Golgi bodies. The inside or matrix of a lysosome has an acidic pH of about 4.8, which is the optimal environment for the enzymes.