An alkene is a hydrocarbon containing double bonds. An alkyne is a hydrocarbon containing triple bonds. Ethene, C 2 H 4, is an example of an unsaturated hydrocarbon with a double bond.ethyne (acetylene), C 2 H 2 is an example of an unsaturated hydrocarbon with a triple bond.thene, C 2 H 4, is an example of an unsaturated hydrocarbon with a double bond. ethyne (acetylene), C 2 H 2 is an example of an unsaturated hydrocarbon with a triple bond.
Mitochondria and chloroplasts are also surrounded by membranes, but they have unusual membrane structures â specifically, each of these organelles has two surrounding membranes instead of just one. The outer membrane of mitochondria and chloroplasts has pores that allow small molecules to pass easily.
Mitochondria have two membranes, an outer membrane and an inner membrane. The outer membrane is smooth and studded with channels that let small molecules flow freely in and out from the human cell cytosol. The inner membrane is full of deep inward folds, or cristae, and impermeable to most molecules.