An Overview of Biological Basics - Bioprocess Engineering: Kinetics, Biosystems, Sustainability and Reactor Design - page 35

Inner membrane
Outer membrane
Ribosome
Crista
Matrix
FIGURE 2.8 Diagram of a mitochondrion.
oxidative reactions that produce hydrogen peroxide. Glyoxysomes are also very small
membrane-bound particles that contain the enzymes of the glyoxylate cycle.
Golgi bodies are very small particles composed of membrane aggregates and are respon-
sible for the secretion of certain proteins. Golgi bodies are sites where proteins are modified
by the addition of various sugars in a process called glycosylation. Such modifications are
important to protein function in the body.
Vacuoles are membrane-bound organelles of low density and are responsible for food
digestion, osmotic regulation, and waste product storage. Vacuoles may occupy a large frac-
tion of the cell volume (up to 90% in plant cells).
Chloroplasts are relatively large green organelles containing chlorophyll that are respon-
sible for photosynthesis in photosynthetic eukaryotes, such as algae and plant cells. Every
chloroplast contains an outer membrane and a large number of inner membranes called
thylakoids. Chlorophyll molecules are associated with thylakoids, which have a regular
membrane structure with lipid bilayers. Chloroplasts are autonomous units containing their
own DNA and protein-synthesizing machinery.
Certain prokaryotic and eukaryotic organisms contain flagella d long, filamentous struc-
tures that are attached to one end of the cell and are responsible for the motion of the cell.
Eukaryotic flagella contain two central fibers surrounded by 18 peripheral fibers, which exist
in duplets. These fibers are arranged in a tube structure called a microtubule and are
composed of proteins called tubulin. The whole fiber assembly is embedded in an organic
matrix and is surrounded by a membrane.
The cytoskeleton (in eukaryotic cells) refers to filaments that provide an internal framework
to organize the cell's internal activities and control its shape. These filaments are critical to
cell movement, transduction of mechanical forces into biological responses, and separation