The Cytomembrane System

Components: Endoplasmic Reticulum Golgi Bodies Vesicles Rough Smooth Golgi Bodies Vesicles Technically not part of it, but necessary for the Cytomembrane System to function: Nucleus and nuclear membrane, ribosomes and the cytoskeleton.

Functions: Lipids are assembled Polypeptide chains are modified into final proteins Lipids and proteins are sorted and shipped

The Nucleus Contains the cell’s genetic information which codes for proteins. mRNA is transcribed from the DNA in the nucleus, leaves the nucleus.

The Nuclear Membrane Bilipid layer Contains pores which allow large molecules to leave the nucleus.

Ribosomes Located in the cytoplasm or attached to the ER Site of protein synthesis mRNA is translated to create new protein

Free Ribosomes Attached to the ER Usually make proteins that will be used in the cytoplasm Attached to the ER Usually make proteins that will be exported or used in the plasma membrane

In the Rough ER Some proteins have a specific signal which allows them to enter the space within the rough ER As the protein travels through the ER enzymes attach side chains and the protein become folded

In the Smooth ER Lipids are assembled

Materials from the ER are shipped to the Golgi Bodies Vesicles bud off the ER and travel through the cytoplasm to the Golgi body

The vesicles travel through the cytoplasm on motor proteins that travel on the microtubules and microfilaments of the cytomembrane system

Golgi Bodies Enzymes finish modifications of proteins and lipids The materials are then sorted based on where they will be used and the modifications made to them

Materials from the Golgi Bodies are enclosed in membranes to form vesicles and then shipped from the Golgi to locations where they are needed. Vesicles may be excreted or become specific structures such as lysosomes

Specialized Cells Pancreatic cells – have large amounts of rough ER to produce enzymes that are secreted into the small intestine to help digest food Liver cells – have large amounts of smooth ER where drugs and some toxic substances are inactivated