Cell Organelles, Function and Characteristics

Plasma Membrane

• It is composed of a phospholipid bilayer, with proteins embedded in the layer.
• The membrane is selectively permeable and regulates the transport of materials into and out of the cell. Separates cell contents from outside the environment.

Cytoplasm

• A thick, gelatinous, semi-transparent fluid
• Maintains cell shape and stores chemicals needed by the cell for metabolic reactions.

Nucleus

• The largest organelle of a eukarotic cell and is surrounded by a nuclear envelope. The envelope has nuclear pores which allow the movement of molecules through it. It also contains chromatin.
• It controls cellular activity and houses genetic material called chromatin, DNA and proteins, from which comes the instructions for making proteins.

Nucleolus

• Dense spherical structure in the middle of the nucleus
• The nucleolus makes RNA and ribosomes.

Rough Endoplasmic Reticulum (rough ER)

• Network of membrane bound flattened sacs called cisternae studded with ribosomes
• Protein synthesis takes place on the ribosomes and the newly synthesised proteins are tranported to the Golgi apparatus.

Smooth Endoplasmic Reticulum (smooth ER)

• Network of membrane bound flattened sacs called cisternae. No ribosomes.
• Responsible for the synthesis and transport of lipids and carbohydrates.

Golgi apparatus

• A stack of membrane bound flattened sacs.

• Newly made proteins are recieved here from the rough ER. The Golgi apparatus modifies the proteins and packages them into vesicles to be transported to where they are needed.

Vesicles

• Small spherical membrane bound sacs with fluid inside
• Transport vesicles transport materials inside the cell and secretory vesicles transport proteins that are to be released from the cell, to the cell surface membrane.

Lysosomes

• Small spherical membrane bound sacs containing hydrolytic enzymes.
• They break down waste material including old organelles

Ribosomes (80s)

• Tiny organelles attached to the rough ER or freely floating in the cell. They consist…