Summary of Structure and Function of Cytoplasmic Organelles (Table 3.1 pg.37)

Cytoskeletal elements: microfilaments, intermediate filaments, microtubules

Location and Function: Form an internal scaffolding called cytoskeleton. Provide cellular support; function in intracellular transport. Microfilaments are formed largely of actin, a contractile protein, and thus are important in cel mobility, particularly in muscle cells. Intermediate filaments are stable elements composed of a variety of proteins and resist mechanical forces acting on cells. Microtubules form the internal structure of the centrioles and help determine cell shape.

Mitochondria

Location and Function: Generally rod-shaped bodies with a double-membrane wall; inner membrane is shaped into folds, or cristae; contain enzymes that oxidize foodstuffs to produce cellular energy (ATP); often referred to as "powerhouses of the cell"

Endoplasmic reticulum (ER)

Location and Function: Membranous system of tubules that extends throughout the cytoplasm; two varieties: rough and smooth. Rough ER is studded with ribosomes; tubules of the rough ER provide an area for storage and transport of the proteins made on the ribosomes to other cell area. Smooth ER, which has no function in protein synthesis, is a site of steroid and lipid synthesis, lipid metabolism, and drug detoxification

Centrioles

Location and Function: Paired, cylindrical bodies that lie at right angles to each other, close to the nucleus. Internally, each centriole is composed of nine triplets of microtubules. As part of the centrosome, they direct the formation of the mitotic spindle during cell division; form the bases of cilia and flagella and in that role are called basal bodies.

Peroxisomes

Location and Function: Small lysosome-like membranous sacs containing oxidase enzymes that detoxify alcohol, free radicals, and other harmful chemicals. They are particularly abundant in liver and kidney cells.

Golgi apparatus

Location and Function: Stack of flattened sac with bulbous ends and associated small vesicles; found close to the nucleus. Plays a role in packaging proteins or other substances for export from the cell or incorporation into the plasma membrane and in packaging lysosomal enzymes.

Ribosomes

Location and Function: Tiny spherical bodies composed of RNA and protein; floating free or attached to a membranous structure (the rough ER - Endoplasmic reticulum) in the cytoplasm. Actual sites of protein synthesis.

Lysosomes

Location and Function: Various-sized membranous sacs containing digestive enzymes including acid hydrolases; function to digest worn-out cell organelles and foreign substances that enter the cell. Have the capacity of total cell destruction if ruptured and are for this reason referred to as "suicide sacs."