Teacher Training College 2008 - EDI

"The goal of science is to build better mousetraps. The goal of nature is to build better mice"
Anonymous

M ITOCHONDRIAprovide the energy a cell needs to move, divide, produce secretory products, contract - in short, they are the power centers of the cell. They are about the size of bacteria but may have different shapes depending on the cell type.
Mitochondria are membrane-bound organelles, and like the nucleus have a double membrane. The outer membrane is fairly smooth. But the inner membrane is highly convoluted, forming folds called cristae. The cristae greatly increase the inner membrane's surface area. It is on these cristae that food (sugar) is combined with oxygen to produce ATP - the primary energy source for the cell.

R IBOSOMES: Ribosomes are the large, ribonucleoprotein factories in which proteins are synthesized. In this process, messenger RNA (mRNA) codons are read by the anticodons of adaptor, transfer RNAs (tRNAs) that carry codon-specific amino acids. These amino acids are added to a growing protein chain by peptide bond formation in the heart of the ribosome.
These ribosomes provide the structural site where the mRNA sits. The amino acids for the proteins are carried to the site by "transfer RNAs".


E NDOPLASMIC RETICULUM: Throughout the eucaryotic cell, especially those responsible for the production of hormones and other secretory products, is a vast amount of membrane called the endoplasmic reticulum, or ER for short. The ER membrane is a continuation of the outer nuclear membrane and its function suggests just how complex and organized the eucaryotic cell really is.
When viewed by electron microscopy, some areas of the endoplasmic reticulum look "smooth" (smooth ER) and some appear "rough" (rough ER). The rough ER appears rough due to the presence of ribosomes on the membrane surface. Smooth and Rough ER also have different functions. Smooth ER is important in the synthesis of lipids and membrane proteins. Rough ER is important in the synthesis of other proteins.

Information coded in DNA sequences in the nucleus is transcribed as messenger RNA. Messenger RNA exits the nucleus through small pores to enter the cytoplasm. At the ribosomes on the rough ER, the messenger RNA is translated into proteins. These proteins are then transferred to the Golgi in "transport vesicles" where they are further processed and packaged into lysosomes, peroxisomes, or secretory vesicles.

GOLGI COMLEX: The Golgi apparatus is a membrane-bound structure with a single membrane. It is actually a stack of membrane-bound vesicles that are important in packaging macromolecules for transport elsewhere in the cell. The stack of larger vesicles is surrounded by numerous smaller vesicles containing those packaged macromolecules. The enzymatic or hormonal contents of lysosomes, peroxisomes and secretory vesicles are packaged in membrane-bound vesicles at the periphery of the Golgi apparatus.

LYSOSOMES: Lysosomes (common in animal cells but rare in plant cells) contain hydrolytic enzymes necessary for intracellular digestion. In white blood cells that eat bacteria, lysosome contents are carefully released into the vacuole around the bacteria and serve to kill and digest those bacteria. Uncontrolled release of lysosome contents into the cytoplasm is also a component of necrotic cell death.
S ECRETORY GRANULES: A membrane-bound particle, usually protein, formed in the granular endoplasmic reticulum and the Golgi complex.