The focus of this section is to understand the organelles of the cell, how they interact with each other, and how they function during transport, growth and division in the cell. You will learn about the controlled chemical environment a cell maintains and what restrictions this places on the types of chemical reactions it can perform.
This background is vital to understanding key processes such as how a cell releases energy from glucose, makes and folds proteins, and goes through growth and cell division. Think of a city and the various jobs within a city. A cell is similar with each organelle serving a specific purpose. There are organelles whose job is to provide shape and structure to the cell, much like the city streets and bridges. These protein rich organelles include intermediate filaments , microtubules , and microfilaments.
Some of these actually move other organelles around the cell or change the shape of the cell. When a muscle cell contracts or shortens it does so by the microfilaments made up of the proteins actin and myosin. One special organelle composed of microtubules is located in an area near the nucleus, the centrosome. The centrosome contains a pair called of microtubule bundles known as the centrioles.
Centrioles are important because they move chromosomes to opposite ends of the cell during cell replication termed mitosis. Neurons do not have centrioles and cannot replicate. Other organelles help synthesize the proteins needed by the cell. These protein factories are called ribosomes. They can be scattered within the cell or attached to a membrane channel system called the endoplasmic reticulum or ER.
When the ER has ribosomes attached to it, it is termed the rough ER the ribosomes give it a rough or grainy appearance. They are typically found in all eukaryotic cells and are a component of the cytoskeleton, as well as cilia and flagella.
A type of cellular reproduction in which the number of chromosomes are reduced by half through the separation of homologous chromosomes, producing two haploid cells. A process of asexual reproduction in which the cell divides in two producing a replica, with an equal number of chromosomes in each resulting diploid cell.
Mitosis and the cell division. Consist of cytosol, organelles and inclusions. Site of most activities carried out by the cell. Pores allow passage of protein and RNA molecules.
Contains the pores that allow passage of RNA and protein molecules. Other vesicles mature into lysosomes. Define mitosis two daughter nuclei that are genetically identical to the mother nucleus, is nuclear division. Define cytokinesis is the division of the cytoplasm, which begins after mitosis nearly complete. Plasma membrane external boundary of cell; regulates flow of materials into and out of the cell; site of cell signaling. Nucleolus One or more nucleoli are usually present within each nucleuls.
Dark staining, they are specialized regions of the chromatin in and on which are synthesized the type of RNA that eventually becomes part of the ribosome. Nondividing cells often have a dark structure within their nuclei called a nucleolus. Strands of chromatin that hold the codes for ribosomal RNA are associated with this nucleolar region, and the information carried by these regions of DNA is enzymatically copied into RNA molecules.
Small packages of protein and this RNA are then combined and exported from the nucleus into the cytoplasm to become ribosomes. Transcription DNA molecules are freed of their histone, and the two strands unwind. A large enzyme complex RNA Polymerase binds to one of the strands. Although the nuclear DNA contains all of the information or codes necessary to make proteins, protein synthesis does not occur in the nucleus.
This process is called transcription because DNA information is being transcribed or "converted" into RNA information. The RNA copies move out of the nucleus and associate with ribosomes in the cytoplasm, where the processing of assembling the final protein actually takes place. These RNA molecules act as messengers, therefore, ferrying the information from the DNA 'store' to the protein assembly points on the ribosomes.
Figure legend:.
0コメント