The Cell Membrane and The Cell Cycle
The cell membrane is important, because it’s a selectively permeable barrier that protects the cell. The membrane plays an important role in cytokinesis(in mitosis), which will be discussed later. The nucleus is known as the control center in the cell. The nucleus is a membrane bound organelle that contains genes in the form of chromatin. Exact duplicates of the DNA in chromosomes are passed on to daughter cells. Nuclear division occurs during the M or the mitotic phase during the cell cycle. The nuclear membrane dissolves during prometaphase of mitosis. Centrioles are located in the cytoplasm near the nucleus and are the location for organizing microtubules. Centrioles operate in the formation of the spindle apparatus. During prophase of mitosis, centrioles duplicate, then migrate to opposite poles and affix to spindle fibers. The cytoplasm is located between the cell membrane and the nucleus. It contains organelles, cytoskeletons, and other fragments. The cytoplasm divides during cytokinesis. Microtubules are spindle fibers that lie between the centrioles and chromosomes. They function in moving the chromosomes around during mitosis. Proteins attach to centromeres creating kinetochores. Microtubules attach to kinetochores and help align chromosomes at the center of the cell to form the metaphase plate during metaphase. Microtubules also play a role in cytokinesis. Animal cells split by a process called furrowing. The microtubules constrict allowing the cell to pinch together in the center and create two daughter cells. This process occurs differently in plant cells, because plant cells have a cell wall. The Golgi apparatus plays an extremely important role in the division of plant cells. Vesicles from the Golgi apparatus, line up vertically at the center of the cell and fuse together to form a cell plate. The cell plate grows making a cell wall and splitting the cell into two daughter cells. Cytokinesis splits organelles such as the mitochondria, ribosomes, and the cytoplasm randomly between the two daughter cells.
The cell cycle can seem complicated at first, but when broken down into smaller pieces, just like anything else in Biology, absolute fascination will win over any deterrance that once existed. Get beyond the learning for just a second. Let this all soak in.