Biology Cell Parts Essay -- essays research papers

Nucleus- â€Å"the brain† or control center of the cell. The Nucleus, a membrane-bound structure of a cell, plays two crucial roles in controlling the cell. The nucleus carries the cell's genetic information that determines if the organism will develop, for instance, into a tree or a human; and it directs most cell activities including growth, metabolism, and reproduction by controlling protein synthesis. The presence of a nucleus distinguishes the more complex eukaryotic cells of plants and animals from the simpler prokaryotic cells of bacteria and cyanobacteria that lack a nucleus. The nucleus is the most predominate structure in the cell. It is typically round and occupies 10% of the cells total volume. The nucleus is wrapped in a double-layered membrane called the nuclear envelope. The space between the nuclear envelope layers is called perinuclear space. The nuclear envelope is attached to a network of membrane-enclosed tubules that extends throughout the cell called the endoplasmic reticulum. The nuclear envelope is perforated by many holes, called nuclear pores, that permit the movement of selected molecules between the nucleus and the rest of the cell, while blocking the passage of other molecules. The nucleus contains the nucleolus, which manufactures the organelle known as the ribosome, or the protein producing organism. Genetic information in the form of deoxyribonucleic acid(DNA) is stored in threadlike, tangled structures called chromatin within the nucleus. During the process of cell division known as mitosis, in which the nucleus divides, the chromatin condense into several distinct structures called chromosomes. Each time the cell divides, the heredity information carried in the chromosomes is passed to the two newly formed cells. The DNA in the nucleus also contains the instructions for regulating the amount and types of proteins made by the cell. These instructions are copied, or transcribed, into a type of ribonucleic acid(RNA) called messenger RNA (mRNA). The mRNA is transported from the nucleus to ribosomes, where proteins are assembled.   Ã‚  Ã‚  Ã‚  Ã‚   Nuclear Envelope- The nucleus is wrapped in a double-layered membrane called the nuclear envelope. The space between the nuclear envelope layers is called perinuclear space. The nuclear envelope is attached to a network of membrane-enclosed tubules called the endoplasmic ret... ...g the lungs, and does this by sweeping them into mucus where they are swallowed, as opposed to inhaled. Cell Wall- The most predominate feature that distinguishes plant cells from animal cells, is the cell wall. The Cell wall surrounds and protects the plasma membrane located within it, and helps it to maintain its shape. The pores in the cell wall allow objects to flow freely through the walls, into and out of the cell. The strength of the wall also allows for the central vacuole to be filled with water, or in a turgid state, without bursting. The strength of the cell walls is portrayed in the firmness of stems, leaves and flowers. It is also divided into a primary and a secondary cell wall. Extracellular matrix- Functions in support, adhesion and movement and development. In animal cells like cell walls of plants. It also functions in a cells dynamic behavior. It Helps to control the activity of the genes in the nucleus. Intercellular Junctions- integrate cells into higher levels of structure and function. The cell wall of plants are perforated by plasmodesmata which allow cytoplasm to pass through. This allows water and small solutes to pass freely from cell to cell.