There's a number of different types of cell, sizes and shapes in the body. The definition of a "Generalized Cell" is used for descriptive purposes. This contains characteristics from all types of cells. A cell is composed of three parts: a cell membrane, a nucleus, and a cytoplasm between the two. Intricate arrangements of fine fibers and hundreds or even thousands of miniscule but distinct structures , called organelles, lie within the cytoplasm.
Cell membrane
Every cell in the body is bound by a plasma. The cell membrane divides the material intracellular, outside the cell, from the material within the cell. It maintains a cell 's integrity and controls the passage of materials inside and out of the cell. For the necessary exchange all materials inside a cell must have access to the cell membrane.
Cell membrane is a double layer of molecules containing phospholipids. Proteins in the cell membrane provide structural support, form channels for materials to move through, serve as receptor sites, function as carrier molecules and provide markers for identification.
Nucleus and Nucleolus
The nucleus, formed around a fluid nucleoplasm by a nuclear membrane, is the cell's control centre. Chromatin strings within the nucleus contain deoxyribonucleic acid ( DNA), the cell's genetic content. The nucleolus is a dense ribonucleic acid (RNA) region within the nucleus and is the site of ribosome formation. The nucleus defines how the cell and the basic structure of that cell can function.
Cytoplasm
Cytoplasm is the substance that resembles gel inside the cell. It is the chemical-reaction medium. This provides a basis on which other organelles inside the cell can act. The cytoplasm of a cell performs all of the functions for cell expansion, growth, and replication. Materials travel by diffusion within the cytoplasm, a physical process which can only function for short distances.
Cytoplasmic organelles
Cytoplasmic organelles are "small bodies" suspended inside the cell's cytoplasm. Each type of organelle has a definite structure and a particular role in the cell function. The mitochondrion, ribosomes, endoplasmic reticulum , golgi apparatus, and lysosomes are examples of cytoplasmic organelles.
Structural and functional characteristics of different cell types are determined by the character of the proteins present. Cells of various types have different functions, because the structure and function of the cells are closely related. It's clear that a very thin cell is not well suited for a defensive purpose. The bone cells do not have a good structure for conducting nerve impulses. Much like there are several types of cells , the cell functions are complex. The generalized cell functions include transferring substances around the cell membrane, dividing cells to produce new cells and synthesizing proteins.
Substances pass through the cell membrane
The cell's survival depends on preserving the distance between extracellular and intracellular material. Mechanisms of cell membrane movement include simple diffusion, osmosis, filtration, active transportation, endocytosis and exocytosis.
Simple diffusion is the motion of particles from a region of higher concentration of the solute to a region of lower concentration of the solution. Osmosis is the diffusion, across a selectively permeable membrane, of solvent or water molecules. Filtration uses pressure to push a membrane through the substances. Active transport transfers substances from a region of lower concentration to a region of higher concentration, toward a concentration gradient. A carrier molecule is needed and it uses energy. Endocytosis refers to vesicle formation for the movement of particles and droplets from outside to within the cell. Secretory vesicles are transferred from inside by exocytosis to the outside of the cell.
Cell division
It is the process whereby new cells are produced in the body for development, repair , and replacement. The method involves the separation of nuclear material and cytoplasm division. All the cells in the body (somatic cells) replicate by mitosis except those that give rise to the eggs and sperm (gametes). A special process of nuclear division called meiosis produces egg and sperm cells, in which the number of chromosomes is halved. Cytoplasm division is termed cytokinesis.