Eukaryotes
Living organisms can be sorted into two groups; these are the Prokaryotes and the eukaryotes. Eukaryotes are organisms that contain cells with a membrane-bound nucleus as well as membrane-bound Organelles. Examples of eukaryotes include all animals, plants, fungi and protists. Eukaryotes may variably be multicellular or unicellular. Conversley, Prokaryotes contain no nucleus, no membrane bound organelles and the majority are known to be unicellular, very rarely are they multicellular. Examples of prokayotes are, bacteria and cyanobacteria
Cell Structure
- Plasma Membrane:
Plasma membranes protect the internal parts of the cell from the environment. Proteins and lipids, importantly Phospholipids, make up the majority of the plasma membrane. The lipids are arranged in a fluid bilayer, with protein embedded which control the movement of molecules and ions in and out of the cell.
May also be referred to as the cytosol. This is a gel-like substance that is contained by the plasma membrane, and within it is found all the organelles of that cell.
There are two types of endoplasmic reticulum; rough and smooth. Rough endoplasmic reticulum, so called due to the ribosomes found on its surface, synthesises proteins, and smooth endoplasmic reticulum synthesizes lipids and steroids and metabolizes carbohydrates and steroids. The general structure is a network of sac-like structures called cisternae, held together by the cytoskeleton.
- Golgi Apparatus:
The Golgi apparatus gathers simple molecules and combines them to make molecules that are more complex which then get packaged them in vesicles, and either stores them for later use or sends them out of the cell. It is builds lysosomes. The structure of the Golgi apparatus can be described as a series of flattened sacs.
- Mitochondria:
Mitochondria are vital organelles that provide energy for the cell to carry out all its functions, for example division. Mitochondria have double membranes, with the outer membrane fairly smooth, and the inner membrane folded in to cristae, which greatly increases the surface area. It is on these cristae that sugar is combined with oxygen to produce ATP - the primary energy source for the cell.
- Nucleus:
The nucleus controls all functions of the cell and contains genetic information in the form of DNA, and its associated protein, histone, which forms chromosomes. The nucleus is bounded by a double membrane, called the nuclear envelope. Within the double membrane nuclear envelope are passages which large molceules can pass through called nuclear pores.
- Cell Wall:
Cell wall are present in fungi and plant cells, and exist around the outside of the plasma membrane. In fungi peptidoglycan forms the cell wall and in plants, the strongest component of the cell wall is a carbohydrate called cellulose. Cells walls provide structural support and have no affect on the passage of molecules and ions into and out of the cell.
Reproduction
The cell cycle of eukaryotic cells has two major phases: the interphase and cell division. During the interphase, the cell takes in nutrients, grows, and duplicates its chromosomes. During the cell division phase, the nucleus divides in a process called mitosis and then the divided nuclei are established in separate cells in a process called cytokinesis. Each daughter cell produced will be genetically identical to that of the parent cell.