Certain Molecules Across Cell Membranes example essay topic

The Cell Theory The cell theory states that all living matter is made up of cells and some living organisms consist of a single cell. Other cells serve a special purpose within advanced organisms like nerve cells. One theory of a cell states that the first form of life on this earth consisted of a lot of different types of small proto cells. Proto cells are cell like organism.

These organisms were able to reproduce in a very limited environment because they are so simple. After many years some of the proto cells came together and shared their DNA with each other. These proto cells eventually became the cells we are studying now. Type of Cells There are two types of cells one is the Prokaryote, a Prokaryote is a cell with no nucleus or organelles with membranes, the other, a Eukaryotes are cells that contain a nucleus and organelles and are surrounded by a membrane Cell Structure Thin membranes surround cells; this is called the cell membranes, they separate the inside from the out. The cell membrane is just like the other organelles in a cell because it has its own specialized jobs. One of its jobs is to control what enters and exits the cell and to protect the cell.

Cell membranes are made up of fats with big protein molecules inside them. Molecules move across cell membranes by two processes diffusion or active transport. Diffusion is the movement from a high level of molecules to a low level of molecules. Molecules can diffuse across membranes through the phospholipid bi layer or using a protein. Either kind of diffusion does not need energy from the cell.

Some special proteins move certain molecules across cell membranes only with the help of cell energy. Moving molecules with cell energy is called active transport. When water diffuses the process is called osmosis. Water moves from a high level of water (to a low concentration of water. This means that water would cross a selectively permeable membrane from a dilute solution to a concentrated solution.

Water can cross the cell membrane through the lipid bi-layer and with special proteins. If enough water enters the cell by osmosis, the cell can swell enough to burst open and die. Function Relationships The cell is the most advanced molecule. The cell is so small, it is microscopic, yet each cell functions as part of a big family that controls your body. Each cell has its own organelles; these are the parts in the cell which make the cell function.

Cells do more than just produce protein and such, it also breaks down fat (also called lipids) and transfers them to energy. Secretion is the process in which the organelles in a cell combine with each other, send information to each other, make proteins, and then they are released outside the cell. Secretion is first started in the nucleus; the nucleus is the positively charged center of a cell, it is the control center of a cell. After the process has reached and finished dealing with the nucleus, it is then turned into a stage called protein synthesis, this is the process in which protein is produced.

Next come the Ribosome, the Ribosome is the non-membrane bound organelle in the nucleus where enzymes and other proteins are assembled. After the Ribosome has completed its process in secretion, it is then transferred to the Endoplasmic Reticulum. The Endoplasmic Reticulum is the part of the cell that has a series of highly folded membranes, it is surrounded by cytoplasm, cytoplasm is the site of cellular chemical reactions. The Endoplasmic Reticulum has finished its job in the process; it is now time for the Golgi to start working. The Golgi is the organelle in Eukaryotic cells, it has a system of flattened tubular membranes, it modifies proteins and then sends them to their appropriate destination.

This is no time for the Vesicle, the Vesicle is basically just a transporter in a cell, it gives all this information and apparatuses to membrane. The membrane then finishes the process of secretion by releasing the made material to the outside of a cell.