Discovery and Cell TheoryEdit
In 1663 a scientist by the name of Robert Hooke discovered cells. He noticed while looking at a cork under a microscope, that there was small pores that looked like the cell that monks lived in. What Hooke was actually looking at was the cell walls of a non-living object. The first person to actually observe a living cell was Antony van Leevwenhoek.
How cells and living things coincide is the Cell Theory. Five major scentists were involved in creating the Cell Theory: Hooke, Leevwenhoek, Schleiden, Schwann, and Virchow. The Cell Theory states three things, first, that all cells come from other cells, second, all living things have cells, and third, cells are the basic unit of life. While these are the general rules for cells, this does not mean that all cells are the same. For example: plant and animal cells.
Plant Cells and Animal CellsEdit
Plant cells have some different features than animal cells. If you look at a plant cell under a microscope, you will notice a cell wall. The cell wall gives plants structure and support. Which is why it is found in plant cells, not animals. Another major difference between plant and animal cells is that a plant cell has no chloroplasts, which is the pigment for photosynthesis. Plants also have large vacuels. Animal cells have centrioles and plant cells do not. One thing to remember is that, while the two cells are different in someways, all of the other organelles are found in both plant and animal cells.
The word prokaryotic actually means before the nuclues. So, in a prokaryotic cell it does not have a nucleus. It does, however, have a nucleiod. A nucleiod contains a long DNA strand, but it is not a nucleus. Prokaryotic cells are unicellular and generally live in colonies or alone. Bacteria is an example of a prokaryotic cell.
The word eukaryotic means having a true nucleus. Any organism with more than one cell, is made up of eukaryotic cells. A true nucleus contains chromosomes, which is the genectic information of the cell. A eukaryotic cell is more complex and larger than a prokaryotic cell. Plants and animals are examples of eukaryotic cells. cond section of your page here.
Levels of OrganizationEdit
Cells are the basic unit of life. Cells organize into tissue and tissues organize into organs. An organ organizes into an organ system. For example: a nerve cell organizes into a nerve tissue and then finally a heart. (Organ System)
Organelles and FunctionsEdit
Understanding how a cell works can be difficult, so we compared the parts of a cell to a farm so it would be easier to understand.
The cell wall gives shape and support to a cell. It is like the fences around the farm, because they give it shape.
The cell membrane controls what enters and leaves the cell. It is like the gates into the farm, because they also control what enters and leaves.
The cytoplasm suspends the organelles and is everything inside the cellular membrane. It is like the grass, because it is inside the fence. Technically, the cytoplasm would be like everything that is inside the fence that isn't the house.
The mitochondria are the power houses of the cell and make energy for the cell to use. They are like cows, because they produce the milk that the farmers get money for so the farm can continue to function.
The Endoplasmic Reticulumn transports cellular products and allows cellular communication. It is like the tractors on a farm, because they transport different things to parts of the farm.
Ribosomes make proteins for use inside the cell as well as exporting. They are like the bailer, because it's makes bails, which are kind of like proteins.
Lysosomes break down cellular products and destroy the cell at the end of its life. They are like a compost pile, because it breaks down various things to make compost. Vacuoles store products, waste, and water. They are like hay bails, because they storing food for the cows.
The golgi body packages and marks products made by the cell. It is like the barn, because that is where the milk is collected and distributed.
Centrioles form spindle fibers during cell division. They are like paths or roads on the farm, because if people were going to split off and start their own farm, they would follow them to the gates leaving the farm.
The nucleus is the control center of the cell. It is like the farm house because that is also the control center.
The nuclear membrane separates the nucleus from the rest of the cell. It is like the walls of the house, because it separates the house from the rest of the farm.
The chromatin holds the DNA and information for the cell. It is like people who work on the farm, because they have the information about how the farm runs.
The nucleolus controls ribosome and protein production. This is like the main farmer that lives on the farm, because he controls the bailer and the production of hay bales for the cows.
The chloroplasts provide pigment for photosynthesis. They are like gardens on the farm, because they are used to make the food and there actually are chloroplasts in the plants in a garden.
Concentration gradient is transport from high concentrations to low concentrations, and vice versa. The names for these transactions are passive transport and active transport.
Passive transport is when something goes from a high concentration to a low concentration. This particular type of transport requires no energy to be done. There are two examples of this type of transport: diffusion and osmosis.
Diffusion is when a substance spreads out so there is an equal concentration of the substance in the area it is confined in.
In osmosis, the substance being referred to is always water, and it is always moving through a semipermeable membrane. All osmosis is also diffusion. However, not all diffusion osmosis.
Permeability can play a role is osmosis. There are several things that affect permeability, including time, size, concentration, and solubility. Solubility often affects permeability with fats.
When a solutions are at equilibrium, that means that they are of equal concentration. Another way to say that a solution is at equilibrium is to say that it is an isotonic solution. There are two other types of solutions as well, hypotonic and hypertonic.
Hypotonic means that there is barely any solute, the substance being dissolved. A cell in surrounded by this type of solution would expand in size. This is because there is a higher concentration of proteins and things inside the cell that cannot get out through osmosis, so the cell instead takes in water to make things equal.
Hypertonic is the opposite. This is when there is an exorbitant amount of solute in a solution. A cell in surrounded by this type of solution would shrink. This is because the concentration of the substances in the hypertonic solution is greater than the subtweets inside the cell. Therefor, the cell must get rid of some of it's water to make the concentrations the same.
All of the things mentioned above had to do with passive transport, but there is another type of transport as well. Active transport is when something goes from a low concentration to a high concentration. This type of transport is much more difficult and requires energy to be done. It is used when something the cell needs is too large to pass through the membrane, when something is in high concentration, or when the cell needs something quickly.
Phagocytosis is a type of active transport when a cell surrounds a particle it wants to take in and pulls it inside the membrane. Endocytosis is bringing things in and exocytosis is getting things out of the cell. Pinocytosis is very similar to phagocytosis, except instead of a particle, the cell takes in water or some other liquid.
The last type of active transport is the Sodium-Potassium pump. It uses proteins in the membrane as channels in order to work and it does three things. It pumps sodium out of the cell, pumps potassium into the cell, and it is used for nerve and muscle functions.
Mitosis is the splitting of all eukariotic cells, except for sex cells. During this process the nucleus divides and forms two nuclei. After the process is complete, there is two daughter cells with identical nuclei. Mitosis has five parts that include: Interphase, Prophase, Metaphase, Anaphase, and Telophase.
Interphase is the time between cell divisions. During this time, the cell grows and each chromosome duplicates. DNA is also duplicated and proteins are synthesized. Now the cell is ready to begin splitting.
During prophase, the chromosomes coil up and the nuclear membrane breaks down and dissapears.
In metaphase, the chromosomes are pushed to the center of the cell by spindle fibers.
The duplicated chromosomes separate from eachother and they migrate to opposite poles during anaphase.
Telophase, the last part of cell division, is when the cell actually divides. Every other phase is just preparing the cell for this last part. The individual chromosomes become thinner and longer and the nuclear membrane re-forms around each set of chromosomes. Cytokinesis happens during telophase and is when cytoplasm divides. In animal cells a groove appears in the membrane and curves inward until a complete membrane forms and separates the two daughter cells. In a plant cell it forms a cell plate and the plate expands until a wall is formed that separates the two cells.
After telophase, mitosis begins again and the two daughter cells begin with interphase.
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