Compendium Review unit 1

Human Evolution:
Evolution can explain the slow progression of the cell from a very simple Prokaryotic cell to a complex Eukaryotic cell and eventual progress into an organism. If you look back at history the story of evolution is clear. As with any controversial theory there are those who do not believe in the theory of evolution, they hold there ideas to other theories with no substantial proof. Today with modern technology there is strong evidence that all life as we know it started from one simple cell, and over millions of years that single cell evolved and became more advanced. Before the cell was formed you first had the atom, the fundamental building block of everything. The atom makes up all things organic and inorganic. From the atom the molecule was formed as the basis for living cells. From the cell all other life can be explained, an human organism is nothing if not millions of individual cells and molecules combined together.

Organic chemistry:
The study of one major element on the periodical table the Carbon Molecule. The Carbon Molecule is unique because it can for very long chains. The study of Carbon Molecules is biochemistry.
All cells are formed using 4 major molecules.

4 major molecules which make up a carbon-chain
- Carbohydrates = Are simple sugars broken down and used by the mitochondria in a cells metabolism process for energy.
- Proteins = Are made from amino acids, which are folded as amino chains in very complex and long forms to cause specific reactions (catalyzing specific chemical reactions). There can be thousands of different proteins used for specific reactions determined by there particular complex form.
Scientists are using super computers in a project called GenBlue to breakdown the proteins amino acid chains and try to understand there complex makeup. Even these super computers with the most advanced technology are having trouble understanding the complex makeup of proteins and how they fold.
- Fats = Also called Lipids form the cells membrane which separates the cell from the outside environment and allows the cell to maintain a homeostasis internal environment. (lipids basically do for the cell what the skin on our body does for us, protects from outside environment, helps regulate the internal environment and restricts what elements can enter via the proteins embedded it the cell membrane wall.
- DNA/RNA = Is made of nucleotides which form bases or a genetic sequence (A,C,T/U,G) millions of bases long. DNA has the ability to duplicate itself because it is very stable in its helix form. DNA holds all the genetic information for the cell and reproduction. DNA information is protected by chromosomes contained in the nuclear plasma and sent outside of the nuclear envelope using messenger mRNA.

Why does a cell need energy and what does a cell actually do? A cell needs to constantly produce energy just like a human organism. We constantly eat and drink to supply are body with nutrients, and many of those nutrients in one way or another go to the cells inside of us to supply them with energy for cellular metabolism and other functions. A cell uses energy to cause chemical reactions and when combined with thousands of other chemical reactions from thousands of other cells us life. Cells also use energy to reproduce themselves in cellular mitosis. When cells reproduce they can replace or repair dying or damaged cells or continue to help the body grow. The last concept here to point out is it takes thousands of chemical reactions to keep the simplest cells (e. coli bacteria) alive.
Cell Types:
Organism such as humans and plants are made of complex cells called Eukaryotic cells. Another much simpler and basic cell is the Prokaryotic cell. In the evolution of the cell there is proof that eukaryotic cells came from the prokaryotic cells combining together.
Prokaryotic Cells:
Are simple cells which are relatively small and generally have no organelles of there own. Prokaryotic cells are organelles such as mitochondria and chloroplasts in eukaryotic cells. All bacteria are prokaryotic cells.

Eukaryotic Cells:
Are 100X the size of prokaryotic cells and are very complex with organelles which are internally organized for maximum efficiency. Again the reason cells are so effacement at producing energy and reproducing is through a very long evolutionary process.
Prokaryotic Cells and Eukaryotic cells share some common traits. Both have a cell membrane and cytoplasm (fluid inside the cell). Each type of cell has ribosome’s for producing proteins from DNA. In the prokaryotic cell DNA molecules are free floating in the cytoplasm, while in eukaryotic cells there is a nucleus which houses the DNA with larger ribosome’s and all organelles are organized by an internal structure called the cytoskeleton. Both types of cells also have structures formed from microtubules for movement called flagella and cilia.

In describing the Eukaryotic cell and all its major functions I am going to start with the cell membrane and work inwards ending with cell reproduction.
Cell Membrane = As I have said before is the protection and separation of the cell from the outside environment. The membrane is formed from two layers of lipids (phospholipids bi layer) with proteins embedded in them which act as a gate to allow certain elements in and keep others out (selectively permeable). The cell needs a constant source of energy and a constant way to dispose of waste just like a human.
The cell has 5 major ways of movement across the plasma membrane. Diffusion, Osmosis, Facilitated transport, active transport and Endocytosis and exocytosis.
Since water is the universal solvent Osmosis is the diffusion of water molecules from an area of higher concentration to an area of lower concentration (diffusion). Using an anology of fire the smoke starts at the fire where there is a high concentration and wants to move away from the fire to a lower concentration in the air, eventually dissipating all together. When dealing with Osmosis the ideal situation is for the cell to have the same amount of water solute inside as the environment has outside called Isotonic. If there is too much water solute inside the cell compared to the environment outside the osmosis will pusch water out of the cell to equalize causing the cell to dry up (hypotonic). If the oposite occurs then the cell will get too much water and burst its normall shape (hypertonic).
With the concept of diffusion there is facilitated transport where the molecules will cross the the plasma membrane from higher concentration to lower concentration using a specific protein carrier imbedded with the lipids ( the protein carriers act as gates or pumps in the case of Active transport).
In a way active transport is opposite of the other three types of transport because regardless of the concentration levels a protein pump will use molecules of energy (ATP as the source of energy) and move molecules across the membrane.
The last two methods of transport are very similar, endocytosis is transporting molecules by ingesting them into the plasma membrane and forming a vesicle. Like forming a small version of the plasma membrane inside the cell as the molecule is transported inside. Exocytosis is the opposite and is used when the molecule inside is getting transported to the plasma membrane for removel out side of the cell.

For a cell the nucleus is the equivlent of our brain. All the information for reproduction and catalyzing reactions is housed in the nucleus in the form of DNA. The nucleus itself is housed in a nuclear envelope filled with nucleoplasm. Surronding the DNA are its personal group of proteins called chromatin which help in the transfer of information. Ribosomal RNA (rRNA) is transported to the Ribosomes by way of messanger mRNA.
Ribosome’s are used for proteins synthesis using the rRNA information and with the help of the rough endoplasmic reticulum. The ribosomes are attached to the endoplasmic reticulum, using an anology of a productin line. The ribosomes would be the robots on the assembly line and the endoplasmic reticulum would be the conveyor belt. the mRNA would be the computer controlling what type of product the robots are making, and the proteins would be the acutall product.
The smoth endoplasmic reticulum is similar in a way but without the ribosomes they do not produce proteins instead they make lipids and carbohydrates for energy.
Some of the proteins , carbohydrates and lipids are used immediately and some need to be shipped to other parts of the cell or even outside of the cell. Vesicles are like packaging boxes they are small sacs used for transport.

The golgi apparatus would be the next phase after the proteins, lipids, and carbohydrates have been formed. In the golgi apparatus these molecules are packaged and ready for shipment. golgi apparatus also has lysosomes which have digestive enzymes for breaking down incoming molecules. The enzymes attach themselves to incoming vesicles to breakdown molecules entering from the cell membrane.
The cell still needs a constant source of energy to power all of the organelles, just like any city or house needs energy to run equipment. For the cell the mitochondria provides the source of energy. The mitochondria shares many characteristics of a eukaryotic cell and produces ATP (adenosine troposphere) as energy. For the mitochondria to make ATP it first process simple sugars normally in the form of glucose. The glucose is broken down in a citric acid cycle and ATP is formed. There are a few other ways the cell can get energy besides ATP, carbohydrates, proteins and lipids from the cell membrane.
There is another process where energy is made which does not include ATP or oxygen. Fermentation is a process which occurs in the cytoplasm using glycolysis, 2 ATP molecules and lactate are made and can supply a burst of energy.
The cell has its own special way of moving around in your body and also moving molecules it wants closer to the cell membrane. The cell uses cilia and flagella which are basically arms extending from the cell made of microtubules.

So far I have discussed in detail the different functions a cell performs to stay alive and active, now I will talk about what a cell can do for a living organism. Cells can organize with other cells in a common goal and create something very functional and a necessity to all living things, tissue and skin. There are four major tissue types in a human organism, connective, muscular, nervous, and epithelial. There are of course other types of tissues besides these four but these are the major ones for a human.
The epithelial tissues is like a sheet covering the body. These tissues are bonded together in a tight network around the body and provide protection to other body parts.
The connective tissue are tissues like tendons, bone, cartilage, and blood vessels to name a few. They support other body parts and can range from solid to liquid. There are three main types of connective tissues, fibrous, supportive, and fluid.
The muscle tissue help with body and vital organ movement. These tissues are made of muscle fibers and protein fibers called actin and myosin. They generally come in three types skeletal (you can feel on the outside of the body), smooth (is on the inside of the body), and cardiac (which as one example makes up the heart and can beat).
The nervous tissue connects all the different parts of the body to each other and sends the data and communications so all the different parts can work together. There are two major types of cell for this group, neurons which carry the actual messages, and neuroglia which support the neurons.