Unit 1

Humans are multicellular beings, they are made up of many different types of cells. Cells are the fundamental unit of life. There is nothing smaller than a cell. All living things are made up of cells. New cells come from preexisting cells. To be classified as life item needs to energy to survive, it needs to reproduce, it grows and develops over time, it maintains a stable condition which is called homeostasis and it responds to stimulus.
Let's get back to cells. The first life was a cellular life. All cells are made up of molecules. There are two types of cells Prokaryotic cells and Eukaryotic cells. Prokaryotic cells are simple cell, they are pretty small, there are no orangelles in the cytoplasm. An example of this kind of cell is bacteria cells. There is no nucleus in this type of cell. A nucleus is a membrane enclosed structure where DNA is found. Prokaryotic cells all have a cell membrance, small ribosomes where proteins are assembled from DNA information, flagella and cilia which are microtubule structures, DNA that's loose in the cytoplasm, and mitochondria and chloroplasts.
Eukaryotic cells are complex, about 100 times bigger than prokaryotic cells, they are organized internally with membrane bound organelles. These are the types of cells that multicellular organisms are made of. Euraryotic cells all have a cell mambrane, a nucleus, mitochrondria and chloroplasts, and an internal membrane. The internal membrane organizes the cellular spaces and the distribution of molecules of life with in the cell.
A cells membrane or a plasma membrane seperates the cell from the outside world, it helps regulate the internal environment.

Organelles - small structures that perform specific functions
Cytoplasm - semifluid medium that contain water and various types of molecules suspended or dissolved in the medium

Now lets go back to molecules, there are different types of molecules. Carbohydrates, proteins, fats and lipids are all types of molecules that are unique to each cell. Carbohydrates are simple sugars used for energy storage in a complex form. They are broken down into simple sugars that fuel cellular metabolism in mitochondria. Proteins are complex amino acids. They are complex because the amino acid chain is folded. The complexity allows specific chemical reactions to occur. Fats/lipids are fundamental to life, they seperate the interior of cell from the outside environment. They are also used for long term storage.

There are many different components that make up a cell. There is the plasma membrane, the nucleus, mitochondria, ribosomes, cilia and flagella to name just a few. There is also DNA in each cell. In the following paragraphs I will talk a little about each of these.
First lets discuss mitochondria and chloroplasts. These are little bacterial cells within our cells that are functionally integrated. They each perform a fundamental cell function. Mitochondria uses sugars to produce energy in the form of ATP and chloroplasts make sugars by using photosynthesis. They also maintain their own DNA and genetic control. Mitochondria are a folded ogranelle in the eukaryotic cell.
DNA and RNA are composed of nucleotides also called bases. One strand of DNA can be millions of bases long. The function of DNA is to use and store information. DNA duplicates itself to pass on information. I will discuss more about this topic later on.
The plasma membrane helps keep the shape of the cell. It lets some substances into the cell and keeps other substances out of the cell. The pm is embedded with proteins and contains cholesterol, carbohydrates, and lipids. There are different way things move in the plasma membrane. The first is diffusion, this is when the molecules move randomly from a high concentration to a low concentration. The next type is facilitated transport, a protein carrier moves molecules across the pm from high concentration to low concentration. Active transport is when a protein carrier moves molecules from a low concentration to a high concentration using ATP as energy. ATP gives people bursts of energy. ATP is produced in the mitochondria and uses glucose, carbohydrates, proteins, or lipids. The process of making ATP is called cellular respiration. Endocytosis transports molecules into a cell to form a vesicle. Exocytosis transporst molecules outside of a cell.
Cilia and flagella are microtubules that are used in the movement of a cell. Cilia are 20 times shorter than flagella.

Lets talk a little about protein synthesis. Proteins are what control a cell metabolism, the cell metabolism is what make a cell alive. The process begins in the nucleus. The nucleus contains DNA and proteins which are called chromatin. It also contains ribosomes. Ribosomes are made of RNA and proteins. This where the protein synthesis takes place. Here is a brief overview of the process. Molecules are transported into a cell. The rough er is studded with ribosomes, this is where the proteins are made. The smooth er makes the lipids and carbohydrates. The golgi apparatus is where the proteins and lipids are processed, packaged and delivered to the er. The vesicles are used to transport the proteins. Before the proteins enter the cell, they go through they lysosomes which contains digestive enzymes that break down the parts/substances entering the vesicle.

Tissue is a multi-cellular organism and is made of millions of cells. Tissue is composed of the same type of cells that all work together to perform common functions. There are four different types of tissue connective, muscle, nervous and epithelial. Connective tissue binds and supports certain parts of the body. It holds together tendons, bone, cartilage, and supports blood vessels, verves and cells. Connective tissue is composed of ground substance and protein fibers. Ground substance is noncellular and can range from a solid to a fluid. The next type of tissue is muscle. This tissue lets the body move. It is made of muscle and protein fibers. The three types of muscle tissue are skeletal, smooth and cardiac. The next type of tissue is nervous. This type is the communication between cells through the use of sensory input, integration of data and the motor output. There are two types of nervous tissue neurons which carry the messages and neuroglia which supports the neurons. The last type of tissue is epithelial tissue. This kind is composed of a group of cells that form a tight and continuous network. Epithelial tissue lines the body cavities, covers the bodies surfaces and is also found in glands. The cells in this tissue are anchored on one side and are free on the other side.

The next section goes over DNA in more detail, genetics and cancer. The first topic I will go over is DNA and the various process involved with it.
DNA is a double helix that is two strands wound in a spiral. DNA is made to replicate, it does so when the two strands seperate. DNA replicates to pass on information. When DNA replicates is goes through a process called gene expression. DNA is transcribed to make proteins run the cells metabolism, it is then transcribed to mRNA, mRNA is transcribed to amino acid sequence, the amino acid folds up into the protein, and then the proteins catalyze the reactions of cell metabolism. This process happens so that the cell metabolism can function.
Each long strand of DNA in a nucleus are called chromosomes. Each chromosome is organized and wrapped up with proteins giving it a certain shape. There are 23 pairs of chromosomes, 1 in each pair is from the mother and 1 in each pair is from the father.
Mitosis is the process of the DNA/chromosome replicating. In this process cells divide. There are only three reasons why cells divide and that is for growth, repair or replacement. Mitosis keeps the body functioning, it is constantly occuring. In the end it produces two daughter cells. The first phase in mitosis is called the prophase. In this phase the chromosomes appear, the nucleolus disappears, the centrosomes move to opposite sides and the spindle fibers appear and attach to the centrosomes.
The second phase is called the metaphase. During this time the chromosomes line up down the middle of the cell. The spindle fibers are now fully formed as well. Anaphase is the next one. During this the sister chromatids are seperate at the centromeres and start to move towards each pole.
The last phase is telophase and cytokinesis. During this phase the chromosomes arrive at their poles and become chromatin again. The nucleoli reappear and the spindles disappear. The nuclear envelope reassambles. And finally the two daughter cells are formed.
Here are some terms to know:
Transcription - DNA is read to make a mRNA in the nucleus of the cells. During this DNA opens and the mRNA transcript is made from the DNA template.
Translation - the reading of the mRNA to make a protein in the cytoplasm. This happens outside the nucleus. The ribosomes do the translation, they attach onto the mRNA and line up amino acids according to the mRNA sequence.
Lastly I will go over cancer. Cancer cells do not contribute to body functioning and they lack differentiation. They have an abnormal nuclei and an abnormal amount of chromosomes. They have an unlimited ability to divide, they do so for no reason at all. Cancer cells become abnormal gradually, they go through a multistage process. The first stage they go through is called initiation. During this process the cell becomes mutated, which causes it to constantly divide. The second stage is promotion. In this stage the cell developes a tumor. The thrid stage is progression. During this stage cells mutate and start invading the surrounding tissues.
Oncology is the study of cancer. There are five different types of cancer:
Carcinomas - cancers of the epithelial tissue
Adenocarcinomas - cancers of glandular epithelial cells
Sarcomas - cancers of the muscle and connective tissues
Leukemias - cancers of the blood
Lymphoma - cancers of the lymphatic tissues
There are different causes of cancer, one of them is genetic. Environmental is another one. This could be from to much exposure to radiation, environmental carcinogens such as tobacco smoke, and viruses. In order to develope cancer you must have more that one mutation within your lifetime.
There are seven warning signs of cancers:
1. a change in bowel or bladder movements
2. a sore that doesn't heal
3. unusual bleeding or discharge
4. a lump in the breast or somewhere else
5. indigestion or a difficulty swallowing
6. an obvious change in a mole or wart
7. a nagging cough or hoarseness
It is a good idea to do routine screening to make sure you don't develope cancer or to detect it faster and start treatments. Skin cancer is one of the most common types of cancer. Some of the treatments include surgery, radiation therapy, chemotherapy and bone marrow transplants. These are just a few of the types of therapy a person with cancer can get.