Regulating the Cell Cycle
The cell cycle is controlled by regulatory proteins both inside and outside the cell. Cyclins proteins that regulate the timing of the cell cycle in eukaryotic cells. Internal regulators proteins that respond to events inside a cell. They allow the cell cycle to proceed only once certain processes have happened inside the cell. External regulators proteins that respond to events outside the cell. They direct cells to speed up or slow down the cell cycle. Growth factors are external regulators that stimulate the growth and division of cells. They are important during embryonic development and wound healing.
When an injury such as a broken bone occurs, cells are stimulated to divide rapidly and start the healing process. The rate of cell division slows when the healing process nears completion. These are all controlled by regulatory proteins.
Cells end their lives in one of 2 ways By accident due to damage or injury Apoptosis
A process of programmed cell death. Plays a key role in development by shaping the structures of tissues & organs in plants & animals.
Cell growth has to be regulated carefully because uncontrolled cell growth can be severe. Ex. Cancer
Oral Cancer Disorder in which body cells lose the ability to control growth. Cancer cells do not respond to the signals that regulate the growth of most cells. As a result, the cells divide uncontrollably. Cancer cells form a mass of cells called a tumor. Cancer: http://www.youtube.com/watch?v=lepttolebqo&feature=related
Adisease characterized by uncontrolled cell division & growth. Tumors are of 2 types: 1. Benign Tumor: stays in one place, usually harmless. 2. Malignant Tumor: cells move around in the body. Results in CANCER. The spread of cancer cells is called metastasis. Cancer cells absorb nutrients needed by other cells, block nerve connections, prevent organs from functioning.
Chen Zongtao with 154 LB. tumor on his right leg.
Caused by defects in genes that regulate cell growth & cell division. A damaged or defective p53 gene is common in cancer cells. The damage causes cells to lose the information needed to respond to growth signals. Some sources of gene defects are: smoking tobacco, radiation exposure, defective genes, viral infection.
Lung Cancer- smoking
UV exposure Karposi Sarcoma
Some localized tumors can be removed by surgery. Ex. Melanomas most serious form of skin cancer. (Early detection)
300 lbs Tumor Removed Video http://www.youtube.com/watch?v=dvdux KegwZw Lai Thi Dao, a 15 year old Vietnamese girl, endured a huge facial tumor called a Schwannoma for most of her life
Many tumors can be treated with targeted radiation. Ex. Cancer cells that growth rapidly Chemotherapy is the use of compounds that kill or slow the growth of cancer cells. Problems with the fact it kills normal cells.
Cell Differentiation
The human body contains ~100,000,000,000,000 (100 trillion) cells. All produced from 47 cell cycles. We all started life as one cell We all pass through an early stage of development stage called an embryo.
During development, an organism s cells become more differentiated and specialized for particular functions. For example, a plant has specialized cells in its roots, stems, and leaves.
The process by which cells become specialized is known as differentiation. During the development of an organism, cells differentiate into many types of cells. Ex. Nerve, skin, cardiac cells, etc.
Important because it helps to determine the cell s ultimate identity. Ex. Will the cell spend its life as a nerve cell or a muscle cell.
The unspecialized cells from which differentiated cells develop are known as stem cells.
There are two types of stem cells: embryonic and adult stem cells.
All the cells in the body formed from a fertilized egg cell Totipotent cell, able to form all the tissues of the body. Fertilized egg and the cells produced by the first few cell divisions of embryonic development are truly totipotent.
After about four days of development, a human embryo forms into a blastocyst, Blastocyst: a hollow ball of cells with a cluster of cells inside known as the inner cell mass.
The cells of the blastocyst have started to specialize: Outer cells form the tissue that attach the embryo to its mother. Inner cell mass form the embryo Inner cell mass is called pluripotent cells
Cells capable of developing into many, but not all, of the body's cell types.
Embryonic stem cells are pluripotent. embryonic stem cells have the capacity to produce most cell types in the human body.
Adult stem cells are multipotent They can produce many types of differentiated cells. Adult stem cells of a given organ or tissue typically produce only the types of cells that are unique to that tissue.
Stem cell research may lead to new ways to repair the cellular damage that results from heart attack, stroke, and spinal cord injuries. One example is the approach to reversing heart attack damage illustrated below. Finger regrown video: http://www.youtube.com/watch?v=u3ni psfba
Ethical Issue: Harvesting, or gathering, embryonic stem cells cause destruction of the embryo. Political Issue: Government funding of embryonic stem cell research is an important political issue. VIDEO: http://www.teachersdomain.org/asset/nsn08_vid_stemcell2/ OR http://www.pbs.org/wgbh/nova/teachers/body/stem-cells-breakthrough.html
Groups seeking to protect embryos oppose such research as unethical. Other groups support this research as essential to saving human lives and so view it as unethical to restrict the research.