QOD 9/14  Name 2 pieces of safety equipment that may be used in case of a fire in our laboratory?

Cell Biology Structure and Function

Cell Theory  Cell Theory: 3 Main Principles  All organisms are composed of one or more cells  Cells are the smallest units of life  And all cells come from pre-existing cells  How did we develop this theory?  Robert Hooke first described cells in 1665: observed a cork  Antonie van Leeuwenhoek observed the first living cell: animalcules (little animals)  1838: Mathias Schleiden: described plant cells as independent, separate beings  1839: Theodor Schwann made a similar statement about animal cells

How do we know all cells must come from pre-existing cells?  Louis Pasteur (1860’s)  Performed an experiment by sterilizing chicken broth  Sterile broth did not have any growth until it was exposed to the atmosphere

Modern interpretations  More recently, scientists have added another aspect to the cell theory:  All cells contain hereditary information (DNA) which is passed on from cell to cell during cell division

Are there any exceptions?  Cells may vary in size and shape, but have certain commonalities:  Cell membrane  Genetic material  Chemical reactions catalyzed by enzymes  Production of energy (ATP) through respiration

Exceptions  Some exceptions DO EXIST  Red blood cells  Lack a nucleus and organelles, cannot synthesize proteins  Fungal cells  Can have multiple nuclei  Striated muscle cells  Have a single surrounding membrane, but may contain up to 100’s of nuclei

Functions of life  All organisms are either unicellular or multicellular  Unicellular: one cell  Multicellular: more than one cell  Functions of life include: (remember, a unicellular organism CAN carry out the following)  Metabolism: the chemical reactions that occur in organisms in order for them to maintain life, such as the synthesis of ATP during cellular respiration  Growth: increase in size (volume and surface are) until the cell is too large to function efficiently  Reproduction: majority of prokaryotes reproduce through binary fission while single cell eukaryotes reproduce generally asexually, however some can also reproduce sexually through meiosis and then mitosis  Response: organisms respond to their environment  Homeostasis: maintaining a stable internal environment within the cell  Nutrition: creating or synthesizing their own organic molecules or consuming organic molecules

Functions of Life continued  Metabolism: all chemical reactions that occur within an organism  Growth may be limited but is always evident in some way  Reproduction involves hereditary molecules that are passed down to offspring  Response to environment: essential for survival

Cells and Sizes  Cells need to exchange substances with their surroundings  Food, waste, heat, and gases  In the cytoplasm, chemical reactions (called metabolic reactions) take place.  These reactions produce heat, wastes, and also consume resources  The RATE of reactions is proportional to the volume of the cell, while the exchange of these materials and heat energy is a function of the cell’s surface area  As the size of an object or a cell increases, its volume increases faster in comparison to the surface area of that object because  Volume is cubed (X^3) while surface are is only squared (X^2)

Limits to cell size  As a cell increases in size, its surface area to volume ratio will decrease

Limits to Cell Size  As the SA to volume ratio decreases (cell is getting bigger) the rate of exchange or the cell’s ability to exchange materials through diffusion or radiation decreases  Remember: the cell is constantly working to absorb substances such as oxygen and remove waste products such as carbon-dioxide, this balance must be kept at an optimum rate  Also, if too much heat is produce during metabolism (metabolic reactions also produce heat) and is not removed quickly enough, the cell may overheat  Best conditions:  The greater the SA/Volume ratio, the faster the cell can remove waste and heat and absorb oxygen and nutrients essential for the cell to function properly

Multicellular organisms  The whole is greater than the sum of its parts  Complex life systems involve millions of small simple interactions that work together to allow the complex system to function properly  Ex. Cohesive properties of water allow it to move up trees from the roots to cells in the leaves (for photosynthesis to take place).  The component parts: the interactions between molecules: the hydrogen bonding between oxygen and hydrogen molecules  These interactions between molecules allow the plant to function properly

Cellular Differentiation  Differentiation: the process where a less specialized cell becomes a more specialized cell  Large, multicellular organisms need to have specialized cells in order to live and function efficiently  What happens?  Differentiation changes a cell’s size, shape, membrane potential, metabolic activity, and responsiveness to signals  This happens during development:  After the zygote divides to from the blastocyst (around cells)

Gene Expression  Differentiation is controlled by gene expression  Some genes are turned on or turned off in specific cells that relates to their function  A nerve cell will contain all genetic information that other cells have, BUT, the genes for the nerve cell are turned on or EXPRESSED while the genes for other cells are shut off  When a gene is turned on, it will produce specific proteins or products that allow that cell to function properly  Some cells lose their ability to reproduce when they differentiate while other cells retain this ability throughout their lives  Ex. Nerve and muscle cells cannot reproduce once they differentiate while skin epithelial cells are able to reproduce

Stem Cells  What are they?  Cells that may divide through mitotic cell division and differentiate along different pathways to become a range of specialized cell types  Stem cells have the ability to become any type of cell until they express a certain gene and differentiate into a specific cell type  2 types  Adult stem cells: found in adult tissues such as bone marrow  Embryonic stem cells: found in the inner cell mass of blastocysts  Another source: cord blood stem cells found in the umbilical cord of newly born fetuses

Research  Bone marrow transplants:  Used to treat leukemia or lymphomas  Uses hematopoietic stem (HS) cells derived from bone marrow tissue  Continually divide to produce new red and white blood cells  The patient undergoes chemotherapy and radiation in preparation for the transplant  Stem cells move into the bone marrow of patient and begin reproducing healthy new blood cells  Embryonic stem cells  Used to regenerate skin tissue (for extreme burns) or treating diseases such as Type 1 diabetes (replaces damaged insulin producing cells)

Stem Cell Research continued  Cord blood stem cells:  cord blood stem cells cord blood stem cells  Adult Stem Cells  Adult Stem Cells cure Blindness Adult Stem Cells cure Blindness

Ethical Concerns  Therapeutic use of stem cells involves the creation of a new embryo  is it ethically acceptable to create a human embryo for research purposes if it has the potential to save human lives? Many views exist on when human life actually begins  Other issues  Could lead to human cloning  May lead to the selling of eggs for stem cell research  Health risks for women undergoing treatment with hormones (to induce hyperovulation for research purposes)  Arguments for use of stem cells is that it allows treatment of previously incurable diseases and conditions