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The Cell Cycle Chapter 2: Section 3 What Is The Cell Cycle? The regular sequence of growth and division that cell undergo Check out Pages 54 & 55! Know the events that occur as one parent cell becomes two daughter cells! Remember This? multicellular organism: cells are the same size if you are a whale or a mouse Reasons Why Cell Size Is Limited: size is related to function; i.e. red blood cells volume increases more rapidly than surface area surface area of membrane cannot support volume of cytoplasm inside (diffusion): cell would die nucleus can only control so much cytoplasm INTERPHASE Interphase - period between cell divisions - genetic material in form of chromatin - nucleus surrounded by membrane - nucleolus (1 or more) present and visible - DNA replicates (makes a copy of itself) Interphase Mitosis cell division; process of duplicating and dividing chromosomes; growth and repair parent cells: cells that divide daughter cells: cells that result from division; each daughter cell has exactly the same number and type of chromosome as parent cell mitosis is an ongoing cell process but we can identify 5 main stages or phases: Prophase "first" phase - chromatin shortens and thickens into chromosomes - chromosomes are paired into sister chromatids - nucleoli & nuclear membrane "disappear" - spindle fibers form from each pole(end) of cell - middle of cell now called equator Prophase Metaphase "middle" phase - chromosomes move to equator and line up - paired chromosomes are attached to spindle fibers Metaphase Anaphase - sister chromatids separate toward opposite poles - appear to be pulled by shortening spindle fibers - phase ends when chromatids reach poles Anaphase Telophase - chromosomes become chromatin again - spindle fibers disappear - "new' nuclei appear with nucleoli - cytoplasm divides at equator (cytokinesis) - 2 new daughter cells result Telophase Cytokinesis Cytoplasm divides Organelles distributed into each new daughter cell Animal cell = “cleavage” Plant cell = “cell plate” Daughter cells enter Interphase Animal vs. Plant Cell *animal cells: cell membrane pinches off **plant cells: formation of cell plate which becomes new cell wall some cells are so specialized that they don't divide; red blood cells; nerve cells cells spend most of their time in interphase Chromosomes & Replication Replication Process •2 sides of DNA molecule unwind and separate; like a zipper •new nitrogen bases floating in nucleus pair up with exposed bases •A with T & C with G •continues until both sides are complete; two new molecules are exactly like the original! •Cell can now proceed with cell cycle Chapter 2 Section 4 CANCER What is Cancer? a disease in which cells grow and divide uncontrollably, damaging parts of the body around them 100’s of types of cancer How cancer begins something damages a portion of DNA in achromosome mutation = a change in DNA disrupts the cell cycle, causing cells to divide in an uncontrolled way CANCER 2. How Cancer Spreads a. tumor = a mass of abnormal cells that develops when cancerous cells divide and grow uncontrollably b. some cancerous cell break off and enter the bloodstream Lung Cancer! CANCER 3. Treating Cancer surgery can be used if the cancer has not spread radiation (high-energy beams) may be used on fast-growing cancers chemotherapy (using drugs to kill cancer) is effective because it can spread throughout the body all treatments can have serious side effects, so scientists are always looking for new treatments CANCER 4. Cancer Prevention a. 2/3 cancer deaths are due to tobacco or unhealthy diet