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5.3 Regulation of the Cell Cycle Chapter 5 Cell Growth and Division Mr. Shilala DAHS KEY CONCEPT Cell cycle regulation is necessary for healthy growth. Internal and external factors regulate cell division. External Factors • External factors include physical and chemical signals. – Physical • Cell to cell contact – Chemical • Growth factors are proteins that stimulate cell division • Most mammal cells form a single layer in a culture dish and stop dividing once they touch other cells. External Factors • Growth factors – Broad group of Proteins Growth Factor Examples – Platelets – sticky fragments of bone marrow that help form clots • Contain a type of growth factor that helps the body repair wounds – Triggers the growth of many types of cells – Erythropoietin • Protein • Stimulates red blood cell production in absence of O2 Internal factors • External factors trigger internal factors, which affect the cell cycle • Two of the most important internal factors are kinases and cyclins. Internal Factors • Kinases – A kinase is an enzyme, when activated, transfers a phosphate group – which typically increases the energy of the target molecule or changes its shape • Cells have many types of kinases Internal factors – Cyclins are a group of proteins that are rapidly made and destroyed at certain points in the cell cycle • Kinases in cell cycle are activated by cyclins Apoptosis • Apoptosis is programmed cell death – Normal feature of healthy organisms balanced by cell division – Caused by a cell’s production of selfdestructive enzymes • Cells collapse inward – Occurs in • Development of infants • Plants – when leaves fall off • Injury – necrosis – Cell swells and bursts webbed fingers Cell division is uncontrolled in cancer. • Cancer cells form disorganized clumps called tumors. – Benign tumors remain clustered and can be removed. – Malignant tumors metastasize, or break away, and can form more tumors. normal cell cancer cell bloodstream • Cancer cells do not carry out necessary functions making tumors harmful • Cancer cells come from normal cells – Most cancer cells contain mutations or damage to genes involved in cell-cycle regulation proteins – Examples • Oncogenes - accelerate cell cycle • Others act as cell cycle brakes Mutations in cell cycle genes • Inherited – Breast cancer • Exposure to radiation or chemicals – Melanoma • Carcinogens are substances known to promote cancer. – Tobacco or pollutants • Viruses Cancer Treatments • Standard cancer treatments typically kill both cancerous and healthy cells. – Radiation and chemotherapy – Damage cells DNA • Most of what is known comes from lab grown cancer cells – HeLa Cells – Obtained from cervical tumor Henrietta Lacks in 1951 • Immortal????