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10.1 Cell Growth • Living things grow because it produces more and more cells. • Are the cells of an adult larger than the cells of a baby? NO!!! Adults just have more cells than babies do. Limits to Cell Growth • Volume increases faster than surface area • The larger a cell becomes, there are more demands put on that cell. “DNA overload.” – Nutrients and waste have a hard time going in and out of the cell. Hammond population and highways Ratio of Volume to Surface Area Surface area= (length x width x 6) cm2 Volume= (length x width x height) cm3 Ratio of volume S.A. to Volume= SA/ Volume What happens when a cells gets too large? • Cell division- process whereby the cells divide into two daughter cells • Before the cell divides all the DNA is copied. • Each new daughter cells gets its own “genetic library” they each get all the DNA. 10.2 Cell Division • Process in which the cell divides into two daughter cells. Each has the same exact information as the original cell. – Before cell division occurs the cell must replicate or copy all its DNA. – Solves the problem of DNA overload by dividing (reduces the cell’s volume) – Allows efficient exchange of materials with the environment. Chromosomes • Structures found in the nucleus of a cell that contain genetic information. • Human cells have 46 chromosomes • 23 chromosomes from mom • 23 chromosomes from dad Make up of a chromosome • A chromosome is composed of two . identical chromatids attached by a centromere. Each chromatid is made up of tightly wound DNA wrapped around histones. Chromosomes • DNA coils around a special protein called a HISTONE. • DNA and HISTONE make up NUCLEOSOMES. Cell Cycle • A cell grows, prepares for division, and divides to form two daughter cells…each of which repeat the cycle again. • From One mitosis to the next mitosis • Interphase, Cell division (mitosis), cytokinesis Interphase • • • • G1=cell growth S phase= DNA is replicated G2=cell prepares for mitosis Kind of like intermission…can’t really see this happening, but happens behind the scene. Interphase Mitosis • Process in which the nucleus of a cell divides. • Divided into four phases – Prophase-1st, longest phase. Chromatin condenses and chromosomes become visible. – Metaphase-2nd phase (shortest) chromosomes line up at center of cell – Anaphase-3rd phase chromatids split and separate to opposite poles – Telophase-4th phase. Almost two new cells, but not completely separated. Mitosis Prophase Metaphase Anaphase Telophase Cytokinesis • The cytoplasm pinches in half. Each daughter cell has an identical set of duplicate chromosomes. Fine TUNING what you’ve learned. • http://www.youtube.com/watch?v=ODwt6 OdN-8Y 10.3 Regulating the Cell Cycle • Cyclin Protein Regulators- regulate the timing of the cell cycle. – Internal Regulators- make sure that mitosis has waited for chromosomes to replicate all the DNA. – External Regulators- speed up or slow down mitosis. Cancer • Uncontrolled cell growth is called cancer • Most healthy cells will stop dividing when they come into contact with one another. • Cancer cells do not stop when touch another cell. Grows until the nutrient supply is gone. Cancer What do cells do incase of injury? • Cells rush to the cite of the wound and rapidly divide. • They start to slow down when they get close to each other. • When do they stop? – When they touch one another… – At this time…you most likely have a scab. On that note…we are done with this chapter.