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Date: January 14, 2016 Aim #46: Why do cells need to divide? Do Now: Warm-Up Notebook Date Title of Activity 1/14 Surface Area to Volume Ratio Page # 79 HW: 1) Read Chapter 10-1 (Cell Growth) pages 241-243 2) Quarterly Exam Tuesday 1/26 (periods 1 & 7) and Wednesday 1/27 (period 5) 3) Plant Packet due Monday, February 1st!!! (follow calendar of deadlines) Aim #46: Why do cells need to divide? Compare the size of these organisms Vs. Vs. 1) Do these organisms have different size cells? No, the cells of a large organism are the same size of a small organism. 2) How do organisms get so big? Cell Division 3) Why do cells divide rather than grow in size? XX XX XX XX XX XX XX XX + XX XX DNA “Overload” Small Town DNA Library The larger the cell, the greater the demands on the DNA library. Eventually, the cell’s DNA would no longer be able to serve the increasing needs of the growing cell. City 4) Exchange of Materials What part of the cell is responsible for the exchange of materials in and out of the cell? Cell Membrane The rate at which particles are able to move across the cell membrane depends on the surface area of the cell (the amount of the cell surface exposed to the environment). SA Rate of Exchange 5) Surface Area Small particles have a relatively larger surface area than large particles. Why? What will melt first? The smaller chips have more surface area. Vs. Ice Cube Ice Chips Smaller cells have more surface area and can exchange materials across membrane more efficiently. 6) What is Cell Division? The process by which a cell divides into 2 new daughter cells. 7) What happens to chromosomes before a cell divides? Replication is the The chromosomes are replicated process by which DNA before a cell divides. makes a copy of itself 9) Why is it beneficial for daughter cells to be smaller? Smaller size of daughter cells increases the surface area and increases rate of exchange of materials across the membrane. Chromosomes What are chromosomes made up of? DNA and Protein The chromosomes are replicated before a cell divides. Centromere Chromatids Chromosome Replication Chromosome 2 Chromatids + Centromere When do cells divide? Organism Growth Cells at the root tips divide very rapidly When do cells divide? Repair 12) What tissues in our body need to undergo a lot of cell division? Skin Stomach Why? Bone The cells of these tissues are constantly growing or repairing themselves. Cell Cycle 1) G1 Phase- Cells increase in size and synthesize new proteins and organelles. 2) S Phase- DNA (chromosomes) are replicated. 3) G2 Phase- Many of the molecules and organelles for cell division are produced. 4) M Phase- the cell undergoes cell division. Does anybody know what the “M” stands for? Mitosis Chromosomes Mitosis Images Spindle Fibers Mitosis is the process that divides the cell’s nucleus into two, each with a complete set of genetic material from the parent cell.