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Explore the critical reasons why cells need to divide, including DNA overload, surface area-to-volume ratio, and the cell cycle phases like mitosis. Learn how cells ensure proper growth and function through division.
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Why Cells Divide • DNA overload • Small cell – information stored in DNA meets all the cells needs • Cell growth without limits leads to “information crisis”
Why Cells Divide • Exchange of materials • Nutrients and waste leave the cell through the cell membrane • Rate of exchange depends on surface area of cell • Rate at which nurtrients are used and waste products produced depends on volume of cell
Why Cells Divide • Ratio of surface area to volume • As a cell increases in size, volume increases much more rapidly than surface area • Ratio of surface area to volume decreases • Decrease in ratio causes problems for the cell
Cell Division • To avoid decreasing ratio of surface area to volume, cells divide before they become too large • Each daughter cell has increased the ratio of surface area to volume
The rate at which materials enter and leave through the cell membrane depends on the cell’s a. Volume b. Weight c. Mass d. Surface area
Cell Cycle and Mitosis • Genetic information that is passed from one generation to the next is carried by chromosomes • Chromosomes are made up of DNA and protein • Cells of every organism have a specific number of chromosomes
Chromosomes are not visible in most cells except during cell division • At beginning of cell division, chromosomes condense • Before cell division, each chromosome is copied • Each chromosome consists of two identical “sister” chromatids attached at a centromere
Chromosomes • Replicated chromosome • Consists of 2 sister chromatids • Exact copies of each other • Connected by a centromere • Cell division separates chromatids • Each new cell gets one copy of each chromosome
Genetic information that is passed on from generation to generation is carried by ____________ Chromosomes.
Chromosomes are made up of _______________ DNA and proteins
Pairs of identical chromatids are attached to each other at an area called the a. Centriole b. Centromere c. Spindle d. chromosome
The Cell Cycle • The cell cycle is the series of events that cells go through as they grow and divide • During the cell cycle a cell… • Grows • Prepares for division • Divides to form two daughter cells
The Cell Cycle • G1 – cell growth • S – chromosomes are replicated; synthesis of DNA molecules • G2 – organelles and molecules required for cell division are produced • M – mitosis and cytokinesis
Interphase • The cell grows and replicates its DNA and centrioles
4 Phases of Mitosis • Prophase • Metaphase • Anaphase • Telophase
Prophase • Chromatin condenses into chromosomes • Centrioles separate • Spindle begins to form • Nuclear membrane breaks down
Metaphase • Chromosomes line up across center of cell (the “metaphase plate”) • Each chromosome is connected to a spindle fiber at its centromere
Anaphase • Sister chromatids separate into individual chromosomes and are moved apart
Telophase • Chromosomes gather at opposite ends of the cell • Two new nuclear membranes form
The cell cycle is the a. Series of events that cells go through as they grow and divide b. Period of time between the birth and death of a cell c. Time from prophase until cytokinesis d. Time it takes for one cell to undergo cytokinesis
Which of the following is a phase of the cell cycle? a. G1 phase b. G2 phase c. M phase d. All of the above
Which of the following is NOT a correct statement about the events of the cell cycle? a. Interphase is usually the longest phase b. DNA replicates during the S phase c. Cell division ends with cytokinesis d. The cell grows during the G2 Phase
The two main states of cell division are called a. Mitosis and interphase b. Synthesis and cytokinesis c. The M phase and the S phase d. Cytokinesis and mitosis