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44 Cards in this Set
- Front
- Back
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Name 2 reasons why cells divide rather than continue to grow indefinitely.
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1)DNA "Overload" - DNA in cell is not enough to meet needs of the cell.
2) Exchanging Materials - food, oxygen & water enter the cell and waste products leave the cell. If the cell grows too large and the ratio of volume to surface area changes, this exchange of materials is no longer effective. |
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When a cell grows in size, does it make extra copies of it's DNA?
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No, that's why the cell has to divide. The small amount of DNA cannot work for a cell that keeps increasing in size.
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What determines the rate at which food and oxygen in a cell are used and waste products produced?
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Cell's volume
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How do you determine a cell's ratio of surface area to volume?
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Divide the cell's surface area by it's volume
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As a cell grows in size, which increases more rapidly -- the cell's volume or the cell's surface area?
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Volume of the cell increases much more rapidly than surface area as the cell grows
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What happens to a cell's ratio of surface area to volume as the cell grows?
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The ratio of surface area to volume decreases which causes serious problems for the cell.
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Before a cell becomes too large, a growing cell divides forming two _____________ cells.
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Daughter
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The process by which a cell divides into 2 daughter cells is known as _______ ___________.
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Cell Division
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How does cell division solve the problem of increasing size?
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The cell copies all its DNA and each daughter cell gets one complete set of genetic information. Cell division also reduces cell volume, solving the problem of surface area to volume ratio and allowing efficient exchange of materials through the cell membrane.
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Is cell division more complicated in a prokaryote or a eukaryote?
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Eukaryote
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What are the 2 stages of cell division in a eukaryote?
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mitosis and cytokinesis
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In eukaryotic cells, how is genetic information passed from one generation of cells to the next?
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chromosomes
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What are chromosomes made up of?
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DNA
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Chromosomes in most cells are not visible except during _______ __________.
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Cell division
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Before cell division, chromosomes are copied and consist of two identical "sister" _____________.
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chromatids
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Each pair of chromatids is attached at an area called ___________
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centromere
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What do we call the period of growth in between cell divisions?
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interphase
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Describe the four phases of the cell cycle.
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Mitosis and cytokinesis = M phase
Cell growth, new proteins and organelles = G1 Chromosome replication or synthesis = S phase Preparation for Mitosis = G2 |
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What is the cell cycle?
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Series of events that cells go through as they grow and divide.
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Name the 4 phaes of Mitosis.
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Prophase, metaphase, anaphase and telophase
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What is the first and longest phase of mitosis?
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prophase -- 50-60% of the time required for mitosis
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Name the two tiny structures located in the cytoplasm that separate and move to opposite sides of the nucleus during prophase.
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centrioles
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What is the spindle?
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a fanlike structure that helps separate the chromosomes during prophase
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What happens during metaphase?
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The chromosomes line up across the center of the cell.
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What is the third phase of Mitosis?
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Anaphase
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What happens during anaphase?
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The centromeres that join the sister chromatids split allowing the sister chomatids to separate and become individual chromosomes. The chromosomes move until they separate into 2 groups near the poles of the spindle.
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What is the fourth and final phase of mitosis?
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Telophase
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What happens in telophase?
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The chromosomes being to disperse and a nuclear envelope reforms around each cluster of chromosomes. The spindle begins to break apart and a nucleosus become visible in the daughter nucleus. Mitosis is complete, but cell division is not complete.
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In which phase of mitosis do the chromosomes become visible?
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prophase
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In which phase of mitosis do the chromosomes move to form two groups near the poles of the spindle?
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anaphase
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In which phase of mitosis does a nuclear envelope re-form around each cluster of chromosomes?
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telophase
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In which phase of mitosis do the centrioles take up position on the opposite sides of the nucleus?
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prophase
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In which phase of mitosis do the chromosomes line up across the center of the cell?
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metaphase
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In which phase of mitosis does the nucleolus become visible in each daughter nucleus?
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telophase
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What is cytokinesis?
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The division of cytoplasm during cell division
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How does cytokinesis occur in most animal cells?
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The cell membrane is drawn inward until the cytoplasm is pinched into two nearly equal parts.
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In plants, name the structure that forms midway between the divided nuclei during cytokinesis?
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cell plate
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What happens to cell at edges of an injury when a cut in the skin or a break in a bone occurs?
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They are stimulated to divide rapidly producing new cells and starting the process of healing
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What happens to the rate of cell division when the healing process nears completion?
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The rate or cell division slows down and controls on growth are restored.
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What do cyclins regulate?
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The timing of the cell cycle in eukaryotic cells.
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What are internal regulators?
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proteins that respond to events inside the cell and only allow the cell cycle to proceed when certain processes have taken place.
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What are external regulators?
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Proteins that respond to events outside the cell and direct cells to speed up or slow down the cell cycle. They include growth factors and prevent excessive cell growth and keep tissues of the body from disrupting each other.
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What is cancer?
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A disorder in which some of the body's own cells lose the ability to control growth.
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Cancer cells form masses of cells called
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tumors
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