Cell Size Limitations. The Cell Cycle. The Cell Cycle. Cell Size Limitations. Unit 5: Cellular Reproduction. Unit 5: Cellular Reproduction

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1 Cell Size Limitations Unit 5: Cellular Reproduction Transport of substances Diffusion Motor Proteins Chapter 9: Pages Cellular communications How do cells send signals to each other? Unit 5: Cellular Reproduction Cells and in a cycle called the cell cycle. I. Cellular Growth II. Mitosis and Cytokinesis III. Three main stages: 1. Interphase 2. Mitosis 3. Cytokinesis I. Cellular Growth Cell Size Limitations Most cells are less than 100 µm (100 x 10-6 ) in diameter. Factors that influence cell size: Ratio of surface area to volume. of substances Cellular communication Interphase: Stage during which the cell, carries out cellular functions, and makes copies of it s. 3 substages: G 1, S, G 2 Cell Size Limitations Remember A cell is not flat, but a 3D structure that is filled with cytoplasm and organelles. Ratio of Surface Area to Volume SA=Area covered by plasma membrane. V=space taken up by cytoplasm and organelles. SA:V Ratio =

2 Interphase First stage G 1 (Gap 1) Cell grows, functions, and prepares to it s DNA (replicate = make a copy of) Mitosis Stage during which the cell s and nuclear material divide. 4 substages: P M A T Interphase Second stage S (Sythesis) The cell replicates it s DNA. In what structure is the cell s DNA found? Cytokinesis Method by which a cell s divides. Creates two. Where is the cell s DNA found? Chromosomes The structures that contain the that is passed from generation to generation of cells. Prokaryotic cell division: What type of cells are prokaryotic? They divide through binary fission. Chromatin The form of DNA in a cell s nucleus. Interphase Third stage G 2 (Gap 2) The cell prepares for division of it s. The cell takes inventory and makes sure it is ready to continue. When ready, it will continue on to the next stage. Relate cell size to cell function. Why is cell size limited? Summarize the primary stages of the cell cycle. Describe what happens to DNA during S phase.

3 Make a diagram of the cell cycle and describe what happens in each. Prophase What is the difference between chromatin, chromosomes and sister chromatids? If a cube representing a cell is 5 µm on a side, calculate the SA:V ratio. Is this a good size for the cell? Explain Centromere: structure at the center of the chromosome where sister chromatids are attached. II. Mitosis and Cytokinesis Chromosomes Mitosis The key activity of mitosis is the accurate of the cell s replicated DNA. Enables the cell to produce two genetically daughter cells. Growth Replace damaged cells. The Stages of Mitosis Prophase Chromatin into chromosomes. Metaphase Chromosomes align along the middle of the cell using spindle apparatus. disappears. Spindle fibers begin to form between poles. Nuclear disintegrates. Prophase Anaphase The microtubules of the spindle apparatus begin to shorten. Sister chromatids are pulled apart and towards the of the cell. Spindle apparatus: spindle fibers, centrioles, and aster fibers.

4 Telophase The chromosomes arrive at the poles and begin to relax. Two new nuclear membranes begin to form and the nucleoli reappear. The result? The spindle apparatus disassembles. III. The timing and rate of cell division are important to the health of an organism. A mechanism involving and controls the cell cycle. Cytokinesis In animal cells, microfilaments constrict, or pinch, the cytoplasm. In plant cells, a new structure, called a cell plate, forms. Normal Cell Cycle Cyclin: protein that bind to CDKs Cyclin-dependant kinases: enzymes to which cyclin binds during interphase and prophase. ***The binding of cyclin and CDKs and activities during the cell cycle. Explain why cytokinesis alone does not produce daughter cells. Normal Cell Cycle Describe the events of each stage of mitosis. Diagram and label a chromosome in prophase. Identify the stage of mitosis in which a cell spends the most time. Contrast cytokinesis in a plant and animal cell. Normal Cell Cycle Apoptosis: Programmed cell death Hypothesize what would happen if a drug that stopped microtubule movement but did not affect cytokinesis was applied to a cell. If a plant cell completes the cell cycle in 24 hours, how many cells will be produced in a week? Why would a cell purposely kill itself?

5 Apoptosis Most of an organism s cells are specialized for a certain. Stem Cells Unspecialized cells that can into specialized cells under the right conditions. Try think of a situation where apoptosis should occur, but it doesn t. Stem Cells. Abnormal Cell Cycle: Cancer: The uncontrolled growth and division of cells. Embryonic Stem Cells After fertilization, the resulting mass of cells divides repeatedly until there are about cells. These cells have not become. Each cell has the to specialize into a wide variety of cell types. - Cancer The changes that occur in the regulation of cell growth and division of cancer cells are due to. Various factors can affect the occurrence of cancer cells. Stem Cells Why might embryonic stem cells be valuable to medicine? Carcinogens: substances and agents that are known to cause cancer. Cancer Known carcinogens: Asbestos Tobacco Ultraviolet radiation Other forms of radiation Acetaldehyde Probable carcinogens Talc Stem Cells Adult Stem Cells Found in various tissues in the body and might be used to maintain and repair the same kind of tissue. Less controversial because the adult stem cells can be obtained with the consent of their donor Harvard: NS tissue used to restore lost brain tissue in mice Florida: Pancreatic tissue used to restore pancreas function in mice.

6 Describe how cyclins control the cell cycle. Describe a possible application for stem cells. Explain how the cancer cell cycle is different from a normal cell cycle. Explain the difference between embryonic and adult stem cells. Identify three carcinogens. Contrast apoptosis and cancer. Hypothesize what might happen if apoptosis did not occur in cells that have significant DNA damage.