Presentation on theme: "Warm-up 11/11/14 Why is there a limit to cell size? Why do we not have cells as big as buildings?"— Presentation transcript:
1 Warm-up 11/11/14Why is there a limit to cell size? Why do we not have cells as big as buildings?
2 Which turtle has bigger cells? Neither!!!Their cells are the same size… this one just has MORE!
3 Why don’t cells continue to grow? There are two main reason why cells divide instead of continue to grow:The larger the cell becomes, the more demands the cell places on its DNAThe cell has more trouble moving enough nutrients and wastes across the cell membrane.
4 DNA “Overload”Information that controls a cell’s function is stored in a molecule knows as DNAIn eukaryotic cells, DNA is found in the nucleus
5 DNA “Overload”When a cell is small, the information stored in the DNA is able to meet all of the cell’s needsIf a cell was too large an “information crisis” would occur and the cell would not function properly
11 Ratio of Surface Area to Volume The volume increases much faster than the surface area, causing the ratio of surface area to volume to decrease.This decrease creates serious problems for the cell.Formula for calculating ratio:Ratio = Surface Area/Volume
13 Cell DivisionIn eukaryotes, cell division occurs in two major stages. The first stage, division of the cell nucleus, is called mitosis. The second stage, division of the cell cytoplasm, is called cytokinesis.
18 When the cell divides, the chromatids separate When the cell divides, the chromatids separate. Each new cell gets one chromatid.
19 The Cell CycleThe cell cycle is the series of events that cells go through as they grow and divide. Interphase is the period of growth that occurs between cell divisions.
20 During the cell cycle: a cell grows prepares for division divides to form two daughter cells, each of which begins the cycle again
21 The cell cycle consists of four phases: G1 (First Gap Phase)S PhaseG2 (Second Gap Phase)M PhaseG0 Phase (Restingphase)
22 Events of the Cell Cycle During G1, the cellincreases in sizesynthesizes new proteins and organelles
23 During the S phase,chromosomes are replicatedDNA synthesis takes placeOnce a cell enters the S phase, it usually completes the rest of the cell cycle.
24 The G2 Phase (Second Gap Phase) organelles and molecules required for cell division are producedOnce G2 is complete, the cell is ready to start the M phase—Mitosis
25 Cell CycleDuring the cell cycle, the cell grows, replicates its DNA, and divides into two daughter cells. DNA synthesis takes place during the S phase. Cell division takes place during the M phase. G1 and G2 are gap phases.
26 MitosisBiologists divide the events of mitosis into four phases: (PMAT)ProphaseMetaphaseAnaphaseTelophase
27 MitosisMost eukaryotic cells go through a regular cycle of interphase, mitosis and cytokinesis. Mitosis has four phases: Prophase, Metaphase, Anaphase and Telophase. The events shown here are typical of animal cells.Mitosis
28 Chromosomes (paired chromatids) Section 10-2Spindle formingProphaseMitosisProphaseChromosomes (paired chromatids)CentromereMost eukaryotic cells go through a regular cycle of interphase, mitosis and cytokinesis. Mitosis has four phases: Prophase, Metaphase, Anaphase and Telophase. The events shown here are typical of animal cells.
29 Prophase Prophase is the first and longest phase of mitosis. The centrioles separate and take up positions on opposite sides of the nucleus.SpindleformingCentromereChromosomes(paired chromatids)
30 SpindleformingThe spindle is forming and the pairs chromosomes are visible. The centrosome helps to organize the spindle, a fanlike microtubule structure that helps separate the chromosomes.CentromereChromosomes(paired chromatids)
31 SpindleformingChromatin condenses into chromosomes. The centrioles separate and a spindle begins to form. The nuclear envelope breaks down.CentromereChromosomes(paired chromatids)
33 Metaphase The second phase of mitosis is metaphase. The chromosomes line up across the center of the cell.Microtubules connect the centromere of each chromosome to the poles of the spindle.CentrioleSpindle
35 Anaphase Anaphase is the third phase of mitosis. IndividualchromosomesAnaphaseAnaphase is the third phase of mitosis.The sister chromatids separate into individual chromosomes.The chromosomes continue to move until they have separated into two groups.
40 During cytokinesis, the cytoplasm pinches in half During cytokinesis, the cytoplasm pinches in half. Each daughter cell has an identical set of duplicate chromosomes
41 Cytokinesis in PlantsIn plants, a structure known as the cell plate forms midway between the divided nuclei.Cell plateCell wall
42 The G0 Phase (resting phase) The cell leaves the cell cycle and quits dividing.This may be a temporary resting period or more permanent.Ex: Nerve cells and heart muscle cells no longer divide after reaching maturity.