Chapter 9: Cell Growth & Division
9.1Objectives:
1. Explain why cells are relatively small. 2. Summarize the primary stages of the cell cycle. 3. Describe the stages of interpahse.
Chapter 9
Cellular Reproduction
9.1 Cellular Growth
Ratio of Surface Area to Volume
9.1 Cellular Growth
As the cell grows, its volume increases much more rapidly than the surface area. The cell might have difficulty supplying nutrients and expelling enough waste products.
9.1 Cellular Growth
Transport of Substances Substances move by diffusion or by motor proteins.
Diffusion over large distances is slow and inefficient. Small cells maintain more efficient transport systems.
9.1 Cellular Growth
Cellular Communications The need for signaling proteins to move throughout the cell also limits cell size.
Cell size affects the ability of the cell to communicate instructions for cellular functions.
Cell Division • Chromosomes – made up of DNA, which carries the cell’s genetic coded information. – Cells of every organism have a specific # of chromosomes: • Fruit flies = 8 chromosomes • Humans = 46 chromosomes • Carrot = 18 chromosomes
Cell Division Before cell division, each chromosome is replicated or copied. Each chromosome consists of 2 identical sister chromatids. Each pair of chromatids are attached at the centromere, which is located near the middle of the chromatids
The Cell Cycle Cell division prevents the cell from becoming too large.
It also is the way the cell reproduces so that you grow and heal certain injuries. Cells reproduce by a cycle of growing and dividing called the cell cycle. During the cell cycle: a cell grows, prepares for division, and divides to form 2 daughter cells, each of which then begins the cycle again.
The Cell Cycle • The cell cycle consists of 4 phases: G1, S, G2 & M. • G1, S & G2 are also known as Interphase. • Interphase is the normal, functioning phase and not one of active cell division, however it should be noted that replication of DNA and the duplication of the centrosome takes place in interphase--both necessary before mitosis can take place.
The Cell Cycle G1 phase
M phase
S phase
G2 phase
9.1 Cellular Growth
Interphase is the stage during which the cell grows, carries out cellular functions, and replicates. Mitosis is the stage of the cell cycle during which the cell’s nucleus and nuclear material divide.
Cytokinesis is the method by which a cell’s cytoplasm divides, creating a new cell.
The Stages of Interphase The first stage of interphase, G1 (1st growth) The cell is growing, carrying out normal cell functions, and preparing to replicate DNA. They increase their (size) protoplasm and synthesize . Some organelles are made as well.
The Second Stage of Interphase, Ssynthesis phase During this period, the chromosomes are replicated. This means that new DNA material is made. It is an exact copy of the original DNA material that is in the nucleus.
The Third Stage of Interphase, G2, (growth of parts, 2nd growth) G2 is the phase where final production of organelles takes place and the cell finishes preparations for cell division. The cell prepares for the division of its nucleus.
• M is the phase where mitosis takes place. It consists of mitosis and cytokinesis. It results in two identical daughter cells being produced.
9.2 Objectives 1. Describe the events of each stage of mitosis. 2. Explain the process of cytokinesis.
Mitosis consists of
• 4 subphases: – Prophase, Metaphase, Anaphase, and Telophase
• Cytokinesis – This process occurs during telophase. – The cytoplasm is divided by the cell membrane. • Animal cells pinch inward from the edges • Plant cells build a cell plate between the cells.
9.2 Mitosis and Cytokinesis
The Stages of Mitosis Prophase The cell’s chromatin tightens. Sister chromatids are attached at the centromere.
Spindle fibers form in the cytoplasm.
9.2 Mitosis and Cytokinesis
The nuclear envelope seems to disappear. Spindle fibers attach to the sister chromatids.
9.2 Mitosis and Cytokinesis
Metaphase Sister chromatids are pulled along the spindle apparatus toward the center of the cell.
They line up in the middle of the cell.
9.2 Mitosis and Cytokinesis
Anaphase The microtubules of the spindle apparatus begin to shorten. The sister chromatids separate. The chromosomes move toward the poles of the cell.
9.2 Mitosis and Cytokinesis
Telophase The chromosomes arrive at the poles and begin to relax. Two new nuclear membranes begin to form and the nucleoli reappear. The spindle apparatus disassembles.
9.2 Mitosis and Cytokinesis
Cytokinesis In animal cells, microfilaments constrict, or pinch, the cytoplasm. In plant cells, a new structure, called a cell plate, forms.
Visualizing the Cell Cycle
Section 10-2
Spindle forming Centrioles
Nuclear envelope
Chromatin
Centromere Chromosomes (paired chromatids)
Interphase
Prophase
Cytokinesis
Go to Section:
Spindle Centriole
Telophase Nuclear envelope reforming
Centriole
Individual chromosomes
Anaphase
Metaphase
Section 10-2
Spindle forming Centrioles
Nuclear envelope
Chromatin
Centromere Chromosomes (paired chromatids)
Interphase
Prophase
Cytokinesis
Go to Section:
Spindle Centriole
Telophase Nuclear envelope reforming
Centriole
Individual chromosomes
Anaphase
Metaphase
Section 10-2
Spindle forming Centrioles
Nuclear envelope
Chromatin
Centromere Chromosomes (paired chromatids)
Interphase
Prophase
Cytokinesis
Go to Section:
Spindle Centriole
Telophase Nuclear envelope reforming
Centriole
Individual chromosomes
Anaphase
Metaphase
Section 10-2
Spindle forming Centrioles
Nuclear envelope
Chromatin
Centromere Chromosomes (paired chromatids)
Interphase
Prophase
Cytokinesis
Go to Section:
Spindle Centriole
Telophase Nuclear envelope reforming
Centriole
Individual chromatids
Metaphase
Anaphase
Karyokinesis
Section 10-2
Spindle forming Centrioles
Nuclear envelope
Chromatin
Centromere Chromosomes (paired chromatids)
Interphase
Prophase
Cytokinesis
Go to Section:
Spindle Centriole
Telophase Nuclear envelope reforming
Centriole
Individual chromosomes
Anaphase
Metaphase
Section 10-2
Spindle forming Centrioles
Nuclear envelope
Chromatin
Centromere Chromosomes (paired chromatids)
Interphase
Prophase
Cytokinesis
Go to Section:
Spindle Centriole
Telophase Nuclear envelope reforming
Centriole
Individual chromosomes
Anaphase
Metaphase
Section 10-2
Spindle forming Centrioles
Nuclear envelope
Chromatin
Centromere Chromosomes (paired chromatids)
Interphase
Prophase
Cytokinesis
Go to Section:
Spindle Centriole
Telophase Nuclear envelope reforming
Centriole
Individual chromosomes
Anaphase
Metaphase
Mitosis Foldable
Objectives: 1. Describe what happens during the four phases of mitosis.
Interphase
Cell membrane
Nuclear membrane Chromatin material Nucleolus Centrosome Cell Membrane
Interphase
• G1 – cell growth • S – DNA replication • G2 – Prepares for mitosis
Prophase Chromosome
Spindle fibers
Prophase • • • •
1. Chromatin condensed into chromosomes 2. Nucleolus fades and disappears 3. Centrosomes divides forming 2 centrioles 4. Nuclear membrane fades and disappears
Metaphase Chromosomes
Spindle Fibers
Metaphase • 1. Chromosomes in middle of cell • 2. Nuclear membrane and nucleolus are gone • 3. Spindle fibers formed and attach to chromosomes
Anaphase Membrane Pinches in
Chromatids
Animal cell
Anaphase • 1. Chromosomes separate as chromatids move to opposite ends of cell = Karyokinesis • 2. Plasma membrane pinches inward in animal cell • Plant Cell • 3. Cell plate develops - no pinching • 4. Lacks centrioles
Telophase
Pinching of the cell membrane
Nucleolus Chromatin Nuclear Membrane Centrioles
Cell Membrane
Telophase • 1. Nuclear Membrane and nucleolus reform • 2. One centriole in each new cell
Cytokinesis
Cell Membrane
Nucleolus
Chromatin Nuclear Membrane Centrioles
Cytokinesis • 1. Cytoplasm pinches in half with each daughter cell having identical set of chromosomes • 2. Plant Cell creates a cell plate dividing the cell into daughter cells having identical set of chromosomes
Quiz 12/11/09
YOU HAVE 5 MINUTES TO PREPARE FOR YOUR POP QUIZ
Quiz 1. What are the 3 stages of Interpahse? What happens in each? 2. What are the stages of mitosis in order? 3. What stage of mitosis do the chromosomes line up in the middle of the cell? 4. What stages does Karyokinesis occur? 5. What stage does the cytoplasm divided?
9.3 Objectives 1. Summarize the role of cycline proteins in controlling the cell cycle. 2. Explain how cancer relates to the cell cycle. 3. Describe the role f apoptosis. 4. Summarize the two types of stem cells and their potential uses.
9.3 Cell Cycle Regulation
Normal Cell Cycle Different cyclin/CDK combinations signal other activities, including DNA replication, protein synthesis, and nuclear division throughout the cell cycle.
9.3 Cell Cycle Regulation
Quality Control Checkpoints The cell cycle has built-in checkpoints that monitor the cycle and can stop it if something goes wrong.
Spindle checkpoints also have been identified in mitosis.
9.3 Cell Cycle Regulation
Abnormal Cell Cycle: Cancer Cancer is the uncontrolled growth and division of cells.
Cancer cells can kill an organism by crowding out normal cells, resulting in the loss of tissue function.
9.3 Cell Cycle Regulation
Causes of Cancer The changes that occur in the regulation of cell growth and division of cancer cells are due to mutations.
Various environmental factors can affect the occurrence of cancer cells.
9.3 Cell Cycle Regulation
Apoptosis Programmed cell death Cells going through apoptosis actually shrink and shrivel in a controlled process.
9.3 Cell Cycle Regulation
Stem Cells Unspecialized cells that can develop into specialized cells when under the right conditions
9.3 Cell Cycle Regulation
Embryonic Stem Cells After fertilization, the resulting mass of cells divides repeatedly until there are about 100–150 cells. These cells have not become specialized.
9.3 Cell Cycle Regulation
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 Cellular Reproduction
