Cell Growth, Division, and Reproduction
Why are cells small? What are some of the difficulties a cell faces as it increases in size? Difficulties Larger Cells Have: More demands on its DNA Less efficient in moving nutrients/waste across its cell membrane Information Overload Cells store DNA (info is used to build the molecules needed for cell growth) As a cell increases in size, its DNA does not If a cell were to grow without limit, an information crisis would occur
Information Crisis Compare a cell to a growing town. The town library has a limited number of books. As the town grows, these limited number of books are in greater demand, which limits access. Growing cells makes greater demands on its genetic library Cells can only get so big before they quit functioning
Surface Area to Volume Why cells must divide as they grow? For a growing cell, a decrease in the relative amount of cell membrane available creates serious problems Surface area the total area of the surface of a 3D object Volume the amount of space inside 3D object Volume grows more rapidly then the surface area, thus decreasing surface area a quicker rate
Cell Division Before a cell grows too large, it copies all its DNA and divides Cell division process by which a cell divides into two new daughter cells it then divides into two daughter cells, each daughter cell receives a complete set of DNA cell division reduces cell volume an increased ratio of surface area to volume for each daughter cell allows for efficient diffusion within a cell (movement of materials across the membrane)
Cell Reproduction Asexual Reproduction: production of genetically identical offspring from a single parent Sexual Reproduction: production of offspring that inherit its genetic information from each their two parents
Asexual Reproduction Both prokaryotic/eukaryotic single celled organisms and many multicellular organisms can reproduce asexually In single celled organisms, cell division is a form of reproduction Advantages? Disadvantages? Bacteria reproduce by binary fission Plants form plantlets Hydras reproduce by budding
Sexual Reproduction Offspring are produced by the fusion of two sex cells one from each of two parents Offspring inherit genetic information from both parents Most animals/plants and many single celled organisms reproduce sexually Advantages? Disadvantages?
Cell Cycle
Chromosomes Chromosomes genetic information bundled into packages of DNA Carries the genetic info that is hereditary Chromosomes make it possible to separate DNA precisely during cell division. Ball of yarn example
Prokaryotic Chromosomes Lack nuclei (DNA found in cytoplasm) Contain a single chromosome holds organism sdna.
Prokaryotic Cell Cycle The prokaryotic cell cycle includes: 1. Growth 2. DNA replication 3. Cell division called binary fission Simpler than eukaryotic
Prokaryotic Cell Cycle Binary fission form of asexual reproduction during which two genetically identical cells are produced. Ex: Bacteria
Eukaryotic Chromosomes Eukaryotic cells have more DNA than prokaryotes and contain multiple chromosomes
Eukaryotic Cell Cycle Four phases: G 1, S, G 2, and M. Interphase is the time between cell divisions (consists of the G 1, S, and G 2 ) M phase is the period of cell division (consists of Mitosis, Cytokinesis)
G 1 Phase: Cell Growth In G 1 phase: cells increase in size make new proteins/ organelles
S Phase: DNA Replication In the S phase: DNA replication
G 2 Phase: Preparing for Cell Division In the G 2 phase: Getting ready to divide Organelles required for cell division are produced
M Phase: Cell Division In eukaryotes, M phase (cell division) occurs in two stages: 1. Mitosis division of cell nucleus. 2. Cytokinesis division of cytoplasm.
Stages of Cell Division Mitosis
Prophase (Phase 1) Duplicated chromosome condense and become visible
Prophase (Phase 1) The centrioles move to opposite sides of nucleus and help organize the spindle fibers
Prophase (Phase 1) Animal Cell Plant Cell
Metaphase (Phase 2) Centromeres of the duplicated chromosomes line up across the center of the cell. Spindle fibers connect the centromere of each chromosome to the two poles of the spindle
Metaphase (Phase 2) Animal Cell Plant Cell
Anaphase (Phase 3) Centromeres are pulled apart and the chromatids separate to become individual chromosomes near the poles of the spindle
Anaphase (Phase 3) Animal Cell Animal Cell Plant Cell
Telophase (Phase 4) Chromosomes spread out and uncoil A nuclear envelope reforms around each cluster of chromosomes The spindle breaks apart
Telophase (Phase 4) Animal Cell Plant Cell
Cytokinesis Division of Cytoplasm Cytokinesis: splits one cell into two Animal Cells membrane folds in and cytoplasm is pinching into two equal parts Plant Cells cell wall is less flexible so a cell plate forms between the 2 new nuclei, eventually forming new cell membrane and wall
Cell Cycle
REMEMBER! Interphase Prophase Metaphase Anaphase IPMATC Telophase Cytokinesis IPlay Music At The Concert
Mitosis Review Plant Cells versus Animal Cells
Animal Mitosis Review Put the following phases in order and label them! 1. 2. 3. 4. 5. 6.
Plant Mitosis Review Put the following phases in order and label them! 1. 2. 3. 4. 5. 6.
Regulating the Cell Cycle
Controls on Cell Division Cell Cycle controlled by regulatory proteins Proteins can be inside and outside the cell Proteins control cell growth and division Can be turned on and off EXAMPLE: when an injury such as a broken bone occurs, cells are stimulated to divide rapidly and start the healing process. The rate of cell division slows when the healing process nears completion.
Cyclins Cyclins - a family of proteins that regulate timing of the eukaryotic cell cycle Cyclins are continually produced and destroyed within cells. Cyclin production signals cells to enter mitosis, while cyclin destruction signals cells to stop dividing and enter interphase.
Cancer: Uncontrolled Cell Growth Cancer: a disorder in which body cells lose the ability to control cell growth How do cancer cells differ from other cells? Don't respond to the signals that regulate growth Cells divide uncontrollably Absorb nutrients needed by other cells, block nerve connections, and prevent organs from functioning
Tumors Tumor: when cells divide uncontrollably to form a mass of cells Benign Tumor: noncancerous, doesn t spread to surrounding healthy tissue Malignant tumor: cancerous, invades and destroys surrounding healthy Metastasis: the spread of cancer cells to other parts of the body