1 / 17

Why are cells so small and how do they grow?

Why are cells so small and how do they grow?. AKA: surface area to volume ratios and mitosis. Why not grow BIGGER?. Cells usu. Do not grow indefinitely bigger 1st reason: high demand on DNA, “DNA” overload

valiant
Download Presentation

Why are cells so small and how do they grow?

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. Why are cells so small and how do they grow? AKA: surface area to volume ratios and mitosis

  2. Why not grow BIGGER? • Cells usu. Do not grow indefinitely bigger • 1st reason: high demand on DNA, “DNA” overload • Ex: public library with 1000 books serves 2,000 people. Population increases to 10,000 people, wait lists… • 2nd reason: difficult moving nutrients/waste across cell membrane/exchanging material • Surface area to volume, volume increase and surface area does not keep pace • Ex: Town has a 2 lane main street, population jumps from 2,000 to 10,000…congestion moving things in and out.

  3. Division of the cell • Before a cell becomes too large, forms daughter cells • 1 cell = 1 daughter cells; cell division • First what has to happen? - DNA replication, need another copy of the DNA; • G 1 phase • S phase • G 2 phase • Mitosis • Cytokinesis

  4. Cell Cycle

  5. Mitosis: prophase • Interphase: cell growth G1, DNA replication S phase, G2 preparation for mitosis • Cell Division • Prophase: chromatin chromosomes, centrioles separate, spindle forms, paired up in chromatids • Pro= before/start

  6. Mitosis: metaphase (meta=middle) • Metaphase: Chromosomes line up in middle, spindle fiber connected to centromere • Meta=middle

  7. Mitosis: anaphase • Anaphase: sister chromatids separate into individual chromosomes and are moved apart • Ana=apart

  8. Mitosis: telophase Telophase: chromosomes gather at opposite ends, new nuclear envelopes will form. Cleavage furrow forms-animal cells, pinch apart Cell plate- plant cells forms in middle and pushes apart

  9. Mitosis is done, Now comes… • Cytokinesis: Cytoplasm splits; cytoplasm pinches in half, each daughter cell as an identical set of duplicate chromosomes

  10. What do you remember? • Chromatin • Centrioles • Chromosomes • Sister Chromatid • Individual chromosomes • Centromere • Spindle fiber • Nuclear envelope • Cleavage furrow • Cell plate

  11. Chromatin • Centrioles • Chromosomes • Sister Chromatid • Individual chromosomes • Centromere • Spindle fiber • Nuclear envelope • Cleavage furrow • Cell plate • DNA, unwound with proteins • In cyto, holds onto the spindle fiber • Condensed package of DNA • Pairs of duplicated chromosomes • Located in the middle of the sister chromatids, spindle fiber attaches here • Fan like microtubule structure that helps to separate the chromosomes • Dissolves to allow mitosis to begin • The cell membrane pinches in during telophase • The cell plate/wall forms and pushes the plant cells apart

  12. Label this…

  13. Label this…

  14. Label this…

  15. Regulating the Cell Cycle • Controls on cell division: • Proximity • IInjury • Cyclin- a protein that tells cells to enter the cell cycle • Cell Cycle regulators • Internal regulators: proteins assure that the previous steps have been completed. Ex: protein that checks that the spindle fiber has attached before anaphase continues • External regulators: proteins outside cell speed up/slow down cell cycle. Ex: growth factors that aid in healing

  16. Uncontrolled Cell Growth • Cancer: a disorder in which some of the body’s own cells lose the ability to control growth • Cancer cells do NOT respond to the signals that regulate the growth of most cells • As a result they divide uncontrollably; cell cycle is broken down • Many cancers have a defect at gene p53 = causes cells to lose info needed to respond to signals that would control growth

More Related