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Passive transport Active transport Exocytosis Endocytosis

Membrane Transport. Passive transport Active transport Exocytosis Endocytosis. Membrane Transport. Facilitated diffusion. Channel proteins and carrier proteins. Membrane Transport. Active transport requires energy to move molecules across a membrane. Lower solute concentration.

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Passive transport Active transport Exocytosis Endocytosis

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  1. Membrane Transport • Passive transport • Active transport • Exocytosis • Endocytosis

  2. Membrane Transport Facilitated diffusion Channel proteins and carrier proteins

  3. Membrane Transport • Active transport requires energy to move molecules across a membrane. Lower solute concentration Solute ATP Higher solute concentration

  4. Membrane Transport *Active transport Example: sodium-potassium pump

  5. Membrane Transport *Voltage *Membrane potential *Some ion pumps generate voltage across membranes Electrogenic pump:

  6. Membrane Transport *Each cell membrane has characteristic set of carrier proteins

  7. MEMBRANE TRANSPORT Passive Transport (requires no energy) Active Transport (requires energy) Diffusion Facilitated diffusion Osmosis Higher solute concentration Higher water concentration (lower solute concentration) Higher solute concentration Solute Solute Solute Water Solute ATP Lower water concentration (higher solute concentration) Lower solute concentration Lower solute concentration

  8. Traffic of Large Molecules • Exocytosis is the secretion of large molecules within vesicles. Outside of cell Plasma membrane Cytoplasm

  9. Traffic of Large Molecules • Endocytosis takes material into a cell within vesicles that bud inward from the plasma membrane.

  10. Transport of large molecules Exocytosis Types of endocytosis found in animal cells: Endocytosis *Phagocytosis *Pinocytosis *Receptor-mediated endocytosis

  11. Cellular Reproduction Cell division Functions of cell division: *reproduction *growth and development *repair

  12. Cellular Reproduction • In asexual reproduction: • Single-celled organisms reproduce by simple cell division • There is no fertilization of an egg by a sperm FUNCTIONS OF CELL DIVISION Asexual Reproduction LM Sea stars African Violet Amoeba

  13. Cellular Reproduction • Sexual reproduction requires fertilization of an egg by a sperm using a special type of cell division called meiosis.

  14. Eukaryotic Chromosomes LM Chromosomes

  15. Eukaryotic Chromosomes DNA double helix Histones • The DNA in a cell is packed into an elaborate, multilevel system of coiling and folding. • Histones are proteins used to package DNA in eukaryotes. • Nucleosomes consist of DNA wound around histone molecules. “Beads on a string” TEM Nucleosome Tight helical fiber Looped domains Duplicated chromosomes (sister chromatids) TEM Centromere

  16. Chromosome Structure Chromosome Centromere Sister Chromatids

  17. The Cell Cycle S phase (DNA synthesis; chromosome duplication) • The cell cycle consists of two distinct phases • Interphase • Mitotic phase Interphase (90% of time) G1 G2 Mitotic phase (M) (10% of time) Mitosis Cytokinesis

  18. Interphase INTERPHASE Centrosomes (with centriole pairs) Interphase Chromatin • G1: Metabolism and growth • End of G1: Cell signaled to divide • S (synthesis): DNA is duplicated • G2: Cell forms chromosomes, completes preparations for cell and nuclear division Nuclear envelope Plasma membrane LM

  19. Prophase and Prometaphase PROPHASE Fragments of nuclear envelope Early mitotic spindle Centrosome Centromere Chromosome, consisting of two sister chromatids Spindle microtubules

  20. Metaphase, Anaphase, Telophase METAPHASE ANAPHASE TELOPHASE Nuclear envelope forming Cleavage furrow Daughter chromosomes Spindle

  21. Cytokinesis Animal cells Plant cells

  22. Meiosis • Sexual reproduction requires fertilization of an egg by a sperm using a special type of cell division called meiosis.

  23. Meiosis Homologous chromosomes separate. Chromosomes duplicate. Sister chromatids separate. Duplicated pair of homologous chromosomes Pair of homologous chromosomes in diploid parent cell Sister chromatids MEIOSIS II MEIOSIS I INTERPHASE BEFORE MEIOSIS

  24. Meiosis MEIOSIS I: INTERPHASE PROPHASE I METAPHASE I ANAPHASE I Microtubules attached to chromosome Sister chromatids remain attached Centrosomes (with centriole pairs) Sites of crossing over Spindle Sister chromatids Nuclear envelope Centromere Pair of homologous chromosomes Chromatin Homologous chromosomes pair up and exchange segments. Pairs of homologous chromosomes split up. Pairs of homologous chromosomes line up. Chromosomes duplicate.

  25. Meiosis MEIOSIS II: SISTER CHROMATIDS SEPARATE TELOPHASE II AND CYTOKINESIS TELOPHASE I AND CYTOKINESIS PROPHASE II METAPHASE II ANAPHASE II Cleavage furrow Sister chromatids separate Haploid daughter cells forming Two haploid cells form; chromosomes are still doubled. During another round of cell division, the sister chromatids finally separate; four haploid daughter cells result, containing single chromosomes.

  26. Meiosis Cross over: How do we account for genetic variation? *Independent assortment *Crossing over *Random fertilization Independent Assortment:

  27. Mitosis and Meiosis

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