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CYTOLOGY

CYTOLOGY. THE STUDY OF CELLS - FUNCTION. CELLULAR ACTIVITIES. Transport systems – Processes of Transport Across Cell Membrane The Cell Cycle – Cellular Activities from Formation to Death or Division Protein Synthesis – using DNA & RNA to make proteins. TRANSPORT SYSTEMS.

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CYTOLOGY

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  1. CYTOLOGY THE STUDY OF CELLS - FUNCTION

  2. CELLULAR ACTIVITIES • Transport systems – Processes of Transport Across Cell Membrane • The Cell Cycle – Cellular Activities from Formation to Death or Division • Protein Synthesis – using DNA & RNA to make proteins

  3. TRANSPORT SYSTEMS • Passive Transport (does not require energy) • Active transport (does require energy; ATP most common form)

  4. PASSIVE TRANSPORT SYSTEMS • Diffusion • Facilitated diffusion • Osmosis

  5. PASSIVE TRANSPORT SYSTEMS: DIFFUSION • Molecules in constant motion • Molecules move from [high] to [low] • Continues until Equilibrium

  6. DIFFUSION

  7. Diffusion through a membrane

  8. FACILITATED TRANSPORT OR DIFFUSION • Requires special proteins (enzymes) • Integral Membrane Proteins • “Escort” molecules across membranes (e.g. Glucose)

  9. Facilitated Diffusion

  10. OSMOSIS • “Special case” of diffusion • Only water moves • Water moves across a selectively permeable membrane • Water moves from [low solute] to [high solute]

  11. OSMOSIS

  12. Tonicity • Concentration of solutes in a solution (relative to the concentration inside the cell) • Isotonic = concentration is the same • Hypotonic = lower concentration of solutes • Hypertonic = higher concentration of solutes

  13. TONICITY

  14. ACTIVE TRANSPORT SYSTEMS • Facilitated active transport • Endocytosis • Exocytosis

  15. FACILITATED ACTIVE TRANSPORT • Molecules are moved against a concentration gradient • Integral Proteins act as Carrier Molecules • Sodium and potassium pump moves Na+ out of cell and K+ into cell

  16. ENDOCYTOSIS • Materials accumulate at surface of plasma membrane • Membrane evaginates or invaginates, pinches off • Includes: • phagocytosis – engulfment of large solids (e.g. WBCs & bacteria/viruses) • pinocytosis – engulfment of extracellular fluid

  17. EXOCYTOSIS • Releases substances outside cell • Secretory vesicles fuse to cell membrane • Cellular products, e.g., secretion • Cellular wastes

  18. Endocytosis Exocytosis

  19. CELL CYCLE • Interphase • Cell Division • Mitosis • Cytokinesis

  20. CELL CYCLE: INTERPHASE • High metabolic activity • Protein synthesis • DNA replication (46  92)

  21. CELL CYCLE: MITOSIS • Growth & Repair • 4 phases: • Prophase • Metaphase • Anaphase • Telophase

  22. MITOSIS: PROPHASE • Chromatin condenses into chromosomes • Centrioles organize spindle • Spindle fibers attach to centromeres • Nuclear membrane disassembles • Nucleolus disassembles

  23. MITOSIS: METAPHASE • Spindle aligns chromosomes • Alignment is around “equator” • Alignment is random

  24. MITOSIS: ANAPHASE • “Daughter” chromosomes separate • Chromosomes are moved toward poles • Cytoplasm elongates & cytokinesis begins

  25. MITOSIS: TELOPHASE • “Reverse” of prophase • Chromosomes relax into chromatin • Nuclear membrane reassembles • Nucleolus reassembles

  26. CELL CYCLE: CYTOKINESIS • Division of the cytoplasm and organelles • Begins during anaphase • Completed following telophase

  27. Mitosis

  28. CYTOLOGY PROTEIN SYNTHESIS

  29. PROTEIN SYNTHESIS • Involves DNA & RNA • DNA codes for proteins • RNA assembles proteins • Gene = a segment of DNA that codes for one protein • The sequence of bases (nucleotides) carries the information

  30. Protein Synthesis cont. • T, A, C, G in DNA • U, A, C, G in RNA • A single gene has between 300 – 3000 base pairs • In DNA, each 3-base sequence (triplet) specifies one amino acid

  31. PROTEIN SYNTHESIS • Each strand of DNA is complementary to the other • Messenger RNA is complementary to DNA & carries instructions from DNA to ribosomes • Protein synthesis occurs at ribosomes

  32. RIBONUCLEIC ACID (RNA) • Messenger RNA (mRNA) • polynucleotide strand that is complementary to DNA • carries instructions from DNA to ribosomes • Transfer RNA (tRNA) – transports amino acids to ribosomes • Ribosomal RNA (rRNA) – part of ribosomes

  33. The preview Image has been scaled down to fit the screen. Actual image is both larger and clearer.

  34. DNA Replication

  35. PHASES OF PROTEIN SYNTHESIS • Transcription • Complementary mRNA is made from a DNA gene (sequence coding for a protein) • Translation • mRNA’s information is used to assemble proteins with the help of tRNA & rRNA

  36. Overview of Protein Synthesis

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