Dsa

761
-1

Published on

Published in: Education, Technology
0 Comments
0 Likes
Statistics
Notes
  • Be the first to comment

  • Be the first to like this

No Downloads
Views
Total Views
761
On Slideshare
0
From Embeds
0
Number of Embeds
1
Actions
Shares
0
Downloads
0
Comments
0
Likes
0
Embeds 0
No embeds

No notes for slide

Dsa

  1. 1. 1 Cell Structure Prof.ssa Patrizia Mauri ISISS Cicognini- Rodari - Prato
  2. 2. 2 The cell Cell means “little room” The first cells were observed in the 1655 by Robert Hook, with a rudimentary Optical Microscope – they were cork cells, a plant tissue. Then Antony Van Leewenhoek observed for the first time Protozoa (unicellular animals), Sperm Cells and Bacteria.
  3. 3. 3 Cork tissue Paramecium Sperm Cells Escherichia Coli
  4. 4. 4 Cell Theory (19th century) • All organisms are composed of one or more cells. • Cells are the smallest living units of all living organisms. • Cells are generated only by the division of previously existing cells.
  5. 5. 5 Cell Characteristics  Plasma membrane encloses the cell  Cytoplasm fills cell interior, it contains organelles and any kind of molecules  Genetic material – DNA - prokaryotes: single circular molecule - eukaryotes: more linear molecules (enclosed into a nucleus) Phospholipid Membrane proteins
  6. 6. 6 Generic Eukaryotic Cell
  7. 7. 7 Cell Size •Most cells are relatively small because as size increases, volume increases much more ---> longer diffusion time
  8. 8. 8 Visualizing Cells
  9. 9. 9 Prokaryotic Cell • Simplest organisms (unicellular) commonly called Bacteria – Cytoplasm is surrounded by plasma membrane and encased in a rigid cell wall  NO distinct interior compartments – no nucleus (DNA is free in the cytoplasm) - no organules
  10. 10. 10 Prokaryotic Cell • Some use a flagellum for locomotion – threadlike structures protruding from cell surface Bacterial cell wall Flagellin Rotary motor Sheath
  11. 11. 11 Bacterial shapes
  12. 12. 12 Bacteria images
  13. 13. 13 Eukaryotic Cell • Bigger and more complex. It is characterized by an endomembrane system which forms organules. There are: - NUCLEUS (DNA) - Cytoskeleton (internal protein scaffolding) - Organules , Vesicles - Cell wall – Only plant and fungi cells
  14. 14. 14
  15. 15. 15
  16. 16. 16 Nucleus • It is the repository for genetic material (DNA) • It directs activities of the cell • Usually is single, some cells have several, RBC none - Nucleolus – a region of intensive ribosomal RNA synthesis - Nuclear envelope - is the surface of nucleus made by two phospholipidic bilayer membranes Nuclear pores – protein gatekeepers
  17. 17. 17 Nucleus
  18. 18. 18 Chromosomes • DNA of eukaryotes is divided into linear chromosomes. – It exists as strands of chromatin, except during cell division – Is associated with packaging proteins - histones - to form nucleosomes
  19. 19. 19
  20. 20. 20 Cytoskeleton • It is network of protein fibers supporting cell shape and anchoring organelles – Actin filaments  cell movement – Microtubules  Hollow tubes  Facilitate cell movement – Intermediate filaments  Stabilize – support cell structure Actin Microtubules Intermediate filaments
  21. 21. 21 Cytoskeleton
  22. 22. 22 Endomembrane System An inner system of organelles linked one to the other by a stream of molecules. It includes: - Endoplasmic Reticulum - Golgi Apparatus - Vesicles and Lysosomes
  23. 23. 23 Endomembrane System – Endoplasmic Reticulum: an inner labyrinth  Rough ER - studded with ribosomes  Smooth ER - no ribosomes
  24. 24. 24 Endoplasmic Reticulum • Composed of a membranes system • Functions in storage and secretion • Rough ER is “rough” because of associated ribosomes (sites of protein synthesis) • Smooth ER - lacks associated ribosomes – synthesis of carbohydrate and lipid molecules
  25. 25. 25 Endomembrane System • Golgi Apparatus > Cisternae – stacked membrane tanks > Front - cis , Back – trans > Collect, package, and distribute molecules synthesized in ER
  26. 26. 26 Endomembrane System • Vesicles Trasport vesicles -transfer molecules from ER to Golgi Apparatus and from there to the Membrane Lysosomes - vesicles containing digestive enzymes – from Golgi Apparatus
  27. 27. 27 Cytoplasm Phagocytosis Food vesicle Golgi apparatus Lysosomes Plasma membrane Digestion of phagocytized food particles or cells Endoplasmic reticulum Transport vesicle Old or damaged organelle Breakdown of old organelleExtracellular fluid Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
  28. 28. 28 Ribosomes • Ribosomes are RNA-protein complexes composed of two subunits that join each other - they are assembled in nucleolus - they are the site of protein synthesis
  29. 29. 29 Mitochondria (in all eukaryotic cells) Powerhouse of the cell ( through the degradation of sugars and fats) Structure- outer and inner membranes, cristae Have their own DNA
  30. 30. 30 Chloroplasts (only in photosynthetic cells) Thet are the site of Photosyntesis Chloroplasts are larger and more complex than mitochondria. Outer and inner membranes Thylakoids, disc-shaped structures, with light capturing pigments, they form grana Have their own DNA
  31. 31. 31 Theory of Endosymbiosis • Endosymbiotic theory suggests that engulfed prokaryotes became hosts within an eukaryotic cell, providing advantages associated with specialized metabolic activities
  32. 32. 32 Theory of Endosymbiosis
  33. 33. 33 Evidence for the endosymbiont theory is that mitochondria and chloroplasts: - Are appropriate size to be descendants of ancestral bacteria - Replicate by splitting, as prokaryotes - DNA is circular and different from the DNA of the cell nucleus - Have ribosomes similar to prokaryotes
  34. 34. 34 Plant Cells - Central vacuole It is often found in the center of the cell and serves as a storage for water and other materials - Cell wall It is made of cellulose. It supports the cell and glues cells together - Chloroplasts They are the sites of Photosyntesis which provides nutrition to the cell (glucose)
  35. 35. 35
  36. 36. 36 Fungal cell
  37. 37. 37
  38. 38. 38
  39. 39. 39 See you after Christmas with two more topics: 1. MEMBRANE TRANSPORT 2. OPTICAL MICROSCOPE
  40. 40. 40 Merry Christmas and Happy New Year !!

×