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Cell Organelles

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  1. Cell Organelles

  2. Cell Theory • Virchow, Schleiden and Schwann • Every organism is composed of one or more cells • Cells are the smallest units having properties of life • Continuity of life arises from growth and division of single cells - Cells arise only from pre-existing cells.

  3. How many cells in your body? • 50 million million (trillion) • That’s 50,000,000,000,000 cells!!!!!! • And not only that, there are many different types. • Cells are diverse • But only two basic types

  4. Two Basic Cell Types

  5. Prokaryotic Cell • Note the lack of nucleus, DNA free floating (nucleoidarea) • DO HAVE plasma membrane, ribosomes, and cell wall (sometimes)

  6. Endosymbiotic Theory • It is believed that eukaryotic cells arose from groups of prokaryotic cells living together. • Smaller ones inside larger ones.

  7. EVIDENCE… For Endosymbiosis • Some eukaryotic organelles resemble bacteria • Mitochondria and Chloroplast – double membrane • Mitochondria and bacteria have similar size • Mitochondria and Chloroplast DNA circular like Bacteria • Mitochondria divide as bacteria do

  8. Eukaryotic Cell • More Advanced, larger & have organelles • DO HAVE nucleus, ribosomes, mitochondria, chloroplasts (plants), cell wall (plants), endoplasmic reticulum, golgi complex, lysosomes, and vacuoles

  9. Eukaryotic Cell Lots of internal membrane-bound structures!

  10. Why are cells so small? • Cells exchange all materials with their environment through the cell membrane. • Exchange is faster in a smaller cell. • Need a surface area proportional to their volume – Surface area to volume ratio decreases as cell gets larger. • Cells that are specialized for absorption have folds in plasma membrane to increase surface area

  11. Plasma Membrane

  12. PlasmaMembrane Both prokaryotic and eukaryotic cells have this “outer wall” Holds the CYTOPLASM inside the cell Gives cells their shape and flexibility Helps to maintain HOMEOSTASIS by allowing substance to flow in and out of the cell – SELECTIVEPERMIABILITY

  13. Structure of Plasma Membrane • The plasma membrane is aPHOSPHOLIPIID BILAYER • PHOSPHOLIPIDBILAYER

  14. Fluid Mosaic Model Phospholipids, cholesterol, and proteins all flow like the surface of a wavy lake, moving and shifting. Structure of Plasma Membrane

  15. What are the structures and functions of the cell membrane?

  16. Components of the Cell Membrane Phospholipid Bilayer • Contains lipids, carbohydrates, and functional proteins • Double layer of phospholipid molecules: • hydrophilic heads—toward watery environment, both sides • hydrophobic fatty-acid tails—inside membrane Membrane Proteins • Integral proteins: • within the membrane • Peripheral proteins: • inner or outer surface of the membrane

  17. Cytoplasm • All materials inside the cell and outside the nucleus: • cytosol (fluid): • dissolved materials: • nutrients, ions, proteins, and waste products • organelles: • structures with specific functions

  18. What are cell organelles & their functions? • Nonmembranous organelles: • no membrane • direct contact with cytosol • Membranous organelles: • covered with plasma membrane • isolated from cytosol • cilia • ribosomes • proteasomes • 6 types of nonmembranous organelles: • cytoskeleton • microvilli • centrioles

  19. The Cytoskeleton • Structural proteins for shape and strength • Microfilaments • Thinfilaments composed of the protein actin: • provide additional mechanical strength • interact with proteins for consistency • Pairs with thick filaments of myosin for muscle movement • Intermediate • Mid-sized between microfilaments and thick filaments: • durable (collagen) • strengthen cell and maintain shape • stabilize organelles • stabilize cell position

  20. The Cytoskeleton • Microtubules • Large, hollow tubes of tubulin protein: • attach to centrosome • strengthen cell and anchor organelles • change cell shape • move vesicles within cell (kinesin and dynein) • form spindle apparatus

  21. Microvilli • Increase surface area for absorption • Attach to cytoskeleton

  22. Centrioles in the Centrosome • Centriolesform spindle apparatus during cell division • Centrosome: cytoplasm surrounding centriole Cilia Power Hair-like cilia move fluids across the cell surface

  23. Ribosomes Proteasomes • Build polypeptides in protein synthesis • Two types: • free ribosomes in cytoplasm: • proteins for cell • fixed ribosomes attached to ER: • proteins for secretion outside cell • Contain enzymes (proteases) • Disassemble damaged proteins for recycling

  24. MembranousOrganelles • 5 types of membranous organelles: • endoplasmic reticulum (ER) • Golgi apparatus • lysosomes • peroxisomes • mitochondria

  25. Endoplasmic Reticulum (ER) • endo = within • plasm= cytoplasm • reticulum = network • Cisternae are storage chambers within membranes

  26. Functions of ER • Synthesis of proteins, carbohydrates, and lipids • Storage of synthesized molecules and materials • Transport of materials within the ER • Detoxification of drugs or toxins

  27. Smooth Endoplasmic Reticulum (SER) • No ribosomes attached • Synthesizes lipids and carbohydrates: • phospholipids and cholesterol (membranes) • steroid hormones (reproductive system) • glycerides (storage in liver and fat cells) • glycogen (storage in muscles) Rough Endoplasmic Reticulum (RER) • Surface covered with ribosomes: • active in protein and glycoproteinsynthesis • folds polypeptides protein structures • encloses products in transportvesicles

  28. Golgi Apparatus • Secretory vesicles: • modify and package products for exocytosis • Membrane renewal vesicles: • add or remove membrane components • Vesicles enter forming face and exit maturing face • Transport vesicles: • Carry materials to and from Golgi apparatus Cis face, closer to ER Trans face, closer to cell exit

  29. Primary lysosome: • formed by Golgi and inactive enzymes • Secondary lysosome: • lysosome fused with damaged organelle • digestive enzymes activated • toxic chemicals isolated Lysosomes • Powerful enzyme-containing vesicles: • lyso = dissolve, soma = body • Exocytosis • Ejects secretory products and wastes

  30. Lysosome Functions • Clean up inside cells: • break down large molecules • attack bacteria • recycle damaged organelles • ejects wastes by exocytosis

  31. Autolysis • Self-destruction of damaged cells: • auto = self, lysis = break • lysosome membranes break down • digestive enzymes released • cell decomposes • cellular materials recycle Peroxisomes • Are enzyme-containing vesicles: • break down fatty acids, organic compounds • produce hydrogen peroxide (H2O2) …TOXIC • replicate by division

  32. KEY CONCEPT • Cells: basic structural and functional units of life • respond to their environment • maintain homeostasis at the cellular level • modify structure and function over time

  33. Mitochondrion Structure • 2 Membranes • Have smooth outer membrane and folded inner membrane (cristae) • Matrix: • fluid around cristae

  34. Mitochondrial Function • Mitochondrion takes chemical energy from food (glucose): • produces energy molecule ATP

  35. Nucleus

  36. Nucleus • ControlCenter of the cell • Contain CHROMATIN (loose DNA) • Bundles into CHROMOSOMES when cell is ready to divide (it packs before moving) Chromatin Chromosomes

  37. Chromatin in the Nucleus • Directs PROTEINSYNTHESIS (building proteins) • It contains the “blueprints” • “Blueprints” are Called DNA • DNA in loose coils called chromatin

  38. How does the nucleus control the cell? • Nucleus: • largest organelle • Nuclearenvelope: • double membrane around the nucleus • Perinuclearspace: • between 2 layers of nuclear envelope • Nuclearpores: • communication passages

  39. Nucleus Controls Cell Structure and Function • Direct control through synthesis of: • structural proteins • secretions (environmental response) • Indirect control over metabolism through enzymes

  40. Within the Nucleus • DNA: • all information to build and run organisms • Nucleoplasm: • fluid containing ions, enzymes, nucleotides, and some RNA • Nuclearmatrix: • support filaments Nucleoli in Nucleus Are related to protein production Are made of RNA, enzymes, and histones Synthesize rRNA and ribosomal subunits

  41. Organization of DNA • Nucleosomes: • DNA coiled around histones • Chromatin: • loosely coiled DNA (cells not dividing) • Chromosomes: • tightly coiled DNA (cells dividing) Figure 3–11

  42. What is genetic code? DNA and Genes • DNA: • instructions for every protein in the body • Gene: • DNA instructions for 1 protein Genetic Code • The chemical language of DNA instructions: • sequence of bases(A, T, C, G) • triplet code: • 3 bases = 1 amino acid

  43. KEY CONCEPT • The nucleus contains chromosomes • Chromosomes contain DNA • DNA stores genetic instructions for proteins • Proteins determine cell structure and function

  44. Cell Walls • Outside of the plasma membrane • Can be made of thick fibers of cellulose (plants), chitin(fungi), or peptodoglycan (some bacteria) • Plant cells have openings in cell wall called GAP JUNCTIONS for cell to cell communication • Animal cells DO NOT have cell walls

  45. Cell Wall of Plants Is this a prokaryotic or eukaryotic cell?