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A Tour of the Cell Cell Structure and Function

A Tour of the Cell Cell Structure and Function. THE MICROSCOPIC WORLD OF CELLS. Cells are the basic units of life. Cell function limits cell size Cell size is from 5 to 50 um. Cell Theory. All living things are composed of cells Cells are the basic unit of life

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A Tour of the Cell Cell Structure and Function

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  1. A Tour of the Cell Cell Structure and Function

  2. THE MICROSCOPIC WORLD OF CELLS • Cells are the basic units of life • Cell function limits cell size • Cell size is from 5 to 50 um

  3. Cell Theory • All living things are composed of cells • Cells are the basic unit of life • Cells come from pre-existing cells

  4. The Two Major Categories of Cells • The countless cells on earth fall into two categories • Prokaryotic cells • Eukaryotic cells

  5. Prokaryotic and eukaryotic cells differ in several respects Prokaryotic cell Nucleoid region Eukaryotic cell Organelles Nucleus Figure 4.4

  6. Cell Types • Prokaryotic: (Bacteria) • Smaller, simple structure, single celled • No membrane bound organelles • No nucleus: instead, it has a nucleoid region • One chromosome, found in the nucleoid region • Eukaryotic: (Prostista, Plants, Fungi, Animals) • Larger, more complex, simple and multicellular • Has membranous organelles • Has a nucleus • Multiple chromosomes

  7. Generalized Prokaryote Nucleoid DNA Flagellum PlasmaMembrane

  8. Generalized Animal and Plant Cell AnimalCell Chloroplasts Centrioles Mitochondria Golgi Nucleus EndoplasmicReticulum PlantCell

  9. Generalized Plant and Animal Cell AnimalCell Nucleolus Ribosomes Central Vacuole PlantCell Smooth E.R. Cell Wall

  10. A Panoramic View of Eukaryotic Cells • An idealized animal cell Centriole Ribosomes Not in most plant cells Lysosome Flagellum Cytoskeleton Plasma membrane Nucleus Mitochondrion Rough endoplasmic reticulum (ER) Smooth endoplasmic reticulum (ER) Golgi apparatus Figure 4.6A

  11. An idealized plant cell Not in animal cells Cytoskeleton Mitochondrion Central vacuole Nucleus Cell wall Rough endoplamsicreticulum (ER) Chloroplast Ribosomes Plasma membrane Smooth endoplasmic reticulum (ER) Plasmodesmata Golgi apparatus Figure 4.6B

  12. Nucleus and Ribosomes: Genetic Control of the Cell • The nucleus is bordered by a double membrane called the nuclear envelope (separates nuclear material from the cytoplasm, contains pores/exchange of material) Structure and function of Nucleus and Ribosomes • It contains chromatin (genes/DNA in threadlike chromosomes) • It contains a nucleolus (site of ribosome assembly) • Ribosomes make all the cell’s proteins

  13. Ribosomes Chromatin Nucleolus Pore Nuclear envelope Figure 4.9

  14. The Nucleus Nucleolus Pores Chromatin Threads(Chromosomes) NuclearEnvelope

  15. How DNA Controls the Cell • DNA controls the cell by transferring its instructions to RNA DNA 1 DNA gives Instructions to RNA RNA • The information in the RNA is used to make proteins Nucleus Cytoplasm RNA 2 Movement of RNA into cytoplasm via nuclear pore Ribosome RNA carries instructions to make proteins to the ribosomes 3 Protein Figure 4.10

  16. THE ENDOMEMBRANE SYSTEM: MANUFACTURING AND DISTRIBUTING CELLULAR PRODUCTS • Many of the membranous organelles in the cell belong to the endomembrane system which include the following: • Endoplasmic reticulum • Golgi apparatus • Lysosomes • Vacuoles

  17. The Endoplasmic Reticulum • The endoplasmic reticulum (ER) Nuclear envelope • Series of interconnecting membranes, enclosed tubes and channels in the cytoplasm • Produces an enormous variety of molecules • Is composed of smooth and rough ER Ribosomes Rough ER Smooth ER Figure 4.11

  18. Endoplasmic Reticulum UnitMembrane Ribosomes Vesiclesforming

  19. Rough ER • The “roughness” of the rough ER is due to ribosomes that stud the outside of the ER membrane • Ribosomes are the site of protein synthesis - types of proteins produced are as follows: • Membrane proteins – produce new membrane • Secretory proteins – proteins that are secreted by the cell and transported elsewhere • Example: salivary glands contain a lot of rough ER, the ribosomes there make lots of enzymes to help disolve food in the mouth.

  20. After the rough ER synthesizes a molecule it packages the molecule into transport vesicles 4 Transport vesicle buds off Secretory protein inside transport vesicle Ribosome 3 Protein 1 Rough ER 2 Polypeptide Figure 4.12

  21. Smooth ER • The smooth ER lacks the surface ribosomes of ER and produces lipids, including steroids • Examples: • Ovaries and Testes – smooth ER produces sex hormones, which are steroids. These organs are enriched with smooth ER • In the liver, smooth ER produces enzymes that detoxify harmful drugs and metabolic by products

  22. The Golgi Apparatus • The Golgi apparatus • Works in partnership with the ER, its membranes are derived from the ER • Sorts, modifies, packages and distributes the products of cells Transport vesicle from ER “Receiving” side of Golgi apparatus Golgi apparatus New vesicle forming Transport vesicle from the Golgi “Shipping” side of Golgi apparatus Plasma membrane Figure 4.13

  23. Golgi Apparatus Summary: How it works • Vesicles from the ER fuse to one side of golgi, they empty their contents into the golgi sacs. The contents are then modified and repackaged. • On the opposite side of the stack of membranes, vesicles carry away proteins, lipids and other complex molecules to other parts of the cell or body.

  24. The Golgi Complex Material ReceivedFrom ER Material Destinedfor Export TEM

  25. Lysosomes • A lysosome is a membrane-enclosed sac • It contains digestive enzymes and serves as cells digestive system • The enzymes break down lipids, carbohydrates and proteins and also old organelles • In the golgi, these digestive enzymes are packaged into lysosomes

  26. Lysosomes break down damaged organelles Lysosome Digestion Damaged organelle (b) Lysosome breaking down damaged organelle Figure 4.14b

  27. The Flow of Membrane Destined forExport Lysosome Golgi EndoplasmicReticulum Destined forGolgi

  28. A review of the endomembrane system Rough ER Transport vesicle from ER Golgi apparatus Secretory vesicle from Golgi Vacuole Lysosome Secretory protein Plasma membrane Figure 4.16

  29. Vacuoles • Vacuoles are membranous sacs: function in water regulation, support and storage • Types are the contractile vacuoles of protists, the central vacuoles of plants and food vacuoles Central vacuole Contractile vacuoles (a) Contractile vacuoles in a protist (b) Central vacuole in a plant cell Figure 4.15

  30. Contractile Vacuole • Expels water out of single-celled freshwater animals

  31. Contractile Vacuoles Expandedwith Water Paramecium sp. 1 2 Expelling Waterto Outside

  32. Central Vacuoles • Large, water-filled spaces • Can take up over 90% of cell volume • Functions: • Gives support and shape to plant cells

  33. Plant Wilting &the Central Vacuole NormalPlant Cell In Drought Normal Cytoplasm In Drought Space between Cell Walland Cell Membrane Cell Wall Vacuole

  34. CHLOROPLASTS AND MITOCHONDRIA: ENERGY CONVERSION • Cells require a constant energy supply to do all the work of life • Two types of organelles involved in supplying energy to cells are: • Chloroplast • Mitochondria

  35. Chloroplast • Site of photosynthesis, only in plant cells • Convert light energy into chemical energy of food • Captures light energy and turns it into sugar • Contains the green pigment pigment

  36. The Chloroplast

  37. Mitochondria • Called the “Powerhouse” of the cell • Cellular respiration, uses the chemical energy of sugar molecules and converts it into another form of chemical energy called ATP

  38. Mitochondria OuterMembrane Matrix Cristae

  39. THE CYTOSKELETON:CELL SHAPE AND MOVEMENT • The cytoskeleton is a network of fibers that extend throughout the cytoplasm of the cell • Functions: • Support: The cytoskeleton gives mechanical support to the cell and maintains cell shape • Movement: Organelles move within the cell by the means of microtubules that are attached to the organelles

  40. The Cytoskeleton PlasmaMembrane Mitochondrion Microtubule EndoplasmicReticulum

  41. Cilia and Flagella • Cilia and flagella are motile appendages or extensions of the cell that aid in locomotion • Cilia and flagella are composed of microtubules • Functions: • Flagella: Singular whip like structures that propel the cell by undulating whip like motion • Cilia: Shorter and more numerous than flagella, promote movement by a coordinated back-forth movement

  42. Human sperm have flagella, used to propel the sperm • Protist such as the paramecium have cilia that move in a back-and-forth motion Figure 4.20A, B

  43. Movement of Flagella Water Water Corkscrew Movement(Pulls) Whipping Movement(Pushes) Scanning E.M.of sperm on egg

  44. Cilia are also found in non-motile cells such as those of the lungs Your windpipe also has a ciliated lining Figure 4.20C

  45. Movement of Cilia Power Stroke Recovery Stroke Water Scanning E.M.of a ciliate

  46. The Endof Chapter 7

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