Cells and Microscopy

1. Cells and Microscopy What you can’t see…

2. Microscopy branch of field of optics

3. Janssen-single convex lens as a magnifier. Antony van Leeuwenhoek-1st to make and use real microscope (single-lens or simple microscope). Compound microscope: Magnification by more than one lens. Lens closer to object viewed-"objective", closer to eye-"eyepiece“.

6. Tube:  Connects eyepiece to objective lenses. Revolving Nosepiece or Turret:  Holds two or more objective lenses and can be rotated to easily change power. Objective Lenses:  3 or 4 objective lenses (4X, 10X, 40X, 100X).  Total magnification: When coupled w/10X eyepiece lens, we get 40X (4X times 10X), 100X , 400X and 1000X. Shortest lens is lowest power, longest lens is greatest power. Stageclips: Hold slides in place.  Diaphragm or Iris: Rotating disk under stage w/different size holes. Varies intensity/size of cone of light that is projected upward into slide. Illuminator:  Steady light source used in place of a mirror.  Eyepiece Lens:  lens at top you look through (usually 10X or 15X) Arm:  Supports tube and connects it to base Stage:  Flat platform where slides are placed.  Coarse adjustment knob: large knob used to focus, moves stage or upper part of microscope. Fine adjustment knob: small knob used to fine-tune focus Base:  Bottom of microscope, used for support

7. How to focus • Start w/lowest power objective lens. • While looking from side, crank lens down as close to the specimen as possible without touching it.  • Look through eyepiece lens and focus upward only until image is sharp.  Repeat until sharply focused. • Turn to next power lens and do minor adjustments with fine adjustment focus knob.  • Continue with subsequent objective lenses and fine focus each time. 

8. Homework: Please print out the picture of the microscope on slide 5. Label it from slide 4 and write down the functions from slide 6. Be sure you understand how to focus a microscope. You will have a quiz on the parts and functions of parts of the microscope.

9. Magnification-increase in apparent size of an object. (up to 2000 times) Resolving power-measure of clarity of image: Ability to show two objects as separate. Any optical device is limited by its resolving power. Light Microscopes (LM)

10. Diffraction limits resolution to ~0.2 micrometers 1 micrometer (micron)=1/1000 mm ~25,000 mm= 1 inch Can’t distinguish objects smaller than ½ wavelength of light: White light-average wavelength-0.55 μm, ½=0.275 Any two lines that are closer together than 0.275 micrometers will be seen as a single line. Any object with a diameter smaller than 0.275 micrometers will be invisible or, at best, show up as a blur.

11. Electron microscope (EM) • Uses a beam of electrons. • Much higher resolving power than LM. • 1 nm = 1/1,000,000 mm • 1 angstrom = 1/1,000,000,000 m • Wavelength 1/100,000 of white light • Magnify objects up to 1 million times. • Serious drawback: • Living specimen can’t survive under high vacuum. • Can’t show ever-changing movements.

12. Fly foot

13. Transmission Electron Microscopy (TEM) • Advantages: • Magnifications up to 1,000,000 times (limitations ~0.05 nm) • Great depth of field gives sharp 2-D images with finest details of structure. • Limitations: • Cannot view living specimens (involves high-energy particles) • Image brightness is low.

15. Scanning Electron Microscopy (SEM) • Electrons scan specimen surface • Advantages: • Large depth of field-allows much more of specimen to be in focus at one time. • Produces images of greater resolution-3-D images. • Magnifications up to 300,000 times (limitations ~ 10 nm) • Limitations: • Cannot produce color. • As resolution increases, field of view decreases-difficult to view molecular detail.

17. Scanning tunneling microscope (STM) • 3-D images of atoms on surfaces of materials (can manipulate atoms). • Resolution = 1 nanometer (1 nm) or less (few Angstroms).

18. Tip is one atom wide

20. Robert Hooke-discuss cells (1665). 1838-Dutch botanist Matthias Schleiden-all plants composed of cells. 1839-German zoologist Theodor Schwaan-all animals composed of cells. 1855-German doctor Rudolph Virchow-all cells must come from other cells by the process of cell division. All their work combined into Cell Theory. All living things are made of cells. Cell is smallest living thing that can perform all the functions of life. All cells must come from preexisting cells. Discovery of cells and the Cell Theory

21. Homework: Do worksheet pg. 29 http://www.glencoe.com/sec/science/biology/bio2000/pdfs/bdol7-1.pdf

22. Eukaryotes Cells are complex. Contain a nucleus and other membrane-bound structures. Include animals, plants, protists, fungi. With exception of protists/yeasts (single-celled fungi), all are multicellular. Prokaryotes-bacteria Much simpler in structure. Have no internal membranes. Colonized Earth 2 billion years before eukaryotes showed up. Most are unicellular. All life on Earth can be divided into 2 categories:

24. Homework: Read 8.1, pp. 189-195, then answer these questions: • Compare and contrast simple and compound microscopes. • Why was the development of the electron microscope an advantage over the light microscope? • Explain the differences in production of image and magnification of TEM, SEM and STM. • What are the three parts of the cell theory? • Compare and contrast eukaryotic and prokaryotic cells. • What is an organelle?

25. Organization • Cells-smallest unit of matter that can carry on all life processes • Organelles-internal structures in cells that performs specific functions and maintain the life of the cell.

27. Plasma membrane (cell membrane) • Surrounds all cells in an organism • Separates cell from external environment. • Thin lipid/protein layer that controls what enters and leaves cell (selectivelypermeable) • Cell cannot survive if totally isolated from environment.

28. Plant cells, almost all bacteria, fungi, and some protists have cell wall: Plant-made of cellulosethat form fibers that are interwoven-produce strong network thatprotects cell/gives plant support. Fungi-made of chitin-nitrogen-containing polysaccharide.

30. Nucleus-control center of cell-most prominent structure within a cell • Most cells have a single nucleus, though some have more than 1.

31. Nuclear membrane (envelope) Double-layered membrane surrounding the nucleus. Covered with many small pores. Connected to the ER. Selectively permeable. Nucleoplasm-jellylike fluid in which the nucleoli and chromatin are suspended.

32. Nucleoli (nucleolus) Functions in RNA and ribosome synthesis

33. Chromatin Long, uncoiled strand DNA Chromosomes-chromatin coils and condenses into during cell division

35. Cytoplasm • Everything between plasma membrane and nucleus. • Where most cellular activities take place. • Cytosol- • Jellylike mixture. • Mostly water, w/proteins, carbs, salts, minerals and organic molecules. • Contains cytoskeleton. • Organelles- • Structures (miniature organs) carrying out specific functions in the cell. • Most surrounded by membrane.

37. Cytoplasmic OrganellesRibosomes Not surrounded by a membrane. Site of protein synthesis. Most numerous organelles in almost all cells. Some free in cytoplasm; others line membranes of rough ER.

39. Cytoplasmic OrganellesEndoplasmic Reticulum (ER) • Fluid-filled canal system used to transport molecules (mostly proteins) throughout the cell. • Connects nuclear envelope to plasma membrane. • Provide large surface area for chemical reactions to occur.

40. Can be rough or smooth. Rough ER-studded w/ribosomes. Smooth ER-Is not covered with ribosomes. Associated with Golgi apparatus.

41. Cytoplasmic OrganellesGolgi Apparatus (Golgi Bodies) • System of membranes made of flattened sac-like structures (cisternae) that process, package and secrete.

43. Cell demolition site. Small, single membrane, contain digestive enzymes. Fuse with food vacuole and digest food, worn out or unusable cell structures and most harmful foreign substances that enter the cell. http://highered.mcgraw-hill.com/olc/dl/120067/bio01.swf Cytoplasmic OrganellesLysosomes

44. Homework: Read 8.2, pp. 196-210, then answer these questions: • Define selectively permeable and explain why plasma membranes must exhibit this characteristic. • What is the function of the cell wall? • Why are there pores in the nuclear envelope? • What is the function of the nucleolus? • How are ribosomes different from most other organelles (2 ways)? What is their function? • What is the function of the endoplasmic reticulum? Describe the two types of ER. • Why are there many folds in the membrane of the ER? • Explain the process by which a protein is prepared for export in the Golgi apparatus. • What substances that are broken down in the lysosomes?

46. Cytoplasmic OrganellesVacuoles Single membranous sacs consisting mostly of water. Contractile vacuoles Each plant cell has a large, single vacuole that typically takes up most of the room in the cell. (50-90%) Turgor pressure

48. Cytoplasmic OrganellesMitochondria • Powerhouse of the cell • Organic compound energy  ATP during cellular respiration C6H12O6 (food) + 6O2 6CO2 + 6H2O + 36 ATP molecules • Cells with high energy requirements (liver, muscle) have hundreds while unfertilized egg has few. • Have own DNA-can grow and divide.

49. Surrounded by two membranes. Smooth outer membrane-boundary between mitochondria and cytosol. Inner membrane-many long folds-cristae-increase surface area for chemical reactions to occur.