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Topic 1: Cell Biology

Topic 1: Cell Biology. Harvard Animation. Why are cells cool? https://www.youtube.com/watch?v=wJyUtbn0O5Y http://multimedia.mcb.harvard.edu/. Cell Theory. Discuss the theory that living organisms are composed of cells. The Cell Theory states that:

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Topic 1: Cell Biology

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  1. Topic 1: Cell Biology

  2. Harvard Animation • Why are cells cool? • https://www.youtube.com/watch?v=wJyUtbn0O5Y • http://multimedia.mcb.harvard.edu/

  3. Cell Theory • Discuss the theory that living organisms are composed of cells. • The Cell Theory states that: • All organisms are composed of one or more cells. • All cells arise from pre-existing cells. • All vital functions of an organism occur within cells. • Cells are the most basic unit of life. • Cells contain hereditary information. Why?

  4. Think and Discuss! What sort of evidence would be needed to validate cell theory?

  5. Evidence for Cell Theory • What is Evidence? • What is a theory? • Evidence for Cell theory: • Living tissues= composed of cells • Cells of an organism can sometimes survive on their own but smaller cell components can NOT. • Classic experiments showed that spontaneous generation of life does NOT happen.

  6. Nature of Science (Cell Theory Trends and Discrepancies) Exceptions to aspects of Cell theory (Evaluate) • Striated Skeletal Muscle– multinucleate cytoplasm, longer than typical cells

  7. Some fungal hyphae- multinucleate cytoplasm.

  8. Giant Algae– Single nucleus but much larger than a typical cell (up to 100mm) Extracellular material (material outside the cell membrane), such as teeth and bone, forms a significant part of the body. Discuss: Do you think these constitute exceptions to cell theory? Justify your answer.

  9. Unicellular organisms carry out ALL the functions of life. • What are the necessary functions of life? • Metabolism • Response to stimuli • Homeostasis • Growth/development • Reproduction • Nutrition • Excretion of wastes

  10. Application: Functions of life in unicellular organisms • Example 1: Paramecium (mandatory!)

  11. Application: Functions of life in unicellular organisms Example 2: Chlorella (a type of unicellular algae) Note: must have unicellular photosynthetic organism

  12. Cell Size Discuss: How big are cells? Image: National Institutes of Health

  13. Not in New Syllabus but questions still asked in new sample exams: • Compare the relative sizes of molecules, cell membrane thickness, viruses, bacteria, organelles and cells, using appropriate SI units. • Molecules (1 nm) (Smallest) • Cell membrane thickness (10 nm) • Viruses (100 nm) • Bacteria (1 µm) • Organelles (<10 µm) • Most cells (<100 µm) (Largest) • Interactive http://www.cellsalive.com/howbig.htm

  14. Calculate linear magnification of drawings. • Scale bars: • ex. = 1 µm • Magnification: ×250 • To calculate magnification: • Magnification = Measured Size of Diagram ÷ Actual Size of Object

  15. Explain the importance of the surface area to volume ratio as a factor limiting cell size. • The rate of exchange of materials (nutrients/waste) and energy (heat) is a function of its surface area. (Why?) • As cell size increases, the surface area to volume ratio decreases • This can make the exchange rate inadequate for large cells • Cell size, therefore, remains small

  16. So, Cells can’t be very big! • Giant alien amoeba movie = not accurate…

  17. Discussion If cells must be small, how is it possible for organisms to be large?

  18. Explain that cells in multicellular organisms differentiate to carry out specialized functions by expressing some of their genes but not others. • Differentiation: becoming specialized in structure and function. (due to gene expression) • Results in specialized tissues • Supporting examples? • Multicellular organisms show emergent properties (What??) • See ex. Next slide… Video: http://www.pbs.org/wgbh/nova/sciencenow/archive/title-m-z.html

  19. Define tissue, organ and organ system. • Tissue: An integrated group of cells that share stucture and are adapted to perform a similar function. • Organ: A combination of two or more tissues which function as an integrated unit, performing one or more specific functions. • Organ system: A group of organs that specialize in a certain function together.

  20. STEM CELLS • Stem cells • Retain the capacity to divide* • Able to differentiate along different pathways* *The above characteristics are necessary for embryonic development and make stem cells suitable for some therapies…

  21. Therapeutic Use of Stem Cells • Many possibilities (in research phase) to repair damaged tissues etc. • Actual uses • Restore neural insulation tissue in rats. • Embryonic stem cells to treat Stargardt’s macular dystrophy (an eye disease). • Stem cells from umbilical cord blood or from bone marrow for leukemia patients.

  22. Application: Stargardt’s disease (mandatory) Stem Cell Treatment: • Injection of retinal cells (derived from embryonic stem cells) • Encouraging results: No rejection, no tumors, vision improvement as retinal cells attached • Background: Stargardt’s disease • the most common form of inherited juvenile macular degeneration. • progressive vision loss • death of photoreceptor cells in the macula (central part of the retina) • Due to mutation in a gene that controls a transport protein in retinal cells.

  23. Application: Leukemia • Stem Cell Treatment: • Extract healthy bone marrow fluid (usually from pelvis) • Extract stem cells and freeze them • Chemotherapy to kill cancer cells • Return stem cells to bone. • Cures leukemia in many cases • Background: Leukemia • A cancer in bone marrow that produces excessive white blood cells

  24. Sources and Ethical Issues (see p. 15 of book for more…) Video (Stem Cells Breakthrough): http://www.pbs.org/wgbh/nova/sciencenow/archive/title-m-z.html • Sources and ethical/technical issues: • Embryonic • placenta/umbilical cord • Many other tissues have stem cells • totipotent/omnipotent vs. Pluripotent

  25. Microscopy and Types of Cells

  26. Explain three advantages of using light microscopes. • NOTE: not in new syllabus… • color instead of monochrome (black and white) images. • large field of view. • Facilitate preparation of sample material. • Allow for the examination of living material and the observation of movement. • Relatively inexpensive

  27. Outline the advantages of using electron microscopes. 1) much higher resolution and magnification than light microscopes. • Resolution refers to the ability to distinguish two objects as separate entities. • Magnification refers to the ability to increase the size of a viewed object. 2) Allow us to see cell ultrastructure. Types of Electron Microscopes: (not in syllabus) • Scanning Electron Microscopes (SEM) provide images of the specimen's surface • Transmission Electron Microscopes (TEM) provide images of a sample's interior. The resolution of an SEM is approximately half that of a TEM. TEM SEM

  28. Cell Types

  29. Prokaryotic Cells • Simple cell Structure • No Compartmentalization (No Nucleus, no membrane-bound organelles)

  30. Prokaryotic Cells • Draw a generalized prokaryotic cell as seen in electron micrographs • The diagram should include: • the cell wall, • plasma membrane, • cytoplasm, • Pili • Flagella • Ribosomes (70S) • nucleoid ( region containing naked DNA).

  31. State one function for each of the following: the cell wall, plasma membrane, cytoplasm, Pili Flagella, Ribosomes, nucleoid • Cell Wall:Maintains the cell's shape and give protection. • Plasma Membrane: Regulates the flow of materials (nutrients, waste, oxygen, etc.) into and out of the cell. • Cytoplasm: Holds and suspends the cell's ribosomes and enzymes. • Pili:Adhering to surfaces • Flagella: Motility • Ribosome:Protein synthesis. • Nucleoidregion: Contains the cell's genetic material (naked DNA)

  32. Binary Fission • Prokaryotic cells divide by binary fission • Asexual • splits directly into two equal-sized offspring, each with a copy of the parent's genetic material.

  33. State that prokaryotes show a wide range of metabolic activity including fermentation, photosynthesis and nitrogen fixation. (note: from old syllabus EX. • Cyanobacteria (blue-green algae)--photosynthesis. • Bacteria can convert organic substances into other organic substances. (i.e., glucose to lactic acid during anaerobic respiration) • Nitrogen fixation– convert N2 in air to ammonia. Cyanobacteria Video: http://www.pbs.org/wgbh/nova/sciencenow/3401/04.html Bacteria

  34. Eukaryotic Cells • More complex cell Structure • Compartmentalization

  35. Eukaryotic Cells Draw a diagram to show the ultrastructure of a generalized animal cell (liver cell) as seen in electron micrographs. • Should include free ribosomes, rough and smooth ER, lysosome, Golgi apparatus, mitochondria, and nucleus.

  36. An Animal Cell

  37. Define organelle. • An organelle is a discrete structure within a cell, and has a specific function.

  38. State one function of each of these organelles: ribosomes, rough endoplasmic reticulum, lysosome, Golgi apparatus, mitochondrion and nucleus. • Nucleus: contains genetic material • Ribosomes (80S): protein synthesis • Rough endoplasmic reticulum (rER): Packages proteins • Golgi apparatus: Modifies, stores and routes products of the endoplasmic reticulum. • Lysosome: digests old cell parts, macromolecules (food) and engulfed viruses/bacteria • Mitochondrion: cellular respiration.

  39. Explain how vesicles are used to transport materials within a cell between the rough endoplasmic reticulum, Golgi apparatus, and plasma membrane. • Proteins synthesized by ribosomes • enter the rough endoplasmic reticulum. • Vesicles bud from rER and carry the proteins to the Golgi apparatus. • Golgi apparatus modifies the proteins. • Vesicles bud off from the Golgi apparatus and carry the modified proteins to the plasma membrane. http://www.sumanasinc.com/webcontent/animations/content/vesiclebudding.html

  40. Skill: Interpret electron micrographs ID organelles Deduce function of specialized cells

  41. Hints Lysosomes = dark circles Vesicles or vacuoles= light circles Golgi = surrounded by vesicles, with separate sacs Mitochondria= look for cristae (folds of inner membrane)

  42. ER vs. Golgi

  43. Plant Cell (Palisade mesophyll for example)_

  44. lysosomes

  45. Liver cell electron micrographs • 1. Nucleus2. Mitochondria3. Cell border4. Nucleoli5. Red blood cell

  46. Types of Eukaryotic Cells: Plant vs. Animal Cells(not in syllabus directly) • Look at the diagrams of plant and animal cell diagrams(see p. 114/ch.7 of Campbell…) • What differences do you see?

  47. Describe three differences between plant and animal cells. (not in syllabus directly) Only plant cells have: • Cell walls • Chloroplasts • Large central vacuoles and tonoplast • Plasmodesmata • Starch granules for storage of carbohydrates Only animal cells have: Centrioles Lysosomes Glycogen for storage of carbohydrate Also: Plant cells usually have much less cholesterol in their plasma membranes.

  48. Roles of extracellular components (2.3.6) (not in syllabus directly) • Animal cells • Extracellular matrix (secreted glycoproteins) • Support • Adhesion • Movement • Plant cell wall (see next slides)

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