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Transcript
Lesson 1: What is life? What is Biology? The study of life. What is life? All living things are able to carry out the Functions of Life: Reproduction – creating genetically related offspring Metabolism – controls the chemical reactions of life Growth – increase in size and mass through nutrition and metabolism Nutrition – acquires the chemical building blocks needed to sustain life Homeostasis – maintaining a balanced internal environment Excretion – removal of waste products created by living Responsiveness – changing actions or behavior due to environmental signals Lesson 2: Introduction to Cells What is a cell? The usually microscopic unit from which living things are built A “bag” of gel-like cytoplasm inside a plasma membrane The smallest unit capable of all the functions of life Egg and sperm cells Cell Theory: living things are composed of cells Evidence: All organisms ever investigates (millions), no matter their size, are made of one or more cells. Cholera bacteria Elephant cells These cells are of similar sizes and have similar chemicals and structures (membrane, ribosomes, etc.) Cell Theory: living things are composed of cells Challenges: 1.Aseptate fungal hyphae: the fungal “threads” dissolve the cell walls and combine the cells into one. 2.Muscle cells (fibres): mitosis produces many nuclei but all the nuclei remain within a single cell. 3.Acetabularia (a giant alga): there is only a single “cell”, so large that the word “cell” seems inappropriate. Unicellular v. Multicellular Unicellular organisms: cells are generalists -- each cell capable of performing every life function Multicellular organisms: cells are specialists -- each cell is adapted to a specific function. Often no single cell can do all life functions. Light microscopes View natural color Can observe movement Can use live specimens Cheap and easy! Range includes larger objects than electron microscopes Electron Microscopes SEM: scanning electron microscope, surface image TEM: transmission electron microscope, view through a thin slice of specimen MAJOR advantage: HIGHER resolution! Electron microscopes can achieve better than 50 pm (1000 pm = 1 nm) resolution and magnifications of up to about 10,000,000x whereas ordinary light microscopes are limited by diffraction to about 200 nm resolution and useful magnifications below 2000x. 1 m = 1,000 mm 1 mm = 1,000 µm 1 µm = 1,000 nm Relative sizes (lengths) Organelle Scale interactives here (microscope) and here (universe). Determining sizes Magnification = image size specimen size Resizing changes magnification Scale bar: a line added; the scale shows the actual length the line represents. Resizing image also resizes scale bar x4000 Example calculations A mitochondrion has a length of 12 um. It is drawn 8.4 cm long. What is the magnifcation? Mag. = Image / Specimen = 8.4 cm / 12 um = 84,000 um / 12 um = 7,000 x 8.4 cm Example calculations An image of a nucleus is 122 mm wide The image has a magnification of 1500x How wide is the nucleus? Mag = Image size / Specimen size Specimen size = Image size / maginfication Specimen size = 122 mm / 1500 Specimen size = .081 mm = 81 um 3.4 cm 9.8 cm Example calculations: Microscopes Cow embryo 400x Given: the microscope has a field of view (FOV) of 500. um at 400x What is the size of the cell? FOVimage/FOVactual=magnification 9.8 cm / 500 um = 196 3.4 cm / actual size of cell = 196 Actual size of cell = 170 um Example calculations: scale bar Scale bar must represent a reasonable, appropriate, round value (1, 5, 10, 20, etc.) An image is magnified 4000 x. How long would a scale bar of 10 um be? Magnification = Image size / Specimen size 4000 x = image size / 10 um Scale bar image = 40000 um = 40 mm Determine the magnification of the image Determine the size of the viral head. 16 cm Mag = Image / Specimen = 20 cm / 100 nm = 200000000 nm / 100 nm = 2,000,000 x Specimen = Image / Mag X = 16 cm / 2,000,000 x X = .000008 cm = 80 nm 20 cm Interested in Microscopy? Check out some great SEM images here. Recent microscope image award winners here and here. Lesson 3: Cell Origins and Differentiation Where do cells come from? Cells come only from pre-existing cells. Frogs do not form from mud; flies are not made by a piece of meat, etc. Cells divide to create new cells. Binary fission Mitosis Pasteur: Cells from pre-existing cells • When existing bacteria cannot reach the broth, no bacteria will ever be found. • Once existing bacteria reach the broth, a large population of bacteria will soon develop. Pasteur’s Variations Connections: What is pasteurization? Interested in pasteurization of milk? Read more here and here! Alternative views here. Then where did the first cells come from? ABIOGENESIS: The first cells came from non-living material. Conditions were different on early Earth. The building blocks of cells would have formed spontaneously. Over time, the most stable forms, especially forms that could divide and multiply with time, became more common. Interested in abiogenesis? Learn more: Read chapter 2 from the classic book The Selfish Gene (Haiku) Watch a video here. Many cultures and Miller and Urey simulated the conditions of early Earth and found organic molecules religions have other stories about the start of life. Multicellular organisms: why not one big cell? The answer has to to with surface area and volume. Surface area finds the area Volume finds the amount of of each face of a solid (2D) space taken by a solid (3D) Ex. A cube has 6 faces, with all sides the same length. 6(s x s) = SA (units2) Ex. A height, length, and width of a cube are equal. s x s x s = volume (units3) Surface area to volume ratio Surface area / Volume 2: SA Explore surface area and volume here. V SA:V Calculate the surface area to volume ratio of cubes with sides of 2, 4, or 8 cm. Volume increases faster than surface 4: SA area V SA:V = 24 cm2 = 8 cm3 = 24:8 =3 = 96 cm2 = 64 cm3 = 96:64 = 1.5 8: SA = 384 cm2 V = 512 cm3 SA:V = 384:512 =0.75 Advantage of increased surface area Surface area determines the rate of exchange (how quickly nutrients are absorbed and wastes removed.) Volume determines the rate of resource use and waste production. DISCUSS which cube (right) would be better for a living thing. These two cubes have equal volume but different surface areas They need to use the same amount of resources Resources must cross the surface in order to enter The bottom cube: much easier to absorb enough nutrients and get rid of wastes. How does a multicellular organism get different types of cells? Most multicellular Genes that are “turned organisms start as one on” make specific cell that then divides proteins Each cell has exactly the Proteins influence what same DNA (genome) a cell can do and how it develops BUT each cell uses only SOME of its genome Known as differentiation Stem cells are needed for embryonic development • It is not enough that the starting cell can divide; it must be able to differentiate. • Stem cells can differentiate along different chemical pathways; activating some genes & turning others off. • Adult humans do not have (totipotent) stem cells, but early embryos do. Why? Emergent properties When all cells in the multicellular organism work together, new abilities appear The whole is greater than the sum of the parts These abilities are not found in any of the individual cells or groups of cells Ex. Conscious thought Life itself can be considered an emergent property Just for interest: Origins of different cell types Just for interest: How is DNA turned off (or on)? Methylation of DNA (turns off) Transcription factor proteins Zinc fingers, leucine zippers, etc. Stem cell therapy Some human cells will NOT heal if damaged or destroyed Many severe or deadly illnesses could be cured if stem cells could be controlled Embryos are a controversial source of stem cells Adult cells can be chemically reprogrammed as stem cells (to some extent) Stem Cell Controversy Possible sources of stem cells: Embryonic tissue (specially created, left over from IVF or aborted) Fetal blood from the umbilical cord “Reprogrammed” adult cells Conditions that might be treated: Stargardt’s Disease Leukemia and lymphoma Type 1 Diabetes Paralysis from spinal cord injury Parkinson’s Disease Links to help explore stem cell therapies Stargardt’s Leukemia Wikipedia StemEx Personal blog proliferation study A teen’s story Factsheet on stem cells for blood cancers (Haiku) (woman w/ Stargardt’s and a stem-cell recipient) Stem-cell company ACT website ACT progress report (Haiku) For your interest: Stem-Cell Burgers Cow and other animal muscle can be grown in the lab. Possible advantages include: Less energy needed More sanitary Fewer carbon emissions Less land needed Lesson 4: Types of Cells There are many types of cells Eukaryotic Plant Animal Fungus Protist Prokaryotic Bacteria Archaea Two major divisions of cells Prokaryotic Bacteria Only one membrane (the cell plasma membrane) One compartment (the inside of the cell) Relatively simple internal structure Eukaryotic Everything else Cell plasma membrane AND lots of membranes inside cell Multiple compartments (closed off by internal membranes) Relatively complex internal structure Further Differences between Prokaryotic and Eukaryotic Cells Prokaryotes Smaller or about the size of a mitochondrion Single, circular DNA without histones DNA in cytoplasm (no nucleus) Small ribosomes (70S) Eukaryotes Larger, containing multiple mitochondria Multiple strings of DNA organized by proteins DNA in nucleoplasm (protected inside nucleus) Large ribosomes (80S) Functions of Prokaryotic Cell Parts Cytoplasm – mostly water and free floating molecules; it provides the environment for all cell reactions Nucleoid – area that contains the DNA, which controls cell functions Cell plasma membrane – phospholipid bilayer that controls what enters and leaves the cell 70s Ribosomes – made of protein and rRNA, they build proteins according to mRNA messages Function of Prokaryotic Cell Parts Cell wall – stiff layer of carbohydrate and protein that provides shape and support and prevents the cell from absorbing too much water Flagella – protein “propeller” used for motion Pili – proteins extending from the cytoplasm to the outside, used for exchange of genetic info and adhesion E. Coli electron micrographs CELL MEMBRANE FLAGELLA PILI CYTOPLASM Identify Prokaryotic Structures ribosome nucleiod Cell membrane Cell wall cytoplasm Animal cell Cytoplasm 80s Functions of Eukaryotic Cell Parts Plasma membrane, cytoplasm, sometimes cell wall – function same as in bacteria 80s Ribosomes – link amino acids into proteins Free ribosomes make proteins for use in cytoplasm Ribosomes bound to ER make proteins for excretion or use in lysosomes Mitochondria – double membrane, for aerobic respiration / energy release Nucleus – double membrane protects the DNA, site of ribosome manufacture (nucelolus) Functions of Eukaryotic Cell Parts Rough ER Ribosomes “Other” membrane bound organelles Golgi apparatus – folded membrane for processing and packaging lipids and proteins Rough ER – folded membrane with attached ribosomes, makes proteins for outside the cell Sometimes lysosomes – enzymes for digestion and protection Sometimes chloroplasts for photosynthesis Eukaryotic Cell Micrographs Rough ER Mitochondrion Free ribosome / cytoplasm Eukaryotic Cell Micrographs Mitochondrion Rough ER Cell membrane Nucleus Intracellular Transport animated Membranes are flexible; they can pinch apart or merge together. Proteins for export: 1. Rough ER 2. vesicle 3. Golgi 4. vesicle 5. plasma membrane Exocrine Gland Pancreas Cells • A special example of transport • Exocrine cells release lots of protein • Protein for export is made by ribosomes on the rough ER • Golgi apparatus processes the proteins forming vesicles (condensing vacuoles) • The Golgi packages products, converting condensing vacuoles into secretory vesicles (zymogen granules) . • These vesicles (granules) fuse with the plasma membrane to release protein from the cell. • Role of DNA? Mitochondria? Palisade Mesophyll Leaf Cell Palisade mesophyll is long for best light absorption Chloroplasts for photosynthesis are many, mitochondria are few The vacuole and cell wall provide structure and support Why are mitochondria few? Origins of Eukaryotes The first cells on Earth would have been prokaryotes How did eukaryotes evolve? Endosymbiosis Mitochondria Chloroplasts Cilia / Flagella? Nucleus? (more evidence for progressive infolding of plasma membrane) Endosymbiosis: Let’s work together - FOREVER Usually prokaryotes were engulfed to digest for food, but in this case kept for useful genes, prokaryote protected, both benefit! Endosymbiotic origin of mitochondria and chloroplasts EVIDENCE – what would you imagine if they were once free-living prokaryotes? Double membranes (one from prokaryote, one from the vesicle in endocytosis) Grow and divide on their own schedule by binary fission Have their own circular DNA (naked, without histones) containing vital genes Make some of their own proteins on (small, bacterial sized) 70S ribosomes Interesting article here about possible 3-parent babies when mother has a mitochondrial disorder Paramecia and Chlorella are known to show endosymbiosis! Origin of Nucleus Infolding of plasma membrane leads to ER and nuclear envelope. NOT endosymbiotic - OR - DNA from two species (green and black) combines. Endosymbiotic.