Transcript Biology
Welcome to General Cell Biology Biol&160 A & B Today Introduction- class roll Syllabus/Expectations Intro to science & scientific method Organization of life Cell chemistry and molecules Syllabus Questions? Study Habits Find out what works best for YOU Try different methods – Combine methods Use shorthand Read the chapter BEFORE lecture and be prepared with any questions What is science? To Know Seeks natural causes to phenomenon – Therefore limited to things that we can OBSERVE and MEASURE Ex: Rate of flow of water over a dam Ex: Deity Explanatory –study of the world around us to explain our observations Testable – based on observations or measurements Reproducible – others must be able to confirm and duplicate scientific findings Predictive – we use scientific knowledge to predict answers to questions Tentative – each new discovery can change the way we look at other things we know What is science Observational science – What is observed in nature Experimental science – Usually derived from observational science – Attempts to answer/understand specific questions about what is observed What is Biology Study of life – Encompasses Ethology Evolutionary Biology Physiology Genetics Molecular Biology Morphology Systematics Ecology And more….. Hypothesis based science Hypothesis- a tentative statement that proposes a possible explanation to some phenomenon or event Testable – may include a prediction Simple and concise Falsifiable – Accept or reject Scientific Theory Explanation of something that has been substantiated by a large amount of data collected over multiple experiments Best possible explanation at the time based on experiments and available data Theories are altered, revised, adapted or simply abandoned as new data becomes available Scientific method Observation Question – This turns into a testable… Hypothesis Prediction Experimentation – Controlled – Replication Analysis of results Evaluate hypothesis against results Generate Scientific Theory Reasoning Inductive- Extrapolate general principles from specific examples Deductive- Extrapolate specific examples from general principles Humans are made of cells Inductive – Every biological sample for the past 200 years has been made of cells (specific) THEREFORE – All organisms (including humans) are made of cells (general) Deductive IF – all organisms are made of cells & humans are organisms (general) THEN – Humans are made of cells (specific) Spontaneous Generation Living things arrive from lifeless matter – Air had a “life force” Rotting meat, when left, produced flies Redi’s blowfly experiment Spontaneous Generation Observation- Flies spontaneously appear on rotting meat Question- Does rotting meat produce flies Hypothesis- Rotting meat produces flies Prediction- A flask of rotting meat will produce flies in 21 days Experimentation- 3 jars of meat were subjected to being open, semi-sealed with parchment paper or sealed while other variables remained identical – Control is flask of meat set out with no cover – Experiment is 2 flasks semi-sealed and sealed Analysis of results- Presence/absence of flies was recorded. No flies were present in closed jars, semi-closed jars had fly eggs on the parchment Evaluate hypothesis against results- Reject hypothesis as sealed jars did not produce flies and semi-sealed jars had fly eggs on the parchment paper – Flies came from other flies not from the meat ©Barrons 2009 Experiments & Theories Experiments & hypotheses only test NEVER prove theories – The very next experiment may falsify theory – Always falsify a hypothesis, not prove it Correct- A sealed jar will not produce flies Not- an unsealed jar will produce flies Data Interpretation A team of scientists designed an investigation that used artificial snakes to test the following hypotheses. – – – – H1: The coral snake’s bright color pattern serves to warn off potential predators. H2: The king snake suffers less predation because it mimics or looks like the coral snake. H3: The protection that king snakes receive by mimicking coral snake will depend on the presence of coral snakes. Both 1 and 2 Data Interpretation Biologists placed artificial snake mimics in two different localities to test the hypothesis that looking like a poisonous snake only works where the poisonous snake is found: 1. Outside of the coral snake range—only king snakes present. 2. Inside the coral snake range—both coral and king snakes are present. Data Interpretation The graphed data __________ the hypothesis that the effectiveness of mimic coloration depends upon the presence of the poisonous model is: – – – supports does not support is irrelevant to Data Interpretation Based on this data which of the following is a logical hypothesis or prediction? – – – King snakes outside of the range of coral snakes will more closely resemble coral snakes than populations of king snake living within the range of coral . King snakes outside of the range of coral snakes will not resemble coral snakes as closely as populations of king snakes that live within the range coral snakes. Neither prediction is valid. Why do I care about Hypothesis testing and scientific method? Used in every day life and decision making – Ex: Medical- use scientific method to determine cause of patients ailment Organization of Life Life’s levels of organization define the scope of biology Hierarchical organization Levels organized according to complexity – “Higher” and “lower” order life forms do not exist, simply a matter of complexity Emergent properties – Properties that were not present at the previous lower level and result from the specific arrangement and interactions between components “The whole is greater than the sum of its parts” Environmental interactions Living organisms and their environments form interconnecting webs Environmental Interactions Producers – Organisms that produce organic compounds from inorganic compounds These organisms are autotrophs Photosynthesis, chemosynthesis, etc Consumers – Organisms that obtain nutrients from other organisms Heterotrophs Decomposers – Decay organic matter, releasing energy back into the ecosystem Saprobes Common features of all living forms Order/organization Regulation Growth & Development Energy utilization/processing Response to the environment Reproduction Evolution In-class Exercise Get into groups Each group identify a scientific question, hypothesis and experimental outcome for each scenario – Don’t worry about figuring out an experiment, just make up the results of one Decide if your outcome supports or refutes your hypothesis Example While walking to class today, I notices a fire hydrant in the middle of the pathway Question- Why was the hydrant placed in the middle of the path Hypothesis- The middle of the path was the most accessible location for the hydrant Experimental outcome- The middle of the path was not found to be the most accessible location for a hydrant My findings do not support my hypothesis and thus, my hypothesis is rejected. Exercise Scenario 1-While hiking in the forest one day, you notice that while on the left side of the trail, the frogs are bright green, but on the right, they are a mottled greenbrown color. Scenario 2- As a nurse, one of your patients presents with an unusually low temperature, but no other symptoms Scenario 3-You are fishing out in Puget Sound and find that all the other fishermen are pulling up salmon, but you are catching fish. Cellular Chemistry Ch 2 Life primarily consists of carbon, hydrogen, oxygen, and nitrogen Rest are present in trace amounts Table 2.1 Trace elements Are essential to life, but occur in minute amounts Trace elements are common additives to food and water Dietary deficiencies in trace elements can cause various physiological conditions These Interpreting Data are the results of a laboratory experiment to test the effect of trace nutrients on the productivity of Pacific Ocean water. After 6 days which nutrient had the greatest effect on productivity? – – – – Iron Manganese Copper Zinc Adapted from Coale, Kenneth H. 1991. Effects of Iron, Manganese, Copper and Zinc Enrichments on Productivity and Biomass in the Subarctic Pacific. Limnology and Oceanography. 36: 1851-1864 Subatomic Particles Protons- positive charge Neutrons- neutral charge – – 2e– + + + + Protons and neutrons occupy the nucleus Electrons- negative charge Arranged in electron shells around the nucleus Electron cloud Nucleus 2 + Protons 2 Neutrons 2 – Electrons Mass number = 4 Figure 2.4A Differences in Elements Atoms of each element always have the same number of protons Atomic Number=# protons Mass Number (atomic weight) = Protons + neutrons Electron cloud 6e– ++ Nucleus 6 6 6 Atoms have no overall charge, thus… + Protons Neutrons – Electrons Figure 2.4B Mass # = 12 Thus…. Number of protons (+ charge) must be equal to the number of electrons (-) For any element: Number of Protons = Atomic Number Number of Electrons = Number of Protons = Atomic Number Number of Neutrons = Mass Number Atomic Number Example Kr Krypton Atomic # = 36 Atomic weight = 84 # Protons=? # Neutrons=? # Electrons=? Compounds Chemical elements combine in fixed ratios to form compounds Different combinations of atoms determine the unique properties of each compound Chlorine Sodium Figure 2.3 Sodium Chloride Isotopes The number of neutrons in an atom may vary Table 2.4 Variant forms of an element are called isotopes Some isotopes are radioactive Isotopes aX z A = mass number (the total number of protons + neutrons) Z = atomic number (the total number of protons) X = element symbol Ex: Ordinary hydrogen is written 1H1, deuterium is 2H1 (heavy water, label in chemistry experiments) tritium is 3H1 (radioactive) Radioactive isotopes Particles that are emitted from the nuclei as a result of nuclear instability Usefulness of radioactive isotopes Irradiation – Material is subjected to radiation for the purposes of disinfestations, pasteurization or sterilization Research – Radioactive tracers enable researchers to follow particular molecules as they undergo change such as through photosynthesis Usefulness of isotopes Medical Diagnosis – Kidney disorders – Medical Imaging PET scans PET scan image of Parkinson's diseased brain Brown.edu 2008 Electrons, Electrons, Electrons! The active part of the atom – They are the only part directly involved in chemical activity Interactions between electrons form chemical bonds Electron shells – Arranged in shells, which may contain different numbers of electrons Electron Shells Electron arrangement determines the chemical properties of an atom – Electrons in an atom are arranged in shells, which may contain different numbers of electrons Outermost electron shell (can hold 8 electrons) First electron shell (can hold 2 electrons) Electron Hydrogen (H) Atomic number = 1 Figure 2.6 Carbon (C) Atomic number = 6 Nitrogen (N) Atomic number = 7 Oxygen (O) Atomic number = 8 Electron shells Valence electron shell – Outermost shell of electrons – These electrons interact with other atoms Outermost electron shell (can hold 8 electrons) First electron shell (can hold 2 electrons) Electron Hydrogen (H) Atomic number = 1 Figure 2.6 Carbon (C) Atomic number = 6 Nitrogen (N) Atomic number = 7 Oxygen (O) Atomic number = 8 Ions Created when an atom gains or looses and electron Results in an net positive or negative charge depending on if the atom gained or lost the e- Ionic Bonds •Attractions between ions of opposite charge – An electrical attraction between ions with opposite charges results in an ionic bond – – + Transfer of electron Na Cl Na Sodium atom Cl Chlorine atom – Na Cl Na+ Sodium ion Cl– Chloride ion Sodium chloride (NaCl) Figure 2.7A NaCl Na has 1 e- in the outer shell Cl has 7 e- in the outer shell Na “donates” its e- to Cl, leaving Na with only 2 shells and Cl with a full outer shell – This moves 1 “unit” of negative charge from Na to Cl, resulting in a net electrical charge of +1 for Na and -1 for Cl NaCl The atom is now an ion – Recall that an ion is an atom or molecule with an electrical charge form either gaining or loosing electrons Covalent Bonds Two atoms share one or more pair of outer e–# of bonds is equal to additional enecessary to fill the outer shell –Valence or bonding capacity of the atom Join atoms into molecules through the electron sharing Covalent bond Diamond with 4 covalent bonds info.lu.farmingdale.edu/.../atomicbonds.html Polar molecules Unequal e- sharing produces polar bonds Electronegativity – Atom’s attraction for shared electrons – Greater the electronegativity, stronger the pull on (+) e- (–) (–) O H H (+) Figure 2.9 Water Molecule Polar molecules If the atoms exert a equal pull on the e-, bond is non-polar covalent – Overall charge of 0 If the atoms exert an unequal pull on the e-, bond is polar covalent – Overall charge on the more electronegative atom is partially negative and the less electronegative atom is partially positive Polar molecules (–) (–) Polar molecules have an unequal distribution of charges O H H (+) (+) Figure 2.9 Water Molecule Visual representation of a molecule – Molecules can be represented in many ways Table 2.8 Hydrogen Bonds Partial + charge allows shared attractions with – charged molecules + charged region always H (–) Hydrogen bond (+) H (+) O (–) H (–) (+) (–) (+) Figure 2.10 The importance of hydrogen bonding Cohesion between H20 molecules – Droplet formation – Transportation Adhesion to substrate Surface tension Temperature moderation (body and climatic) – H bonds absorb a great deal of energy before breaking, thus, a lot of energy is required before an increase in temp occurs Density – Ice vs. liquid water Solvent Water is the solvent of life dissolving any charged or polar substances Solution Aqueous solution Solvent – Dissolving agent Solute – Dissolved substance EX: Salt water – Water is the solvent and salt the solute Ph Scale Some H20 molecules disassociate into H+ and OH A compound that releases (donates) H+ ions in solution is an acid – Increases the net H+ ions in solution A compound that accepts (removes) H+ ions in solution is a base – Increases the net OH- ions in solution Ph Scale H+ H+ OH– H+ OH– H+ H+ H+ H+ Acidic solution OH– OH– OH– H+ H+ – OH– OH H+ H+ H+ Neutral solution OH– OH– OH– H+ OH– OH– OH– – OH H+ NEUTRAL [H+]=[OH–] 1 2 Lemon juice, gastric juice 3 Grapefruit juice, soft drink 4 Tomato juice 5 6 Human urine 7 Pure water Human blood 8 Increasingly BASIC (Lower concentration of H+) H+ Increasingly ACIDIC (Higher concentration of H+) 0 pH scale Seawater 9 10 Milk of magnesia 11 Household ammonia 12 Household bleach 13 Oven cleaner Basic solution 14 0-14 7 is neutral 0-6.9 acidic 7.1-14 basic/alkaline Each unit is 10 fold change in concentration of H+ ions Buffers act to minimize Ph changes CHEMICAL REACTIONS Chemical reactions change the composition of matter reactants Figure 2.17A 2 H2 O2 products 2 H2O Interpreting Data This is the general equation for photosynthesis—the process of capturing sunlight energy and converting it to chemical energy. Which of the following are the reactants of this reaction? – C6H12O6 and O2. – CO2 and H2O. Interpreting Data Earth’s oceans are immense. Small floating plants called phytoplankton contribute to ocean productivity. As ocean productivity (the rate of photosynthesis) goes up what would you predict would happen to global carbon dioxide levels? – CO2 levels should also go up. – CO2 levels should go down – CO2 levels should remain constant.