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Bio Lab Midterm 1 Study Guide

by: Jade Geiger

Bio Lab Midterm 1 Study Guide BIO 204 LAB

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Jade Geiger

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These notes cover (along with a few other subjects) natural selection, biomolecules, concentration/absorbance, diffusion/osmosis, and enzymes. They explain everything which will be on the first mid...
Fr Mol Cel Evo Lfe Ea Ge Bio 204 Lab
Michelle Priest
Study Guide
Biology, Naturalselection, biomolecules, concentration, absorbance, Diffusion, Osmosis, Enzymes
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This 8 page Study Guide was uploaded by Jade Geiger on Friday September 23, 2016. The Study Guide belongs to BIO 204 LAB at Chapman University taught by Michelle Priest in Fall 2016. Since its upload, it has received 6 views. For similar materials see Fr Mol Cel Evo Lfe Ea Ge Bio 204 Lab in Biology at Chapman University.


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Date Created: 09/23/16
BIOL 204 Lab Midterm Study Guide Exam Format 2 The midterm is worth 100 points. Any extra credit points from the R challenges will be added to your final midterm score, designated on the first page when you receive your graded exam. There will be 9-12 short answer questions similar to those at the end of the chapters in the lab manual. There may be 1-3 questions as part of a lab practical section, in which you will be asked to demonstrate some of the lab techniques you have learned in class. Lab Concepts 1. Be able to describe the process of natural selection, and use this process to explain changes occurring in populations. The process in which individuals with certain traits survive and reproduce at higher rates than individuals lacking those traits. Adaptations are inherited traits that enhance survival and reproduction in a specific environment. a. Individuals in a population vary in their traits b. Most of these traits are controlled by genes. Thus, these traits are said to be heritable. c. Some individuals – termed “fit” individuals – possess traits (and genes coding for those traits) that allow them to survive better and leave more offspring than less fit individuals. d. Subsequent generations have a disproportionate number of offspring from the “fit” parents. e. Over many generations, favorable traits accumulate in a population; unfavorable traits diminish. Natural selection can only act on existing traits! These variations in traits arise through mutation. 2. Understand how environment influences the traits in a population, through the process of natural selection. Over a large period of time, an organism can change a physical appearance in order to blend in with the environment it is in. Take the bean lab experiment we did for example . . . the beans that blended in with the environment it was placed in took longer to find. Blending in with where it is placed in allows it to hide from predators trying to eat them. This allows this certain colored species to survive longer, therefore the next generations will have similar traits. Those who cannot blend in will not survive and that certain species will eventually go extinct. 3. Know the 4-step process of scientific method and be able to apply scientific method to solve new problems. Objective observation – can be in the form of objective background research, or perhaps the objective observations made in laboratory while running another experiment. It can also be objective observations made in the field (natural environment). Hypothesis formulation – experimental question (simple, What is the effect of x on y?) note the difference between affect (verb) and effect (noun). Hypotheses are possible answers to the experimental question. An increase in X will cause an increase in Y. You should be able to develop an alternative hypothesis An increase in X will cause a decrease in Y. Also consider the null hypothesis X has no effect on Y. Hypothesis testing by experimentation – Develop appropriate methods that allow you to collect the information about the effect of X on Y. a. Identify experimental variables - conditions of the experiment that VARY between treatment groups (there are independent and dependent variables) b. Determine the best way to carry out the experiment, determine how to collect data c. Identify the control group in order to measure change d. Control outside variables Analysis and conclusion – analyze data, this almost always involves graphing (bar graph, X-Y scatterplot). Decide whether your hypothesis is supported or rejected by the data. Cite limitations of the study, address possibility of follow up studies. 4. Be able to identify independent and dependent variables in a study, and consequently, how to display these variables on a graph, as well as which type of graph to utilize (bar or scatter). Independent is on x axis, dependent on y axis. Scatterplot is for a graph over time 5. Be able to also identify constants (things unchanged throughout an experiment). For example, keeping Biuret constant in protein standards. 6. For Carbohydrates, Lipids and Proteins, know: a. Key Characteristic (how we define the class of molecules) Carbohydrates – (CH O)2polnr, monomers – energy source for cells, cellular respiration, storage molecules and structural molecules Lipids – fats and oils, little or no affinity for water, nonpolar and hydrophobic, presence of C’s and H’s in a long chain; monomers – fatty acids; linked to backbone such as glycerol, cell membrane, lipid bilayer, phospholipids; saturated – the carbons in the carbon chain are single bonded to each other, unsaturated – at least one double bond in the hydrocarbon chain Proteins – structure dictates function, C-C-N backbone, characterized by amino acids, “R” group, amino acids joined by peptide bonds; catalytic proteins called enzymes b. Monomers and polymers Monomers are single units, and may exist on their own, or as part of a polymer.Apolymer is a long molecule consisting of many similar or identical building blocks linked by covalent bonds. Carbohydrates – monosaccharides (glucose, fructose); polysaccharides (amylose (starch)) lipids – proteins - c. Function in living cells Carbohydrates – cells extract energy stored in monosaccharides to power cellular processes, monosaccharides provide carbon skeleton to serve as raw material for the synthesis of other types of organic molecules, such as nucleic acids; polysaccharides serve storage molecules – monomers can be broken from the polysaccharide via hydrolysis reactions to provide simple sugars as fuel for cells (ex: starch, glycogen) Polysaccharides also serve as structural molecules (ex: cellulose, chitin) giving cell walls their rigidity lipids – fatty acids and oils provide a large amount of energy for the cells – 1 fatty acid molecule provides more energy than a molecule of glucose; forms a triglyceride which is used for energy storage proteins – polypeptide (sequence of amino acid) spontaneously undergo folding to form 3D structure (conformation), role protein plays in cell depends on its conformation; catalyzes cell reactions. They also transport material within the cell, aid in signaling between the cells, defend organisms against foreign substances, and allow for movement in animals (muscle contractions) d. How to qualitatively test for presence of biomolecules (reagent used, color changes, and appropriate negative and positive controls) Carbohydrates – monosaccharides: benedict’s test, positive (orange), negative (blue); polysaccharides: Lugol’s IKI test, positive (blue/black), negative (yellow) Lipids – paper bag test, positive (grease stain), negative (dried wet spot) Proteins – biuret test, positive (purple), negative (light blue) e. Examples of each of these classes of biomolecule Carbohydrates – monosaccharides, polysaccharides, disaccharides glycogen, cartilage Lipids – fats, phospholipids, oils cholesterol, vitaminsA, D, E, K Proteins – actin & myosin (structural proteins), alcohol dehydrogenase (an enzyme) 7. Know specific information for proteins: a. Why are proteins so diverse? Diverse due to the diversity of monomers - amino acids (20) b. What determines the three-dimensional shape of a protein? The folding of a polypeptide c. What holds the three-dimensional shape in place? Hydrogen bonds 8. Be able to determine whether a molecule (or regions of a molecule) are polar or nonpolar by examining the atoms of the molecules and how they are arranged. 9. Understand how polarity (or non-polarity) affects whether molecules will interact with each other or repel each other. Opposite charges attract one another (polar to nonpolar) 10. Know how polarity relates to being hydrophilic or hydrophobic. Hydrophobic – water fearing, nonpolar; hydrophilic – water loving, polar 11. Know what a spectrophotometer does, what absorbance means, and how concentration of a substance relates to its absorbance value. Spectrophotometer – used to measure color intensity in a sample (wavelength of light) Absorbance – the amount of light the sample absorbs and therefore does not pass through the sample, the darker a solution is, the higher the absorbance will be Concentration and absorbance are in a direct relationship, Higher concentration = higher absorbance 12. Know what a standard curve is used for, and describe and perform the step- by-step process of setting one up. Also, know what is meant by the term “standard” in this context. Standard curve – a line that shows the direct relationship between concentration of a solution and the absorbance of light 1. To create curve, obtain a series of “standards” – solutions with known concentrations of the sample. One standard is the blank sample, 0% concentration of the solution you are measuring (serves as a negative control) variable is the concentration of the sample 2. Collect absorbance of each standard and plot absorbance vs. concentration on an X-Y scatterplot graph, add trendline and equation of the line 13. Know how to combine information on standard curve with Beer’s Law equation to find concentrations of specific molecule in an unknown sample. Collect absorbance of each standard and plot absorbance vs. concentration on an X-Y scatterplot graph, add trendline and equation of the line. Use linear equation provided by excel to solve for concentrations of unknown samplesA=ec.Ais absorbance, e is slope of the standard curve, c is the concentration 14. Describe Brownian motion, diffusion and osmosis. Brownian motion - the erratic random movement of microscopic particles in a fluid, as a result of continuous bombardment from molecules of the surrounding medium. Diffusion – the spontaneous spreading out of molecules in a gas or liquid from a place of higher concentration to a place of lower concentration Osmosis – the diffusion of molecules across a semipermeable membrane; the diffusion of solvent not solute 14b. Understand differences in molarity vs. osmolarity vs. tonicity. Molarity – the number of moles of solute per liter of solution Osmolarity – total solute particle concentration of a solution; a solution containing 1 mole of solute particles is said to be at a concentration of 1 osmolar Tonicity – whereas a solution’s osmolarity is based solely on its total solute concentration, its tonicity is determined by how it affects cell volume, which depends not only on the solute concentration but also on the solute permeability of the cell membranes 15. Describe factors that will influence a solute’s ability to diffuse across a cell membrane, and how these differ from factors that influence diffusion across dialysis tubing. Influential factors: Solute size – small molecules diffuse more rapidly Temperature – diffusion occurs more rapidly when heat is added to the system Concentration gradient – the greater the concentration gradient between the outside and inside of the membrane the greater the rate of diffusion Change (+/-) and polarity – ions or molecules with a charge cannot easily pass through the lipid bilayer by diffusion, unless facilitated by transport proteins. Non-polar molecules more readily cross the cell membrane than polar molecules 16. Know which direction water will diffuse across a membrane when a cell is placed in hyper-, hypo- or isotonic conditions. Know also how these conditions affect cells lacking a cell wall (e.g. animal cells with only a cell membrane and intracellular components) vs. cells that do have a cell wall (e.g. plant cells with a cell wall, cell membrane and intracellular components). Hypotonic- water diffuses into cell; animal cell – causes a cell to swell and burst (lyse); plants – turgid cell wall (normal) Hypertonic – water diffuses out of cell; animal cell – causes a cell to shrink; plant cell – cell membrane shrinks away from cell wall - plasmolyzed/shrunk Isotonic – water is in equilibrium; animal cell – normal; plant cell – limp/flaccid 17. Know what causes turgor pressure and how it will impact osmosis. Turgor pressure- the pressure of water inside the cell (hydrostatic pressure) 18. Define “enzyme” and explain why enzyme conformation is so important. Enzyme – catalytic (chemical agent that speeds up a reaction without being consumed by the reaction) protein; in the absence of regulation by enzymes, chemical traffic through the pathways of metabolism would become hopelessly congested because many chemical reactions would proceed at a vastly slower rate. Cells could not survive without catalysts 19. How did we determine the rate of an enzymatic reaction, and why do we look specifically at the V0? Enzyme catalysis is detected by measuring either the appearance of product or disappearance of reactants. To measure something, you must be able to see it. Enzyme assays are tests developed to measure enzyme activity by measuring the change in concentration of a detectable substance. Vo is the initial velocity of a reaction. We look specifically at the Vo in order to describe the reaction. The enzyme’s velocity must be determined during an early time interval when the amount of product is increasing in a linear manner (Vo is also the slope of the line of a graph). 20. Think about how we might be able to carry out similar steps to find V , but 0 using disappearance of substrate, rather than appearance of product. Substrate – a substance or layer that underlies something, or on which some process occurs 21. Define and be able to use the term “denaturation” correctly when necessary. Denaturation is a process in which proteins or nucleic acids lose the quaternary structure, tertiary structure, and secondary structure which is present in the native state. In other words, denaturation is the process in which proteins lose their folded structure and cease to function. 22. Be able to explain and apply the following concepts: a. How (and why) does pH affect enzymatic reaction rate? pH affects the shape of the enzyme. pH is a measure of proton (H+) concentration. Remember from chem in high school when we did this: pH<7 is acidic (higher proton concentration), pH>7 is basic (lower proton concentration), and pH of 7 is neutral.As with heat, pH that is too acidic or too basic can alter the shape and chemical properties of the enzyme. Each enzyme has an optional pH – the pH where the enzyme is most active.ApH outside the optimal range may denature the enzyme (question 21) b. How does temperature affect enzymatic reaction rate, and why? (Specifically know how both cold and heat affect the enzyme). Temperature affects the speed of molecules in a system.At cold temperatures, molecules move about more slowly, and tend to collide and react at a slower rate. Increasing temperature (hot) will increase the speed at which substrate and enzymes collide to form product. c. How (and why) does substrate concentration affect enzymatic reaction rate? The more substrate molecules are available, the more frequently they access the active site on the enzyme molecules. However, there is a limit to how fast the reaction can be pushed by adding more substrate to a fixed concentration of enzyme.At some point, the concentration of substrate will be high enough that all enzyme molecules have their active sites engaged.As soon as the product exits an active site, another substrate molecule enters.At this substrate concentration, the enzyme is said to be saturated, and the rate of the reaction is determined by the speed at which the active site can convert substrate to product. Lab Techniques Generally, graphs should be able to stand alone so that readers can understand the content of an experimental result simply by looking at all components of figures and their captions, as in a journal article. The graphs you are making in Bio 204Labout your experiments should provide the observer with enough information to understand the lab results. Some general concepts below & more detailed info here Using_figures.htm< Using_figures.htm> TITLE: brief statement, introduces topic presented in the graph (but does not give away the result and does not re-state the axes labels 'x' versus 'y') AXES: correct placement of variables on the independent (x-axis) and dependent (y-axis), including the appropriate scale, and correct units. LEGEND: brief, use if needed to explain experimental groups or symbols. CAPTION: informative and detailed description of the graph content in a few lines, take-home message of the graph, any important experiment details, statistical analyses or how and where data was gathered, may include a key to any symbols or abbreviations. 1. Be able to produce a graph by hand or Excel, adding correct labels and units for axes. 2. Be able to take volume measurements using correct pipetting technique. 3. Be able to set calibrate a spectrophotometer and collect absorbance reading for a sample. 4. Understand aspects of basic microscopy as descried in labs to date. Review your experiments, think about their purpose In addition to reviewing concepts and techniques above, you should also review your specific lab activities and in-lab questions. Although you will not be asked to memorize exact procedures, knowledge of experiments may be useful for some questions. Some questions will bridge concepts from two labs. Here is an example: Recall your dialysis tubing membrane experiment which asked you to add the glucose/ starch mixture inside the tube and place it in tap water. Here we observed diffusion of solutes across a membrane. a. What factor affected diffusion of solute across a membrane in this experiment? b. How did we determine whether or not the solute had passed through the membrane (be specific!). Notice question (a) relates to study guide concept 14 which comes from Chapter 3, but question (b) relates to study guide concept 6.d which comes from Chapter 2.


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