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Weekly Essay Prompts Fall Semester Essay Prompt #1 (Due Tues. 9/7)** You must WRITE using a pen or pencil. A typed response will not be accepted. The unique properties (characteristics) of water make life possible on Earth. Select three properties of water and a)for each property, identify and define the property and explain it in terms of the physical/chemical nature of water. b)for each property, describe one example of how the property affects the functioning of living organisms. **Don’t Forget to Paste the Question on the 3rd page of your quad-ruled book and to have a BRAINSTORM Section. Essay #1 -Prop. of water Note: you will need to print this slide out to see the words better. Essay Prompt #2 Carbon is a very important element in living systems. a. Describe the various characteristics of the carbon atom that makes possible the building of a variety of biological molecules. b. Explain how reactions involving carbon-containing compounds can contribute to the greenhouse effect. c. The following structures are examples of two different categories of biological compounds. Describe how each category of compounds is important to the structure and function of living systems. STANDARDS: A. CHARACTERISTICS OF CARBON ATOMS: (Max of 4 points) __Ready availability, abundance __Atom small in size, outer (valence) electrons close to nucleus, so forms stable (strong) bonds __4 electrons in a valence-capacity of 8, forms 4 bonds to 4 other atoms __Forms covalent bonds __Can bond to other carbon atoms, no upper limit to size of carbon compounds __Bond angles form tetrahedron, resulting in 3-D structures, chains, rings, not just planar __Can form multiple C-C, C=C, C=C bonds __Can form isomers, different structures - same number and kind of atoms __Functional groups/combine with a variety of other elements __BONUS POINT: if get 3 above - Uniqueness, only Carbon has all of these characteristics B. REACTIONS CONTRIBUTING TO GREENHOUSE EFFEC (Max of 4 points) __Overview: Increase in gas concentration (CO2, CO, CFC) causes greenhouse effect __CO & CO2 from respiration and combustion, or volatilization of limestone __CH4 from correct source - livestock, microbes, landfills, swamps, oil wells, etc. __CFCs from industrial activities, refrigerants, plastic foam, etc. PHYSICAL MECHANISMS OF HEATING: __Ozone destruction / more energy (UV) gets in __Trapping of Energy - "Blanket" traps heat or Reflection of Sun's Energy (technically incorrect but common use in texts) __Good technical description of absorption, reradiation and wavelength shift leading to production or long wave infrared absorbed by greenhouse gases __Concept of sinks: CO2 removal by photosynthesis, CaCO3 formation, soluble in oceans, etc. CO2 addition by forest destruction, industry, etc. C. BIOLOGICAL MOLECULES: (Max of 5 points) (Cannot get 10 points for this question without mentioning both category I and II) CATEGORY I: __Identification of molecule / category: Phospholipid, phosphoglyceride, fat, lipid, phosphatidylethanolamine / polypeptide. __Characteristics of molecule: Hydrophobic/hydrophilic, polar/nonpolar, amphipathic, or non-water soluble, high E bonds, sat/unsat C-C bonds. __Structural uses of molecule: membrane, lipid bilayer, fluid mosaic. __Functions of molecule (for example): (2 Max) Phospholipids: Regulation of membrane permeability, fluidity Fats: Structural, insulation, energy storage, water-proofing Steroids/Sterols: Hormonal, membrane fluidity Cholesterol: Animal membranes Fat soluble Vitamins: Coenzymes Prostaglandins: Neural modulators Waxes: Water-proofing CATEGORY II: __Identification of molecule / category: Amino acid / protein / cysteine __Recognizing cysteine's role in disulfide bond formation __Characteristics of molecule: Side chains variable Peptide bonds may be formed Subunit (monomer, building block) of protein Levels of protein structure / zwitterion / as buffers __Structural roles: Keratin, collagen, cytoskeletal (tubulin, actin), etc. __Functional roles: Enzymatic - speed reactions (2 Max) (pepsin, glucose oxidase, etc.) Transport (Hb, Myb, permeases, HDL/LDL) Regulatory (oligopeptides, ex. hypothalamic releasing factors, insulin, glucagon, etc.) Contractile - actin, myosin Protection - antibodies ESSAY #3 Osmosis is a driving force for homeostasis in plant and animals. DEFINE osmosis and DISCUSS how the movement of water molecules regulates THREE of the following activities: A. Water and solute transport (through plants)-Revised B. Solute concentration in the mammalian kidney C. Stomatal opening in the leaves D. Blood pressure in humans **NOTE: Be sure to use your textbook to help you answer the three topics and include a drawing with key structures labeled. ESSAY #3 – Grading Rubric QUESTION #1 • Definition: (1 pt max) • 1 pt. Definition of osmosis: the diffusion of water across a selectively permeable membrane. • - High concentration of water to low concentration of water • - High water potential to low water potential • - Low water solute potential to high water solute potential • 1 pt. Osmosis is maintained through the use of concentration gradients. Part A: 1 pt. each (4 pt max; an be from root to stem category)-see Ch. 36 • Water enters the root hairs through osmosis • Water moves through cells walls from one cell to another through the apoplast • Water moves from one cell to another through the symplast. • The endodermal calls allow water to enter the vascular cylinder (stele) but are selective • A concentration gradient is maintained between the soil and the root • Water is continuously moved out of the root by the xylem and by high solute concentration in the vascular cylinder • Root pressure is an osmotic force that can force water u the xylem (not common – use of term guttation) ESSAY #3 – Grading Rubric (cont’d) STEM (See C. 36) • Capillary action is the rise of liquids in tubes • Adhesion is the molecular attraction between unlike substances such as the water and the sides of the vascular cylinder • Transpiration at the leaf causes a negative pressure to develop within the laves and xylem • Cohesion between water molecules causes water to move up the xylem • Bulk flow occurs at water molecules are lost from the leaf to transpiration Part B: 1 pt. each (4 pt max)- See Ch. 44 (pgs. 931-938) • site of osmosis is the nephron • as salt moves from the filtrate to the interstitial fluid, water follows by osmosis • interstitial fluid bathing the tubule is hyperosmotic to the filtrate in the descending loop of Henle • ascending loop of the Henle reabsorbs NaCl without giving up water, making the filtrate dilute • In the collecting duct the filtrate loses more and more water to the hyperosmotic interstitial fluid • Antidiuretic hormone (ADH) increases the permeability of the epithelium to water • Water is absorbed in the nephron, reducing urine volume ESSAY #3 – Grading Rubric (cont’d) Part C: 1 pt. each (4 pt max) – See Ch. 36 (Pgs. 749-751) • Stomata are pores in a leaf • When stomata are open water moves to the leaf • Each stoma is surrounded by two guard cells • When water enters a guard cell, the guard cell becomes turgid • The turgidity of the guard cell causes an expansion or bulging of the cell creating an opening • Stomatal opening is accompanied by a diffusion of K+. As K+ from surrounding cells enter the guard cell, a gradient is created, Water will then enter the guard cell (As K+ leaves, so does water) Part D: 1 pt. each (4 pt max) – See • when blood pressure drops the enzyme renin is secreted • Angiotensinogen is converted to angiotensin • Angiotensin stimulates the reabsorption of water, raising blood pressure • Angiotensin constricts arterioles, raising blood pressure • Aldosterone is secreted by the adrenal glands • Aldosterone increases reabsorption of Na+ in the nephron’s distil tubule, increasing blood pressure and volume • When blood pressure increases the release of renin is reduced ESSAY Prompt #4 Enzymes are important biological molecules. They are one of the primary means of regulating chemical processes within cells. A. Describe how enzymes affect chemical reactions. B. Describe environmental factors that affect enzyme action. C. Describe how enzymes are important for the process of DNA replication. (see chapter 16) **NOTE: Be sure to include the structure and what enzymes are composed in your answer. Grading Rubric for Essay #4 Part A: (1 point for each of the following) 1. Enzymes increase the rate of chemical reactions 2. Enzymes bind to the substrate at the active site 3. The enzymes and substrate bind through hydrogen bonding 4. The substrate that binds to the enzyme is one of the reactants in the reaction 5. The substrate is changed to products and consumed by the reaction 6. The enzyme is not consumed by the reaction and can be used again 7. The enzyme reduces the activation energy of the reaction causing the increase in reaction rate 8. The enzyme is a protein with a complicated three dimensional shape 9. The shape of the enzyme’s active site had to be complementary to the substrate molecule Part B (4 pt max-1 pt for each of the following 1. An increase in temp. causes substrate and enzyme molecules to move more rapidly 2. The increased movement causes more collisions that increase the reaction rate 3. Extreme temp. denature enzymes and slow reaction 4. Competitive inhibitors are shaped similarly to the substrate 5. Competitive inhibitors compete for the active site with the substrate, slowing the reaction rate 6. Noncompetitive inhibitors bind to the site outside of the active site 7. The non competitive inhibitors change the shape of the enzyme and its active site and slow the reaction 8. Each enzyme operates most efficiently at an optimum pH 9. pHs outside of that optimum can disrupt or denature Part C (3pt max; 1 pt for each of the following) 1. Helicase causes the DNA double helix to unwind 2. DNA polymerase copies the exposed single strands of DNA 3. DNA polymerase can only add nucleotides to a free three prime side 4. DNA ligase seals Okazaki fragments together 5. DNA polymerase proof-reads the new strands Other Information about Enzymes (2000 AP Question) Enzyme question QUESTION I-2000 1. The effects of pH and temperature were studied for an enzyme- catalyzed reaction. The following results were obtained. a) How do (1) temperature and (2) pH affect the activity of this enzyme? In your answer, include a discussion of the relationship between the structure and the function of this enzyme, as well as a discussion of how structure and function of enzymes are affected by temperature and pH. b) Describe a controlled experiment that could have produced the data shown for either temperature or pH. Be sure to state the hypothesis that was tested here. • Question I • Part a. (maximum 6 points) • Optimum temperature and pH concept [must include both temp and pH] • Enzyme/Substrate Fit concept (function dependent on conformation complernentarity between enzyme and substrate) • Tertiary (and sometimes quarternary) structure determines function • Description of enzyme structure or function, e.g. Structure • Elegant description of primary to tertiary or primary to quarternary levels of structure • Protein folding/coiIing • Co-enzymes/co-factors • Zymogens • Allosteric effectors • Function • Increases rate of reaction • Increases proximity of reactants • Decreases activation energy of the catalyzed reaction • Decreases time to reach equilibrium • Induced fit and/or orbital steering ("bond stress") • Denaturation concept [temp and/or pH] linked to decreased enzyme activity (e.g. "denaturation" in context or unfolding or change in 3D shape. not "enzyme breaks down") • How temperature affects conformation (increased temperature breaks specific bonds e.g. hydrogen, Van dcr Wuals, eljsrtllide bridges) • How pH affects conformation (change in H concentration causes a change in specific bond interactions, e.g. hydrogen: ionic, R-group interactions) • Kinetics (increased or decreased molecular movement ) linked to effect on enzyme activity due to increase or decrease in temperature up to the optimum. • Part b. (maximum 6 points) Experimental design must be relevant to the data shown • What is measured (e.g. product formed or substrate used) • How is it measured (titration or spectrophotometry or color change or bubbles counted. etc.) • The independent variable (temperature/pH) is manipulated to produce the results at least 3 data points are identified] • The described experiment could produce these data Experimental design included sufficient range, varied the temp/pH of the reaction mix not the enzyme, what was measured, and how it was measured) • Held experimental factors constant (specified at least one) • Specified a control group for comparison (no enzyme or boiled enzyme or no Substrate) • Verified results (e.g. repeated trials: results represent an average) • Hypothesis clearly related to experiment of choice, and clearly identified as a hypothesis can use the if/then... form. Essay Prompt #5 • Explain how the molecular reactions of cellular respiration transform the chemical bond energy of Krebs Cycle substrates into the more readily available bond energy of ATP. Include in your discussion the structure of the mitochondrion and show how it is important to the reactions of the Krebs Cycle and the Electron Transport Chain. Be sure to include all the intermediate molecules (# of carbons) as well as all of the products released. Also, indicate where all of the dehydrogenase & Kinase enzymes would be working. You may want to include labeled diagrams to support your answer Answer Key to Essay #5: STANDARDS: 1/2 point for each of the following -Krebs and ETS occur within mitochondria -Krebs - enzymes freely present in matrix fluid -ETS - respiratory chain (respiratory assembly) arranged in order inner membrane of mitochondria (Diagram OK) -More active cells - more respiratory assemblies & more cristae -Aerobic - O2 necessary as final H acceptor (-> H2O) (most eukaryotic cells all of the time) -Glycolysis is 1st required (outside mitochondria) -Glucose (6C) is broken down into 2 Pyruvic Acid (3C) molecules -Phosphorylation must 1st occur -Net production: 2 ATP & 2 NADH MITOCHONDRIA -Pyruvic Acid & 2NADH enter mitochondria -2 NADH will transfer H (electrons) into ETS -yields 2 x 2 ATP = 4 ATP (some loss due to point of entry into ETS) KREBS CYCLE SUBSTRATES • 2 Pyruvic Acid loses CO2 & H -> 2 NADH & combines w/CoA -> Acetyl CoA • (2C) Acetyl CoA + (4C) Oxaloacetic Acid -> (6C) Citric Acid • Citric Acid -> Isocitric Acid • (6C) Isocitric Acid - DEHYDROGENATION & loss of CO2 -> (5C) Ketogluatric Acid NAD -> NADH • (5 C) Ketoglutaric Acid - DEHYDROGENATION & loss of CO2 -> (4C) Succinic Acid NAD -> NADH • (4C) Succinic Acid - DEHYDROGENATION -> (4C) Malic Acid FAD -> FADH2 • (4C) Malic Acid - DEHYDROGENATION -> Oxaloacetic Acid NAD -> NADH • specific mention of 2 x 3 NADH & 2 x 1 FADH2 produced during Krebs • ATP (1) produced in Krebs • ETS RECEIVES THE FOLLOWING: NADH or FADH2 WHICH RESULTS IN ATP PRODUCTION • Glycolysis -> 2 NADH x 2 ATP = 4 • Pyruvic Acid -> Acetyl CoA + 2 NADH x 3 ATP = 6 • Krebs -> 8 NADH (FADH2) x 3 ATP = 24 Total = 34 • 34 ATP gained through ETS • Respiratory Assembly: CoQ, cytochromes b, c, a, a3 • Ring Compounds w/Fe (porphyrin ring) • Changing Oxidation states as "go down" assembly • Fe III -> Fe II change ionic state as accept electrons • Release energy in "packets" - small amounts sufficient to produce ATP (about 7 kcal/mole) • Occurs at 3 places in the chain for each NADH, FADH2 • mention of various hypotheses: Chemiosmotic, Conformational, Chemical Coupling • O2 final acceptor ( -> H2O) EssayPrompt #6 Discuss the process of cell division in animals. Include a description of the entire cell cycle and provide specific details of the key events that occur in each of the phases. Do not include meiosis. Be sure to include the major proteins associated with the process of cell division. Answer Key/Grading Rubric for Essay #6 PART I. DESCRIPTION OF MITOSIS IN ANIMAL CELLS: Max. = 7 points General • __ division of nucleus • __ daughter cells acquire the same number and kinds of chromosomes as in the mother cell • __ process for growth or repair or asexual reproduction • __ list phases in correct order (P,M,A.T) Prophase (one point each / max. 2) __ • centrioles move apart • __ chromosomes condense • __ nucleolus is no longer visible • __ nuclear envelope disappears • __ asters and spindle form Metaphase • __ sister chromatids (chromosomes) are in a line at the midpoint of the spindle Anaphase (one point each / max. 2) • __ centromeres uncouple (split) • __ chromosomes move to opposite poles • __ microtubules involved in the push/pull movement Telophase (one point each / max. 2) • __ reverse of prophase • __ nuclear envelope reforms • __ nucleolus reappears • __ chromosomes become diffuse • __ spindle and aster disappear • __ centrioles are replicated Points less frequently mentioned: • __ function of centrioles • __ definition of kinetochores • __ description of polar microtubules and kinetochore microtubules • __ definition of chromatids *In order to obtain a score of 10, there must be points in all three sections. If only two sections are written PART II. CYTOKINESIS: • division of cytoplasm • formation of a cleavage furrow • occurrence of cytokinesis in the cell cycle Points less frequently mentioned: -function of cytokinesis -dense belt of actin and myosin microfilaments -purse-string mechanism -furrow occurs at location of equatorial plane -cytochalasin blocks activity of microfilaments (stops cytokinesis) PART III. OTHER PHASES OF THE CELL CYCLE (INTERPHASE): General -list G1, S, and G2 in correct order -G1, S, and G2 are part of interphase -Chromosomes appear as a mass of chromatin material G1 -Synthesis of cell organelles or cell doubles in size -Restriction (decision) point or point of no return S -Synthesis or replication of DNA or DNA replication occurs during interphase G2 -Synthesis of microtubular assembly, or prepare for mitosis Points less frequently mentioned: • description of nucleosomes • times in each phase • growth factors • some cells do not go beyond G1 • after cell passes "S", mitosis will usually continue • colchicine prevents the formation of microtubules Essay Prompt #7 • The Cell Cycle functions in regulating information flow through organisms. a. Explain how these controls prevent errors in inheritance and what happens when errors do occur. b. Discuss the key characteristics of Cancer and the genes commonly mutated that cause cancer to form. c. Discuss how alleles are distributed by the process of meiosis to the gametes. Essay Prompt #7 No Rubric Available Yet. We might grade this one specifically in class!!! So make sure that you’ve included as much detail as possible to receive full credit. Essay Prompt #8 • Read the following question and on a separate sheet op paper give your answer in an ESSAY FORM. Outline alone is not acceptable. Labeled diagrams may be used to supplement discussion, but in no case will a diagram alone suffice. It is important that your read each question completely before you begin to write. • In Fruit flies, the phenotype for eye color is determined by a certain locus. E indicates the dominant allele and e indicates the recessive allele. The cross between a male wild-type fruit fly and female white-eyed fly produced the following offspring: Wild-type Wild-type White-eyed White-eyed Brown-eyed Male Female Male Female Female F1 0 45 55 0 1 • The wild-type and white-eyed individuals from F1 generation were then crossed to produce the following offspring: Wild-type Wild-type White-eyed White-eyed Brown-eyed Male Female Male Female Female F2 23 31 22 24 1 **Answer the Questions on the Next Slide -------------- Essay Prompt #8 (cont’d) 1.Determine the genotype of the original parents (P generation) and explain your reasoning. You may use Punnett squares to enhance your description, but the results from the Punnett squares must be discussed in your answer. 2. Use a Chi-squared test on the F2 generation data to analyze your prediction of the parental genotypes. Show all your work and explain the importance of your final answer. BE sure to write the Chi-Square formula next to your work. The brown-eyed female in the F1 generation resulted from a mutational change. Explain what a mutation is, and discuss two types of mutations that might have produced the brown- eyed female in the F1 generation. **Note: Your response to these three questions will be a major part of your grade for this lab. Therefore, be thorough and complete in your response ESSAY Prompt #8: Rubric (Key) A) maximum 4 pts – 1 pt Genotypes of the parents (words or symbols) XEY (or X+Y) and XeXe – 1 pt Discuss/show how these resulted in this F1 (may be annotated Punnett) – 1 pt Explain that it is a sex-linked (X-linked) gene (not just the word) – 1 pt How you know which type is dominant – 1 pt F2 results (may be annotated Punnett square) B) Maximum 4 pts 1 pt Correct F2 hypothesis (1:1:1:1 or 25/genotype) 1 pt Show work (components): o e o-e (o-e)2 (o-e)2/e (or correct numbers (4/25 of 36/25 + 1/25 + 9/25 = 50/25 = 2; or at least the last term) 1 pt Sum; correct chi-square result ~ 2.0 or 1.85 1 pt degrees of freedom = 3 (critical value is 7.82) 1 pt correct interpretation of chi-square in terms of p p = probability that the difference between the observed and the expected value is due to chance alone. This p value shows we accept our hypothesis. The null hypothesis is supported in this case. (alternative: 2 X2 tests of white vs. red males and white vs. red females. C) Maximum 4 pts 1 pt Explain what a mutation is: (heritable) change in the DNA (code) 1-2 pts Discuss 2 types of mutations May be: point mutation, frameshift (deletion/duplication), insertion, transposition, break, inversion within gene, base substitution, nonsense/stop, missense) May NOT be: chromosomal aberration, nondisjunction, silent/neutral, transcription or translation or processing error 1 pt Molecular or biochemical elaboration beyond the explanation required Essay Prompt #9 • Describe the chemical nature of genes. (a) Discuss the replication process of DNA naming all of the steps and key enzymes involved. (b) Name TWO types of gene mutations that occur during replication. Essay Prompt #9-Rubric (Key) A gene is a hereditary unit located at a specific locus along a chromosome. Genes are made up of DNA, and DNA is made up of repeating subunits of nucleotides. A nucleotide consists of three parts: a 5-carbon sugar (ribose), a phosphate group, and a nitrogenous base. When a chromosome replicates, the two DNA strands unwind and the hydrogen bonds between them are broken (Helicase). Single stranded binding protein will stabilize and hold open the strands. Topoisomerase will then cut each side of the replication fork alleviating strain that reults from excessive coiling. Each strand serves as a template for the synthesis of a complementary strand. Once the process initiated (by RNA primase), DNA polymerase III adds the nucleotides to each growing strand. One strand serves as the leading strand (made continuously) and the other strand serves as the lagging strand (made discontinuously). Each base matches the appropriate bases in the template strand: they are complementary. DNA Polymerase I then will replace the RNA nucleotides (Uracil-to-Thymine) that were laid down with DNA nucleotides. Essay Prompt #9-Rubric (Key) Cont’d Once the complementary strands are formed, hydrogen bonds form between the new base pairs, leaving two identical copies of the original DNA molecules. The process was determined by Meselson & Stahl to be semiconservative. A gene mutation is a change in the sequence of base pairs in a DNA. It results from defects in the sequence of bases. Mutations that involve a single base change in the DNA sequence are called point mutations. Point mutations fall into two general categories: base substitutions and insertions/ deletions. A base substitution involves a single DNA nucleotide replaced by another nucleotide. An insertion or deletion occurs when a base pair is added or removed from the DNA sequence. Any insertion or deletion results in a frame shift when the mRNA is translating resulting in a completely new unique protein formed. The beginnings of possible adaptations and maybe an advantage evolutionarily. Essay Prompt #10 Describe the process of how genes are expressed (transcription & translation) in a eukaryotic cell. Be sure to include a discussion of how point mutations affect proper protein synthesis at the level of translation. You must mention all the key structures, molecules, and enzymes involved (ex. mRNA, tRNA, snRNA, RNA polymerase, aminoacyl-tRNA synthetase, ribosome & sites, TATA box, etc) NOTE: Labeled drawings & diagrams may be useful in your response but you must draw them don’t cut & paste images in.
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