Essay prompt Week #1 • Discuss the web of life in a biological community. Your essay should focus on energy flow, conversion, and loss in food chains, including the concepts of trophic levels and pyramids. Grading Rubric for Essay Prompt #1 • Structural hierarchy • Define community • Producer’s-consumers; provide examples • 10% loss at every level; explain why • Energy is lost in a system • Explain plant photosynthesis • Need to eat at the carnivore level and cellular respiration • Explain detritovore • Define food chain and food web; provide sample diagrams • Discuss/diagram energy pyramid, biomass pyramid; biomagnification pyramid • Bonus: discuss exceptions inverted pyramid Essay #2 AP BIO QUESTION 1996 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. Key for Essay #2 -Prop. of water Note: you will need to print this slide out to see the words better. ESSAY #3 AP BIO QUESTION 1991: 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. Grading Rubric for Essay #3 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 #4 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 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. Grading Rubric for Essay #4 ESSAY #4-Grading Rubric ESSAY #5 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 #5 • 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 the enzyme 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 ESSAY # 6 • CELL RESPIRATION ESSAY 1993: Membranes are important structural features of cells. • (a) Describe how membrane structure is related to the transport of materials across a membrane. • (b) Describe the role of membranes in the synthesis of ATP in either respiration or photosynthesis. Answer key to essay #6 • PART A. (6 Maximum) Membrane Structure • __ Phospholipid structure - hydrophilic, hydrophobic, amphipathic • __ Phospholipid bilayer / fluid mosaic description • __ Proteins embedded in the membrane • __ Sterols embedded in the membrane • __ Well-labeled diagram may replace one of the above Membrane Transport (3 Internal Maximum) • __ Use of the term "selectively permeable" or a good definition of selective permeability or an explanation of the role of phospholipids or proteins including nuclear pore proteins in determining selective permeability • __ Description of the effect of size, charge, polarity, lipid solubility on membrane permeability Mechanisms + description related to structure: membrane gradient • __ Ion channel: transport as a mechanism for a change in permeability • __ Facilitated diffusion: description (symport, antiport, uniport) • __ Active transport: description • __ Exocytosis, endocytosis, phagocytosis, pinocytosis: description (1 pt additional) A good example of one of the above mechanisms • PART B. Role of the Membrane in the Production of ATP in Photosynthesis or Respiration • (6 Maximum) Chemiosmosis: __ Involved molecules are embedded in the membrane __ Electron carriers are sequentially organized __ The energy comes from the flow of electrons __ H+ / Proton / pH gradient established __ Movement through the membrane generates ATP __ A specific protein makes ATP • RESPIRATION • __ Site is the mitochondrion • __ Inner mitochondrial membrane • __ Folded membrane present Cell membrane is involved in prokaryotes • __ Correct direction of H+ flow • PHOTOSYNTHESIS • __ Site is the chloroplast • __ Thylakoid / grana membranes (cristae) are involved in eukaryotes are involved in eukaryotes • __ Folded membrane present __ • __ Thylakoid / grana membranes prokaryotes involved • __ Correct direction of H+ flow ESSAY #7 • AP Bio question 1995: Energy transfer occurs in all cellular activities. For 3 of the following 5 processes involving energy transfer, explain how each functions in the cell and give an example. Explain how ATP is involved in each example you choose. 1. Cellular movement 2. Active transport 3. Synthesis of molecules 4. Chemiosmosis 5. Fermentation KEY TO ESSAY #7 • 1 pt function of process • 1 pt example • 1 pt additional for detail • 1 pt ATP involvement 4 pts = MAX/process • ATP <====> ADP + Pi + Energy 1 pt CELLULAR MOVEMENT • Function: Locomotion, Mitosis, Cytoplasmic Streaming, Muscle Contraction (sliding filaments) • Examples: Cilia, Flagella, Pseudopodia, Exocytosis, Endocytosis, Microfilaments, Spindle Fibers • Details: 9 + 2 Microtubules, Dynein, Actin- Myosin (Myosin heads), Kinesins • ATP Involvement: ATP used Motor molecules powered by ATP hydrolysis (Conformational ACTIVE TRANSPORT • Function: Concentration gradient low to high / Protein carrier w/use of ATP • Examples: Sodium/Potassium Pump, Other Transports Specified • Details: Protein carrier related to example • ATP Involvement: ATP used Conformational SYNTHESIS OF MOLECULES • Function: Small to Large / Monomer to Polymer • Examples: Intermediates to Monosaccharides to Polysaccharides Intermediates to Fatty Acids (Glycerol) to Lipids Intermediates to Amino Acids to Proteins Intermediates to Nucleotides to Nucleic Acids Intermediates to Vitamins • Details: Charging tRNA Reactions CHEMIOSMOSIS • Function: Form electrochemical proton (H+) gradient • Examples: Mitochondria, Chloroplasts, Bacterial Cell Membrane • Details: Cristae, Thylakoids, Direction/ H+ vs e- • ATP Involvement: ATP formed Proton FERMENTATION Start with glucose • Function: breakdown of organic compounds • Examples: Ethanol / Lactic Acid • Details Anaerobic, Less energy produced Cytosolic process, Yeast, Muscle • ATP Involvement: ATP used and formed Substrate-level Start with pyruvate • Function: recycling NADH • Examples: Ethanol / Lactic Acid • Details: Anaerobic, Regenerate oxidized OVERALL COMMENTARY ON QUESTION: • This question was a cell biology energetics question that required both breadth and depth of knowledge to answer the question successfully. Full credit could only be obtained by responding to three of the process examples listed in the question. Also, if more than three processes were discussed, readers were directed to grade the first three unless specifi indications directed one to be omitted. Each process had a four point maximum score. One point was available for description of the function of the process, which might also be a definition or description of a mechanism. One point came from an example in context with the process. One point was ESSAY #8 CELL QUESTION 1987: Discuss the process of cell division in animals. Include a description of mitosis and cytokinesis, and of the other phases of the cell cyle. Do not include meiosis. ANSWER KEY For Essay #8 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 the maximum is 9. • 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 #9 GENETICS QUESTION: 1996 An organism is heterozygous at two genetic loci on different chromosomes. a) Explain how these alleles are transmitted by the process of mitosis to daughter cells. b) Explain how these alleles are distributed by the process of meiosis to gametes. c) Explain how the behavior of these two pairs of homologous chromosomes during meiosis provides the physical basis for Mendel's two laws of inheritance. Labeled diagrams that are explained in your answer may be useful.