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1977 1982 1989 1990
CELLULAR RESPIRATION QUESTION 1977: L. PETERSON/ECHS 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. 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 ATS ___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)
CELLULAR RESPIRATION QUESTION 1982: L. PETERSON/ECHS Describe the similarities and differences between the biochemical pathways of aerobic respiration and photosynthesis in eukaryotic cells. Include in your discussion the major reactions, the end products, and energy transfers. STANDARDS: 7 points Maximum for Photosynthesis section 7 points Maximum for Respiration section PHOTOSYNTHESIS: ___Conversion of light energy to chemical energy ___Fixation of CO2 ___Occurs in chloroplasts ___Split H2O (photolysis) ___Chlorophyll needed ___ATP in light reaction ___NADPH2 produced ___Anabolic (Constructive) ___Oxygen released LIGHT REACTION (Diagram and/or Discuss) ___Photosystem I & II ___Energy "input" (electron flow) ___Chemiosmotic DARK REACTION (CO2 FIXATION) ___Carboxylative phase ___Reductive phase ___Regenerative phase NET REACTION ___ENERGY + CO2 + H20 -> C6H12O6 = O2 ___"Uphill" Reaction - possess more free energy and/or stores 686,000 cal/mole glucose ___Coupling of light and dark reactions RESPIRATION ___Conversion of chemical energy to metabolic ___Release of CO2 ___Occurs in mitochondria ___Form H2O (reduction) ___Cytochromes needed ___ATP in oxidative phosphorylation ___NADH produced ___Catabolic (destructive) OXIDATIVE PHOSPHORYLATION (Diagram and/or Discuss) ___ETS (NAD, FAD, cytochromes) ___Energy "release" (electron flow) ___Chemiosmotic ___Glycolysis ___Krebs Cycle NET REACTION ___O2 + C6H12O6 -> CO2 + H2O + ENERGY ___"Downhill"Reaction - possess less free energy and/or releases 686,000 cal/mole glucose BONUS POINTS 3 points MAX ___Dark reaction is reverse of anaerobic glycolysis ___Both processes are complementary and/or supply materials for each other ___Thorough contrast of photosynthesis and cellular respiration
CELLULAR RESPIRATION QUESTION 1989: L. PETERSON/ECHS Explain what occurs during the Krebs (citric acid) cycle and electron transport by describing the following: a. The location of the Krebs cycle and electron transport chain in the mitochondria b. The cyclic nature of the reactions in the Krebs cycle c. The production of ATP and reduced coenzymes during the cycle d. The chemiosmotic production of ATP during electron tranpsort STANDARDS: 3 points Maximum for each of the four sections 1 point for any of the following: LOCATION ___Description of internal structure (compartmentalization) of mitochondrion ___Krebs in matrix (inner or M compartment) ___Krebs' enzymes mostly dissolved in matrix ___ETS in cristae (inner membrane) ___ETS components are embedded in the inner membrane 5 pts MAX 3 CYCLIC NATURE OF KREBS ___Acetyl CoA (C2) starts Krebs ___C2 joins with OAA (C4) to form citric acid (C6) ___2 CO2 removed during Krebs ___OAA is recycled or overall cycle concept (diagram OK) ___Position of Krebs in Aerobic Respiration (2 cycles/glucose, uses products of glycolysis) 5 pts MAX 3 PRODUCTION OF ATP AND REDUCED COENZYMES ___ 1 ATP/cycle ___NADH and/or FADH2 formed (or NADH2, NADH + H+, NAD red) ___Amount of NADH (3) and/or FADH2 (1) per cycle ___ATP formed from released energy; substrate level phosphorylation ___ATP specific reaction: Succinyl CoA -> Succinic Acid; GTP --> GDP ADT -> ATP ___NADH or FADH2 formed by H or e- 6 pts MAX 3 CHEMIOSMOTIC PRODUCTION OF ATP ___Electron transfer (redox) through carriers; O2 final acceptor ___Gradient drives ATP formation or battery (electrochemical, charge separation, etc.) ___Protons pumped to inter-membrane space; proton carriers alternate w/electron carriers; charge separation; gradient established; lowers pH in inter-membrane space; + between membranes; - matrix ___Inner membrane impermeable to H+ except for and/or proton channel (ATP synthetase; ATPase) is permeable ___ATP synthetase structure F0 + F1 ___Specifics of # of ATPs formed (ETS = 32 ATP; 2 ATP/FADH2; 3ATP/NADH) 6 pts MAX 3
CELL RESPIRATION QUESTION 1990: L.PETERSON/ECHS The results below aer measurements of cumulative oxygen consumption by germinating and dry seeds. Gas volume measurements were corrected for changes in temperature and pressure. Cumulative Oxygen Consumption (mL) Time (minutes) 0 10 20 30 40 220 C Germinating Seeds 0.0 8.8 16.0 23.7 32.0 Dry Seeds 0.0 0.2 0.1 0.0 0.1 100 C Germinating Seeds 0.0 0.0 0.2 0.1 0.2 Dry Seeds 0.0 0.0 0.2 0.1 0.2 a. Using the graph paper provided, plot the results for the germinating seeds at 220 C amd at 100 C. b. Calculate the rate of oxygen consumption for the germinating seeds at 220 C, using the time interval between 10 and 20 minutes. c. Account for the differences in oxygen consumption observed between: (1) germinating seeds at 220 C and at 100 C.; (2) germinating seeds and dry seeds. d. Describe the essential features of an experimental apparatus that could be used to measure oxygen consumption by a small organism. Explain why each of these features is necessary. STANDARDS: Parts a, b, and c together = 8 pts MAX one point for each of the following: a. GRAPH(S) ___Correct orientation of x (independent) and Y (dependent) axes ___Scale and label axes ___Curves plotted (both lines drawn and identified as 100/220). Histograms accepted if correctly drawn. ___Title of graph b. RATE CALCULATION ___Setup (16 - 8.8)/(20 -10) or number 7.2 or 0.72 ___Rate Concept - units (volume/time) 7.2 mL/10 min. or 0.72 mL/min. c. EXPLANATIONS 1. TEMPERATURE VARIATION ___Seeds show no temperature regulation (at environmental temperature); do not increase O2 consumption to maintain preset temperature ___Temperature increase causes increased activity (or increased respiration or metabolism) ___Extended explanation of respiratory enzyme reaction rate, rate increases (to limit) with increased temperature (enzymes generally have Q10 about 2.) ___220 vs. 100 rates reversed in cold hardiness (genetically determined) seeds 2. GERMINATING SEEDS VS. DRY SEEDS ___Dry seeds dormant and/or germinating seeds metabolically active ___Extended explanation of dormancy and/or metabolism ___Explanation of water based chemistry of respiratory enzyme reactions d. EXPERIMENTAL APPARATUS 3 pts MAX ___ Method to separate O2 consumption vs. CO2 release Something (KOH, etc.) to remove CO2 (gas -> solid) ___Closed System ___Method to measure pressure/volume change = graduated tube/pipet, containing bubble/water/Brodie ___Method to control temperature = water bath ___Method to control volume = glass beads or some other inert material vs. seeds ___Timing device ___Equal numbers of organisms in experimental and control Other techniques/methods for measuring O2 consumption one point for any of the following: Winkler titration to determine O2 concentration before and after Polarographic, oxygen electrode, Clark-type electrode EPR measurement of O2 concentration changes, in gas flow-thru system one point for a detailed explanation for any one of the above techniques None of these require special techniques to distinguish volume of CO2 from volume of O2; all are specific for O2. None of these depend on pressure changes. Other features of procedure (constant temperature, appropriate controls, etc.) remain the same.