10 19 10 BSC2010 Dr Dennis 8 00 am Test Corrections 2 Reactants capable of interacting to form product in a chemical reaction must first overcome a thermodynamic barrier known as the reaction s A Activation Energy Activation energy is the amount of energy that reactants must absorb before a chemical reaction will start 3 The mechanism in which the end product of a metabolic pathway inhibits an earlier step in the pathway is known as B Feedback inhibition A metabolic pathway is switched off by the feedback inhibitory binding of its end product to an enzyme that acts early in the pathway 4 How does a noncompetitive inhibitor decrease the rate of an enzyme reaction A By changing the shape of a reactant A noncompetitive inhibitor decreases the rate of an enzyme reaction by changing the shape of a reactant by binding to another part of the enzyme This cases the enzyme to change its shape in such a way that the active site becomes less effective at catalyzing the conversion of substrate to product 6 Starting with one molecule of isocitrate and ending with fumarate what is the maximum number of ATP molecules that could be made through substrate level phosphorylation B 1 From Isocitrate to Ketoglutarate isocitrate is oxidized reducing NAD to NADH and loses a CO2 From Ketoglutarate to Succinyl CoA another CO2 is lost and the resulting compound is oxidized reducing NAD to NADH and the remaining molecule is attached to coenzyme A by one unstable bond 8 How many reduced dinucleotides would be produced with four turns of the citric acid cycle E 4 FADH2 AND 12 NADH Each rotation of the citric acid cycle produces 1 FADHe and 3 NADH If there are 4 rotation then 4 FADH2 s are produced and 12 NADH s 9 Which of the following bests describes the reaction A Negative G spontaneous Thermodynamically this is an exergonic reaction with a negative G and the reaction occurs spontaneously 10 Which of the following represents the G of the reaction D D D is where G is unaffected by the enzyme 11 Which of the following represents the activation energy required for the enzyme catalyzed reaction B B B is where the EA with enzyme is lower 17 Substance A functions as E An allosteric inhibitor An enzyme that can be in two states active and inactive in the first instance the process is relatively normal where the inhibitor binds to its binding Site and carries out its reaction In the second instance the enzyme is unable to attach itself to the binding Site This is due to a modulator molecule which alters the shape of the binding Site making it inactive 19 Cell membranes are asymmetrical Which of the following is a most likely explanation E Cell membrane proteins are determined as the membrane is being packaged in the ER and Golgi they Asymmetrical cell membrane means that the distribution of structures such as protein carbohydrate and lipid complexes charged units in the 2 layers is not uniform This is decided when the cell membrane is being packaged in the ER and the Golgi 25 CAM plants keep stomata closed in daytime thus reducing loss of water They can do this because C Fix CO2 into organic acids during the night CAM plants keep stomata closed in the daytime reducing the loss of water by storing the organic acids they fix from CO2 in their vacuoles during the night till the morning 27 The ATP made during glycolysis is generated by D Chemiosmosis Chemiosmosis is the process in which energy stored in the form of Hydrogen ion gradient across a membrane is used to drive cellular work such as synthesis of ATP 29 Where does glycolysis take place A Cytosol Glycolysis takes place in the cytosol and begins the degradation process by breaking glucose into two molecules of a compound called pyruvate 30 During aerobic respiration electrons travel downhill in which sequence B Food NADH electron transport chain oxygen To be more specific the electron travel downhill in the sequence of Glucose NADH electron transport chain oxygen 31 Which of these are not embedded in the lipid bilayer at all D Peripheral Proteins Peripheral proteins are not embedded in the lipid bilayer at all they are appendages loosely bound to the surface of the membrane 32 Where are the proteins of the electron transport chain located A Mitochondrial inner membrane The proteins of the electron transport chain are located in the mitochondrial inner membrane the plasma membrane in prokaryotes The folding of the inner membrane to form cristae increases its surface area providing space for thousands of copies of the chain in each mitochondria 33 The primary role of oxygen in cellular respiration is to D Act as an acceptor for electrons and hydrogen forming water The one step exergonic reaction of hydrogen with oxygen to form water releases a large amount of energy in the form of heat and light an explosion 34 Why is ATP an important molecule in metabolism B It provides energy coupling between exergonic and endergonic reactions ATP releases free energy when its phosphate bonds are hydrolyzed 35 The molecule that functions as the reducing agent electron donor in a redox or oxidation reduction reaction E Loses electrons and loses energy In many chemical reactions there is a transfer of one or more electrons from one reactant to another redox reactions The loss of and electron from one substance is oxidation The addition of electron to another substance is a reduction 36 A molecule that is phosphorylated A has an increased chemical reactivity it is primed to do cellular work The definition of phosphorylated is a molecule that is covalently bonded to a phosphate group 38 When ATP releases some energy it also releases inorganic phosphate What purpose does this serve if any in the cell D It can be added to other molecules in order to activate them ATP s release of inorganic phosphate serves the purpose of activating other molecules along with being reusable to form ATP again from ADP and Pi 39 When a molecule of NAD nicotinamide adenine dinucleotide gains a hydrogen atom not a hydrogen ion the molecule becomes D Reduced The addition of an electron to another substance is known as reduction 40 Whenever energy is transformed there is always an increase in the B Entropy of the universe Every energy transfer or transformation ivreases the entropy of the universe This is the 2 nd law of thermodynamics 43 The oxygen consumed during cellular respiration is involved directly in which process or event B Accepting electrons at the end of the electron transport chain Oxygen is
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