hello everybody my name is Iman welcome back to my YouTube channel today we're doing practice problems for chapter 11 which was about bioenergetics and regulation of metabolism let's go ahead and get started problem one says adding heat to a closed biological system will do all of the following except blank all right a says increase the internal energy of the system B says increase the average of the vibrational rotational and translational energies C cause says cause the system to do work to maintain a fixed internal energy and D says increase the enthalpy of a system in a closed biological system enthalpy heat and internal energy are all directly related because there's no change in pressure or volume and because pressure and volume are fixed work cannot be done all right and so adding heat to a closed biological system will increase the internal energy of the system it will increase the average of the vibrational rotational and translation energies and the enthalpy but what it will not do is because the system to do work so one is going to be C two says that 25 degrees Celsius the Delta G for a certain reaction is zero if the concentration of a b and c in the Cell at 25 degrees Celsius are all 10 millimolar how does the Delta G compare to the measurement taken with one millimolar concentration all right so to solve this question we're going to use the equation Delta g equals Delta G not standard plus r t lnq Q is the reaction coefficient quotient it's going to be products over reactants and so in this case Q is going to look like product is B and C and there's two C's so where we add a squared here over reactive which is a all right for this VI now plugging in the variables that were given that Delta G naught is zero R is the universal gas constant T is temperature standard temperature so 25 degrees Celsius and we have all the concentrations here it's 10 millimolar so for b c and a you're just plugging in 10 times 10 to the minus 3. all right what you're going to get here is equal to RT natural log of 10 to the minus 4. all right that essentially is going to give you about right natural log 10 to the minus 4 that's just going to give you r t for RT actually let me erase that it's going to give you four RT all right minus 4rt my bad and there's a minus sign right there awesome now because both R and T are positive right R is your universal gas constant T is temperature we know that Delta G has to be negative what that means is it's lower than the original value a negative Delta g means then that this is going to be a spontaneous process all right so Delta G is going to be less than Delta G naught and the reaction is spontaneous and the answer choice that encompasses this is B so 2 is B he says which of the following statements is true about the hydrolysis of ATP the free energy of ATP hydrolysis is independent of pH one mole of creatine phosphate can phosphorylate two moles of ADP the free energy of hydrolysis of ATP is nearly the same for ADP and D says ATP yields cyclic amp after two hydrolysis reactions we're trying to find which statement is true the hydrolysis of ATP is energetically favorable because there are repulsive negative charges that are relieved when hydrolyzed and the new compounds are stabilized by resonance and this is true of both ATP nadp all right now some of these answer choices are tempting like an a ATP hydrolysis relies on ph because of protonated ATP molecule contains less negative charge so therefore experiences less repulsive forces B says the energy released by one mole of creatine phosphate upon hydrolysis is sufficient to phosphorylate two moles of ADP um creatine phosphate donates one phosphate group to a molecule of ATP so one mole of creatine phosphate will only phosphorylate one mole of ADP answer Choice C the free energy of hydrolysis of ATP is nearly the same as ADP that is true we just said that earlier D is tempting again just like a and b but the removal of two phosphate groups from ATP yields amp not cyclic amp all right so that word you know don't don't forget to read that properly it could get you so the correct answer here the only true statement is that the free energy of hydrolysis of ATP is nearly the same as for ADP so 3 is C 4 says the reduction half reaction in the last step of the electron transport chain is blank reduction is a gain of electrons all right gain of electrons so that kind of automatically eliminates B because that's just oxidation you're losing electrons um nadph here for answer Choice C sorry is just the um product of the pentose phosphate pathway so that has nothing to do with electron transport chain that we're talking about then ubiquitin you Bitcoin in sorry transfers electrons during the course of the electron chain but it's actually not the final electron acceptor that title belongs to oxygen so D is also incorrect A however is correct are we're looking for reduction reduction is gain of electrons and here reactants are forming H2O there's a gain of electrons here and so the correct answer for 4 is a 5 says the ability to exist in both an oxidized and reduced state is characteristic of blank this is a characteristic of electron carriers like we talked about earlier in the review in order to transport electrons electron carriers like the flavo protein must be able to exist in a stabilized oxidized State and a stabilize reduced form so 5 is b six says what energy state was described in the introduction of this chapter all right so what I'm going to do is I have that written down here I'm going to read it to you and then we're going to answer it um here is what's written in the introduction to the chapter you got up this morning with a really ambitious plan study for the MCAT the day started with a big breakfast and then you dove into MCAT biochemistry review a few chapters in you noticed your stomach growling but you were having so much fun that you ignored it a little while later your body realized it wasn't getting any more food for a while but it still needed energy where does it come from that introduction describes the post-absorbative state skipping a single meal is not a prolonged fast however the increase in hormones that promote gluconeogenesis and gluconeogenolysis indicated it indicates that the absorbative phase has ended so this is post-absorptive you've taken in the food it's been a while and your body is hungry but you're not feeding it and so it's in a post absorptive quote-unquote fasting State all right so six is b seven says with prolonged fasting the brain can turn to which alternative fuel for energy the answer here is Ketone bodies this was a very important theme in the last chapter and we mentioned it several times in this chapter so you can tell understanding that your brain uses Ketone bodies as an alternative fuel for energy is a very important piece of information that you should know for the MCAT fantastic eight says how do hormone how do hormonal controls of glycogen metabolism differ from allosteric controls hormonal coordinate controls are coordinated to pretty much regulate the metabolism metabolic activity of the entire organism Alistair controls are are more local or systematic and so your hormonal control um again coordinated to regulate the metabolic activity of your the entire organism allosteric controls can be local or systematic so what you're looking for here is that your hormonal control is it's not local so anything with local gets crossed out all right it is systematic because it takes care of the entire organism and there's a system behind it all right the modification of the enzymes of glycogen metabolism by insulin and glucagon is either going to be through phosphorylation or dephosphorylation both which modify covalent bonds so it's going to be systematic and covalent and that's going to be answer Choice a nine says which of the following tissue is most dependent on insulin all right the answer here is going to be B resting skeletal muscle adipose tissue and rusting skeletal muscle require insulin for glucose uptake all right active skeletal muscle no active skeletal muscle uses creatine phosphate and glycogen to maintain its energy requirements all right so the answer here for 9 is B 10 says glucose corticoids have been implicated in stress-related weight gain because well short-term glucocorticoid exposure causes a release of glucose and the hydrolysis of fats from adipocytes however if this glucose is not used for metabolism it will cause an increase in glucose level which will promote fat storage and then the net result is the release of glucose from the liver to be converted into lipids in the adipose tissue under insulin stimulation considering that all in mind then they've been implicated in stress-related weight gain because they increase glucose levels which causes insulin secretion in short and so that means that the answer to 10 is going to be C 11 says in the absence of oxygen which tissue will experience damage most rapidly that is going to be the brain the brain uses aerobic metabolism of glucose exclusively and therefore it's very sensitive to oxygen levels 12 says a respiratory quotient approaching 0.7 indicates metabolism primarily of which macromolecule okay so this is something we didn't cover in the review but we'll talk about it now respiratory quotient gives an indication of the primary fuel being utilized and RQ around 0.7 indicates lipid metabolism one of 0.8 to 0.9 indicates amino acid metabolism and one indicates carbohydrate metabolism and so we're talking about 0.7 that's going to be lipids and so 12 is B 13 says which of the following side effects would be anticipated in someone taking leptin to promote weight loss well leptin acts to decrease appetite by inhibiting the production of erection erection is associated with alertness so decreasing the level of orexin in the body is expected to cause drowsiness but even without this information the answer can still be obtained right it should be apparent because the body tends to maintain an energy balance so if consumption decreases energy um uses are expected to decrease as well and so one of the following side effects of that is going to be drowsiness so 13 is a 14 says which of the following statements is false growth hormone participates in glucose counter-regulation T4 acts more slowly than T3 ATP stores are turned over more than 10 000 Times Daily catecholamines stimulate the synthetic sympathetic nervous system I'm sorry um which of the following statements is false it's going to be C ATP stores are turned over only about 1 000 times per day not 10 000. so 14 is C last but not least which process is expected to begin earliest and prolonged fast a prolonged fast is characterized by an increase in glucagon which accomplishes its cellular activity by phosphorylating and the phosphorylating metabolic enzymes all right and that's going to be answer Choice D alright now B says glycogen storage is halted um that's after and this requires enzyme regulation by glucagon to occur then later in that post-absorptive state you could have protein breakdown and then finally that's answer Choice C eventually then with starvation Ketone bodies will be formed so if you're going to number this and what happens first second third fourth it's one two three four all right but the answer to 15 is D all right that's it I hope this was helpful let me know if you have any questions comments concerns down below other than that good luck happy studying and have a beautiful beautiful day future doctors