BIOL1107: Ch. 9 (cellular respiration)
(In the net reaction for glycolysis, glucose (the electron donor) is oxidized to pyruvate. The electrons removed from glucose are transferred to the electron acceptor, NAD+, creating NADH.)
In glycolysis, as in all the stages of cellular respiration, the transfer of electrons from electron donors to electron acceptors plays a critical role in the overall conversion of the energy in foods to energy in ATP. These reactions involving electron transfers are known as oxidation-reduction, or redox, reactions.
(In substrate-level phosphorylation, an enzyme transfers a phosphate group from one molecule (an intermediate in the breakdown of glucose to pyruvate) to ADP to form ATP. This is very different from the mechanism of ATP synthesis that takes place in oxidative phosphorylation.)
The ATP that is generated in glycolysis is produced by substrate-level phosphorylation, a very different mechanism than the one used to produce ATP during oxidative phosphorylation. Phosphorylation reactions involve the addition of a phosphate group to another molecule.
NADH and FADH2; intermembrane space (the energy released as electrons, which have been donated by NADH and FADH2, is passed along the electron transport chain and used to pump hydrogen ions into the intermembrane space.)
during electron transport, energy from _____ is used to pump hydrogen ions into the _____.
pyruvate
once the electron donor in glycolysis gives up its electrons, it is oxidized to a compound called ______.
a.) cellular respiration and breathing differ in that cellular respiration is at the cellular level, whereas breathing is at the organismal level.
select the correct statement about cellular respiration. a.) cellular respiration and breathing differ in that cellular respiration is at the cellular level, whereas breathing is at the organismal level. b.) animals carry out cellular respiration whereas plants carry out photosynthesis. c.) plants carry out cellular respiration only in organs such as roots that cannot carry out photosynthesis.
decrease (or goes to zero)
the effect that gramicidin would have on rate of ATP synthesis would cause it to ______.
remain the same
the effect that gramicidin would have on the electron transport rate would cause it to ______.
remain the same
the effect that gramicidin would have on the proton pumping rate would cause it to ______.
remain the same
the effect that gramicidin would have on the rate of oxygen uptake would cause it to ______.
decrease (or goes to zero)
the effect that gramicidin would have on the size of the proton gradient would cause it to ______.
oxygen (oxygen is combined with electrons and hydrogen to form water.)
the final electron acceptor of cellular respiration is _____.
kinetic energy that is released as hydrogen ions diffuse down their concentration gradient (concentration gradients are a form of potential energy.)
the proximate (immediate) source of energy for oxidative phosphorylation is _____.
NADH
the reduced form of the electron acceptor in glycolysis is _____.
true
true or false: a bond must be broken between an organic molecule and phosphate before ATP can form.
true
true or false: an enzyme is required in order for the reaction to occur.
true
true or false: one of the substrates is a molecule derived from the breakdown of glucose.
false
true or false: the enzymes involved in ATP synthesis must be attached to a membrane to produce ATP.
false
true or false: the phosphate group added to ADP to make ATP comes from free inorganic phosphate ions.
acetyl CoA (acetyl CoA is a reactant in the citric acid cycle.)
what enters the citric acid cycle?
2 (two NADH molecules are produced by glycolysis.)
how many NADH are produced by glycolysis?
e.) fewer protons are pumped across the inner mitochondrial membrane when FADH2 is the electron donor than when NADH is the electron donor. (electrons derived from the oxidation of FADH2 enter the electron transport chain at Complex II, farther down the chain than electrons from NADH (which enter at Complex I). this results in fewer H+ ions being pumped across the membrane for FADH2 compared to NADH, as this diagram shows. thus, more ATP can be produced per NADH than FADH2.)
NADH and FADH2 are both electron carriers that donate their electrons to the electron transport chain. the electrons ultimately reduce O2 to water in the final step of electron transport. however, the amount of ATP made by electrons from an NADH molecule is greater than the amount made by electrons from an FADH2 molecule. which statement best explains why more ATP is made per molecule of NADH than per molecule of FADH2? a.) FADH2 is made only in the citric acid cycle while NADH is made in glycolysis, acetyl CoA formation, and the citric acid cycle. b.) there is more NADH than FADH2 made for every glucose that enters cellular respiration. c.) the H+ gradient made from electron transport using NADH is located in a different part of the mitochondrion than the H+ gradient made using FADH2. d.) it takes more energy to make ATP from ADP and Pi using FADH2 than using NADH. e.) fewer protons are pumped across the inner mitochondrial membrane when FADH2 is the electron donor than when NADH is the electron donor.
ATP synthase (ATP synthase phosphorylates ADP.)
Structure A is _____.
NAD+
____ is the compound that functions as the electron acceptor in glycolysis.
it is stored in NADH and FADH2 (the electrons obtained from the oxidation of glucose are temporarily stored in NADH and FADH2. the energy derived from the oxidation of NADH and FADH2 is used to drive the electron transport chain and chemiosmotic synthesis of ATP.)
a glucose molecule is completely broken down to carbon dioxide and water in glycolysis and the citric acid cycle, but together these two processes yield only a few molecules of ATP. what happened to most of the energy that the cell obtains from the oxidation of glucose?
a.) pyruvate, ATP, and NADH (ATP is the main product of cellular respiration that contains energy that can be used by other cellular processes. some ATP is made in glycolysis. In addition, the NADH and pyruvate produced in glycolysis are used in subsequent steps of cellular respiration to make even more ATP.)
among the products of glycolysis, which compounds contain energy that can be used by other biological reactions? a.) pyruvate, ATP, and NADH b.) O2 only c.) ATP and NADH only d.) pyruvate and ATP only e.) ATP only f.) CO2 only g.) NADH only
6 (3 NADH + H+ are produced per each acetyl CoA that enters the citric acid cycle.)
for each glucose that enters glycolysis, _____ NADH + H+ are produced by the citric acid cycle.
2 (each glucose produces two pyruvates, each of which is converted into acetyl CoA.)
for each glucose that enters glycolysis, _____ acetyl CoA enter the citric acid cycle.
both electron transport and ATP synthesis would stop. (oxygen plays an essential role in cellular respiration because it is the final electron acceptor for the entire process. without O2, mitochondria are unable to oxidize the NADH and FADH2 produced in the first three steps of cellular respiration, and thus cannot make any ATP via oxidative phosphorylation. in addition, without O2 the mitochondria cannot oxidize the NADH and FADH2 back to NAD+ and FAD, which are needed as inputs to the first three stages of cellular respiration.)
how would anaerobic conditions (when no O2 is present) affect the rate of electron transport and ATP production during oxidative phosphorylation? (Note that you should not consider the effect on ATP synthesis in glycolysis or the citric acid cycle.)
the advantage of an electron transport chain is that a small amount of energy is released with the transfer of an electron between each pair of intermediates. (as the electrons "fall" down the electron transport chain, the energy released is used to actively transport protons into the inner-membrane space.)
in cellular respiration, a series of molecules forming an electron transport chain alternately accepts and then donates electrons. what is the advantage of such an electron transport chain?
oxidative phosphorylation (this process utilizes energy released by electron transport.)
in cellular respiration, most ATP molecules are produced by _____.
2 (it takes 2 ATP to produce 4 ATP.)
in glycolysis there is a net gain of _____ ATP.
substrate-level phosphorylation (a phosphate group is transferred from glyceraldehyde phosphate to ADP.)
in glycolysis, ATP molecules are produced by _____.
glucose
in glycolysis, the carbon-containing compound that functions as the electron donor is _____.
ATP (some ATP energy is used to start the process of glucose oxidation.)
in glycolysis, what starts the process of glucose oxidation?
to function as the final electron acceptor in the electron transport chain (the only place that O2 participates in cellular respiration is at the end of the electron transport chain, as the final electron acceptor. oxygen's high affinity for electrons ensures its success in this role. its contributions to driving electron transport, forming a proton gradient, and synthesizing ATP are all indirect effects of its role as the terminal electron acceptor.)
in mitochondrial electron transport, what is the direct role of O2?
substrate-level phosphorylation (a phosphate group is transferred from GTP to ADP.)
in the citric acid cycle, ATP molecules are produced by _____.
oxygen (oxygen is the final electron acceptor of cellular respiration.)
what molecule is indicated by the letter D?
glucose and oxygen (photosynthesis produces glucose and releases oxygen into the atmosphere.)
what molecules belong in space A and B?
carbon dioxide and water (carbon dioxide and water are by-products of cellular respiration.)
what molecules belong in spaces E and F?
mitochondrion (mitochondria are the sites of cellular respiration.)
what organelle is indicated by the letter C?
glycolysis (glycolysis occurs in the cytosol.)
what process occurs in Box A?
photosynthesis (chloroplasts are the sites of photosynthesis.)
what process occurs in structure H?
the citric acid cycle (the citric acid cycle transfers electrons to NADH and FADH2.)
what process occurs within Box B?
reduced
when a compound accepts (gains) electrons, that compound becomes ____. such a compound is often referred to as an electron acceptor.
oxidized
when a compound donates (loses) electrons, that compound becomes _____. such a compound is often referred to as an electron donor.
(gramicidin causes membranes to become very leaky to protons, so that a proton gradient cannot be maintained and ATP synthesis stops. however, the leakiness of the membrane has no effect on the ability of electron transport to pump protons. thus, the rates of proton pumping, electron transport, and oxygen uptake remain unchanged.)
when the protein gramicidin is integrated into a membrane, an H+ channel forms and the membrane becomes very permeable to protons (H+ ions). if gramicidin is added to an actively respiring muscle cell, how would it affect the rates of electron transport, proton pumping, and ATP synthesis in oxidative phosphorylation? (assume that gramicidin does not affect the production of NADH and FADH2 during the early stages of cellular respiration.)
d.) it represents the first stage in the chemical oxidation of glucose by a cell. (catabolism of glucose begins with glycolysis.)
which of the following describes the process of glycolysis? a.) glycolysis occurs in the mitochondria. b.) glycolysis produces 30 ATP from each molecule of glucose. c.) it requires ATP and NADH. d.) it represents the first stage in the chemical oxidation of glucose by a cell. e.) it converts one glucose molecule to two molecules of pyruvate and carbon dioxide.
b.) the reaction proceeds with a net release of free energy. (chemical reactions are classified based on their free-energy changes. an exergonic reaction proceeds with a net release of free energy, whereas an endergonic reaction is one that absorbs free energy from its surroundings. if a chemical process is exergonic (downhill), releasing energy in one direction, then the reverse process must be endergonic (uphill), using energy.)
which of the following is true for all exergonic reactions? a.) the products have more total energy than the reactants. b.) the reaction proceeds with a net release of free energy. c.) the reaction goes only in a forward direction: all reactants will be converted to products. d.) a net input of energy from the surroundings is required for the reactions to proceed.
c.) the chemiosmotic synthesis of ATP requires that the electron transport in the inner mitochondrial membrane be coupled to proton transport across the same membrane. (chemiosmosis uses the energy of a proton gradient to make ATP; the proton gradient is formed by coupling the energy produced by electron transport with movement of protons across the membrane.)
which of the following statements about the chemiosmotic synthesis of ATP is correct? a.) the energy for production of ATP from ADP comes directly from a gradient of electrons across the inner mitochondrial membrane. b.) oxygen participates directly in the reaction that makes ATP from ADP and P. c.) the chemiosmotic synthesis of ATP requires that the electron transport in the inner mitochondrial membrane be coupled to proton transport across the same membrane. d.) the chemiosmotic synthesis of ATP occurs only in eukaryotic cells, because it occurs in mitochondria. e.) chemiosmotic ATP synthesis requires oxygen.
d.) FADH2 (FADH2 is a product of the citric acid cycle.)
which of these is NOT a product of glycolysis? a.) ATP b.) pyruvate c.) NADH d.) FADH2
d.) acetyl CoA (acetyl CoA enters the citric acid cycle.)
which of these is NOT a product of the citric acid cycle? a.) ATP b.) NADH + H+ c.) FADH2 d.) acetyl CoA e.) CO2
