BIO 203 Reading Quizzes Charles Exam 2
If the products of a reaction have more free energy than the reactants, then that reaction is
not energetically favorable.
Condensation reactions are energetically ___________ and hydrolysis reactions are energetically ___________.
unfavorable; favorable
The first step of glycolysis uses one ATP molecule in order to
phosphorylate glucose
Cellular respiration ___________ energy and produces ___________, whereas photosynthesis ___________ energy and produces ___________.
produces; water + carbon dioxide; consumes; oxygen + sugars
Which of the following correctly matches the cellular location with the production of ATP by oxidative phosphorylation in that cell type?
plasma membrane—bacteria
Refer to the diagram below. If cells that cannot carry out fermentation were grown in anaerobic conditions, at which step would glycolysis halt?
step 6: where NAD+ is converted to NADH
In addition to being converted to acetyl CoA for the citric acid cycle, pyruvate made during glycolysis can be used for
synthesis of alanine and fermentation.
Stage two of photosynthesis (or the light-independent reactions) uses which input molecules to produce organic food molecules?
ATP, NADPH, CO2
The major products of the citric acid cycle are
CO2 and NADH
Each molecule of acetyl-CoA entering the citric acid cycle produces two ___________ and four ___________.
CO2; activated carriers
The citric acid cycle produces which activated carriers that transfer high-energy electrons to the electron-transport chain?
NADH and FADH2
If cells were undergoing glycolysis but could not carry out fermentation, what products would build up in the cytosol?
NADH and pyruvate
What purpose does NADPH serve in biosynthetic reactions like the one pictured below?
donating electrons for a reduction reaction
What is the role of oxygen in the electron transport chain?
electron acceptor
Which of the following has the lowest electron affinity?
NADH dehydrogenase complex
The first living things on Earth probably generated ATP by what mechanism?
fermentation
The food molecule whose breakdown generates most of the energy for a majority of animal cells is
glucose
Glycogen synthetase enzyme, which forms glycogen from glucose, is activated by excess
glucose 6-phosphate
The energies of phosphate bonds for different molecules in glycolysis are shown. Based on this graphic, the transfer of a phosphate from which of the molecules to ADP (to form ATP) is energetically UNFAVORABLE?
glucose 6-phosphate
Individuals with inherited diseases causing mitochondrial dysfunction typically experience which of the following symptoms?
heart problems
Living systems can generate and maintain order without violating the second law of thermodynamics because they generate
heat
Protons are pumped across the mitochondrial inner membrane to accumulate in the
intermembrane space
What is the fermentation product produced in an anaerobic muscle cell?
lactic acid
The cytochrome complexes contain heme prosthetic groups, which have a higher redox potential than the iron-sulfur centers found in other electron-transport chain complexes like NADH dehydrogenase. Where in the electron-transport chain would the cytochrome complexes thus be located relative to iron-sulfur center complexes?
later in the chain
Enzymes increase the speed of a chemical reaction because they
lower the activation energy needed to start the reaction.
The proton flow through the transmembrane H+ carrier of ATP synthase results in
mechanical rotation that is converted into the chemical-bond energy of ATP.
How is pyruvate imported into the mitochondrial matrix for use in the citric acid cycle?
proton gradient-driven symport
In an enzymatic reaction, a molecule gains an electron. This is known as a(n) ___________ reaction.
reduction
Chlorophyll appears green because it
reflects green light
Gluconeogenesis requires a total of ___________ ATP and GTP molecules combined.
six
What is the relationship between ΔG and ΔG0?
ΔG0 is the free-energy change at standard temperature and concentrations.
Glycolysis alone captures approximately what percentage of the free energy available in a molecule of glucose?
10%
Shown is the structure of a mitochondrion with different compartments labeled. Which of the numbers represents the most permeable membrane of the mitochondrion?
3
In the following condensation reaction, how does ATP power the formation of product A-B?
A phosphate is first transferred to reactant A−OH to form a high energy intermediate.
The pH of the mitochondrial matrix is ___________, which is ___________ than that of the intermembrane space.
7.9; higher
In the presence of high levels of ___________, the enzyme phosphofructokinase is inhibited.
ATP
Why do cells use enzymes to harvest energy from food molecules rather than by direct oxidation?
Enzymes transfer energy from food to carrier molecules in small steps.
Which of the following has a higher concentration in the cell to allow it to be available to accept electrons from oxidation of food molecules?
NAD+
Cytochrome c oxidase catalyzes the reaction that reduces molecular oxygen (two oxygen atoms) to two water molecules. The electrons are added sequentially, and during the process cytochrome c oxidase must bind the oxygen tightly in the active site. Why?
Superoxide radicals are formed as an intermediate, and are dangerous to the cell.
Why is the oxidation of NADPH energetically favorable?
The oxidized form of NADPH is more stable than the reduced form.
Shown below is the mechanism believed to be used for pumping protons by cytochrome c oxidase across the inner mitochondrial membrane. One of the steps shown is unidirectional because it is driven by the energy of electron transport. Why must this step be performed only in one direction?
The protons could be also captured from the intermembrane space and released back into the matrix.
Which of the following is a reason why ATP hydrolysis has a negative ΔG0?
The removal of the phosphate is energetically favorable.
How do the high-energy electrons of activated carriers contribute to forming the high-energy phosphate bonds of ATP?
They are used by the electron-transport chain to make a proton gradient.
What is the role of activated carriers in cells?
They capture energy from energy releasing reactions and transfer it to other reactions.
Fatty acids can be used to produce energy by conversion to ___________ in the ___________ of the cell.
acetyl CoA; mitochondria
If a reaction is energetically favorable (exergonic), then it must produce a(n)
decrease in reaction time.
Reactions that build larger molecules in the cell are called ___________; reactions that break down molecules into smaller ones are called ___________.
anabolic; catabolic
Why is CO2 an end product of cellular respiration?
because it is the most stable form of carbon in our atmosphere
Why is sunlight the ultimate source of energy for nearly all living things on Earth?
because photosynthetic organisms produce food molecules using light energy
Why is the presence of oxygen required for the citric acid cycle to operate?
because the NADH passes its electrons to oxygen in the electron transport chain to renew NAD+
In oxidative phosphorylation in mitochondria, high-energy electrons are transferred to the electron-transport chain from activated carriers like NADH. Stage 1 of photosynthesis also uses an electron-transport chain to pump protons and make ATP. In this case, where do the high-energy electrons come from?
chlorophyll
What is gluconeogenesis?
the synthesis of glucose from pyruvate
Shown is a chloroplast with labeled structures. The photosynthetic machinery is found in which of the compartments shown?
thylakoid membrane
What is the function of a kinase?
to add a phosphate group to a molecule
During glycolysis, the number of ATP consumed (per glucose molecule) is ___________, while the number produced is ___________.
two; four
Glycolysis produces ___________ ATP molecules, whereas the complete oxidation of glucose to water and carbon dioxide produces ___________ ATP molecules.
two; thirty
Which of the following is a mobile electron carrier in the electron-transport chain?
ubiquinone
What is the value of ΔG at equilibrium?
zero
The number of ATP molecules that could be synthesized from the energy released by the transfer of two electrons from NADH to molecular oxygen is ___.
2.5
The low redox potential of NADH means that it has a
tendency to give up electrons
