All GRE Subject Test: Biochemistry, Cell, and Molecular Biology Resources
Example Questions
Example Question #1 : Biochemistry
What is the purpose of coenzyme Q10 during the electron transport chain?
Regulate the function of ATP synthase
Bring oxygen to the end of the electron transport chain to accept electrons
Carry protons from the mitochondrial matrix into the intermembrane space
Move electrons from complex I or II to complex III
Move electrons from complex I or II to complex III
Coenzyme Q10 is a fat-soluble molecule that facilitates the transfer of electrons from complex I or II to complex III in the electron transport chain. The mobility of coenzyme Q10 in the membrane allows for this unique function. Each complex in the membrane is then able to use the donated electron to push protons into the intermembrane space, generating the gradient that will eventually be used to synthesize ATP.
Coenzyme Q10 does not directly facilitate the movement of protons. Rather, it aids in the transfer of electrons to initiate the process that allows for proton movement. Coenzyme Q10 is also not involved with the regulation of ATP synthase or with bringing oxygen to the electron transport chain.
Example Question #1 : Help With The Electron Transport Chain
At which complex in the electron transport chain is NADH oxidized?
Complex IV
Complex I
Complex III
Complex II
Complex I
NADH is the first electron carrier to be oxidized by the electron transport chain, a process that occurs at complex I. FADH2 is oxidized further down the chain in complex II, causing it to produce less ATP on average than NADH.
Example Question #1 : Help With The Electron Transport Chain
Which of the following molecules will be most abundant surrounding the electron transport chain?
Sphingolipids
Cytosol
Phospholipids
Glucose
Phospholipids
Electron transport chain (ETC) consists of a series of electron carriers on the inner membrane of the mitochondria. The electrons are transferred down these carriers and this movement is used to generate ATP. The question asks for the molecule most abundant surrounding these electron carriers. Since they are found on the inner membrane, the electron carriers in ETC are surrounded by phospholipids (most abundant molecule in a membrane).
Example Question #1 : Help With The Electron Transport Chain
Which of the following is true regarding the final electron acceptor in the electron transport chain?
It contributes to the production of energy
It picks up electron and protons
It only picks up electrons
It is a byproduct of anaerobic respiration
It picks up electron and protons
The final electron acceptor in electron transport chain is oxygen. The electrons traverse along the electron transport chain and ultimately end up being taken up by an oxygen atom. Upon accepting electrons, the oxygen atom becomes negatively charged and attracts protons (hydrogen atoms). An oxygen atom binds to two hydrogen atoms and forms water.
Energy production in ETC is facilitated by the generation of the proton gradient by the proton pump. This gradient is utilized by ATP synthase to produce ATP. Oxygen does not play a role in this process. Anaerobic respiration is a type of respiration that occurs in the absence of oxygen. Examples of anaerobic respiration include glycolysis and fermentation.
Example Question #91 : Biochemistry
Anaerobic respiration occurs in the __________ and aerobic respiration occurs in the __________.
mitochondria . . . cytosol
cytosol . . . mitochondria
cytosol . . . cytosol
mitochondria . . . mitochondria
cytosol . . . mitochondria
Cellular respiration has three main processes: glycolysis, Krebs cycle, and electron transport chain. Glycolysis is an anaerobic process whereas Krebs cycle and ETC are aerobic processes. A molecule of glucose enters the cell and undergoes glycolysis in the cytosol. Some of the products of glycolysis are transported to mitochondria where they undergo Krebs cycle and then, eventually, the electron transport chain; therefore, anaerobic respiration occurs in the cytosol and aerobic respiration occurs in the mitochondria.
Anaerobic respiration produces very little ATP and the ATP produced is not sufficient to power all of the active processes in a cell. Aerobic respiration, particularly ETC, produces a lot of ATP. This is why mitochondria is called the “powerhouse” of the cell. Note that the products of glycolysis can undergo another type of anaerobic respiration called fermentation. This also produces very little ATP.
Example Question #1 : Help With The Electron Transport Chain
Which of the following is true regarding electron transport chain (ETC)?
I. Proton pump generates ATP
II. Electron affinity of and
is lower than the carriers in ETC
III. Electrochemical gradient of sodium facilitates production of ATP
II and III
I only
I and II
II only
II only
Electron transport chain is a series of electron carriers located on the inner membrane of the mitochondria. Electrons traverse across these electron carriers and this motion allows for the proton pump to generate a proton gradient across the inner membrane. This gradient is generated by pumping protons from the inside of the mitochondria to the periplasmic space (space between inner and outer mitochondrial membranes). The excess protons in the periplasmic space are transported back into the mitochondria and this movement facilitates the generation of ATP by the ATP synthase. Note that ATP is generated by ATP synthase, not the proton pump.
and
are electron carriers that carry electrons from glycolysis and Krebs cycle. These carriers enter the ETC and donate their electrons to the carriers in ETC. This occurs because ETC carriers have higher affinity for electrons. Remember that each subsequent carrier in ETC has a higher affinity for electrons, so that it is able to snatch the electron from the previous carrier. As mentioned, the ATP generation is facilitated by the proton gradient, not the sodium gradient.
Example Question #1 : Help With The Electron Transport Chain
What directly drives ATP synthase to generate ATP from ADP and inorganic phosphate?
Reduction of to
Electron transfer
Ubiquitination
Proton gradient
Phosphorylation
Proton gradient
The correct answer is proton gradient. and
donate electrons to electron transport chain complexes and pass them along the membrane, causing protons
to move from the mitochondrial matrix to the intermembrane space. The high proton concentration gradient causes protons to travel through the inner mitochondrial transmembrane ATP synthase to equilibrate the gradient. Passing of protons through ATP synthase promotes synthesis of ATP from ADP from inorganic phosphate.
Example Question #2 : Help With The Electron Transport Chain
Cytochrome C is a small protein localized to the inner mitochondrial membrane that has an important role in the last steps of the electron transport chain. What is cytochrome C's primary role in the electron transport chain?
Cytochrome C accepts electrons from complex II and shuttles them to Complex III, which is required for further activation of complex IV
Cytochrome C removes electrons from complex IV and transfers them to molecular oxygen in the mitochondria
Cytochrome C accepts electrons from complex III in the mitochondrial membrane and transfers them to complex IV
Cytochrome C catalyzes the conversion of 2 ADP to 2 ATP, thus contributing to the energetic gain in the electron transport chain
Cytochrome C accepts electrons from complex IV and directly transfers these electrons to molecular oxygen
Cytochrome C accepts electrons from complex III in the mitochondrial membrane and transfers them to complex IV
Cytochrome C is responsible for accepting the electrons generated in the bc1 complex (complex III) and transferring them over to complex IV. In other words, cytochrome C oxidizes complex III and is oxidized by complex IV. This is required to then add those electrons to molecular oxygen, which forms water and contributes to the proton gradient required for ATP production.
Example Question #102 : Biochemistry
What is the final electron acceptor in the electron transport chain?
Cytochrome C
The final electron acceptor in the electron transport chain is oxygen gas. one oxygen gas molecule will accept 4 electrons and combine with 4 protons in order to create 2 water molecules. This reaction is the reason water is a byproduct of aerobic cellular respiration.
Example Question #3 : Help With The Electron Transport Chain
Krebs cycle occurs in the __________ and the electron transport chain occurs in the __________.
mitochondrial matrix . . . mitochondrial inner membrane
mitochondrial inner membrane . . . mitochondrial matrix
cytoplasm . . . mitochondrial matrix
mitochondrial matrix . . . cytoplasm
mitochondrial matrix . . . mitochondrial inner membrane
Glycolysis, the first step in metabolism of carbohydrates, occurs in the cytoplasm. The products of glycolysis (pyruvate and NADH) are transported to the mitochondrial matrix. The products undergo series of reactions called the Krebs cycle. The products of Krebs cycle and NADH from glycolysis enter the inner mitochondrial membrane and go through the electron transport chain (ETC). During ETC, oxidative phosphorylation generates most of the ATP used by the cells.
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All GRE Subject Test: Biochemistry, Cell, and Molecular Biology Resources
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