Ch 14- 20 Reading Quiz Flashcards
Which of the following correctly matches the cellular location with the production of ATP by oxidative phosphorylation in that cell type?
a) chloroplasts – plants
b) plasma membrane – bacteria
c) cell wall – photosynthetic algae
d) mitochondria – archaea
b) plasma membrane – bacteria
The electron-transport chain for ATP production by oxidative phosphorylation is found in the plasma membrane of prokaryotic cells like archaea and bacteria. ATP production by oxidative phosphorylation occurs in the mitochondria of all eukaryotic cells, including plant cells, and is mechanistically different from phosphorylation in chloroplasts
Glycolysis alone captures approximately what percentage of the free energy available in a molecule of glucose?
10%
Individuals with inherited diseases causing mitochondrial dysfunction typically experience which of the following symptoms?
a) light sensitivity
b) bone deformities
c) heart problems
d) sterility
c) heart problems
Because muscle cells and nerve cells require large amounts of ATP, mitochondrial diseases manifest most strongly in these tissues. Heart problems are thus a common condition associated with mitochondrial disease.
In a sperm cell, where are the mitochondria located?
the mitochondria form elongated tubes that wrap around the flagellar core.
Mitochondria can take different forms in different types of cells and are located next to structures that require a steady supply of ATP. In sperm cells, large amounts of ATP are needed to power the flagellum, and thus the mitochondria are long tubes wrapped around the flagellum
Which is the most permeable membrane of the mitochondrion?
outer membrane
The mitochondrion outer membrane contains large porin proteins that allow for the passage of all molecules up to a certain size. The inner membrane is highly folded and contains the enzymes of the electron-transport chain
Which activated carriers does the citric acid cycle produce that transfer high-energy electrons to the electron transport chain?
NADH and FADH2
These electron carriers transfer a hydride ion – two electrons and one proton – to the electron-transport chain complexes.
How does the high-energy transfer 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. The proton gradient is used to power ATP synthesis as they flow down their electrochemical gradient through ATP synthase.
What is the electron-transport chain composed of?
3 integral membrane complexes
- NADH dehydrogenase complex
- cytochrome c reductase complex
- cytochrome c oxidase complex
2 mobile carriers
- ubiquinone
- cytochrome c
Which of the following has the lowest electron affinity?
a) cytochrome c oxidase complex
b) NADH dehydrogenase complex
c) cytochrome c reductase complex
d) oxygen
b) NADH dehydrogenase complex
The passage of electrons along the electron transport chain is energetically favorable because electrons are passed from a complex that has a lower electron affinity to one with a higher electron affinity.
Thus, the complex with the lowest affinity is the first complex, NADH dehydrogenase complex.
Protons are pumped across the mitochondrial ______ membrane to accumulate in the ______________.
inner; intermembrane space
The pH of the mitochondrial matrix is _____, which is _____ than that of the intermembrane space.
7.9; higher
The proton flow through the transmembrane H+ carrier of ATP synthase results in
Movement of the protons through the carrier causes rotation of the carrier and stalk (subunits of the ATP synthase), which leads to conformational changes in the head (a subunit of ATP) that drive the formation of ATP.
How is pyruvate imported into the mitochondrial matrix for use in the citric acid cycle?
proton gradient-driven symport
What does the low redox potential of NADH mean?
NADH is more likely to give up its electrons and thus has a low affinity for electrons. The electrons are in a “high energy bond” and the bond is easy to break, making NAD+ and FAD good candidates for carrying and delivering electrons to the electron-transport chain. The members of the chain have higher redox potentials
What is the number of ATP molecules that could be synthesized from the energy released by the transfer of two electrons from NADH to molecular oxygen?
2.5
Technically, 4 ATP molecules can be formed from two electrons of NADH. But in reality, the process operates at around 50% efficiency.
The cytochrome complexes contain heme prosthetic groups, which have a higher redox potential than the iron-sulfur centers in NADH dehydrogenase.
Where in the electron-transport chain would the cytochrome complexes be located relative to iron-sulfur center complexes?
later in the chain
The transfer of electrons from a complex with a low redox potential to one with a higher redox potential (higher electron affinity) is energetically favorable.
Thus, complexes containing chemical groups with higher electron affinities/high redox potential occur later in the electron-transport chain.
Cytochrome c oxidase catalyzes the reaction that reduces molecular oxygen (two oxygen atoms) to two water molecules by adding 4 electrons. 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. they are dangerously reactive and can damage cell components
Why does the H+ transport complex in the electron-transport chain have an irreversible step driven by the energy from electron transport?
Prevents the protons captured from the intermembrane space to be released back into the matrix.
The photosynthetic machinery is found in which part of the chloroplast?
thylakoid membrane
Stage 1 of photosynthesis also uses an electron-transport chain like the one used in mitochondria for oxidative phosphorylation to pump protons and make ATP. Where do the high-energy electrons come from?
The chlorophyll special pair that captured energy from sunlight and transfers it via electron carrier to the electron-transport chain.
Stage two of photosynthesis (the light-independent reactions) uses which input molecules to produce organic food molecules?
ATP, NADPH, CO2
Why does chlorophyll appear green? Which light does it absorb?
Chlorophyll absorbs blue and red lights and reflects green light.
The first living things on Earth probably generated ATP by what mechanism?
fermentation
Which of the following organelles is the site of steroid hormone synthesis in endocrine cells?
