Ch 14- 20 Reading Quiz

Question 1

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

Answer 1

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

Question 2

Glycolysis alone captures approximately what percentage of the free energy available in a molecule of glucose?

Answer 2

10%

Question 3

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

Answer 3

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.

Question 4

In a sperm cell, where are the mitochondria located?

Answer 4

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

Question 5

Which is the most permeable membrane of the mitochondrion?

Answer 5

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

Question 6

Which activated carriers does the citric acid cycle produce that transfer high-energy electrons to the electron transport chain?

Answer 6

NADH and FADH₂

These electron carriers transfer a hydride ion – two electrons and one proton – to the electron-transport chain complexes.

Question 7

How does the high-energy transfer of activated carriers contribute to forming the high-energy phosphate bonds of ATP?

Answer 7

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.

Question 8

What is the electron-transport chain composed of?

Answer 8

3 integral membrane complexes

1. NADH dehydrogenase complex
2. cytochrome c reductase complex
3. cytochrome c oxidase complex

2 mobile carriers

1. ubiquinone
2. cytochrome c

Question 9

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

Answer 9

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.

Question 10

Protons are pumped across the mitochondrial ______ membrane to accumulate in the ______________.

Answer 10

inner; intermembrane space

Question 11

The pH of the mitochondrial matrix is _____, which is _____ than that of the intermembrane space.

Answer 11

7.9; higher

Question 12

The proton flow through the transmembrane H⁺ carrier of ATP synthase results in

Answer 12

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.

Question 13

How is pyruvate imported into the mitochondrial matrix for use in the citric acid cycle?

Answer 13

proton gradient-driven symport

Question 14

What does the low redox potential of NADH mean?

Answer 14

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

Question 15

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?

Answer 15

2.5

Technically, 4 ATP molecules can be formed from two electrons of NADH. But in reality, the process operates at around 50% efficiency.

Question 16

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?

Answer 16

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.

Question 17

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?

Answer 17

Superoxide radicals are formed as an intermediate. they are dangerously reactive and can damage cell components

Question 18

Why does the H+ transport complex in the electron-transport chain have an irreversible step driven by the energy from electron transport?

Answer 18

Prevents the protons captured from the intermembrane space to be released back into the matrix.

Question 19

The photosynthetic machinery is found in which part of the chloroplast?

Answer 19

thylakoid membrane

Question 20

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?

Answer 20

The chlorophyll special pair that captured energy from sunlight and transfers it via electron carrier to the electron-transport chain.

Question 21

Stage two of photosynthesis (the light-independent reactions) uses which input molecules to produce organic food molecules?

Answer 21

ATP, NADPH, CO₂

Question 22

Why does chlorophyll appear green? Which light does it absorb?

Answer 22

Chlorophyll absorbs blue and red lights and reflects green light.

Question 23

The first living things on Earth probably generated ATP by what mechanism?

Answer 23

fermentation

Question 24

Which of the following organelles is the site of steroid hormone synthesis in endocrine cells?