chem 155b quiz 2 review

Consider a substance that can exist in an oxidized form X and a reduced form X-. Such a pair is called a(n)

redox couple

Proton flow through the ATP synthase enzyme

results in the release of ATP from its tightly bound state in the active site.

The electron transport chain uses the transfer of *** between protein complexes to set up a proton gradient.

***= electrons

The energy generation of ATP using ATP synthase can be thought of as the reverse of what chemical reaction?

ATP hydrolysis and proton movement against a gradient

Match each name with the electron‑transport chain complex or electron carrier.

complex 1: NADH-Q oxidoreductase complex 2: succinate-Q reductase complex 3: Q-cytochrome c oxidoreductase complex 4: cytochrome c oxidase ubiquinone: Coenzyme Q

Identify the electron transport chain complex that does not pump protons across the inner mitochondrial membrane.

complex 2

Which complex in the electron transport chain transfers electrons to the final electron acceptor?

cytochrome c oxidase

Determine which complex of the electron transport chain (respiratory chain) each phrase describes.

Complex 1 1. Electron Transfer from NADH to ubiquinone (coenzyme Q) 2. NADH dehydrogenase complex Complex II 1. Electron Transfer from succinate to ubiquinone (coenzyme Q) 2. Succinate dehydrogenase complex Complex III 1. Electron Transfer from Ubiquinol to cytochrome c 2. Cytochrome BC1 complex Complex IV 1. Electron Transfer from Cytochrome c to O2 2. Cytochrome Oxidase

The uncoupler dinitrophenol (DNP) prevents ATP synthesis while allowing electron transport to proceed because

DNP can transport protons across the membrane, dissipating the proton gradient.

Which statement describes the direction of proton movement relative to electron transfer and phosphorylation?

Electron transfer pumps protons out of the matrix. As the protons reenter through the ATP synthase, ATP is produced in the matrix.

pyruvate+NADH+H+⟶lactate+NAD++H+

In the reaction, pyruvate is the oxidant and is the reductant.

Determine whether each of the following causes an increase or decrease in the activity of the electron transport chain.

Increase in Activity 1. high NADH concentration 2. High phosphate concentration 3. High ADP concentration 4. high oxygen concentration Decrease in activity 1. Low Oxygen concentration 2.low phosphate concentration 3. Large difference in H+ across mitochondrial membrane

What is the function of the proton gradient in the mitochondrion?

It is potential energy that the cell uses to generate ATP.

What is the function of cytochrome c in the electron transport chain?

It transports an electron from complex III to complex IV.

Which characteristic of mitochondria points to the endosymbiotic event yielding intercellular mitochondria?

Mitochondria contain circular DNA. Mitochondria have a double membrane. Mitochondria contain specific transcription and translation machinery.

Which compounds donate electrons to the electron transport chain? Which compound is the final electron acceptor? Which compounds are the final products of the electron transport chain and oxidative phosphorylation?

NADH and FADH2 O2 ATP, H20, NAD+, FAD

If glycolysis and gluconeogenesis were simultaneously operating at the same rate, which statement would be false?

Phosphofructokinase activity would inhibit phosphoenolpyruvate carboxykinase activity.

The electron transport chain (ETC), or respiratory chain, is linked to proton movement and ATP synthesis.

Prosthetic groups, such as iron-sulfur centers, are directly involved with electron transfer. The reactions of the ETC take place in the inner membrane of mitochondria. Electrons generated by the citric acid cycle in the mitochondrial matrix enter the ETC. Electron transfer in the ETC is coupled to proton transfer from the matrix to the intermembrane space. Electron carriers are organized into four complexes of proteins and prosthetic groups.

Electron carrier molecules transfer electrons between metabolic pathways. Choose the electron carriers that transfer electrons from glycolysis to the electron transport chain and from the citric acid cycle to the electron transport chain.

glycolysis --> ETC = NADH CAC --> ETC = NADH and FADH2

Which characteristics of mitochondria provide evidence for their prokaryotic past?

have a double membrane replicate by a process similar to prokaryotes contain their own transcriptional machinery

Where does the electron transport chain occur?

inner membrane of mitochondria

Where does oxidative phosphorylation occur?

inner mitochondrial membrane

Which statement is true of fructose 1,6‑bisphosphate but not of fructose 6‑phosphate?

it contains two phosphate groups

What product of contracting muscle tissue is used by the liver as the starting material for gluconeogenesis?

lactate

Type 2 diabetes is most commonly diagnosed

later in life and is primarily caused by insulin resistance.

Although glycolysis can occur in most cells, gluconeogenesis is mostly limited to two tissues. Which two tissues are the primary sites of gluconeogenesis?

liver and kidney

Which compound transfers reducing equivalents (electrons) into the mitochondrial matrix?

malate

The process of glycolysis occurs in the cytoplasm. The electrons from the NADH generated during glycolysis

may enter the electron transport chain either at the level of NADH or FADH2, depending on the shuttle system used to transport them into the mitochondria.

Where does the citric acid cycle occur?

mitochondrial matrix

The process of glycolysis results in the formation of two high‑energy phosphate bonds in the form of ATP. How many high‑energy phosphate bonds are consumed during the process of gluconeogenesis using pyruvate as a starting material?

six

Of the electron transfer complexes associated with the inner mitochondrial membrane, which does NOT directly produce a portion of the proton gradient?

succinate‑Q reductase (Complex II)

How is oxaloacetate modified to a form that can be transported out of the matrix?

transamination

Which process will be immediately inhibited if cytochrome c is unable to interact with cytochrome c oxidase?

transfer of electrons from cytochrome c to O2

Δ𝐺∘′ equation

=-nFΔE∘′ n=electrons transferred F= faraday's constant 96.5 kJ*mol-1*V-1

What is the source of electrons transferred by succinate‑Q reductase (Complex II)?

FADH2 from the citric acid cycle

What is the proton gradient in cellular respiration?

a higher concentration of protons (H+) on one side of a membrane than the other

1. In a hydrogen fuel cell, hydrogen gas and oxygen gas are combined to form water. Write the balanced chemical equation describing this reaction using the lowest whole‑number coefficients. 2. oxidizing agent 3. reducing agent 4. Determine the number of electrons transferred in the balanced chemical equation.

1. 2H2(g)+O2(g)⟶2H2O(l) 2. oxygen 3. gas 4. 4

The path taken by electrons from NADH generated during the citric acid cycle to water will NOT pass through

FAD

Which electron carrier is NOT mobile or diffusible in the mitochondrial electron transport chain?

FAD

Which statement is NOT part of the Mitchell chemiosmotic hypothesis? High‑energy phosphorylated intermediates that serve as phosphate donors to ADP are generated as a result of electron‑transfer reactions.

High‑energy phosphorylated intermediates that serve as phosphate donors to ADP are generated as a result of electron‑transfer reactions.

For a given pair of reduced and oxidized molecules (X− and X), a negative reducing potential suggests that

X has a lower affinity for electrons than H2 does.

Which statement must be true for an electron transfer reaction to be energetically spontaneous

The change in reduction potential (Δ𝐸ο) must be positive.

Select the true statements about the electron transport chain.

The electron transport chain is a series of oxidation-reduction reactions that occurs in the inner mitochondrial membrane. In the electron transport chain, a series of reactions moves electrons through carriers. The major reactants in the electron transport chain are O2 and either NADH or FADH2.

Which statements describe electron transport chain events?

Two electrons pass between cytochromes through a series of redox reactions. NADH releases two hydrogen ions and donates two electrons to coenzyme Q.

Which of the molecules is the major regulator of oxygen consumption during oxidative phosphorylation?

adp

The generation of glucose from glucose 6‑phosphate occurs in which membrane‑bound organelle(s)?

endoplasmic reticulum

Reactive oxygen species (ROS) are unstable, or reactive, compounds that result from the partial reduction of oxygen. ROS can cause damage to molecules, including membrane lipids and nucleic acids, and may be associated with some diseases.

⋅OH H2O2 ⋅O−2