AP Biology Chapter 7

What catabolic processes may have been used by cells on ancient Earth before free oxygen became available?

Glycolysis, pyruvate oxidation, the citric acid cycle, and oxidative phosphorylation, using an electron acceptor other than oxygen

The immediate energy source that drives ATP synthesis by ATP synthase during oxidative phosphorylation is the __________.

H+ concentration gradient across the membrane holding ATP synthase

A glucose molecule is completely broken down to carbon dioxide and water in glycolysis and the citric acid cycle, but together these two processes yield only a few molecules of ATP. What happened to most of the energy that the cell obtains from the oxidation of glucose?

It is stored in NADH and FADH2 **The electrons obtained from the oxidation of glucose are temporarily stored in NADH and FADH2. The energy derived from the oxidation of NADH and FADH2 is used to drive the electron transport chain and chemiosmotic synthesis of ATP**

In an oxidation-reduction reaction, the reducing agent

Loses electrons and loses potential energy

Where are the proteins of the electron transport chain located?

Mitochondrial inner membrane

In cellular respiration, a series of molecules forming an electron transport chain alternately accepts and then donates electrons. What is the advantage of such an electron transport chain?

The advantage of an electron transport chain is that a small amount of energy is released with the transfer of an electron between each pair of intermediates **As the electrons "fall" down the electron transport chain, the energy released is used to actively transport protons into the inner-membrane space. Read about the respiratory electron transport chain**

Most CO2 from catabolism is released during __________.

The citric acid cycle

Carbon skeletons for amino acid biosynthesis are supplied by intermediates of the citric acid cycle. Which intermediate could directly supply the carbon skeleton for synthesis of a five-carbon amino acid?

α-ketoglutarate

Starting with one molecule of isocitrate and ending with fumarate, how many ATP molecules can be made through substrate-level phosphorylation?

1

How many carbon atoms are fed into the citric acid cycle as a result of the oxidation of one molecule of pyruvate?

2

For each mole of glucose (C6H12O6) completely oxidized by cellular respiration, how many moles of CO2 are released in the citric acid cycle?

4

In the complete reactions of aerobic respiration, the energy for the majority of ATP synthesis is provided by

A proton gradient across a membrane

Which process is not part of the cellular respiration pathway that produces large amounts of ATP in a cell? A. Fermentation B. Glycolysis C. Krebs cycle D. Electron transport chain

A. Fermentation **Fermentation is an alternate pathway used when oxygen levels are low**

Which molecule is metabolized in a cell to produce energy "currency" in the form of ATP? A. Glucose B. ADP C. Phosphate D. Carbon dioxide

A. Glucose **Glucose is used to produce high-energy ATP in a cell**

Which of the following describes the process of glycolysis? A. It represents the first stage in the chemical oxidation of glucose by a cell B. It converts one glucose molecule to two molecules of pyruvate and carbon dioxide C. Glycolysis occurs in the mitochondria D. Glycolysis produces 30 ATP from each molecule of glucose E. It requires ATP and NADPH

A. It represents the first stage in the chemical oxidation of glucose by a cell **Catabolism of glucose begins with glycolysis**

Which of the following statements about the electron transport chain is true? A. NADH and FADH2 donate their electrons to the chain B. The electron transport chain is the first step in cellular respiration C. Water is the last electron acceptor D. Electrons gain energy as they move down the chain

A. NADH and FADH2 donate their electrons to the chain **The electrons lose energy as they move down the chain, and this energy is used to create a proton gradient that drives the synthesis of ATP**

Which of the following best describes the main purpose of the combined processes of glycolysis and cellular respiration? A. Transforming the energy in glucose and related molecules in a chemical form that cells can use for work B. Producing complex molecules from chemical building blocks C. Breaking down ATP so that ADP and P can be reused D. Catabolism of sugars and related compounds E. The breakdown of glucose to carbon dioxide and water

A. Transforming the energy in glucose and related molecules in a chemical form that cells can use for work

How do the catabolic products of beta oxidation enter into the citric acid cycle?

As acetyl CoA

Identify all correct statements about the basic function of fermentation. A. The basic function of fermentation is the production of additional ATP by further oxidation of the products of glycolysis B. The basic function of fermentation is the regeneration of NAD+, which allows continued ATP production by glycolysis C. The basic function of fermentation is the production of ethyl alcohol or lactic acid

B. The basic function of fermentation is the regeneration of NAD+, which allows continued ATP production by glycolysis **Fermentation occurs in the absence of oxygen and does not yeild as much ATP**

Which of the following is an accurate description of the events that occur along the electron transport chain depicted in the figure? A. Electron transfer is directly coupled to chemiosmosis B. The potential energy of electrons increases at each step in the pathway C. Each electron transfer between carriers results in oxidation of one carrier and reduction of another D. ATP is generated directly at three points in the pathway

C. Each electron transfer between carriers results in oxidation of one carrier and reduction of another

The figure shows the electron transport chain. Which of the following is initially added to the chain with the highest free energy? A. Oxygen B. Water C. NADH D. CO2 E. FADH2

C. NADH

Which of the following statements about chemiosmotic synthesis of ATP is correct? A. The energy for production of ATP from ADP comes directly from a gradient of electrons across the inner mitochondrial membrane B. Oxygen participates directly in the reaction that makes ATP from ADP and P C. The chemiosmotic synthesis of ATP requires that the electron transport in the inner mitochondrial membrane be coupled to proton transport across the same membrane D. The chemiosmotic synthesis of ATP occurs only in eukaryotic cells because it occurs in mitochondria E. Chemiosmotic ATP synthase requires oxygen

C. The chemiosmotic synthesis of ATP requires that the electron transport in the inner mitochondrial membrane be coupled to proton transport across the same membrane **Chemiosmosis uses the energy of a proton gradient to make ATP; the proton gradient is formed by coupling the energy produced by electron transport with movement of protons across the membrane**

Into which molecule are all the carbon atoms in glucose ultimately incorporated during cellular respiration?

Carbon dioxide **All of the carbon atoms in glucose are incorporated into carbon dioxide: Two molecules are formed as pyruvate is converted to acetyl CoA, and four molecules are formed during the Krebs cycle**

Metabolic pathways that release stored energy by breaking down complex molecules are known as?

Catabolic pathways

Which statement about the citric acid cycle is correct? A. The oxidation of compounds by the citric acid cycle requires molecular oxygen B. The citric acid cycle produces most of the ATP that is subsequently used by the electron transport chain C. The citric acid cycle depends on the availability of NAD+, which is a product of glycolysis E. The last reaction in the citric acid cycle produces a product that is a substrate for the first reaction of the citric acid cycle

E. The last reaction in the citric acid cycle produces a product that is a substrate for the first reaction of the citric acid cycle **The last reaction of the citric acid cycle produces oxaloacetate, which is a substrate for the first enzyme; this is the correct description of the cyclic nature of this sequence of reactions**

Which of the following statements about the redox reactions of the electron transport chain is correct? A. The oxidation of NADH is directly coupled to the reduction of oxygen to water B. The electron transport chain takes electrons from water and gives them to oxygen C. NADH gains electrons in the initial reaction of the electron transport chain D. The redox reactions of the electron transport chain are directly coupled with the synthesis of ATP E. The redox reactions of the electron transport chain are directly coupled to the movement of protons across a membrane

E. The redox reactions of the electron transport chain are directly coupled to the movement of protons across a membrane **The reduction and oxidation of electron carriers in the electron transport chain provide the energy to move protons across a membrane against the chemical gradient of protons**

Which stage of glucose metabolism produces the most ATP?

Electron transport and chemiosmosis **Electron transport and chemiosmosis (oxidative phosphorylation) can yield around 26 molecules of ATP**

What carbon sources can yeast cells metabolize to make ATP from ADP under anaerobic conditions?

Glucose

Yeast cells with defective mitochondria are incapable of cellular respiration. These cells will be able to grow by catabolizing which of the following carbon sources for energy?

Glucose

In the combined processes of glycolysis and cellular respiration, what is consumed and what is produced?

Glucose is consumed, and carbon dioxide is produced **The carbon in glucose is oxidized to carbon dioxide during cellular respiration**

Which metabolic pathway is common to both fermentation and cellular respiration of a glucose molecule?

Glycolysis

Which process in eukaryotic cells will proceed normally whether oxygen (O2) is present or absent?

Glycolysis

Which step of the cellular respiration pathway can take place in the absence of oxygen?

Glycolysis **Glycolysis can take place in the absence of oxygen; its product, pyruvate, enters the cellular respiration pathway or undergoes fermentation depending on the availability of oxygen**

What is the purpose of beta oxidation in respiration?

Oxidation of fatty acids

The final electron acceptor of the electron transport chain that functions in aerobic oxidative phosphorylation is __________.

Oxygen

In mitochondria, exergonic redox reactions __________.

Provide the energy that establishes the proton gradient

What is the oxidizing agent in the following reaction? Pyruvate + NADH + H+ → Lactate + NAD+

Pyruvate

In most cells, not all of the carbon compounds that participate in glycolysis and the citric acid cycle are converted to carbon dioxide by cellular respiration. What happens to the carbon in these compounds that does not end up as CO2?

The carbon compounds are removed from these processes to serve as building blocks for other complex molecules **Glycolysis and the citric acid cycle provide many compounds that are the starting points for the synthesis of amino acids and lipids**

True or false? The reactions that generate the largest amounts of ATP during cellular respiration take place in the mitochondria.

True **Glycolysis takes place in the cytoplasm, whereas the Krebs cycle and the electron transport chain, which generate the largest amounts of ATP during cellular respiration, take place in the mitochondria**

True or false? The potential energy in an ATP molecule is derived mainly from its three phosphate groups.

True **The three phosphate groups in an ATP molecule carry negative charges that strongly repel each other and give ATP a large amount of potential energy**

In the absence of oxygen, what is the net gain of ATP for each glucose molecule that enters glycolysis?

Two ATP **Four ATP are made, but two ATP are consumed to start the process of glycolysis**

The electrons stripped from glucose in cellular respiration end up in which compound?

Water **At the end of the electron transport chain, the electrons and protons are added to oxygen, forming water**