Chapter 6

Where does glycolysis occur in a eukaryotic cell?

Glycolysis occurs in the cytoplasmic fluid.

In glycolysis, what starts the process of glucose breakdown?

Some ATP energy is used to start the process of glucose oxidation.

The electron transport chain is a series of electron carrier molecules. In eukaryotes, where can this structure be found?

mitochondria The electron transport chain molecules are embedded in the inner mitochondrial membrane.

Glycolysis is the only stage of cellular respiration that __________.

requires ATP to make ATP Glycolysis contains an "investment" phase and a "payoff" phase. Two ATP are required to make four ATP.

Sunlight is essential for the varied life on Earth. Sunlight provides energy to photosynthetic organisms by providing __________.

the energy necessary to power the rearrangement of chemical bonds in H2O and CO2 This is what photosynthesis accomplishes in the conversion of water and carbon dioxide to sugars.

Which statement describes the electron transport chain?

This process uses energy captured from electrons flowing to oxygen to produce most of the ATPs in cellular respiration. In the electron transport chain, electrons move from one electron carrier to another, eventually reaching oxygen. The released energy is used to make ATPs.

In an experiment, mice were fed glucose (C6H12O6) containing a small amount of radioactive carbon. The mice were closely monitored, and in a few minutes, radioactive carbon atoms showed up in __________.

carbon dioxide Cellular respiration, or the oxidization of glucose, involves the release of CO2.

A chemist has discovered a drug that blocks phosphoglucoisomerase, an enzyme that catalyzes the second reaction in glycolysis. He wants to use the drug to treat people with bacterial infections. However, he can't do this because _____.

human cells also perform glycolysis; the drug might also poison them The chemist's drug could have a devastating effect on human cells.

We inhale O2 and we exhale CO2. Carbon dioxide is produced __________.

in the reaction that creates acetyl CoA (coenzyme A) from pyruvate Carbon dioxide is produced in the transition between glycolysis and the citric acid cycle when the three-carbon pyruvate is cleaved to a two-carbon acetyl molecule with the remaining carbon of pyruvate released as carbon dioxide. Carbon dioxide is also produced in the citric acid cycle itself.

In oxidative phosphorylation, electrons are passed from one electron carrier to another. The energy released is used to __________.

pump protons (H+) across the mitochondrial membrane The energy harvested from many redox reactions is used to power proton pumps that span the inner mitochondrial membrane.

In glycolysis, ATP molecules are produced by _____.

substrate-level phosphorylation A phosphate group is transferred from glyceraldehyde phosphate to ADP.

In the citric acid cycle (also called the Krebs cycle), ATP molecules are produced by _____.

substrate-level phosphorylation A phosphate group is transferred from GTP to ADP.

Most NADH molecules generated during cellular respiration are produced during __________.

the citric acid cycle There are 6 NADH molecules produced by the citric acid cycle per molecule of glucose. Two molecules of FADH2 are also produced by this cycle, which makes it a big source of high energy electron carriers.

Part complete Sunlight is essential for the varied life on Earth. Sunlight provides energy to photosynthetic organisms by providing __________.

the energy necessary to power the rearrangement of chemical bonds in H2O and CO2 This is what photosynthesis accomplishes in the conversion of water and carbon dioxide to sugars.

What is/are the most important output(s) of glycolysis?

two pyruvic acid and two NADH molecules

Which of these is NOT a product of the citric acid cycle (also called the Krebs cycle)?

Acetyl CoA enters the citric acid cycle.

Which of these is NOT a product of glycolysis?

FADH2 FADH2 is a product of the citric acid cycle.

Which statement describes the citric acid cycle?

This process produces some ATP and carbon dioxide in the mitochondrion. The citric acid cycle breaks down carbon molecules, releasing carbon dioxide and forming some ATP.

Which statement describes glycolysis?

This process splits glucose in half and produces 2 ATPs for each glucose In glycolysis, glucose is split into two molecules of pyruvic acid. The released energy is stored in ATP and the electron carrier NADH.

How many NADH are produced by glycolysis?

Two NADH molecules are produced by glycolysis.

A scientist wants to study the enzymes of the citric acid cycle in eukaryotic cells. What part of the cell would she use as a source of these enzymes?

mitochondrial matrix The water-soluble citric acid cycle intermediates and enzymes of a eukaryotic cell are found in the mitochondrial matrix, where the newly synthesized NADH and FADH2 diffuse to proteins of the electron transport chain held within the inner mitochondrial membrane. The matrix corresponds to the cytoplasm of the bacterium from which mitochondria are descended.

In what organelle would you find acetyl CoA formation, the citric acid cycle, and the electron transport chain?

mitochondrion All of the steps of cellular respiration except glycolysis take place in the mitochondrion.

In the equation shown below, during cellular respiration __________ is oxidized and __________ is reduced.

glucose ... oxygen In cellular respiration, electrons and hydrogen are removed from glucose and added to oxygen.

Which part(s) of cellular respiration require(s) oxygen gas?

the Citric Acid cycle the electron transport chain

The enzyme ATP synthase catalyzes the phosphorylation of ADP to form ATP. In eukaryotic cells, the energy needed for this endergonic reaction is directly derived from __________.

the movement of hydrogen ions across the mitochondrial membrane The electron transport chain is an energy converter that uses the exergonic flow of electrons to pump hydrogen ions across the inner mitochondrial membrane from the matrix to the intermembrane space. Hydrogen ions diffuse back into the matrix via a channel in ATP synthase.

In glycolysis there is a net gain of _____ ATP.

2 It takes 2 ATP to produce 4 ATP.

In the first stage of cellular respiration (glycolysis), two molecules of pyruvate are produced. In the remaining stages of cellular respiration, a number of additional products are produced, such as __________. These other stages occur in the __________.

ATP ... mitochondria ATP, CO2, and H2O are the products of cellular respiration. As pyruvate is oxidized further, it is moved into a mitochondrion where the remaining stages of cellular respiration occur.

Which of these enters the citric acid cycle (also called the Krebs cycle)?

Acetyl CoA is a reactant in the citric acid cycle (also called the Krebs cycle).

What is the correct general equation for cellular respiration?

C6H12O6 + 6 O2 → 6 CO2 + 6 H2O + ATP energy Cellular respiration extracts energy from glucose (C6H12O6) to produce smaller energy packets (ATP).

Which of the following best describes the electron transport chain?

Electrons pass from one carrier to another, releasing a little energy at each step. NADH and FADH2 deliver electrons from the breakdown products of glycolysis and the citric acid cycle to the electron transport chain, which passes these electrons from one molecule to another, releasing a small amount of energy at each step.

In cellular respiration, glucose _____ electrons, whereas _____ electrons.

In cellular respiration, glucose _____ electrons, whereas _____ electrons. During cellular respiration, glucose loses electrons and oxygen gains electrons. Oxidation and reduction always go together, as electron transfer requires both a donor and an acceptor.

Given the relatively modest number of calories burned by anything but the most vigorous activities, why can people consume over 2,000 kilocalories a day, yet maintain a healthy body weight?

Most of the energy consumed in food is spent maintaining the body's functions, so only a fraction of food energy needs to be burned in exercise. This is true, and it's lucky for dieters. If we had to burn 2,000 kilocalories a day in exercise, we'd need to run a marathon every day.

In the absence of oxygen, cells need a way to regenerate which compound?

NAD+ The NAD+ needs to be regenerated, which is why ethanol or lactic acid is formed.

What is the purpose of embedding the electron transport chain in the membrane of a cell?

The electron acceptors can transport H+ across the membrane, which is otherwise impermeable to H+. Chemiosmosis relies on the properties of the membrane that prevent hydrogen ions (H+) from flowing down their concentration gradient. Hydrogen ions are permitted to reenter the cell across the membrane through ATP synthase, which captures their potential energy and uses it to synthesize ATP.

Which of the following best describes the electron transport chain?

This process uses energy captured from electrons flowing to oxygen to produce most of the ATPs in cellular respiration. In the electron transport chain, electrons move from one electron carrier to another, eventually reaching oxygen. The released energy is used to make ATPs.

A gram of fat oxidized by cellular respiration produces approximately __________ as much ATP as a gram of carbohydrate.

Twice Fats are excellent fuels because they store so much energy for their mass.

Through respiration, humans breathe in O2 and breathe out CO2. However, what would happen if we did not breathe in O2?

We would not make enough ATP to meet our energy requirements The electron transport chain accepts electrons from the breakdown products of glycolysis and the citric acid cycle, and it passes these electrons from one molecule to another until they are passed (along with two hydrogen ions) to oxygen to form water.

In nutrient-rich environments (like your mouth), bacteria can use the provided amino acids to synthesize their proteins. However, should the environmental conditions change and become nutrient-poor, bacteria would need to synthesize their amino acids. They can do this using __________.

citric acid cycle intermediates Many intermediates from the citric acid cycle can be siphoned off and used to generate amino acids.

Glycolysis is the multi-step breakdown of _____. Several different _____ play a role in this process.

glucose ... enzymes

During cellular respiration, glucose is oxidized. However, an intermediate __________ can be siphoned off and used to synthesize fats.

glyceraldeyhyde 3-phosphate Glyceraldeyhyde 3-phosphate (G3P) is used in the synthesis of glycerol, which is a constituent of fats.

Which stage of cellular respiration appears to have evolved first?

glycolysis Glycolysis can occur in the absence of oxygen and evolved prior to oxygenic photosynthesis.

Which of the following processes takes place in the cytosol of a eukaryotic cell?

glycolysis Glycolysis, the breakdown of glucose into two molecules of pyruvic acid, takes place in the cytosol, outside the mitochondria.

Select the correct sequence of steps as energy is extracted from glucose during cellular respiration.

glycolysis → acetyl CoA → citric acid cycle → electron transport chain Glycolysis produces pyruvic acid, which enters the mitochondrion. There, it is converted to acetyl CoA, which enters the citric acid cycle. Electron carriers bring electrons from the first three steps to the electron transport chain, and ATP is made.

Unlike the Citric Acid cycle and electron transport, glycolysis occurs _____.

in the cytoplasm

When a car engine burns gasoline, the results of the reaction are similar to when cells burn glucose. Both reactions release carbon dioxide and water. In cells, the chemical energy in food is converted to ATP and heat. In a moving car, the chemical energy in gasoline is converted to __________.

kinetic energy and heat About 25% of the energy released from the gasoline consumed by a car is converted to the kinetic energy of the moving car. The rest is given off as heat, which explains why car engines become so hot.

Sports physiologists at an Olympic training center want to monitor athletes to determine at what point their muscles begin to function anaerobically. They could do this by checking for a buildup of _____.

lactic acid In humans, muscle cells switch to lactic acid fermentation after becoming anaerobic.

In cellular respiration, glucose _____ electrons, whereas _____ electrons.

loses ... oxygen gains During cellular respiration, glucose loses electrons and oxygen gains electrons. Oxidation and reduction always go together, as electron transfer requires both a donor and an acceptor.

A molecule that functions as the electron donor in a redox reaction __________.

loses electrons and becomes oxidized In cellular respiration, glucose is oxidized when it loses electrons in hydrogen atoms. Oxygen is reduced as it gains electrons attached to hydrogen atoms.

Lungs are to breathing as _____ are to cellular respiration.

mitochondria Two of the three main stages of cellular respiration occur in the mitochondria.

Some human cells, such as nerve cells, are restricted to aerobic respiration to recycle NADH and FADH2. If these cells are deprived of oxygen, then __________.

oxidative phosphorylation would come to a halt because there wouldn't be any oxygen to "pull" the electrons down the transport chain Without electronegative oxygen waiting at the end of the chain, electron flow would cease, along with the action of the protein complexes that create the proton gradients.

Cellular respiration requires fuel (glucose) and oxygen gas. The main process that produces these inputs is _____.

photosynthesis

A muscle cell deprived of molecular oxygen will convert glucose to lactic acid to __________.

recycle NADH through fermentation During lactic acid fermentation, pyruvate is reduced directly by NADH to form lactate. This recycles NAD+, so the cycle continues.

In eukaryotes, most of the high-energy electrons released from glucose by cellular respiration __________.

reduce NAD+ to NADH, which then delivers them to the electron transport chain Most of the high-energy electrons released from the glucose are picked up by NAD+ and sent through the electron transport chain.

Oxidative phosphorylation could not occur without glycolysis and the citric acid cycle, because _____.

these two stages supply the electrons needed for the electron transport chain The main function of glycolysis and the citric acid cycle is to supply oxidative phosphorylation with electrons carried by NADH and FADH2.

Fat is the most efficient molecule for long-term energy storage, even compared to carbohydrates, because __________.

with their numerous hydrogen atoms, fats provide an abundant source of high-energy electrons Because oxidative phosphorylation depends on a source of electrons (all of which are extracted from hydrogen atoms), fats, which contain primarily hydrogen and carbon atoms, are an abundant source of high-energy electrons that can be harvested for energy production.