mastering bio chapter 6

Box B

After food is broken down in the digestive system, it is transported to cells via the circulatory system.

What molecules belong in space A and B?

glucose and oxygen; Photosynthesis produces glucose and releases oxygen into the atmosphere.

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

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

How many NADH are produced by glycolysis?

2

In glycolysis there is a net gain of _____ ATP.

2; It takes 2 ATP to produce 4 ATP.

Energy packets that cells use to do work

ATP

For cellular work

ATP

Which energy-rich molecule produced by cellular respiration directly powers cell work?

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.

Box D

ATP is produced with the help of the electron transport chain.

In glycolysis, what starts the process of glucose breakdown?

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

Box A

Eating food provides fuel and building blocks for your body.

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.

Which of these is NOT a product of glycolysis?

FADH2; FADH2 is a product of the citric acid cycle.

Box C

Fuel molecules are broken down further in glycolysis and the citric acid cycle (also called the Krebs cycle).

Water

H2O

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

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.

Gas produced by photosynthesis

O2

Gas we inhale

O2

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

acetyl CoA; Acetyl CoA enters the citric acid cycle.

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

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

Food that plants produce

glucose

Fuel

glucose

Which of the following molecules is broken down in cellular respiration, providing fuel for the cell?

glucose

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

glucose ... enzymes

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.

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.

Sun

light

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.

What molecule is indicated by the letter D?

oxygen; Oxygen is the final electron acceptor of cellular respiration.

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

photosynthesis

What process occurs in structure H?

photosynthesis; Chloroplasts are the sites of photosynthesis.

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.

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.

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.

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.

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.

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.

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.

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

two pyruvic acid and two NADH molecules

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 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.

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

a and b, but not c

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.

What process occurs within Box B?

citric acid cycle; The citric acid cycle transfers electrons to NADH and FADH2.

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.

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.

What process occurs in Box A?

glycolysis; Glycolysis occurs in the cytosol.

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.

End product

heat

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.

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

in the cytoplasm

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.

What organelle is indicated by the letter C?

mitochondrion; Mitochondria are the sites of cellular respiration.

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.

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).

Gas we exhale

CO2

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.

What molecules belong in spaces E and F?

carbon dioxide and water; Carbon dioxide and water are by-products of cellular respiration.

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.

Where does glycolysis occur in a eukaryotic cell?

in the cytoplasmic fluid

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.

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.

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.

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.

Lungs are to breathing as _____ are to cellular respiration.

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

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.

In glycolysis, ATP molecules are produced by _____.

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

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.

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.