Chapter 6 Mastering Biology
In the absence of oxygen, cells need a way to regenerate which compound?
NAD+
What is the mechanism of action for the enzyme ATP synthase? ATP is formed _____.
due to the potential energy of a concentration gradient of hydrogen ions across a membrane
The function of cellular respiration is to _____.
extract usable energy from glucose
Humans depend on oxygen to sustain life. However, at the cellular level, muscle cells are _____.
facultative anaerobes
Rotenone is a poison that blocks the electron transport chain. When it does so, glycolysis and the citric acid cycle eventually halt as well. This is because _____.
they run out of NAD+ and FAD
What is the name of the process in which glucose is converted to pyruvate?
glycolysis
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
Where does glycolysis occur in a eukaryotic cell?
in the cytoplasmic fluid
In cellular respiration, which of the following is performed directly by the electron transport chain (or its components)?
A proton gradient is formed.
Why is the citric acid cycle called a cycle?
Acetyl CoA binds to oxaloacetate that is restored at the end of the cycle.
In the first stage of cellular respiration, two molecules of pyruvate are produced. In the remaining stages, a number of products are produced, including _____. These stages occur in the _____.
CO2 ... mitochondria
When pyruvate is converted to acetyl CoA, _____.
CO2 and NADH are formed
What is the correct general equation for cellular respiration?
C₆H₁₂O₆ + 6 O₂ → 6 CO₂ + 6 H₂O + ATP energy
Electron Transport Chain
Electrons pass from one carrier to another, releasing a little energy at each step.
Dinitrophenol (DNP) is a highly toxic membrane uncoupler. What happens when DNP makes the phospholipid bilayer of inner mitochondrial membranes permeable to protons (H+)?
Many protons would bypass ATP synthase, leading to a sharp decline in ATP synthesis.
The electron transport chain is, in essence, a series of redox reactions that conclude cellular respiration. During these redox reactions, _____.
NAD+ is reduced, which then oxidizes an electron acceptor in the electron transport chain
During electron transport, energy from _____ is used to pump hydrogen ions into the _____.
NADH and FADH₂ ... intermembrane space
_____ is to a mitochondrion as _____ is to a chloroplast.
O2 ... CO₂
What is the role of oxygen in cellular respiration?
Oxygen accepts high-energy electrons after they are stripped from glucose.
What molecule is required to move pyruvate to the citric acid cycle?
O₂
Which of these enters the citric acid cycle (also called the Krebs cycle)?
acetyl CoA
Besides sugars and fats, organisms can use other molecules as fuel for cellular respiration. When protein molecules are used, _____ are produced as waste.
amino groups
During aerobic respiration, molecular oxygen (O2) is used _____.
at the end of electron transport chain to accept electrons and form H2O
Carbon monoxide is a toxic gas because it directly _____.
blocks the transfer of electrons to the final electron acceptor
In an experiment, mice were fed glucose (C6H12O6) containing a small amount of radioactive oxygen. The mice were closely monitored, and in a few minutes radioactive oxygen atoms showed up in _____.
carbon dioxide
The major (but not sole) energy accomplishment of the citric acid cycle is the _____.
formation of NADH and FADH₂
Cellular respiration completely breaks down a glucose molecule through glycolysis and the citric acid cycle. However, these two processes yield only a few ATPs. The majority of the energy the cell derives from glucose is _____.
found in NADH and FADH2
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
During cellular respiration _____ is oxidized and _____ is reduced.
glucose ... oxygen
During cellular respiration, glucose is oxidized. However, an intermediate, _____, can be siphoned off and used to synthesize fats.
glyceraldeyhyde-3-phosphate
Correct sequence of steps as energy is extracted from glucose during cellular respiration.
glycolysis → acetyl CoA → citric acid cycle → electron transport chain
In muscle cells, fermentation produces _____.
lactate and NAD+
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 cellular respiration, glucose _____ electrons, whereas _____ electrons.
loses ... oxygen gains
A molecule is oxidized when it _____.
loses an electron
A molecule that functions as the electron donor in a redox reaction _____.
loses electrons and loses energy
In humans, oxygen and carbon dioxide are exchanged with the atmosphere via the _____.
lungs
Primarily, cellular respiration serves to _____.
make ATP to power the cell's activities
The electron transport chain is a series of electron carrier molecules. In eukaryotes, where can this structure be found?
mitochondria
The final electron acceptor of cellular respiration is _____.
oxygen
Using the ATP generated during cellular respiration, the intermediates of glycolysis and the citric acid cycle can be siphoned off and used to _____.
power the biosynthesis of amino acids, fats, and sugars
In cellular respiration, oxygen becomes __________ to water (H2O) as it gains electrons (in hydrogen atoms) that came from glucose.
reduced
Muscle tissues make lactic acid from pyruvate so that you can _____.
regenerate (oxidized) NAD+
Glycolysis is the only stage of cellular respiration that _____.
requires ATP to make ATP
Which part(s) of cellular respiration take(s) place in the mitochondria?
the Citric Acid cycle and the electron transport chain
Most of the NADH that delivers high-energy electrons to the electron transport chain comes from _____.
the citric acid cycle
Carbon monoxide is a colorless, odorless, and toxic gas. Theoretically, if you were breathing carbon monoxide, how many ATP molecules could you produce from one glucose molecule?
2 ATP
During glycolysis, a molecule of glucose is partially oxidized. What is the net gain of ATP and NADH for each glucose molecule?
2 ATP and 2 NADH
Sodium fluoroacetate, or compound 1080, is a rodent poison that probably disrupts the citric acid cycle. In the body, the molecule is converted to a compound that prevents citrate from being used. Initially, when first exposed to this molecule, what is the theoretical energy produced per glucose molecule through the process of cellular respiration?
2 ATP, 4 NADH, and 0 FADH2
The energy production per glucose molecule through the citric acid cycle is _____.
2 ATP, 6 NADH, 2 FADH₂
Which of the following serves primarily as a hydrogen-atom carrier molecule in cells?
FAD
We inhale O₂ and we exhale CO₂. Carbon dioxide is produced _____.
In the reaction that creates acetyl CoA (coenzyme A) from pyruvate
What happens to the energy that is given up by electrons as they move through the electron transport chain?
It pumps H+ through a membrane.
Lungs are to breathing as _____ are to cellular respiration.
mitochondria
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
In what organelle would you find acetyl CoA formation, the citric acid cycle, and the electron transport chain?
mitochondrion
The principal molecules involved in transporting electrons to the electron transport chain are composed of _____.
nucleotides
In cellular respiration, most ATP molecules are produced by _____.
oxidative phosphorylation
In cellular respiration, glucose becomes ___________ to carbon dioxide (CO2) as it loses electrons (in hydrogen atoms).
oxidized
Bacteria have no membrane-enclosed organelles. However, some still generate ATP through cellular respiration. Where is the electron transport chain found in these organisms?
plasma membrane
Which of the following directly requires molecular oxygen (O2)?
the electron transport chain
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
The ATP synthase in a human cell gets energy for making ATP directly from _____.
the flow of H+ through a membrane
For each glucose that enters glycolysis, _____ NADH enter the electron transport chain.
10
Unlike the Citric Acid cycle and electron transport, glycolysis occurs _____.
in the cytoplasm
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
Describe the citric acid cycle.
This process produces some ATP and carbon dioxide in the mitochondrion.
Describe glycolysis.
This process splits glucose in half and produces 2 ATPs for each glucose.
Describe the electron transport chain.
This process uses energy captured from electrons flowing to oxygen to produce most of the ATPs in cellular respiration.
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
A single glucose molecule produces about 38 molecules of ATP through the process of cellular respiration. However, this only represents approximately 38% of the chemical energy present in this molecule. The rest of the energy from glucose is _____.
converted to heat
In a eukaryotic cell, the electron transport chain is precisely located in or on the _____.
cristae of the mitochondrion
Where in bacterial cells does the citric acid cycle occur?
cytoplasm
Some human 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
NADH delivers electrons to an electron transport chain, which passes the electrons through carrier molecules in a series of redox reactions to the final electron acceptor, _________.
oxygen
A muscle cell deprived of molecular oxygen will convert glucose to lactic acid to _____.
recycle NADH through fermentation
In eukaryotes, most of the high-energy electrons released from glucose by cell respiration _____.
reduce NAD+ to NADH, which then delivers them to the electron transport chain
In glycolysis, ATP molecules are produced by _____.
substrate-level phosphorylation
In the citric acid cycle (also called the Krebs cycle), ATP molecules are produced by _____.
substrate-level phosphorylation
Substrate-level phosphorylation directly generates ATP during a chemical reaction. As a single molecule of glucose is completely oxidized, in the presence of oxygen, how many molecules of ATP are gained by substrate-level phosphorylation?
4 ATP
How many NADH are produced by glycolysis?
2
The overall efficiency of respiration is approximately _____.
40%
Using the ATP generated during cellular respiration, the intermediates of glycolysis and the citric acid cycle can be siphoned off and used _____.
to power the biosynthesis of amino acids, fats, and sugars
What is/are the most important output(s) of glycolysis?
two pyruvic acid and two NADH molecules
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
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
In glycolysis there is a net gain of _____ ATP.
2
How many kilocalories are captured in ATP from 1.5 moles of glucose?
420 kcal
In cellular respiration, organic molecules become oxidized as __________ picks up electrons and H+ and becomes reduced to NADH.
NAD+
Once the citric acid cycle has been completed, most of the usable energy from the original glucose molecule is in the form of _____.
NADH
What is the purpose of embedding the electron transport chain in the membrane of a cell?
The membrane is impermeable to H+.
What is the fate of the electrons that are stripped from glucose during cellular respiration?
They are used to form water.
A small amount of ATP is made in glycolysis _____.
by the transfer of a phosphate group from a fragment of glucose to ADP (substrate-level phosphorylation)
Where does most of the ATP produced in cellular respiration come from?
chemiosmosis
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
A gram of fat oxidized by cellular respiration produces approximately _____ as much ATP as a gram of carbohydrate.
twice
In preparing pyruvate to enter the citric acid cycle, which of the following steps occurs?
A compound called coenzyme A binds to a two-carbon fragment.
In glycolysis, what starts the process of glucose breakdown?
ATP
The energy released from the redox reactions in the electron transport chain is used by the cell to make________.
ATP
Which energy-rich molecule produced by cellular respiration directly powers cell work?
ATP
When growing in a nutrient-rich environment, bacteria can use the provided amino acids to synthesize their proteins. However, should the environment change, they can synthesize their amino acids using _____.
citrate
The transfer of _________ from one molecule to another is an oxidation-reduction reaction, or redox reaction.
electrons
Which of the following is the source of the energy that produces the chemiosmotic gradient in mitochondria?
electrons
Of the metabolic pathways listed below, the only pathway found in almost all organisms is _____.
glycolysis
Where do the reactions of the citric acid cycle occur in eukaryotic cells?
the mitochondrion
The enzyme ATP synthase catalyzes the phosphorylation of ADP to form ATP. In eukaryotic cells, the energy needed for this endergonic reaction is derived from _____.
the movement of hydrogen ions across the mitochondrial membrane
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
