Biology Ch. 7
Most of the electrons removed from glucose by cellular respiration are used for which of the following processes?
1. Reducing NAD+ to NADH in glycolysis the citric acid cycle 2. producing a proton gradient for ATP synthesis in the mitochondria. Electrons from oxidation or glucose are used to reduce NAD+ and produce a proton gradient for ATP synthesis in the mitochondria
Electron transport involves a series of electron carrier. Where are they found in eukaryotic cells? Prokaryotic?
E: inner mitochondrial membrane P: plasma membrane
The steps that converts pyruvate to acetyl CoA at the top of the diagram occurs twice per glucose. This oxidation of pyruvate accounts for two additional reduced _________ molecules and two molecules of CO2
NADH
After completion of the citric acid cycle, most of the usable energy from the original glucose molecule is in the form of _____.
NADH The citric acid cycle produces three NADH per turn of the cycle.
The two electron carrier molecules that feed electrons into the electron transport system are _______ and ________.
NADH, FADH2
Which process is the one in which glucose is oxidized to generate two molecules of pyruvate, and in which are ATP and NADH are produced?
None of the listed responses are correct The process is glycolysis
If a compound that allows protons to freely diffuse across membranes is added to cells that are actively metabolizing glucose via cellular respiration, which of the following processes would stop?
None of the listed responses is correct. The chemiosmotic synthesis of ATP would stop in the mitochondria but substrate-level phosphorylation could continue
Both cellular respiration and photosynthesis are redox rxns. What is the difference bt oxidation and reduction?
O: loss of electrons from one substance R: gain of electrons to another substance
Which of the following is a correct description of the events in cellular respiration and the sequence of events in cellular respiration?
Oxidation of glucose to pyruvate; oxidation of pyruvate; oxidation of acetyl-coA; oxidative phosphorylation
Most of the ATP in cellular respiration comes from which of the following processes?
Oxidative phosphorylation After hydrogen ions are pumped into the mitochondrial intermembrane space they flow back through ATP synthase which produces most of the ATP in cellular respiration
what strongly electronegative atom, pulling electrons down the electron transport chain, is the final electron acceptor?
Oxygen
During the reaction C6H12O6 + 6 O2 → 6 CO2 + 6 H2O, which compound is reduced as a result of the reaction?
Oxygen In cellular respiration glucose is oxidized to carbon dioxide and oxygen is reduced to water
Fermentation allows for the production of ATP without using either ____ or any _____.
Oxygen, electron transport chain
Phosphofructokinase is an allosteric enzyme that catalyze San important step on glycolysis. Explain how this step is a control point in cellular respiration
Phosphofructokinase is the pacemaker of cellular respiration
Explain the overall concept of how ATP synthase uses the flow of hydrogen ions to produce ATP
Proton motive force couples with the redox rxns of the electron transport chain to ATP
In preparing pyruvate to enter the citric acid cycle, which of the following steps occur?
Pyruvate is oxidized and decarboxylated, and the removed electrons are used to reduce an NAD+ to an NADH. In addition to these events a molecule of coenzyme A is attached to the resulting acetyl group
Lactic acidosis fermentation starts with glucose and yields lactate. Explain this process and be sure to describe how NAD+ is recycled
Pyruvate is reduced by NADH to form lactate with no release of CO2+ thus recycling NADH
What is the role of the electron transport chain in forming the H+ gradient across the inner mitochondrial membrane?
Some members on the etc accept and release H+ and electrons and transfer them around eventually into the mitochondrial matrix and inner membrane space
Most of the NADH that delivers electrons to the electron transport chain comes from which of the following processes?
The citric acid cycle Both NADH and FADH2 are produced during the citric acid cycle
Which part of the catabolism of glucose by cellular respiration requires molecular oxygen (O2) and produces CO2?
The combination of the citric acid cycle and electron transport CO2 is produced in the citric acid cycle and O2 is taken up in the electron transport
Where do the reactions of glycolysis occur in an eukaryotic cell?
The cytosol
Describe what happens when NAD+ is reduced. What enzyme is involved?
The enzymatic transfer of 2 electrons and 1 proton (H+) from an organic molecule in food to NAD+ reduces the NAD+ to NADH; the second proton (H+) is released. The enzyme involved is dehydrogenase.
Three types of phosphorylation are covered I. The text and two of these occur in cellular respiration. Explain how the etc is utilized in oxidative phosphorylation.
The etc accepts electrons from the breakdown products of the first 2 stages of cellular respiration and passes the electrons from one molecule to the next
If muscle cells in the human body consume O2 faster than it can be supplied which of the following is likely to result?
The first three answers are correct. 1. Muscle cells would not be able to produce enough ATP to meet demands 2. oxidative phosphorylation would stop, 3. muscle cells would consume glucose at an increased rate.
Which of the following represents the major (but not only) energy accomplishment of the citric acid cycle?
The formation of NADH and FADH2 Each turn of the citric acid cycle releases carbon dioxide, forms one ATP by oxidative phosphorylation, and passes electrons to three NAD+ and one FAD.
Why is the citric acid cycle called a cycle?
The four-carbon acid that accepts the acetyl CoA in the first step of the cycle is regenerated by the last step of the cycle. The cycling referred to is that of the four-carbon compound
Where do the reactions of the citric acid cycle occur in eukaryotic cells?
The matrix of the mitochondrion The citric acid cycle, which takes place in the mitochondrial matrix, completes the degradation of glucose.
Why is the total count about 36 or 38 ATP rather than a specific number?
The number varies depending on what shuttle transports electrons from NADH in the cytosol. And scientists simply don't know for sure
In glycolysis, there is no production of carbon dioxide as a product of the pathway. Which of the following is the best explanation for this?
The products of glycolysis contain the same total number of carbon atoms as in the starting material. All of the carbon in one glucose molecule is accounted for in the two molecules of pyruvate produced by glycolysis
Explain what has happened to each of the six carbons found in the original glucose molecule
They are reduced into CO2
The following is a generalized formula for a redox rxn. Show which component is oxidized and which is reduced Xe- + Y => X + Ye-
Y is the reducing agent Xe- is the oxidizing agent
When protein molecules are used as fuel for cellular respiration, __________ are produced as waste.
amino groups The amino group is a residual product of amino acid catabolism.
During aerobic respiration, molecular oxygen (O2) is used for which of the following purposes?
at the end of the electron transport chain to accept electrons and form H2O O2 is the final electron acceptor
Of the metabolic pathways listed below which is the only pathway found in all organisms?
glycolysis Ancient prokaryotes probably used glycolysis to make ATP long before oxygen was present in Earth's atmosphere. Glycolysis is the most widespread metabolic pathway.
The function of cellular respiration is to __________.
harvest usable energy from glucose The most prevalent and efficient catabolic pathway is cellular respiration in which oxygen is consumed as a reactant along with glucose
Sports physiologists at an Olympic training center wanted to monitor athletes to determine at what point their muscles were functioning anaerobically. They could do this by checking for a buildup of which of the following compounds?
lactate In human muscle cells switch to tractate fermentation after becoming anaerobic
A molecule becomes more oxidized when it __________.
loses an electron
What is the meaning of glycolysis? What occurs in this step of cellular respiration?
"Sugar splitting" Chemical energy is harvested by oxidizing glucose to pyruvate
For the following pair which molecule is the oxidized form and which is reduced? Which molecule holds higher potential energy? Which is lower in potential energy? NAD+_______ NADH_______
NAD+= oxidized and lower NADH= reduced and higher
Which of the following substances is/are involved in oxidative phosphorylation?
ADP, oxygen, and ATP. ADP is converted to ATP during oxidative phosphorylation, and oxygen functions as the terminal electron acceptor for oxidative phosphorylation
The second form of phosphorylation is substrate level. Explain the direct transfer of a phosphate from an organic substrate to ADP to form ATP.
ATP is synthesis is powered by redox rxns on the etc
Explain how AMP stimulates cellular respiration while citrate and ATP inhibit it.
As ATP is used up, AMP accumulates which signals more ATP to be made. The more ATP there is, the slower glycolisis is.
What is the functions of the electron transport chain in cellular respiration?
Break the fall of electrons
Two keys terms are chemiosmosis and proton motive force. Relate both of these terms to the process of oxidative phosphorylation
C: energy coupling mechanism that uses energy from hydrogen ions to drive cellular work like ATP P: potential energy in a proton electrochemical gradient using H+ ions pumped across during chemiosmosis
Explain the difference in energy usage between the catabolic rxns of the cellular respiration and anabolic pathways of biosynthesis
C: energy released A: energy stored
Alcohol fermentation starts with glucose and yields ethanol. Explain this process and be sure to describe how NAD+ is recycled
CO2 releases form pyruvate and is converted to acetaldehyde which is then reduced to NADH to ethanol which regenerates the supply of NAD+ for future glycolysis
Which of the following best describes the electron transport chain?
Electrons are passed from one carrier to another, releasing a little energy at each step. NADH and FAD2 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 the following is the source of the energy that produces the chemiosmotic gradient in mitochondria?
Electrons moving down the electron transport chain Energy flow of the electrons along the etc is used to pump hydrogen ions (protons) across the inner mitochondrial membrane creating the chemiosmotic gradient
Explain the difference between fermentation and cellular respiration
F: partial degradation of sugars/organic fuel WITHOUT oxygen C: partial degradation of sugars/organic fuel WITH oxygen
How many molecules of ATP are generated by substrate-level phosphorylation from the complete breakdown of a single molecule of glucose in the presence of oxygen?
Four 2 ATP from glycolysis and one per each molecule of acetyl CoA oxidized in the citric acid cycle
When compounds lose electrons, they ________________ energy; when compounds gain electrons, they _______________ energy.
Gain, lose
The starting product of glycolysis is the six-carbon sugar _______, and the ending product is two ______ carbon compounds termed _____.
Glucose, organic, pyruvate
In the overall process of glycolysis and cellular respiration______________ is oxidized and_____________ is reduced
Glucose, oxygen In cellular respiration electrons and hydrogen are removed from glucose and added to oxygen
Oxygen stabilizes the electrons by combining with 2 hydrogen ions to form what compound?
H2O
During respiration, the electron transport chain occurs in the_________
Inner membrane of the mitochondrion The etc is an energy converter that uses the exergonic flow of electrons to pump hydrogen ions across the membrane matrix to intermebrane space
Each ATP molecule contains about 1% of the amount of chemical energy available from the complete oxidation of a single glucose molecule. Cellular respiration produces about 32 ATP from one glucose molecule. What happens to the rest of the energy in glucose?
It is converted to heat. The process is only about 38% efficient and the rest is lost as heat
Oxygen is the ultimate electron acceptor. Why is this?
It's very electronegative
For aerobic respiration to continue, the cell must be supplied with oxygen (the ultimate electron acceptor). What is the electron acceptor in fermentation?
NAD+
In cellular respiration electrons are not transferred directly from glucose to oxygen. Following the movement of hydrogens allows you to follow the flow of electrons. What electron carrier is hydrogen transferred to first?
NAD+
In glycolysis in the absence of oxygen cells need a way to regenerate which compound?
NAD+ The NAD+ needs to be regenerated, which is why ethyl alcohol or lactic acid is formed.
Which of the following statements is the best explanation of what happens to the temperature and carbon dioxide concentration during a one-hour class period in a classroom of 300 students if the heating and air conditioning is turned off and all the doors are kept closed?
Temperature and the level of carbon dioxide rise as heat and carbon dioxide are by-products of cellular respiration. The oxidation of organic molecules produces carbon dioxide and as the exergonic process of cellular respiration is not 100% efficient some energy is lost as heat
In an experiment, mice were fed glucose (C6H12O6) containing a small amount of radioactive oxygen. The mice were closely monitored, and after a few minutes radioactive oxygen atoms showed up in __________.
carbon dioxide One molecule of CO2 is formed when pyruvate is converted to acetyl CoA and two molecules of CO2 are produced in the citric acid cycle
Fermentation is essentially glycolysis plus an extra step in which pyruvate is reduced to form lactate or alcohol and carbon dioxide. This last step __________.
enables the cell to recycle the reduced NADH to oxidized NAD+ Normally reduced NADH delivers its electrons to the etc enabling NAD+ to be recycled to glycolysis
Give the formula (with names) for the catabolic degradation of glucose by cellular respiration.
organic compounds + oxygen --> carbon dioxide + water + energy
What are coenzymes?
organic molecules derived from vitamins that function in the transfer of a chemical group
What three organic macromolecules are often utilized to make ATP by cellular respiration?
proteins, carbohydrates, fats
Muscle tissues make lactate from pyruvate to do which of the following?
regenerate NAD+ Human muscle cells make ATP by lactic acid fermentation when oxygen is scarce. This allows them to regenerate NAD+ so that glycolysis can continue.
