Mitochondria and Respiration Flashcards
What do living cells require to do work?
Living cells require energy from outside sources to do work (ATP POWERS WORK)
What does the work of the cell include?
The work of the cell includes assembling polymers, membrane transport, moving, and reproducing
How do animals obtain energy to do work?
Animals can obtain energy to do this work by feeding on other animals or photosynthetic organisms
How do catabolic pathways generate heat?
Catabolic pathways release stored energy by breaking down complex molecules
What plays a main role in catabolic pathways?
Electron transfer plays a major role in these pathways
Is the breakdown of organic molecules exergonic or endergonic?
Exergonic, release of energy
What is fermentation?
Fermentation is a partial degradation of sugars that occurs without O2
What is the purpose of the transfer of electrons during chemical reactions
The transfer of electrons during chemical reactions releases energy stored in organic molecules This released energy is ultimately used to synthesize ATP
What is the purpose of the transfer of electrons during chemical reactions and what are these reactions known as?
The transfer of electrons during chemical reactions releases energy stored in organic molecules. This released energy is ultimately used to synthesize ATP They are known as - redox reactions
Give the chemical formula for respiration
Although carbohydrates, fats, and proteins are all consumed as fuel, it is helpful to trace cellular respiration with the sugar glucose C6H12O6 + 6 O2 → 6 CO2 + 6 H2O + Energy (ATP + heat)
During cellular respiration, what is oxidised and reduced and what does the redox reaction do?
The fuel (such as glucose) is oxidized, and O2 is reduced Energy is released as the electrons associated with hydrogen ions are transferred to oxygen, a lower energy state
Organic molecules with an abundance of hydrogen are excellent sources of high-energy electrons, why?
Because their bonds are a source of “hilltop” electrons, whose energy is released when they are transferred to oxygen
Why do oxidation/reduction always go together?
Because you always need a donor and a reciever for the electrons
How do redox reactions work on covalent bonds?
They add/reduce the electronegativity of molecules to pull the electrons in one direction or another. One side becomes slight oxidized, other slightly reduced.
Why do redox reactions yield chemical energy?
If the redox reaction relocates electrons closer to a more electronegative atom, the atom loses potential energy (it releases energy)
How does respiration yield energy?
It oxidizes glucose, freeing up stored energy from glucose that is available for ATP synthesis.
Electrons from organic compounds are first transfered to what?
Electrons from organic compounds are usually first transferred to NAD+, a coenzyme
What is the function of NAD+?
As an electron acceptor, NAD+ functions as an oxidizing agent during cellular respiration
What is NADH?
Each NADH (the reduced form of NAD+) represents stored energy that is tapped to synthesize ATP NADH passes the electrons to the electron transport chain
Is the electron transport chain a controlled or uncontrolled reaction?
Unlike an uncontrolled reaction, the electron transport chain passes electrons in a series of steps instead of one explosive reaction
How is energy then produced from the electron chain?
O2 pulls electrons down the chain in an energy-yielding tumble The energy yielded is used to regenerate ATP
How does the Ea barrier help in cellular respiration?
It prevents electrons from immediately rushing in and bonding wiht oxygen, allowing the sugar to be oxidized in a series of steps.
What is NAD+?
A coenzyme that hydrogen atoms are transferred to before being transferred to the oxygen
How does NAD+ trap electrons from glucose and other organic molecules and act as an oxidation agent?
Enzymes called dehydrogenases remove a pair of hydrogen atoms from the substrate, thereby oxidizing it. The enzyme delivers the two electrons along with only ONE of the protons to its coenzyme NAD+. The other proton is released as a hydrogen ion into the surrounding solution.
How does NAD+ neutralize its charge? What does it become?
By only accepting ONE proton and accepting TWO electrons, which cancels out the positive charge. NADH: because the hydrogen has been recieved.
What does each NADH molecule represent?
Stored energy that can be tapped to make ATP when electrons complete their journey down their energy gradient from NADH to oxygen, because molecules lose very little of their potential energy when they are transferred from food to NAD+
What is the differenece between cellular respiration and the reaction between hydrogen and oxygen to form water?
1) the hydrogen that reacts with oxygen is derived from an organic molecule 2) respiration uses an electron transport chain
What is the purpose of the electron transport chain?
To break the fall of electrons to oxygen into several energy-releasing steps instead of one explosive reaction
How does travel down the electorn transport chain work?
Electrons removed form food are brought to the top of the chain by NADH, and at the lower energy end, oxygen captures these electrons (H+) forming H2O, water. Each carrier is more electronegative than the last, ending with oxygen (the terminal electron acceptor)
Harvesting of energy from glucose has three stages, what are they?
- Glycolysis 2. Pyruvate oxidation and Citric Acid Cycle 3. Oxidative Phosphorylation
What is Glycolysis?
breaks down glucose into two molecules of pyruvate
What is the citric acid cycle?
it completes the breakdown of glucose
How many molecules of ATP is formed in the cell?
For each molecule of glucose degraded to CO2 and water by respiration, the cell makes up to 32 molecules of ATP
Where does oxidative phosphorylation occur in eukaryotes?
In most eukaryotes, this takes place inside mitochondria.
What is the process that generates almost 90% of ATP and why?
Oxidative phosphorylation because it is powered by redox reactions
What is the process that generates almost 90% of ATP and why?
Oxidative phosphorylation because it is powered by redox reactions. Oxidative phosphorylation (accounts for most of the ATP synthesis)
Where is the smaller amount of ATP formed?
A smaller amount of ATP is formed in glycolysis and the citric acid cycle by substrate-level phosphorylation
Describe glycolysis
Glycolysis (“sugar splitting”) breaks down glucose into two molecules of pyruvate Glycolysis occurs in the cytoplasm and has two major phases -Energy investment phase -Energy payoff phase Glycolysis occurs whether or not O2 is present
Where does Glycolysis occur?
Glycolysis occurs in the cytoplasm
What are the two major phases of glycolysis?
-Energy investment phase -Energy payoff phase
Does glycolysis need oxygen?
No
What is the energy investment phase?
2 ATP’s are used to break down glucose to give off 2 ADP’s and 2 Phosphates
What is the energy payoff phase?
4 ADP’S and 4 Phosphates forms four ATP’s 2 NAD+ + 4é + 4H+ gives 2NADH + 2H+ In this phase, the glucose becomes 2 pyruvate and 2H20
What is the net production of glycolysis?
Glucose -> 2 Pyruvate + 2H20 4 ATP formed - 2ATP used -> 2ATP 2NAD+ +4é + 4H+ -> 2NADH + 2H+
Describe the changes in the energy investment phase?
- Glucose uses ATP to give off ADP and form Glucose-6-Phosphate with help from hexokinase 2. To Fructose-6-Phosphate by Phosphoglucoisomerase 3. Uses ATP to give off ADP and forms Fructose 1,6 - biphosphate by help of phosphofructokinase 4. By aldolase, it forms Glyceraldehyde 3-Phosphate (G3P) and reversibly isomerised to Dihydroxyacetonephosphate (DHAP)
Describe the changes in the energy payoff phase?
- Glyceraldehyde 3-Phosphate (G3P) is coverted to 1,3,Biphosphoglycerate with help from Triosephosphatedehyrogenase and gives off 2NADH + 2H+ from 2 NAD+ + 4é + 4H+ 2. 1,3,Biphosphoglycerate is converted to 3-Phosphoglycerate with help from Phospholycerokinase and releases 2ATP from 2ADP 3. 3-Phosphoglycerate is converted 2- Phosphoglycerate with help from phosphoglyceromutase 4. 2- Phosphoglycerate is converted to Phosphoenolpyruvate (PEP) with help from Enolase and releases 2H20 5. Phosphoenolpyruvate (PEP) is converted to pyruvate with help from pyruvatekinase and releases 2ATP from 2ADP
Describe the oxidation of Pyruvate to Acetyl CoA
In the presence of O2, pyruvate enters a mitochondrion (in eukaryotic cells), where the oxidation of glucose is completed Before the citric acid cycle can begin, pyruvate must be converted to acetyl coenzyme A (acetyl CoA), which links glycolysis to the citric acid cycle This step is carried out by a multienzyme complex that catalyzes three reactions 1. Oxidation of pyruvate and release of CO2 2. Reduction of NAD+ to NADH 3. Combination of the remaining two-carbon fragment and coenzyme A to form acetyl CoA
What processes does the multienzyme complex catalyzes three reactions
- Oxidation of pyruvate and release of CO2 2. Reduction of NAD+ to NADH 3. Combination of the remaining two-carbon fragment and coenzyme A to form acetyl CoA
Before the citric acid cycle can begin, pyruvate must be converted to what and why?
Acetyl coenzyme A (acetyl CoA), which links glycolysis to the citric acid cycle
Describe the citric acid cycle
The citric acid cycle, also called the Krebs cycle, completes the breakdown of pyruvate to CO2 The cycle oxidizes organic fuel derived from pyruvate, generating 1 ATP, 3 NADH, and 1 FADH2 per turn The citric acid cycle has eight steps, each catalyzed by a specific enzyme The acetyl group of acetyl CoA joins the cycle by combining with oxaloacetate, forming citrate The next seven steps decompose the citrate back to oxaloacetate, making the process a cycle The NADH and FADH2 produced by the cycle relay electrons extracted from food to the electron transport chain
What is the purpose of the citric acid cycle?
The citric acid cycle, also called the Krebs cycle, completes the breakdown of pyruvate to CO2 and produce energy which comes in the form of NADH and FADH2
What does the citric acid cycle generate?
The cycle oxidizes organic fuel derived from pyruvate, generating 1 ATP, 3 NADH, and 1 FADH2 per turn
What are the eight steps composed of in the citric acid cycle
The acetyl group of acetyl CoA joins the cycle by combining with oxaloacetate, forming citrate The next seven steps decompose the citrate back to oxaloacetate, making the process a cycle
What are the products of glycolysis?
The net end products of glycolysis are two Pyruvate (three-carbon sugars), two NADH, and two ATP
Describe how the electrons from NADH and FADH2 are fed into the electron transport chain
These two electron carriers donate electrons to the electron transport chain, which powers ATP synthesis via oxidative phosphorylation
What accounts for most of the energy extracted from food?
Following glycolysis and the citric acid cycle, NADH and FADH2 account for most of the energy extracted from food
What processes are in the mitochondria?
Pyruvate oxidation, citric acid cycle, oxidative phosphorylation
Describe the Pathway of Electron Transport
- The electron transport chain is in the inner membrane (cristae) of the mitochondrion - Most of the chain’s components are proteins, which exist in multiprotein complexes - Electrons drop in free energy as they go down the chain and are finally passed to O2, forming H2O - Electron carriers alternate between reduced and oxidized states as they accept and donate electrons - Electrons are transferred from NADH or FADH2 to the electron transport chain - Electrons are passed through a number of proteins including cytochromes (each with an iron atom) to O2 - The electron transport chain generates no ATP directly - It breaks the large free-energy drop from food to O2 into smaller steps that release energy in manageable amounts -Certain electron carriers in the electron transport chain accept and release H+ along with the electrons In this way, the energy stored in a H+ gradient across a membrane couples the redox reactions of the electron transport chain to ATP synthesis. -The H+ gradient is referred to as a proton-motive force, emphasizing its capacity to do work
Where is the electron transport chain located?
The electron transport chain is in the inner membrane (cristae) of the mitochondrion
Most of the electron chain’s components are what and how do they exist?
Most of the chain’s components are proteins, which exist in multiprotein complexes
What are the products of the citric acid cycle?
6 NADH + H+ molecules, two FADH2 molecules, four carbon dioxide molecules, and two ATP molecules.
What is the product of the electron transport chain?
Electrons from NADH and FADH2 pass through the electron transport chain to oxygen, which is reduced to water.
What does oxidative phosphorylation comprise of?
Electron transport chain and Chemiosmosis
Why is the the H+ gradient referred to as a proton-motive force?
Emphasizes its capacity to do work
What is Chemiosmosis?
The use of energy in a H+ gradient to drive cellular Work.
Describe Chemiosmosis: The Energy-Coupling Mechanism
- The energy released as electrons are passed down the electron transport chain is used to pump H+ from the mitochondrial matrix to the intermembrane space - H+ then moves down its concentration gradient back across the membrane, passing through the protein complex ATP synthase - H+ moves into binding sites on the rotor of ATP synthase, causing it to spin in a way that catalyzes phosphorylation of ADP to ATP - This is an example of chemiosmosis, the use of energy in a H+ gradient to drive cellular work
What energy is used for chemiosmosis?
The energy released as electrons are passed down the electron transport chain is used to pump H+ from the mitochondrial matrix to the intermembrane spac
The production of ATP using the process of chemiosmosis in mitochondria is known as what?
Oxidative phosphorylation, after hydrogen ions are pumped into the mitochondrial intermembrane space, they flow back through ATP synthase, which produces most of the ATP associated with cellular respiration
During cellular respiration, what is the sequence for energy flow
Glucose → NADH → electron transport chain → proton-motive force → ATP
How much ATP is made during cellular respiration?
32 ATP, The rest of the energy is lost as heat
What does most cellular respiration depend on?
Electronegative oxygen to pull electrons down the transport chain
What would happen to the electron transport chain without oxygen and what would happen?
Without oxygen, the electron transport chain will cease to operate. In that case, glycolysis couples with anaerobic respiration or fermentation to produce ATP
What does anaerobic respiration use for the final electron acceptor?
Anaerobic respiration uses an electron transport chain with a final electron acceptor other than oxygen, for example, sulfate
Does fermentation use the electron transport chain to generate ATP
Fermentation uses substrate-level phosphorylation instead of an electron transport chain to generate ATP
Compare fermentation with anaerobic and aerobic respiration
i. All use glycolysis to oxidize glucose and harvest the chemical energy of food ii. In all three, NAD+ is the oxidizing agent that accepts electrons during glycolysis iii. The processes have different mechanisms for oxidizing NADH to NAD+: In fermentation, an organic molecule (such as pyruvate or acetaldehyde) acts as a final electron acceptor, whereas in cellular respiration, electrons are transferred to the electron transport chain iv. Cellular respiration produces 32 ATP per glucose molecule; fermentation produces 2 ATP per glucose molecule
Wahat are the two common types of fermentation?
Alcohol and lactic acid fermentation
What does fermentation consist of?
Fermentation consists of glycolysis plus reactions to regenerate NAD+, which can be reused by glycolysis.
Describe how in alcohol fermentation pyruvate is converted to ethanol
i. The first step releases CO2 from pyruvate to form 2 Acetaldehyde ii. The second step produces 2 NAD+ from 2NADH and 2H+ and 2 ethanol
Alcohol fermentation by yeast is used in what?
Brewing, winemaking, and baking
Describe how in lactic acid fermentation, pyruvate is converted to lactic acid
-In lactic acid fermentation, pyruvate is reduced by NADH, forming 2NAD+ and 2 lactate as end products, with no release of CO2
Give applications of lactic acid fermentation
-Lactic acid fermentation by some fungi and bacteria is used to make cheese and yogurt -Human muscle cells use lactic acid fermentation to generate ATP during strenuous exercise when O2 is scarce
What are obligate anaerobes and give examples
Obligate anaerobes carry out fermentation or anaerobic respiration and cannot survive in the presence of O2 Yeast and many bacteria are facultative anaerobes, meaning that they can survive using either fermentation or cellular respiration
Which statement about the citric acid cycle is true? a) It occurs during the movement from the cytosol through the mitochondrial membranes. b) It makes ATP through substrate-level phosphorylation. c) It makes the most ATP compared to the other steps in the breakdown of glucose. d) It occurs in the eukaryotic cytoplasm. e) It splits glucose.
b) It makes ATP through substrate-level phosphorylation.
What is the breakdown of ATP in respiration
Glycolysis: 2 ATP. Krebs Cycle: 2 ATP. Oxidative Phosphorylation (Electron Transport Chain/Chemiosmosis): 28 ATP
What do cells require to sustain high rates of glycolysis under anaerobic conditions? a) functioning mitochondria b) oxygen c) oxidative phosphorylation of ATP d) NAD+ e) all of the above
d) NAD+
ATP synthase at the inner mitochondrial membrane makes ATP and water from ADP and phosphate by coupling this to which other process? a) allowing H+ to move down its electrochemical gradient b) allowing H+ to move against its electrochemical gradient c) synthesis of H+ d) active transport of H+ e) active transport of Na+
a) allowing H+ to move down its electrochemical gradient
Which of the following is not an immediate net product of the typical mitochondrial electron transport chain? a) ATP b) water c) NAD+ d) FAD e) a proton electrochemical gradient
a) ATP
Through beta oxidation, fats are converted to acetyl CoAs. The further respiration of these acetyl CoAs typically bypasses which parts of normal aerobic respiration? a) the citric acid cycle and oxidative phosphorylation b) glycolysis and chemiosmosis c) the citric acid cycle and fermentation d) pyruvate oxidation and the citric acid cycle e) glycolysis and pyruvate oxidation
e) glycolysis and pyruvate oxidation
If you removed the inner membrane of the mitochondrion, could the cell produce any ATP from glucose? a) yes, by glycolysis and fermentation b) yes, by the citric acid cycle c) yes, using the ATP synthase d) yes, by electron transport
a) yes, by glycolysis and fermentation
If your cells were in need of ATP, what could help you? a) substrate-level phosphorylation b) ATP synthase c) glycolysis d) fermentation e) all of the above
e) all of the above
Which of the following contains useful energy for the cell? a) ATP b) NAD+ c) proton gradient d) a and c e) b and c
d) a and c
What has more free energy, carbon dioxide and water or glucose and oxygen, and why? a) glucose and oxygen because they have not yet reacted b) carbon dioxide and water because carbon dioxide is a gas with great molecular motion c) glucose and oxygen because oxygen stores energy for cells d) carbon dioxide and water because water can catalyze many energy-producing reactions
a) glucose and oxygen because they have not yet reacted
Where is the Electron Transport Chain located?
In the cristae or inner membrane of the mitochondria
What are two common electron carriers?
NADH and FADH2
ATP synthase uses an _________________________ to drive ___________________ of ATP.
ATP synthase uses an exergonic reaction to drive phosphorylation of ATP.
How is water created?
Oxygen is the final electron acceptor which when combined with the H+ ions (electrons) is converted into water H2O.
What is the Electron chain net gain?
6 H2O 28-30 ATP
Cellular respiration can best be described as what?
taking electrons from food and giving them to oxygen to make water and using the energy released to drive ATP formation.
Drugs known as uncouplers facilitate diffusion of protons across the membrane. Brown fat can generate heat without ATP by using uncouplers. With an uncoupler, what will happen to ATP synthesis and oxygen consumption if the rates of glycolysis and the citric acid cycle stay the same
ATP synthesis will decrease; oxygen consumption will stay roughly the same.
Newborn mammals have a specialized organ called brown fat, where cells burn fat to CO2 without capturing the energy to reduce electron carriers or drive ATP formation. How can this energy be used instead?
To generate Heat
Name the 3-carbon molecule that is an intermediate compound in both aerobic and anaerobic respiration?
Pyruvic Acid
How many carbons does Acetyl coA have?
2
How many carbons does Pyruvic acid have?
3
What is the name of the two-carbon compound into which pyruvate may be broken down under aerobic conditions
Acetyl Coenzyme A
Describe the fate under aerobic conditions, of Acetyl Co-enzyme A
Enters Krebs Cycle
At the end of the electron transport chain, what happens to the electrons?
Transfered to Oxygen and H+
Suggest a situation in which some cells in the human body may not be able to engage in the second stage of aerobic respiration
-Lack of Oxygen -Exercise -Restricted blood supply
What is the role of ATP in cells?
ATP is a molecule that acts as an intermediary to store chemical energy for cellular work.
Under aerobic conditions, the pyruvate is converted to an acetyl group and in the process a small molecule is released. Name this small molecule
Carbon Dioxide
Why is respiration essential to living things
Provides energy for all reactions in a cell such as movement of muscles, growth of new cells
Why does stage two occur in the matrix of the mitochondria?
Necessary enzymes are found here
How is the Acetyl group formed from the Pyruvic acid?
Removal of CO2 molecule
In the overall process of glycolysis and cellular respiration, __________ is oxidized and __________ is reduced. glucose … oxygen carbon dioxide … water oxygen … ATP ATP … oxygen glucose … ATP
glucose … oxygen
What is the name given to the production of ATP by electron transport chain?
Oxidative Phosphorylation
What is the main significance of electron transport system?
It produces rich ATP
If oxygen is absent, why would aerboic organisms die?
There is no oxygen to accept low energy electron and no ATP is formed - no energy for all cell reactions
What is the purpose of the Krebs cycle?
To make as many NADH molecules as possible
Name a substance produced during aerobic respiration which is not a product of fermentation
Water
Give a brief summary in order of respiration
oxidation of glucose to pyruvate; oxidation of pyruvate; citric acid cycle; oxidative phosphorylation
Oxygen gas (O2) is one of the strongest oxidizing agents known, why?
The oxygen atom is very electronegative
The oxidation of glucose leads to what?
resulting in the production of carbon dioxide
The reduction of oxygen leads to what?
resulting in the production of water
What happens to the temperature and carbon dioxide concentration during a 1-hour class period in a classroom of 300 students if the heating and air conditioning is turned off and all doors are kept closed?
Temperature and the level of carbon dioxide rise as heat and carbon dioxide are by-products of cellular respiration.
A small amount of ATP is made in glycolysis by which process
transfer of a phosphate group from a fragment of glucose to ADP by substrate-level phosphorylation (glucose is phosphorylated at the beginning of glycolysis)
Question 12: 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 kill bacteria in people with infections. However, he cannot do this, why?
human cells must also perform glycolysis; the drug might also poison them
How does one know that there is no production of carbon dioxide in glycolysis
The products of glycolysis contain the same total number of carbon atoms as in the starting material.
n preparing pyruvate to enter the citric acid cycle, what step must occur?
Pyruvate is oxidized and a molecule of carbon dioxide is removed. The electrons removed in this process are used to reduce NAD+ to NADH.
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.
How many molecules of ATP are gained by substrate-level phosphorylation from the complete breakdown of a single molecule of glucose in the presence of oxygen?
There is a net gain of two ATP from glycolysis and one from each molecule of acetyl CoA oxidized in the citric acid cycle for a total of four per glucose.
What happens in the conversion of pyruvate to acetyl CoA before the citric acid cycle?
The carboxyl group of pyruvate is removed as a carbon dioxide molecule. The remaining two-carbon fragment is oxidized to acetate and NAD+ is reduced to NADH.
Energy for synthesizing ATP is obtained by ATP synthase directly from which process?
Hydrogen ions flow along an electrochemical gradient across the inner mitochondrial membrane. The gradient is the source of the energy for ATP production.
When a poison such as cyanide blocks the electron transport chain, glycolysis and the citric acid cycle also eventually stop working, why?
Unless the electron transport molecules (NADH and FADH2) can recycle back to their oxidized states (NAD+ and FAD), they will be unable to receive electrons in the other steps of cellular respiration.
Most of the electrons removed from glucose by cellular respiration are used for what?
producing a proton gradient for ATP synthesis in the mitochondria driving substrate-level phosphorylation in glycolysis
Why is ethanol or lactate formed in fermentation?
The NAD+ needs to be regenerated,
Question 42: If muscle cells in the human body consume O2 faster than it can be supplied, what will occur?
The muscle cells will have more trouble making enough ATP to meet their energy requirements. The cells will not be able to carry out oxidative phosphorylation. The cells will consume glucose at an increased rate.
