Flashcards
Click each question to see the answer! Cards are organized by subject.
Overview of Cellular Respiration:
What is cellular respiration?
The process by which a cell breaks down a glucose molecule to create energy in the form of ATP.
What is the general equation, in words, for aerobic respiration?
Glucose + Oxygen → Carbon Dioxide + Water + Energy
How many ATP does cellular respiration produce??
36-38 ATP
What is the general equation for aerobic respiration?
C6H12O6 + 6O2 → 6CO2 + 6H20 + 36-38 ATP
What are the processes of aerobic respiration?
Glycolysis, acetyl CoA formation, Krebs cycle, and oxidative phosphorylation.
What is ATP?
A main source of energy for cells.
The energy released in aerobic respiration is originally from what?
The food we eat and oxygen we inhale.
The energy from the food we eat is stored as potential energy in the form of what?
Covalent bonds.
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What is reduction?
The gain of electrons.
What is oxidation?
The loss of electrons.
What is a reducing agent?
The donator (loser) of hydrogen/electrons.
What is a oxidizing agent?
The acceptor of hydrogen/electrons from the donator.
Is NAD+ a reducing agent or oxidizing agent?
Oxidizing agent, therefore NADH is the reducing agent.
Is respiration exergonic or endergonic and exothermic or endothermic?
Exothermic and exergonic
What do electron carriers do in the cell?
Help transport electrons.
What are the electron carriers in respiration?
NAD+ and FAD
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Glycolysis:
What is glycolysis?
The first process of cellular respiration in which a glucose molecule is broken into two pyruvic acids.
Where does glycolysis take place in the cell?
In the cytoplasm.
What are the two phases of glycolysis?
The energy investment phase (where glucose is broken down and turned into two trioses by investing two ATP) and the energy yielding phase (will result in making four ATP, two of which are countered by the energy investment phase, making for the output of two net ATP; also outputs two pyruvate and two NADH).
What is the very first step in glycolysis that commits the entire stage of glycolysis will take place afterwards?
The energy investing phase in which an ATP is used to phosphorylate glucose.
What is the key regulatory enzyme of glycolysis?
Phosphofructokinase (PFK)
How does PFK regulate glycolysis?
PFK is an allosteric enzyme that is induced (activated) by high levels of ADP or AMP that show a cell needs ATP, or inhibited (deactivated) by high levels of ATP and citrate (another indication that the cell has enough ATP; learn more in Krebs cycle). By being induced or inhibited, PFK can accelerate, decelerate or stop glycolysis.
What are the inputs of glycolysis?
Glucose + 2NAD+ + 2ADP + 2Pi
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What are the net outputs of glycolysis?
2 Pyruvate + 2NADH + 2H+ + 2ATP
What are electrons shuttles?
Helpers in the cytoplasm that will take the NADH made in glycolysis to the electron transport chain to be regenerated to keep glycolysis going. Electron shuttles go back and forth from gylcolysis in the cytoplasm to the mitochondria to transfer electrons.
What are two examples of electron shuttles?
Glycerol 3-phosphate and malate-aspartate
Substrate level phosphorylation is endergonic or exergonic?
Endergonic
High levels of ATP inhibit what in glycolysis?
Phosphofructokinase (PFK)
What will a molecule that closely mimics the structure of glucose but is not metabolized do to glycolysis?
Act as a metabolic poison and directly interfere with glycolysis.
Will glycolysis occur in aerobic or anaerobic conditions?
Both, as no oxygen is required for as long as stored NAD+ is available.
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Acetyl CoA Formation:
What is the basic concept of acetyl CoA formation?
Pyruvate will be oxidized into acetyl CoA.
Where does pyruvate come from to be made into acetyl CoA?
Pyruvate will come from the cytoplasm, where it has been made through glycolysis, by attatching to a specific transport protein that will bring pyruvate inside the mitochondria.
How many acetyl CoA will be made for each glucose?
Two acetyl CoA per glucose, as glucose is made into two pyruvate and each pyruvate will make one acetyl CoA.
How is acetyl CoA made?
Once pyruvate has entered the mitochondria, a pyruvate dehydrogenase on the mitochondrial membrane will oxidize it into pyruvate and convert it into acetyl CoA.
Where is acetyl CoA made in the cell?
Inside the mitochondria.
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What will inhibit pyruvate dehydrogenase?
High levels of acetyl CoA, NADH or GTP.
What will induce pyruvate dehydrogenase?
High levels of CoA, NAD+, or GDP.
What happens with excess acetyl CoA?
If it cannot be used in Krebs cycle, is will convert to malonyl CoA or other intermediates of acetyl CoA and be stored as fat.
What are the inputs of acetyl CoA formation per pyruvate?
Pyruvate + NAD+ + CoA
What are the outputs of acetyl CoA formation per pyruvate?
Acetyl CoA + NADH
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Krebs Cycle:
What is another name for the Krebs cycle?
The citric acid cycle, or less commonly the tricaboxylic acid cycle.
Where does the Krebs cycle occur in the cell?
Primarily on the matrix of the mitochondria.
What is the first committed step of the Krebs cycle?
The conversion of acetyl coA into six-carbon citrate by citrate synthase.
What are the inducers and inhibitors of citrate synthase?
Induced by AMP, inhibited by ATP.
What is the rate limiting step of the Krebs cycle?
The changing of isocitrate by isocitrate dehydrogenase.
What will accelerate and decelerate the Krebs cycle?
ADP will accelerate the Krebs cycle, as more ATP tells the cell it is running low on ATP. High levels of NADH or ATP will decelerate the Krebs cycle, as they are indicators of enough ATP.
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What is the third level of control of the Krebs cycle?
The activity of a-ketoglutarate dehydrogenase, which will turn a-ketoglutarate and CoA into succinyl CoA.
What will inhibit the a-ketoglutarate dehydrogenase?
NADH, succinyl CoA and ATP.
How many times will the Krebs cycle run per glucose?
Twice, as glucose turns into two pyruvate and then two acetyl CoA, and Krebs cycle uses one acetyl CoA per cycle.
What are the inputs of one Krebs cycle?
Acetyl CoA + 3NAD+ + FAD + ADP + Pi + 2H2O
What are the outputs of one Krebs cycle?
2CO2 + 3NADH + 3H+ + FADH2 + ATP + CoA
How many NADH, H+ and FADH2 are produced per glucose?
6NADH, 6H+, 2FADH2
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Oxidative Phosphorylation:
What is oxidative phosphorlation?
The process by with the most ATP is made in cellular respiration.
Where does oxidative phosphorylation take place?
In the innermemebrane of the mitochondria, where the electron transport chain is located.
What is the electron transport chain?
A series of membrane proteins in the mitochondria's innermembrane that transports electrons from NADH and FADH2 to the final electron acceptor, oxygen.
How does oxidative phosphorylation make ATP?
As NADH and FADH2 lose their protons to oxygen on the electron transport chain, a proton electrochemical gradient is created that has enough power, after the transfer of three or four protons, to fuel ATP synthase and make ATP. Another proton then exports ATP from the mitochondria and into the cytoplasm of the cell.
When is the electron transport chain used in the cell?
The electron transport chain is used throughout cellular respiration to regenerate amounts of NAD+ and FAD, which drive glycolysis, acetyl CoA and Krebs cycle.
How many electrons and protons can NAD+ carry?
NAD+ can carry two electrons and one proton.
How many electrons and protons can FAD carry?
Two electrons and two protons.
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How many ATPs are made due to FADH2's electron transfer? Why does it make this many?
Two ATPs per FADH2 due to FADH2's ability to transfer electrons at a lower energy level than NADH.
What are the inputs of oxidative phosphorylation?
NADH + FADH2 + ADP + Pi + O2
What are the outputs of oxidative phosphorylaiton per NADH and FADH2?
NAD+ + FAD + ATP + H20
How many ATP will oxidative phosphorylation produce?
32-34 ATP
How are so many ATP produced per glucose in oxidative phosphorylation?
Since three to four protons are needed to make and transport a single ATP generated by the electrochemical gradient, and NADH will transport 10 protons and FADH2 will transport six protons, each NADH will make approximately three ATP and each FADH2 two ATP. Per glucose there will be: Two NADH from glycolysis, two NADH from acetyl CoA, and six NADH from Krebs cycle. That totals 10 NADH, and 10 * 3 = 30 ATP. Two FADH2 will be produced in Krebs cycle per glucose, so 2 * 2 = 4 ATP. This totals 34 ATP produced. The 32-34 ATP estimate accounts for the approximation of protons transported per electron.
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The Big Picture:
Where will pyruvate generated from glycolysis go?
It will leave the cytoplasm and be brought to the mitochondria for acetyl coA formation.
Where will the 2NADH, 2H+ and 2ATP go after glycolysis?
Both the NADH and H+ will go to the electron transport chain on the innermembrane of the mitochondria. ATP will stay in the cytoplasm to be used by the cell.
Where will acetyl CoA be taken after being produced from pyruvate?
To the matrix of the mitochondria for the Krebs cycle.
Where does NADH made during acetyl CoA formation go?
To the electron transport chain on the innermembrane of the mitochondria.
Where do the outputs of the Krebs cycle go?
Carbon dioxide will be taken out of the cell, NADH, H+ and FADH2 will go to the electron transport chain, ATP will removed from the mitochondria and taken to the cytoplasm to be used by cells, and CoA will stay in the mitochondria for use in acetyl CoA formation.
What will happen to the outputs of the electron transport chain and oxidative phosphorylation?
NAD+ and FAD will be moved to storage for use in glycolysis, acetyl CoA formation, and the Krebs cycle where is will be replinished to NADH and FADH2 to continue fueling the electron transport chain and in turn all of cellular respiration. ATP will be brought out of the mitochondria into the cytoplasm to be used by the cell. H20 will be used in Krebs cycle or by the cell if needed, or leave the cell with cell waste (ex. sweating).
How is ATP made during respiration?
During substrate level phosphorylation and oxidative phosphorylation.
How does substrate level phosphorylation work?
ATP is made by adding a phosphate to ADP using a kinase enzyme during glycolysis. It will generate a limited amount of ATP's and is the only
source of ATP in anaerobic fermentation.
How does oxidative phosphorylation work?
The transfer of electrons by NADH and FADH2 in the electron transport chain will create a proton gradient to fuel the creation and release of ATP.
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At what point will a cell stop aerobic respiration and switch to anaerobic fermentation?
Oxygen is first needed in oxidative phosphorylation to act as the major electron acceptor on the electron transport chain. O2 will combine with protons, H+, from NADH and FADH2 to produce water. However, Krebs cycle will stop functioning next, as stores of FAD run out. As NAD+ is running out as well, Krebs will not generating CoA. Lack of CoA will shut down acetyl CoA formation. As NAD+ stores empty, Glycolysis will not be able to function, however, anaerobic respiration/fermentation will kick in before glycolysis will halt.
What forms of anaerobic respiration/fermentation are there?
Anaerobic respiration is possible with abundant NO3- or SO4- to accept electrons form the electron transport chain. However, this ONLY occurs with anaerobes. More common is anaerobic fermentation, in forms of alcohol and lactic acid fermentation.
How does alcoholic fermentation work?
Glycolysis will continue to function as pyruvate is broken down by pyruvate decarboxylase into acetaldehyde, which broken down by alcohol dehydrogenase into ethanol to replinish amounts of NAD+. It is ineffcient because per glucose, only two ATP are made. Does not work in animals.
What are the inputs of alcholoic fermentation?
Glucose + 2ADP + 2Pi
What are the outputs of alcoholic fermentation?
2 Ethanol + 2CO2 + 2ATP
How does lactic acid fermentation work?
Lactic acid fermentation is carried out by animals as they lack pyruvate decarboxylase. During O2 deprivation, an animal's muscle cells will make pyruvate though glycolysis, breaking pyruvate down with lactate dehydrogenase to make lactate. This breaking down replinishes NAD+. It is highly ineffcient as only 2ATP are produced per glucose. Only used for quick bursts of energy.
What are the inputs of lactic acid fermentation?
Glucose + 2ADP + 2Pi
What are the outputs of lactic acid fermentation?
2 Lactate + 2ATP
How does cellular respiration drive the processes of the biosphere?
Cellular respiration uses oxygen made by photosynthesis to break down glucose and fuel heterotrophs. In the breaking down of glucose in cellular respiration, carbon dioxide is released. Carbon dioxide can then be used by autotrophs to fuel photosynthesis, who will release oxygen in the formation of glucose. This cycle fuels most organisms in the biosphere.
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