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Questions and Answers
What is the primary source of energy for living cells?
What is the primary source of energy for living cells?
What process generates O2 and organic molecules in ecosystems?
What process generates O2 and organic molecules in ecosystems?
Which type of respiration occurs without the presence of O2?
Which type of respiration occurs without the presence of O2?
What is the main product of aerobic respiration?
What is the main product of aerobic respiration?
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In what organelle does cellular respiration primarily occur?
In what organelle does cellular respiration primarily occur?
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What type of respiration uses compounds other than O2?
What type of respiration uses compounds other than O2?
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How does energy flow through an ecosystem?
How does energy flow through an ecosystem?
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Which statement accurately describes fermentation?
Which statement accurately describes fermentation?
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What is the main purpose of glycolysis?
What is the main purpose of glycolysis?
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How many NADH molecules are generated in glycolysis?
How many NADH molecules are generated in glycolysis?
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What occurs in the mitochondrion after pyruvate is oxidized?
What occurs in the mitochondrion after pyruvate is oxidized?
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What is the total ATP yield from one glucose molecule at maximum, through cellular respiration?
What is the total ATP yield from one glucose molecule at maximum, through cellular respiration?
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Which metabolic pathway is described as the 'splitting of sugar'?
Which metabolic pathway is described as the 'splitting of sugar'?
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What is produced during the energy investment phase of glycolysis?
What is produced during the energy investment phase of glycolysis?
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What is the net gain of ATP from glycolysis per glucose molecule?
What is the net gain of ATP from glycolysis per glucose molecule?
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In terms of energy, what role do electron shuttles play in the mitochondrion?
In terms of energy, what role do electron shuttles play in the mitochondrion?
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Which of the following correctly describes glycolysis?
Which of the following correctly describes glycolysis?
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What role does NADH play during cellular respiration?
What role does NADH play during cellular respiration?
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In which stage of cellular respiration is the majority of ATP produced?
In which stage of cellular respiration is the majority of ATP produced?
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What is the primary outcome of the citric acid cycle?
What is the primary outcome of the citric acid cycle?
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Which process is characterized by an explosive release of energy?
Which process is characterized by an explosive release of energy?
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What represents the controlled release of energy in cellular respiration?
What represents the controlled release of energy in cellular respiration?
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Which reactant is necessary for the oxidative phosphorylation stage of cellular respiration?
Which reactant is necessary for the oxidative phosphorylation stage of cellular respiration?
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What is formed as a direct result of the reaction involving $H_2$ and $1/2 O_2$?
What is formed as a direct result of the reaction involving $H_2$ and $1/2 O_2$?
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What is produced when pyruvate is converted to acetyl CoA?
What is produced when pyruvate is converted to acetyl CoA?
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How many ATP molecules are produced per turn of the citric acid cycle?
How many ATP molecules are produced per turn of the citric acid cycle?
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What role do NADH and FADH2 play in cellular respiration?
What role do NADH and FADH2 play in cellular respiration?
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Which of the following describes the citric acid cycle?
Which of the following describes the citric acid cycle?
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How many NADH molecules are generated from two turns of the citric acid cycle?
How many NADH molecules are generated from two turns of the citric acid cycle?
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What is acetyl CoA's primary function in cellular respiration?
What is acetyl CoA's primary function in cellular respiration?
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What key molecule is produced alongside each turn of the citric acid cycle?
What key molecule is produced alongside each turn of the citric acid cycle?
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Which enzyme complex is responsible for the conversion of pyruvate to acetyl CoA?
Which enzyme complex is responsible for the conversion of pyruvate to acetyl CoA?
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What is the primary final electron acceptor in fermentation?
What is the primary final electron acceptor in fermentation?
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How much ATP is produced during fermentation per glucose molecule?
How much ATP is produced during fermentation per glucose molecule?
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Which of the following describes obligate anaerobes?
Which of the following describes obligate anaerobes?
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What role does glycolysis play in both aerobic and anaerobic processes?
What role does glycolysis play in both aerobic and anaerobic processes?
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Which of the following statements is true regarding the evolutionary significance of glycolysis?
Which of the following statements is true regarding the evolutionary significance of glycolysis?
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What is the end product of lactic acid fermentation?
What is the end product of lactic acid fermentation?
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Which organisms are considered facultative anaerobes?
Which organisms are considered facultative anaerobes?
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What is the main purpose of glycolysis in cellular metabolism?
What is the main purpose of glycolysis in cellular metabolism?
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What is the primary function of the electron transport chain in the mitochondrion?
What is the primary function of the electron transport chain in the mitochondrion?
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What is the final electron acceptor in the electron transport chain?
What is the final electron acceptor in the electron transport chain?
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How does ATP synthase generate ATP during chemiosmosis?
How does ATP synthase generate ATP during chemiosmosis?
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What is the main energy source for the ATP produced during cellular respiration?
What is the main energy source for the ATP produced during cellular respiration?
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What role do protons (H+) play in the electron transport chain?
What role do protons (H+) play in the electron transport chain?
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What percentage of energy from glucose is typically transferred to ATP during cellular respiration?
What percentage of energy from glucose is typically transferred to ATP during cellular respiration?
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What happens to oxygen at the end of the electron transport chain?
What happens to oxygen at the end of the electron transport chain?
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Which component of the inner mitochondrial membrane is primarily responsible for phosphorolating ADP into ATP?
Which component of the inner mitochondrial membrane is primarily responsible for phosphorolating ADP into ATP?
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What process utilizes the proton gradient established by the electron transport chain?
What process utilizes the proton gradient established by the electron transport chain?
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What are the multi-protein complexes within the electron transport chain primarily composed of?
What are the multi-protein complexes within the electron transport chain primarily composed of?
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Study Notes
Cellular Respiration and Fermentation
- Living cells require energy from outside sources
- Some animals eat plants, others eat organisms that eat plants
- Energy flows into an ecosystem as sunlight and leaves as heat
- Photosynthesis generates oxygen and organic molecules which are used in cellular respiration
- Cells use chemical energy stored in organic molecules to regenerate ATP which powers work
- Aerobic respiration consumes organic molecules and O2 and yields ATP
- Anaerobic respiration is similar to aerobic respiration but uses compounds other than O2 for consumption
- Cellular respiration includes both aerobic and anaerobic respiration but is often used to refer to aerobic respiration
- Glucose is the common fuel trace in cellular respiration (C6H12O6 + 6 O2 → 6 CO2 + 6 H2O + Energy (ATP + heat))
The Principle of Redox
- Chemical reactions that transfer electrons between reactants are called oxidation-reduction reactions or redox reactions
- In oxidation, a substance loses electrons, or is oxidized
- In reduction, a substance gains electrons, or is reduced
- OIL RIG = Oxidation Is Loss, Reduction Is Gain
Oxidation of Organic Fuel Molecules during Cellular Respiration
- During cellular respiration, the fuel (such as glucose) is oxidized, and O₂ is reduced
- C6H12O6 + 6O2 → 6CO2 + 6H2O + Energy
Stepwise Energy Harvest via NAD+ and the Electron Transport Chain
- In cellular respiration, glucose and other organic molecules are broken down in a series of steps
- Electrons from organic compounds are usually first transferred to NAD+, a coenzyme
- As an oxidizing agent during cellular respiration, NAD+ accepts electrons
- NADH (the reduced form of NAD+) represents stored energy tapped to synthesize ATP
- NADH passes the electrons to the electron transport chain
- Unlike an uncontrolled reaction, the electron transport chain passes electrons in a series of steps instead of one explosive reaction
- O₂ pulls electrons down the chain in an energy-yielding tumble
- The energy yielded is used to regenerate ATP
The Stages of Cellular Respiration: A Preview
- Harvesting energy from glucose has three stages
- Glycolysis: breaks down glucose into two molecules of pyruvate
- The Citric Acid Cycle: completes the breakdown of glucose
- Oxidative phosphorylation: accounts for most of the ATP synthesis
Glycolysis
- Glycolysis ("splitting of sugar") breaks down glucose into two molecules of pyruvate
- Glycolysis occurs whether or not O2 is present
- Net products of glycolysis: 2 ATP, 2 NADH, 2 pyruvate, and 2H2O
- Energy Investment Phase: uses 2 ATPs
- Energy Payoff Phase: creates 4 ATPs, 2 NADH, net of 2 ATPs.
Oxidation of Pyruvate to Acetyl CoA
- Before the citric acid cycle can begin, pyruvate must be converted to acetyl CoA, which links glycolysis to the citric acid cycle
- This step is carried out by a multienzyme complex that catalyzes three reactions
- The products are CO2, NADH, and Acetyl CoA
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 (per turn x2 = 2 turns) : 2 ATP, 6 NADH, and 2 FADH2
- The citric acid cycle has eight steps, each catalyzed by a specific enzyme
- The NADH and FADH2 produced by the cycle relay electrons extracted from food to the electron transport chain
Oxidative Phosphorylation
- Oxidative phosphorylation accounts for almost 90% of the ATP generated by cellular respiration
- A smaller amount of ATP is formed in glycolysis and the citric acid cycle by substrate-level phosphorylation
- For each molecule of glucose degraded to CO₂ and water by respiration, the cell makes up to 32 molecules of ATP
Chemiosmosis
- Chemiosmosis couples electron transport to ATP synthesis
- NADH and FADH2 donate electrons to the electron transport chain, powering ATP synthesis via oxidative phosphorylation
- The electron transport chain is in the inner membrane (cristae) of the mitochondrion
- Most of the chain's components are proteins in multi-protein complexes
- Protons (H+) are pumped from the matrix to the intermembrane space by the ETC proteins
Fermentation
- Fermentation is a partial degradation of sugars that occurs without O₂
- Most cellular respiration requires O₂ for ATP production
- Without O2, the electron transport chain will stop
- Glycolysis couples with fermentation or anaerobic respiration to produce ATP
- Two common types of fermentation are lactic acid and alcohol fermentation
Lactic Acid Fermentation
- In lactic acid fermentation, pyruvate is reduced to NADH, forming lactic acid as an end product, with no release of CO₂
- 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 when O₂ is scarce
Alcoholic Fermentation
- In alcohol fermentation, pyruvate is converted to ethanol in two steps, with the first releasing CO₂
- Alcohol fermentation by yeast is used in brewing, winemaking, and baking
Comparing Fermentation with Aerobic Respiration
- All use glycolysis (net ATP = 2) to oxidize glucose and harvest chemical energy of food
- In all three, NAD+ is the oxidizing agent that accepts electrons during glycolysis
- The processes have different final electron acceptors: an organic molecule (such as pyruvate or acetaldehyde) in fermentation and O₂ in cellular respiration
- Cellular respiration produces 32 ATP per glucose molecule; fermentation produces 2 ATP per glucose molecule
Other Metabolic Pathways involved in Glycolysis and the Citric Acid Cycle
- Proteins, carbohydrates, and lipids are other metabolic pathways involved in glycolysis and the citric acid cycle
- Amino acids contribute to glycolysis and the citric acid cycle via sugars
Regulation of Cellular Respiration through Feedback Mechanism
- Cellular respiration regulation mechanisms include feedback through glycolysis and citric acid cycle
- Enzymes involved in glycolysis and citric acid cycle can be regulated to maintain overall homeostasis
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Description
Test your knowledge on cellular respiration, energy flow in ecosystems, and the various metabolic pathways involved. This quiz covers topics such as glycolysis, fermentation, and ATP production. Perfect for students studying biology or related fields.
