Test 2-3
Q: What is the main purpose of cellular respiration?
A: To extract energy from glucose and other molecules to produce ATP.
Q: What are the 3 stages of aerobic cellular respiration?
A: Glycolysis, Krebs cycle (Citric Acid Cycle), and Electron Transport Chain (ETC).
Q: Where does glycolysis occur?
A: In the cytoplasm.
Q: What are the inputs and outputs of glycolysis?
A: Input: Glucose, 2 ATP, 2 NAD⁺
Output: 2 Pyruvate, 4 ATP (net gain of 2), 2 NADH
Q: Where does the Krebs cycle take place?
A: In the mitochondrial matrix.
Q: What is the main purpose of the Krebs cycle?
A: To extract electrons via NADH and FADH₂ for the ETC.
Q: What are the final products of the Krebs cycle per glucose molecule?
A: 6 CO₂, 2 ATP, 8 NADH, 2 FADH₂
Q: Where does the electron transport chain occur?
A: In the inner mitochondrial membrane.
Q: What is the final electron acceptor in aerobic respiration?
A: Oxygen (O₂), forming water.
Q: How many ATP can be made from one glucose molecule in aerobic respiration?
A: Up to 36–38 ATP.
Q: What happens if oxygen is not available in a cell?
A: Cells use anaerobic respiration or fermentation.
Q: What is anaerobic cellular respiration?
A: A form of respiration where electrons are passed through an ETC, but the final electron acceptor is not oxygen.
Q: What are common final electron acceptors in anaerobic respiration?
A: Sulfate (SO₄²⁻), nitrate (NO₃⁻), carbon dioxide (CO₂), sulfur.
Q: What kinds of organisms use anaerobic respiration?
A: Some prokaryotes (bacteria and archaea) in low-oxygen environments.
Q: What are methanogens?
A: Archaea that use CO₂ as a final electron acceptor, producing methane.
Q: What are sulfate-reducing bacteria?
A: Microorganisms that use sulfate as an electron acceptor, producing hydrogen sulfide (H₂S).
Q: What is fermentation?
A: An anaerobic process that uses only glycolysis and extra reactions to regenerate NAD⁺.
Q: What is the goal of fermentation?
A: To regenerate NAD⁺ so glycolysis can continue making ATP.
Q: Why can't NADH use the ETC in fermentation?
A: Because oxygen (or an alternate final acceptor) isn't available to receive electrons.
Q: What is lactic acid fermentation?
A: Pyruvate accepts electrons from NADH, forming lactate and regenerating NAD⁺.
Q: What organisms use lactic acid fermentation?
A: Muscle cells (under low oxygen), red blood cells, and yogurt bacteria.
Q: What happens to lactic acid after intense exercise?
A: It's transported to the liver and converted back into pyruvate.
Q: What is alcohol fermentation?
A: Pyruvate is first converted into acetaldehyde and CO₂, then into ethanol using NADH.
Q: What are the products of alcohol fermentation?
A: Ethanol, CO₂, and regenerated NAD⁺.
Q: What organisms perform alcohol fermentation?
A: Yeasts and some bacteria.
Q: Why can't yeast tolerate too much ethanol?
A: Ethanol is toxic; tolerance ranges from ~5% to ~21%, depending on the strain.
Q: What are facultative anaerobes?
A: Organisms that can switch between aerobic respiration and anaerobic pathways.
Q: What are obligate anaerobes?
A: Organisms that cannot survive in the presence of oxygen.
Q: What dangerous bacteria are obligate anaerobes?
A: Clostridium (causes botulism).
Q: How is NAD⁺ regenerated in aerobic respiration?
A: NADH donates electrons to the ETC, and oxygen receives them, forming water.
Q: How is NAD⁺ regenerated in fermentation?
A: NADH gives electrons to pyruvate (or a derivative), regenerating NAD⁺ without the ETC.
Q: How is NAD⁺ regenerated in anaerobic respiration?
A: NADH donates electrons to an ETC, which ends with an inorganic molecule (e.g., nitrate, sulfate) instead of oxygen.
🌟 OVERVIEW
Q: What is the purpose of cellular respiration?
A: To extract energy from glucose to produce ATP for cellular work.
⚡ GLYCOLYSIS
Q: Where does glycolysis take place?
A: In the cytoplasm of the cell.
Q: What are the inputs of glycolysis?
A: Glucose, 2 ATP, 2 NAD⁺, 4 ADP + Pi
Q: What are the products of glycolysis?
A: 2 Pyruvate, 2 NADH, 4 ATP (Net gain: 2 ATP), 2 H₂O, 2 H⁺
Q: What is the net ATP gain from glycolysis?
A: 2 ATP
🌀 PYRUVATE OXIDATION (Link Reaction)
Q: Where does pyruvate oxidation occur?
A: In the mitochondrial matrix.
Q: What are the inputs of pyruvate oxidation?
A: 2 Pyruvate, 2 CoA, 2 NAD⁺
Q: What are the products of pyruvate oxidation?
A: 2 Acetyl-CoA, 2 NADH, 2 CO₂
🔁 KREBS CYCLE (Citric Acid Cycle)
Q: Where does the Krebs cycle occur?
A: Mitochondrial matrix.
Q: What are the inputs per glucose (2 turns)?
A: 2 Acetyl-CoA, 6 NAD⁺, 2 FAD, 2 ADP + Pi, 2 H₂O
Q: What are the products per glucose (2 turns)?
A: 4 CO₂, 6 NADH, 2 FADH₂, 2 ATP, 2 CoA
🧬 ELECTRON TRANSPORT CHAIN (ETC) & CHEMIOSMOSIS
Q: Where does the ETC occur?
A: Inner mitochondrial membrane.
Q: What are the inputs of the ETC?
A: 10 NADH, 2 FADH₂, O₂, ADP + Pi
Q: What are the products of the ETC?
A: ~34 ATP, H₂O, NAD⁺, FAD
Q: What is the final electron acceptor in the ETC?
A: Oxygen (O₂), which forms water.
Q: How is ATP made in the ETC?
A: Via chemiosmosis, as H⁺ ions flow through ATP synthase.
🌫 ANAEROBIC CELLULAR RESPIRATION
Q: What is anaerobic respiration?
A: A form of respiration where the ETC is used but the final electron acceptor is not oxygen (e.g., nitrate, sulfate).
Q: What are common final electron acceptors in anaerobic respiration?
A: Sulfate (SO₄²⁻), nitrate (NO₃⁻), carbon dioxide (CO₂), or sulfur.
Q: Who uses anaerobic respiration?
A: Some bacteria and archaea in low-oxygen environments (e.g., methanogens, sulfate-reducing bacteria).
Q: Products vary, but what’s often produced in anaerobic respiration?
A: Less ATP than aerobic respiration, and byproducts like methane or hydrogen sulfide.
🧪 FERMENTATION
Q: What is fermentation?
A: An anaerobic process using only glycolysis and extra steps to regenerate NAD⁺ from NADH.
Q: Why is NAD⁺ regeneration important in fermentation?
A: It allows glycolysis to continue producing ATP when oxygen isn’t available.
🥛 LACTIC ACID FERMENTATION
Q: What organisms use lactic acid fermentation?
A: Muscle cells (under low oxygen), red blood cells, and some bacteria (like in yogurt).
Q: What are the inputs of lactic acid fermentation?
A: Glucose, 2 ADP + Pi, 2 NAD⁺
Q: What are the products?
A: 2 Lactate (lactic acid), 2 ATP (net), 2 NAD⁺
Q: What happens to lactate after exercise?
A: It’s sent to the liver and converted back to pyruvate.
🍷 ALCOHOL FERMENTATION
Q: What organisms use alcohol fermentation?
A: Yeast and some bacteria.
Q: What are the inputs of alcohol fermentation?
A: Glucose, 2 ADP + Pi, 2 NAD⁺
Q: What are the products?
A: 2 Ethanol, 2 CO₂, 2 ATP (net), 2 NAD⁺
Q: What is the two-step process of ethanol production from pyruvate?
A: 1) Pyruvate → Acetaldehyde + CO₂
2) Acetaldehyde + NADH → Ethanol + NAD⁺
⚖ ENERGY YIELD COMPARISON
Q: How much ATP is made in aerobic respiration?
A: About 36–38 ATP per glucose.
Q: How much ATP is made in fermentation?
A: Only 2 ATP per glucose (from glycolysis).
Q: Why is aerobic respiration more efficient?
A: It fully oxidizes glucose using the Krebs cycle and ETC, extracting much more energy.
Q: What is brown fat and what is its role in the body?
A: Brown fat is a type of fat tissue specialized for heat generation (thermogenesis), especially in infants and hibernating animals.
Q: How does brown fat produce heat?
A: It contains uncoupling proteins in the inner mitochondrial membrane that allow H⁺ ions to flow back into the matrix without going through ATP synthase, releasing energy as heat.
Q: What is thermogenesis?
A: The process of generating heat by proton movement without ATP production, often seen in brown fat.
🚫 UNCOUPLERS
Q: What are uncouplers in the ETC?
A: Proteins or molecules that allow protons (H⁺) to bypass ATP synthase and re-enter the mitochondrial matrix, reducing ATP production and releasing heat.
Q: How do uncouplers affect ATP production?
A: They make ATP production less efficient by dissipating the proton gradient, which results in more heat and less ATP.
⚙ ATP SYNTHASE & CHEMIOSMOSIS
Q: What is ATP synthase and where is it located?
A: An enzyme complex in the inner mitochondrial membrane that synthesizes ATP as H⁺ ions flow through it.
Q: What drives ATP synthase?
A: The proton gradient created by the ETC (chemiosmosis).
Q: What is chemiosmosis?
A: The process by which protons move down their electrochemical gradient through ATP synthase, powering ATP production.
💥 GLYCOLYSIS RECAP
Q: What happens to NAD⁺ in glycolysis?
A: It is reduced to NADH, which carries electrons to the ETC.
Q: What are the key products of glycolysis?
A: 2 Pyruvate, 2 NADH, 2 ATP (net)
🔁 KREBS CYCLE & CO₂ RELEASE
Q: Why is pyruvate important for the Krebs cycle?
A: Pyruvate is converted to Acetyl-CoA, which enters the Krebs cycle.
Q: What happens when CO₂ is “ripped off” pyruvate?
A: Pyruvate (3 carbons) loses a carbon as CO₂, forming a 2-carbon Acetyl-CoA.
Q: What does the release of CO₂ during the Krebs cycle indicate?
A: A reduction in the number of carbon atoms, showing how glucose is gradually oxidized and broken down.
Q: How many CO₂ molecules are released per glucose in the Krebs cycle?
A: 4 CO₂ (2 per cycle × 2 cycles per glucose)
Q: What are the products of the Krebs cycle per glucose?
A: 4 CO₂, 6 NADH, 2 FADH₂, 2 ATP