Chapter 12: Inheritance, Genes, and Chromosomes

• What is the main topic of Chapter 9?

  Pathways That Harvest Chemical Energy
• What are the key concepts covered in Chapter 9?

  • Cells harvest chemical energy from glucose oxidation
  • Glucose is fully oxidized in the presence of oxygen
  • Oxidative phosphorylation forms ATP
  • Energy is harvested from glucose in the absence of oxygen
  • Metabolic pathways are interrelated and regulated
• What is the role of brown fat in human infants?

  It releases energy as heat to keep the baby warm.
• How are mitochondria related to obesity?

  Mitochondria in brown fat help regulate energy expenditure.
• How do cells obtain energy from glucose?

  Through a series of metabolic pathways.
• What are the five principles of metabolic pathways?

  1. Complex transformations occur in a series of separate reactions.
  2. Each reaction is catalyzed by a specific enzyme.
  3. Many metabolic pathways are similar in all organisms.
  4. Metabolic pathways are compartmentalized in specific organelles in eukaryotes.
  5. Key enzymes can be inhibited or activated to alter the rate of the pathway.
• What is the chemical equation for the burning of glucose?

  $C_6H_{12}O_6 +$$6 O_2 \rightarrow 6 CO_2 +$$6 H_2O +$$\text{free energy} \quad \Delta G =$$-686 \text{ kcal/mol}$
• What does a negative ΔG indicate about the burning of glucose?

  It is highly exergonic and drives the formation of ATP.
• What are the three catabolic processes that harvest energy from glucose?

  1. Glycolysis (anaerobic)
  2. Cellular Respiration (aerobic)
  3. Fermentation (anaerobic)
• What are oxidation-reduction (redox) reactions?

  Reactions where one substance transfers electrons to another.
• What happens during reduction in redox reactions?

  There is a gain of electrons.
• What happens during oxidation in redox reactions?

  There is a loss of electrons.
• In glucose metabolism, what is glucose considered?

  Glucose is the reducing agent.
• In glucose metabolism, what is O2 considered?

  O2 is the oxidizing agent.
• What does the transfer of electrons often involve?

  It is often associated with the transfer of hydrogen ions.
• What is the role of coenzyme NAD⁺ in redox reactions?

  NAD⁺ is a key electron carrier.
• What is the reduction reaction of NAD⁺?

  $NAD^+$$+$$H^+$$+$$2e^- \rightarrow NADH$
• What is the oxidation reaction of NADH?

  $NADH +$$H^+$$+$$½ O_2 \rightarrow NAD^+$$+$$H_2O$
• What is the ΔG for the oxidation of NADH?

  <latex}\Delta G = -52.4 \text{ kcal/mol}</latex>
• What happens in aerobic conditions regarding electron acceptors?

  O2 is available as the final electron acceptor.
• What occurs during glycolysis?

  • Takes place in the cytoplasm
  • Converts glucose into 2 molecules of pyruvate
  • Produces 2 ATP and 2 NADH
  • Occurs in 10 steps
• What are the two types of reactions in glycolysis?

  Energy-investing reactions and energy-harvesting reactions.
• What occurs during pyruvate oxidation?

  Pyruvate is oxidized to acetate and CO2.
• Where does pyruvate oxidation occur?

  In the mitochondrial matrix.
• What binds to coenzyme A during pyruvate oxidation?

  Acetate binds to coenzyme A to form acetyl CoA.
• What is the role of the pyruvate dehydrogenase complex?

  It catalyzes the three intermediate steps in pyruvate oxidation.
• What occurs during the citric acid cycle?

  • Acetyl CoA is the starting point
  • Eight reactions oxidize the acetyl group to 2 molecules of CO2
  • Energy is captured by GDP, NAD⁺, and FAD
  • Oxaloacetate is regenerated in the last step
• What is produced from the oxidation of one glucose molecule in the citric acid cycle?

  6 CO2, 10 NADH, 2 FADH2, and 4 ATP.
• What must be replenished for the citric acid cycle to continue?

  Acetyl CoA and oxidized electron carriers.
• What happens to electrons if O2 is present during the citric acid cycle?

  O2 accepts the electrons and H2O is formed.
• What is oxidative phosphorylation?

  • ATP is synthesized by reoxidation of electron carriers in the presence of O2
  • Two components: Electron transport and Chemiosmosis
• What occurs during electron transport in oxidative phosphorylation?

  Electrons from NADH and FADH2 pass through the respiratory chain.
• What is created during chemiosmosis?

  A proton concentration gradient across the inner mitochondrial membrane.
• What is the role of ATP synthase in chemiosmosis?

  It couples the diffusion of protons with ATP synthesis.
• What happens to protons during electron transport?

  They are actively transported into the intermembrane space.
• What is the proton-motive force?

  It is the potential energy created by the proton concentration gradient.
• What can ATP synthase also act as?

  ATPase, hydrolyzing ATP to ADP.
• What do FADH₂ molecules pass through in the respiratory chain?

  Membrane-associated carriers
• What is the result of electron flow in the respiratory chain?

  It creates a proton concentration gradient across the inner mitochondrial membrane
• What is chemiosmosis in the context of ATP synthesis?

  • Electrons flow back across the membrane through ATP synthase
  • This process couples diffusion with ATP synthesis