Unit 2

• What are metabolic pathways?

  Integrated and controlled enzyme-catalysed reactions
• What characterizes irreversible steps in metabolic pathways?

  They cannot be reversed once completed
• What are alternative routes in metabolic pathways?

  Different enzymes can catalyze the same substrate
• What are anabolic reactions?

  Reactions that build large molecules from small ones
• What are catabolic reactions?

  Reactions that break down large molecules
• What roles can membrane proteins have?

  • Protein pores
  • Pumps
  • Enzymes
• How are metabolic pathways controlled?

  By the presence or absence of enzymes
• What do enzymes do in chemical reactions?

  Speed up reactions and remain unchanged
• What do enzymes lower in a reaction?

  Activation energy required for the reaction
• What factors affect enzyme activity?

  Temperature, pH, substrate concentration, inhibitors
• What is induced fit in enzyme action?

  Active site changes shape to fit substrate
• What is the affinity of substrates for the active site?

  High affinity causes enzyme-substrate complex formation
• What happens to products after they are formed?

  They have low affinity and leave the active site
• How can metabolic pathways be controlled?

  Through enzyme inhibition
• What is competitive inhibition?

  Inhibitors bind at the active site, blocking substrates
• How can competitive inhibition be reversed?

  By increasing substrate concentration
• What is non-competitive inhibition?

  Inhibitors bind away from the active site
• Can non-competitive inhibition be reversed?

  No, it cannot be reversed by increasing substrate
• What is feedback inhibition?

  End product inhibits an earlier enzyme in the pathway
• What is cellular respiration?

  Breaking down glucose to release energy
• What is glycolysis?

  Breakdown of glucose to pyruvate in cytoplasm
• Is oxygen required for glycolysis?

  No, oxygen is not required
• What occurs during the energy investment stage of glycolysis?

  ATP is required for phosphorylation of glucose
• What happens during the energy pay-off stage of glycolysis?

  ATP is generated resulting in net gain
• What is acetyl coenzyme A?

  Formed from pyruvate and coenzyme A
• What occurs in the citric acid cycle?

  Acetyl group combines with oxaloacetate to form citrate
• Where does the citric acid cycle occur?

  In the matrix of the mitochondria
• What is ATP used for?

  To transfer energy to cellular processes
• What is produced during glycolysis?

  2 pyruvate and 2 ATP
• What happens to NADH in the electron transport chain?

  It donates hydrogen ions and electrons
• What is the electron transport chain?

  A series of carrier proteins in the membrane
• What happens to electrons in the electron transport chain?

  They release energy as they pass along
• What is ATP synthesis?

  Production of ATP from ADP + Pi
• How are hydrogen ions involved in ATP synthesis?

  They flow back through ATP synthase to produce ATP
• What do hydrogen ions and electrons combine with at the end of the electron transport chain?

  Oxygen to form water
• What do dehydrogenase enzymes do?

  Remove hydrogen ions and electrons to form NADH
• What occurs during fermentation in animal cells?

  Pyruvate is converted to lactate
• What occurs during fermentation in plants and yeast?

  Ethanol and CO2 are produced
• How does fermentation compare to aerobic respiration?

  Fermentation produces much less ATP
• What does a respirometer measure?

  Oxygen uptake per minute