Lecture 2

Question 1

glycolysis

Answer 1

• harvests chemical energy by oxidising glucose to pyruvate

Question 2

NAD+

Answer 2

• nicotinamide adenine dinucleotide
• electron shuttle during cellular respiration
• accepts electrons from glucose
• acts as oxidising agent in many redox steps during catabolism of glucose

Question 3

electron shuffle

Answer 3

• electron from organic cmpds transferred to NAD+ (coenzyme)
• dehydrogenase enzymes strip two H atoms (oxidising it)
• enzyme passes 2 electrons and 1 proton to NAD+
• proton released as H+ to surrounding soln
• by receiving 2 electrons and only 1 proton, NAD+ has charge neutralised when reduced to NADH
• each NADH molecule formed during respiration represents stored enegy later synthesised to ATP

Question 4

formula of ADP

Answer 4

• ATP + H2O –> ADP + Pi
• free energy = -7.3 kcal/mol

Question 5

mitochondrion

Answer 5

• inner membrane: translocation of H+ from matrix
• intermembrane space: high conc. of H+
• matrix: low conc. H+
• cristae: site for ETC

Question 6

substrate-level phosphorylation

Answer 6

• transfer of phosphate grp from substrate to ADP forming ATP
• pyruvate kinase (stg. 10 glycolysis)

Question 7

glycolysis

Answer 7

• occurs in cytoplasm/cytosol (no involvement of organelles or membranes)
• no oxygen (soucre of ATP during fermentation)
• probably evolved in ancient prokaryotes before oxygen in atmopshere
• occurs in most living cells
• two phases: energy investment; energy payoff

Question 8

enzymes involved in glycolysis

Answer 8

• kinase enzymes (transfer of phosphate grps)
  – hexokinase
  – phosphofructokinase
  – phosphoglycerokinase
  – pyruvate kinase
• dehydrogenase enzymes (transfer of hydrogen atoms; electron and proton) (triose phosphate dehydrogenase
• aldolase

Question 9

glycolysis steps

Answer 9

• uncharged glucose
• transfer phosphate grp from ATP to glucose (phosphorylation)
• unstable charged glucose-6-p
  PFK allosterically regulated by ATP and products (phosphorylation rxn)

Question 10

energy investment

Answer 10

• 2 ATP consumed
• sugar phosphorylated using hexokinase and phosphofructokinase enzymes
• glucose split into 2 (of G3P) by aldolase enzyme

Question 11

energy payoff

Answer 11

• dehydrognase enzyme oxidises G3P to form NADH (attaches a P grp) (flow of electrons)
• pi = PO42
• ATP produced by substrate level phosphorylation
• carbonyl grp (sugar) changed to carboxyl grp (organic acid)
• water released with high potential energy in PEP
• ATP produced by substrate level phosphorylation
• removal of 2nd P to form first P-free molecule since glucose