Lecture 7

• siderophore

  siderophore iron complex transport into a gram negative cell

  1. e.coli synthesizes and secretes an iron binding enterochelin that binds Fe3+
  2. complex transported into periplasm and is transported into the cell by ABC
  3. inside the cell, the iron is released and reduced to Fe2+

  A) enterochelin iron complex

  
• metabolism


  all chemical reactions in a cell
• metabolism requires a flow of energy (capacity to do work) and the participation of enzymes

  ATP is the energy currency of cells
• Adenosine Triphosphate

  phosphate groups are high energy

  ribose sugar

  adenine nitrogenous base

  P removal: large negative standard free energy change

  A) adenosine

  B) ribose

  C) phosphate

  D) adenine

  
• The cells energy cycle

  energy generating systems

  • aerobic respiration
  • anaerobic respiration
  • fermentation
  • photsynthesis

  energy can be used for chemical work, transport work, and mechanical work

  A) ATP

  B) ADP + Pi

  
• aerobic and anaerobic respiration

  ATP generated by oxidative phosphorylation
• photosynthesis

  ATP generated by photophosphorylation
• redox reaction pathway

  need enzyme: malatate dehydrogenase

  A) oxidized

  B) reduced

  
• metabolism requires enzymes

  proteins that catalyze reactions

  ribozymes are catalytic RNAs

  act on substrates, convert to products

  activation energy

  energy required to bring reacting molecules together

  enzymes increase reaction rates by lowering activation energy

  often named for reactions they catalyze

  phosphatase, kinase, cellulase
• how do enzymes lower the energy of activation???

  increase local concentrations of substrates

  orient substrates properly for reactions to proceed
• Reduction potential (E0)

  equilibrium constant for redox reactions

  measures tendency of donor to lose electrons

  more negative E0 = better donor

  more positive E0 = better acceptor
• half reactions

  acceptor + number of electrons -> donor

  couples with more negative E0 will donate electrons to couples with more positive E0

  A) negative

  B) positive

  
• electron tower

  greater the difference -> more energy released

  A) donors

  B) acceptor