ENERGY QUESTION 1995:                    L. PETERSON/AP BIOLOGY

   Energy transfer occurs in all cellular activities. For 3 of the following 5 processes     

   involving energy transfer, explain how each functions in the cell and give an example. 

   Explain how ATP is involved in each example you choose.

        Cellular movement

        Active transport

        Synthesis of molecules

        Chemiosmosis

        Fermentation

  1 pt     function of process

  1 pt     example                      1 pt additional for detail

  1 pt     ATP involvement

  4 pts =  MAX/process

  ATP   <====>   ADP  +  Pi  +  Energy  1 pt

  Cellular Movement

     Function  Locomotion, Mitosis, Cytoplasmic Streaming, 

          Muscle Contraction (sliding filaments)

     Examples   Cilia, Flagella, Pseudopodia, Exocytosis, Endocytosis,

          Microfilaments, Spindle Fibers

     Details   9 + 2 Microtubules, Dynein, Actin-Myosin (Myosin heads),

          Kinesins

     ATP Involvement   ATP used

          Motor molecules powered by ATP hydrolysis

          (Conformational change with ATP use)

  Active Transport

     Function   Concentration gradient   low to high / Protein carrier w/use of ATP

     Examples   Sodium/Potassium Pump, Other Transports Specified

     Details   Protein carrier related to example

     ATP Involvement   ATP used

          Conformational change with ATP use

  Synthesis of Molecules

     Function   Small to Large / Monomer to Polymer

     Examples  

          Intermediates to Monosaccharides to Polysaccharides

          Intermediates to Fatty Acids (Glycerol) to Lipids

          Intermediates to Amino Acids to Proteins

          Intermediates to Nucleotides to Nucleic Acids

          Intermediates to Vitamins

     Details   Charging tRNA

          Reactions catalyzed by enzymes

     ATP Involvment   ATP used

          ATP's energy stored in chemical bonds

  Chemiosmosis

     Function   Form electrochemical proton (H+) gradient

     Examples   Mitochondria, Chloroplasts, Bacterial Cell Membrane

     Details   Cristae, Thylakoids, Direction/  H+  vs e-

     ATP Involvement   ATP formed

          Proton pump/gradient with ATP synthase yields ATP

  Fermentation

     Start with glucose                 Start with pyruvate

     Function   breakdown of organic         recycling NADH

                        compounds

     Examples   Ethanol / Lactic Acid        Ethanol / Lactic Acid

     Details   Anaerobic                Anaerobic

          Less energy produced               Regenerate oxidized NAD

          Cytosolic process             Cytosolic process

          Yeast, Muscle                 Yeast, Muscle

     ATP Involvement 

          ATP used and formed           (No direct involvement)

          Substrate-level                    Makes ATP production

          Phosphorylation               possible in glycolysis

  Overall Commentary on Question:

     This question was a cell biology energetics question that required both breadth and depth

  of knowledge to answer the question successfully. Full credit could only be obtained by

  responding to three of the process examples listed in the question. Also, if more than three

  processes were discussed, readers were directed to grade the first three unless specifi indications

  directed one to be omitted. Each process had a four point maximum score. One point was

  available for description of the function of the process, which might also be a definition or

  description of a mechanism. One point came from an example in context with the process. One

  point was available for showing how ATP was involved in the process. For each of these points, it

  was possible to get an additional point for detail (elaboration). In addition, it was possible to obtain

  a point frordescription of the ATP  <==>  ADP cycle.