Biochemistry exam 1

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Biochemistry exam 1
2014-09-27 20:45:51
Biochemistry exam

Biochemistry exam 1
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  1. Do work
  2. The DNA backbone is made from repeating ____________.
    sugar-phosphate units
  3. ____________ The strongest bonds in molecules:
  4. ____________ Matter within a defined region of space.
  5. ____________ For spontaneous reactions the deltaG must be
  6. delta G stands for
    ____________ Gibbs free energy.
  7. 11.    The structure of DNA described by Watson and Crick included
    • A)    a double helix.
    • C)    the base pairs that are stacked on the inside of the double helix.
  8. What did Watson and Crick suggest to be significant about the base pairing found in the helix?
    C)    It was a mechanism for copying.
  9. Approximately what percentage of the human genome encodes for proteins?
  10. What gives proteins such a dominant role in biochemistry?
    D)    their ability to spontaneously fold into complex three-dimensional structures
  11. If the whole chain is used in a non-overlapping frame, how many amino acids are defined by this DNA sequence: ATGTTTGGACTA?
  12. What is the [H+] concentration in a urine sample that has a pH of 6?
    10-6 M
  13. Which of the following is considered as a noncovalent bond?
    • A)    electrostatic interactions    
    • B)    hydrogen bonds    
    • C)    van der Waals interactions
  14. The energies for hydrogen bonds are approximately
    4–20 kJ/mol.
  15. The energies for hydrogen bonds are approximately
    4–20 kJ/mol.
  16. What pairs of atoms in bases are involved in hydrogen bonds?
    N—H and O—H
  17. Typical van der Waals energies are about
    2–4 kJ/mol
  18. What two properties of water are important for biological interactions?
    • A)    the polarity of water    
    • C)    the cohesive properties of water
  19. The First Law of Thermodynamics states
    the total energy of a system and its surroundings is constant.
  20. The Second Law of Thermodynamics states
    the total entropy of a system and its surroundings always increases for a spontaneous process.
  21. List atoms commonly found in biological molecules that are often hydrogen-bond acceptors
    C) nitrogen     B) oxygen
  22. Enthalpy is defined as
    the heat content of a system.
  23. If a particular reaction has a negative G, is it likely to occur?
    Yes, it is spontaneous.
  24. What happens to nonpolar molecules in water?
    They aggregate together.
  25. 28.    What is the [A-]/[HA] ratio when the weak acid is in a solution one pH unit above its pKa?
    10 : 1
  26. Why does DNA denature when the pH is raised above 9?
    Protons dissociate from guanine bases disrupting the hydrogen bonding to the other strand.
  27. Stereochemistry can be easily depicted in a simple form using
    Fisher projections.
  28. What are the primary chemical components present in a phosphate buffer at pH 7.4?
    H2PO4-and HPO4-2
  29. What are some of the medical implications of the human genome project?
    The obvious use is in diagnosing disease and in developing methods to treat and cure diseases. Physicians will be able to account for individual genetic differences in determining the best medical treatment.
  30. What is the significance of hydrogen bonding in biochemical structures such as DNA?
    The bonds are weak enough to be easily disrupted; yet when many are present, they provide the stabilization necessary for larger structures such as DNA.
  31. What adaptation affected evolutionary diversity?
    Alteration of biochemical molecules and components to new roles is key to diversity and evolution.
  32. Describe resonance structures.
    • Resonance structures are ways of writing covalent bonds in which two or more alternate bonding patterns can be achieved. This is due to the sharing of electrons
    • over several atoms. Common examples are found in peptide bonds, and in some
    • of the bases. Benzene is shown in the text.
  33. What is an electrostatic interaction? Give an example.
    It is the attractive force of two oppositely charged atoms. Salts (such as NaCl) are a common example.
  34. How is water able to be a solvent for so many biological molecules?
    Many biological molecules have polar characteristics. Water is extremely polar and is capable of competing with other polar molecules by weakening their electrostatic and hydrogen bonds. The oxygen can act as a hydrogen-bond acceptor, and the hydrogen can act as a donor.
  35. What is the net effect of many van der Waals interactions?
    At the interface of two large molecules, the numerous van der Waals interactions can substantially affect and stabilize the interaction.
  36. If most proteins are found surrounded by water in the cell, what type of functional groups  would you expect to find on the surface of a water soluble protein?
    Polar and charged amino-acid residues would be present on the surface of the protein.
  37. How are electrostatic forces used in protein folding?
    The attraction of two oppositely charged functional groups would be one of the forces helping to form the three-dimensional shape of the protein.
  38. If the First Law of Thermodynamics is true, how can biological processes be carried out?