Biology 107 Introduction to Metabolism I

1
Biology 107Introduction to Metabolism I

• September 12, 2003

2
Introduction to Metabolism I

• Student Objectives As a result of this lecture
  and the assigned reading, you should understand
  the following
• 1. Despite the organized structure of cells, all
  living things tend toward disorder. To maintain
  order, living things and the cells they are made
  up of depend on a continual flow of energy from
  the environment.
• 2. Metabolism is the sum total of an organism's
  chemical processing some chemical processes
  degrade complex molecules into simpler molecules
  (catabolic pathways), and some chemical processes
  synthesize complex molecules from simpler
  molecules (anabolic pathways).

3
Introduction to Metabolism I

• 3. Energy can only be described and measured by
  how it affects matter. Energy is the capacity to
  perform work - all organisms require energy to
  stay alive, and all organisms transform energy.
• 4. There are two (2) forms of energy potential
  energy and kinetic energy.
• 5. The first law of thermodynamics (law of energy
  conservation) the total amount of energy in the
  universe is constant and energy can be
  transferred and transformed, but it cannot be
  created or destroyed.

4
Introduction to Metabolism I

• The second law of thermodynamics energy
  conversions reduce the order of the universe.
  Heat, which is due to random molecular motion, is
  one form of disorder. The second law has direct
  applications to cellular activities - as
  explained in this law, energy cannot be
  transferred or transformed by the cell with 100
  efficiency.
• 7. Chemical reactions in living organisms - the
  starting substances of chemical reactions are
  called reactants reactants interact with one
  another to form new substances called products.
• 8. Chemical reactions, including those in cells,
  are of two types endergonic (energy-requiring)
  and exergonic (energy-releasing).

5
Introduction to Metabolism I

1. In an endergonic biosynthetic reaction, the
   electrons forming the chemical bonds of the
   product are at a higher energy level than the
   electrons of the reactants (i.e., the reaction
   requires input of energy).
2. Cells supply the energy for endergonic reactions
   through coupled reactions in which endergonic
   reactions are linked to exergonic reactions.
3. ATP is the cell's main energy carrier. Most
   frequently, coupled reactions use ATP as the
   energy source, and ATP is renewable energy that
   cells regenerate from exergonic reactions.

6
Metabolic Pathways
Reactions occur in a stepwise fashion Pathways
are interconnected Chemical reactions are
catalyzed by enzymes
7
Free Energy And Capacity To Do Work
8
Need For Continual Flow Of Energy Into Systems
9
Energy Profile For a Chemical Reaction
10
Energy Profiles For Energy-requiring and
Energy-releasing Reactions
11
Enzymes Lower Activation Energy But They Do Not
Change the Overall Energy Profile
12
Coupling Of Energy-releasing Reactions With
Energy-requiring Reactions
13

• Biology 107
• Exam 1 Select the single choice which best
  answers the question or completes the idea in
  each question or statement. For fill in the blank
  questions, write clearly and only in the space
  provided on the answer sheet. Make sure you name
  is clearly written on each page of the exam and
  on your answer sheet.
• ALL ANSWERS MUST BE ON THE ANSWER SHEET TO BE
  GRADED.

• Which of the following influence protein folding
  into functional molecules?
• A. The types of side chains ("R" groups) on the
  amino acids
• B. The temperature (kinetic energy) of the
  environment
• C. The polar nature of its solvent
• D. A and C
• E. All of the above

14

• 2. One of the ways that RNA differs from DNA is
  that
• A. RNA does not contain phosphate groups but DNA
  does
• B. RNA contains a 5-carbon sugar while DNA
  contains a 6-carbon sugar
• C. RNA contains uracil while DNA contains
  thymine
• D. RNA is found only in bacteria and viruses,
  while DNA is found only in animal cells
• E. RNA directs the synthesis of DNA, which in
  turn synthesizes proteins
• 3. Which of the following statements correctly
  describes any chemical reaction that has reached
  equilibrium?
• A. The concentration of products equals the
  concentration of reactants.
• B. The rate of the forward reaction equals the
  rate of the reverse reaction.
• C. Both forward and reverse reactions have
  halted.
• D. The reaction is now irreversible.
• E. No reactants remain.

15

• 4. Which of these terms includes all of the
  others in the list?
• A. Nucleotide
• B. Nucleic acid
• C. Pyrimidine
• D. Purine
• E. Nitrogenous base
• 5. Which of the following IS NOT true regarding
  hydrogen bonds
• A. They result from the unequal sharing of
  electrons in certain covalent bonds
• B. They contribute to some of the higher orders
  of configuration of proteins (i.e., secondary,
  tertiary, quaternary)
• C. They are stronger than covalent bonds
• D. They contribute to the property of surface
  tension in water
• E. They contribute to water's capacity as a
  solvent for polar molecules

16

• 6. Chemical bonds hold __________ together within
  __________.
• A. protons and neutrons atomic nuclei
• B. atoms elements
• C. molecules elements
• D. protons and electrons atoms
• E. atoms molecules
• 7. Aldehydes and ketones contain the
  ______________ functional group.

17

• 8. By definition, for a protein to have a
  quaternary structure, it must
• A. Consist of four polypeptide subunits
• B. Consist of two or more polypeptide subunits
• C. Have at least four disulfide bridges (bonds)
• D. Have four amino acids
• E. Exist in several alternative conformational
  states
• 9. For isomers
• A. They have the same molecular formula but
  differ in molecular structure
• B. One form is created in nature and the other
  isomers are the result of synthetic processes in
  the laboratory
• C. They react the same way in chemical reactions
  
• D. The number of neutrons varies between the
  isomers
• E. All of the above

18

• 10. __________ is a cellular high energy
  compound that donates phosphate groups to other
  molecules to produce more chemically reactive
  intermediate forms of the original molecule.
• 11. Which is the correct ratio of CHO in a
  carbohydrate
• A. 221
• B. 212
• C. 111
• D. 121
• E. None of the above
• 42. Pick an example of a hydrophobic molecule and
  describe the molecular characteristic(s) that
  makes it hydrophobic.

19

• How does an exergonic chemical reaction differ
  from an endergonic reaction?
• Describe what is meant by the general concept
  that hierarchies of biological organization
  produce emergent properties of life.