Chapters 8

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Chapters 8 9Energy in a Cell

• Chapter 8 Photosynthesis
• Chapter 9 Cellular Respiration

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8 Map
11
Photosynthesis!
Light-Dependent Rxns.
Calvin Cycle (Light-Independent Rxns.)
Electron Transport Chain (p. 209)
Photolysis (not in book)
Plant Parts!
Palisade Mesophyll (p. 596)
Stomata (p. 596)
Stroma (p. 208)
Phloem (p. 580)
Xylem (p. 580)
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9 Map
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Cellular Respiration
Aerobic (Respiration)
Anaerobic (Respiration)
Glycolysis
Citric Acid Cycle (Krebs)
Fermentation
Pyruvic Acid (p. 223)
Alcoholic Fermentation
Lactic Acid Fermentation
4
ATP in a Molecule

• What processes in a cell need energy?
• Active Transport, Cell Division, Movement of
  Cilia and Flagella, Movement of Muscles.
• ATP Adenosine Triphosphate p. 203 Fig. 8-3.
• An adenosine molecule with 3 phosphate groups
  attached.
• Bonding phosphates to adenosine takes a lot of
  energy
• Therefore, when ATP is broken down, a lot of
  energy is released

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Formation of ATP

• I could not find the following items in your
  book!
• Adenosine (the backbone of the ATP molecule) is
  the combination of adenine and ribose
• Adenine is a nitrogen base molecule also found in
  DNA, and ribose is a sugar also found in DNA.
• The phosphate groups bind to the ribose. ? ? ?

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Formation of ATP

• Phosphate molecules act as magnets with a north
  and south pole.
• As they are arranged on the adenosine molecule,
  they repel each other as would a magnet.
• One phosphate group- AMP
• Two phosphate groups- ADP
• Three phosphate groups- ATP

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Breaking Down ATP

• A Renewable Cycle!
• A phosphate is released from ATP to form ADP.
• Along with this phosphate group, necessary energy
  is released.
• A free phosphate is then readily reattached to
  the ADP to once again produce ATP.
• ? ? ? Energy is stored in the cell by bonding
  this third phosphate group to an ADP ? ? ?
• As long as the cell has free phosphate groups and
  adenosine, the cell can recycle this energy.

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How a Cell Uses ATP

• ATP is not immediately useful to the cell.
• It must bind with a protein for its phosphate
  group to be released, along with its energy.
• The protein accepts the ATP, helps it release its
  phosphate group, and then releases the leftover
  ADP molecule.
• The protein is now ready to accept a new ATP
  molecule.

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How a Cell Uses ATP
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Photosynthesis

• Photosynthesis The process that plants use to
  trap the light energy of the sun and then build
  and store glucose.
• Broken into two different parts
• Light-Dependent Reactions Where light energy is
  converted into chemical energy (ATP).
• Light-Independent Reactions Where chemical
  energy (ATP) is converted into glucose. No light
  required.
• Equation for Photosynthesis
• ? ? ? 6CO2 6H2O ? C6H12O6 6O2 ? ? ?

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Photosynthesis Where?

• In the leaves of the plant. See p. 596 Fig.
  23.18 ? ? ?
• More specifically in the palisade mesophyll of
  the leaf.
• The palisade mesophyll makes up only part of the
  leafs tissue.
• The palisade mesophyll has tons of chloroplasts
  throughout its cells.
• Where more specifically within the chloroplasts
  does photosynthesis take place?

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Photosynthesis Where?

• Light-dependent rxns. take place in the thylakoid
  membranes.
• The thylakoids use their pigment (chlorophyll) to
  trap the sunlight.
• Review What are stacks of thylakoids called?
• Chlorophyll a and b exist. Between them they
  trap and absorb all wavelengths of visible light
  except green (green is reflected).
• See p. 207, Fig. 8-5.

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Light-Dependent Rxns.

• Sunlight excites electrons in chlorophyll
• Energized electrons are passed through two
  different electron transport chains or strings of
  proteins embedded in the thylakoid membranes that
  are constantly accepting and casting off
  electrons. See p. 211 Fig. 8-10.
• An electron transport chain can be located
  anywhere in the cell, usually on a membrane!
• The electron loses energy with each pass.
• Lost energy can be used to make ATP.
• Extra electrons are important later in
  preparation for the light-independent rxns.

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Photolysis

• Photolysis The process of water being split by
  the suns energy. See p. 211 Fig. 8-10.
• Products of photolysis are
• Oxygen that we breathe ? ? ?
• Half a molecule of O for each H2O
• Two electrons that can go back into chloroplasts
• Needed because chloroplasts cannot continue to
  lose electrons during light-dependent reactions.
• Two hydrogen ions

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9.2 Light-Independent Reactions

• ? ? ? Commonly called The Calvin Cycle simple
  sugars are produced from CO2 and Hydrogen!!
• Named after Melvin Calvin
• The main reactant is CO2 ? ? ?
• Takes place in the stroma of the chloroplast.
• The stroma is the fluid surrounding the grana in
  a chloroplast.
• See p. 212, Fig. 8-11.

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Where does the glucose go?

• Plants have a vascular system just like we do!
• Instead of blood, their veins carry water and
  food, or in this case glucose.
• Phloem cells carry glucose from the leaves to the
  rest of the plant.
• Xylem cells carry water from the roots in the
  ground up to the plants leaves.
• Xylem and phloem cells form tubes through which
  water and sugars can travel.

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Getting Energy to Make ATP

• A Review
• The mitochondria in cells breaks down glucose and
  produces energy in this case ATP.
• This process is referred to as cellular
  respiration.

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Cellular Respiration

• Three stages of cellular respiration
• Glycolysis - anaerobic
• The Citric Acid Cycle - aerobic
• The electron transport chain aerobic
• The aerobic phase produces the most ATP
• ? ? ? The process begins with food molecules
  (glucose) that are broken down into usable energy
  (ATP).

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Glycolysis

• Takes place in the cytoplasm of the cell
• It requires no oxygen (anaerobic).
• Glucose (a 6 carbon molecule) is broken down into
  2 molecules of pyruvic acid (a 3 carbon
  compound).
• It requires 2 ATP
• It produces 4 ATP
• A net gain of 2 ATP

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The Citric Acid Cycle

• Similar to the Calvin Cycle. See p. 227, Fig.
  9-6.
• Takes place in the mitochondria of the cell.
• Review Inner folded membranes.
• The pyruvic acid from glycolysis is slightly
  modified before the citric acid cycle begins.
• These new molecules (called Acetyl Coenzyme A)
  are broken down to form ATP and CO2.
• One ATP per cycle is produced, two cycles occur
  per glucose molecule.

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The Electron Transport Chain

• The final stage of respiration
• Similar to the events of the protein chain in
  photosynthesis.
• Electrons are passed from protein to protein, and
  the energy they give off is used to produce more
  ATPs.
• ? ? ? The final electron acceptor is an oxygen
  atom.
• This is why we cannot live without oxygen!

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Respiration

• One glucose molecule is capable of producing a
  net amount of 38 ATP (although your book says 36-
  it doesnt take into consideration the 2 Citric
  Acid Cycles)
• 2 in glycolysis
• 2 from the 2 Citric Acid Cycles (one per cycle)
• 34 from the electron transport chain

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Fermentation

• When oxygen isnt available, the aerobic stages
  of respiration obviously cant begin.
• In this situation, fermentation begins after
  glycolysis as an alternate form of respiration.
• Why can glycolysis still go on?
• Fermentation provides small amounts of ATP until
  the cell can once again obtain enough oxygen to
  begin the aerobic stages of respiration.

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Fermentation

• Two main types p. 224
• Alcoholic Fermentation
• Common in yeast cells. CO2 and alcohol is
  produced.
• Lactic Acid Fermentation
• Occurs in animal muscle cells. Lactic acid is
  produced.

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Important Study Tips

• Figure 9.10 on p. 232.
• Aerobic/Anaerobic
• Photosynthesis/Respiration/Fermentation
• Alcoholic/Lactic Acid Fermentation
• Citric Acid Cycle/Calvin Cycle
• Light Dependent/Light Independent Rxns.
• ATP/ADP
• Stroma/Stomate/Stomata
• Xylem/Phloem
• What is the definition of a cycle?