Cellular Respiration

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Cellular Respiration
7.1 Glycolysis and Fermentation 7.2 Aerobic
Respiration
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Cell Respiration

• Living cells constantly use energy for activities
  such as movement, protein synthesis, active
  transport and cell division.
• Most of the energy to power these processes
  comes from ATP.
• A cell must constantly replace ATP

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• The cell does this by breaking down organic food
  molecules. Releasing energy that is used to join
  ADP and phosphate to form ATP
• The breakdown of food to release energy occurs
  by 2 kinds of processes
• 1. respiration 2. fermentation

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Cell Respiration

• A fuel molecule such as glucose is oxidized to
  form carbon dioxide and water.
• Energy is captured through the formation of up to
  36 to 38 ATPs per glucose molecule

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• It is the process by which cells extract fee
  energy from the energy stored in chemical bonds
  of food molecules (glucose)
• This is done in a series of catabolic pathways
  featuring redox reactions and using oxygen as the
  final electron acceptor

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• The energy released is used to regenerate the
  cells supply of ATP
• ATP donates the energy to various energy
  requiring processes such as metabolic reactions,
  active transport, muscle contractions, etc

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3 Metabolic stages of Cell Respiration

• 1.Glycolysis
• 2. Kreb Cycle
• 3. Oxidative phosphorylation

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Mitochondria

• Site of cell respiration
• Most ATP production occurs here
• Parts of the Mitochondria
• 1. Cristae folds of mitochondria is where
  electron transport occurs
• 2. Matrix open area of mitochondria, where kreb
  cycle occurs
• 3 Cytosol outside mitochondria , where
  glycolysis occurs.

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d. Outer membrane
a. Matrix
b. Cristae
c. Inner membrane
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ATP
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Glycolysis

• Occurs in cytosol outside mitochondria
• Converts the 6-carbon glucose into 2 3-carbon
  pyruvic acid molecules
• 4 ATP are make, but due to a deficiency of 2 ATP,
  the step generates a positive 2 ATP
• If oxygen is present then the reaction proceeds
  to kreb cycle

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• If oxygen is absent, it will proceed to
  fermentation
• Fermentation occurs in the cytosol, has a net
  gain of 2 ATP per glucose and is only 2.1
  efficient
• Between glycolysis and kreb cycle is a transition
  reaction in which pyruvate ( pyruvic acid) is
  converted to acetyl CoA and 2 CO2 are removed

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Glycolysis
Lactic Acid Fermentation
Alcoholic Fermentation
Krebs Cycle
Electron Transport Chain
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Kreb Cycle

• Is located within the mitochondria matrix
• Also called Citric acid cycle, or TCA
• Completes glucose oxidation by breaking down a
  pyruvic acid derivative (acetyl CoA) into carbon
  dioxide
• Is a circular sect of reactions because the
  reaction is ongoing, never reaching an endpoint.

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• Requires 2 turns of the kreb cycle per glucose (
  each turn releasing 2 carbon dioxides, 3 NADH, 1
  ATP, 1 FADH2
• NADH and FADH2 are coenzymes (NAH accepts 2
  electrons and 1 hydrogen while FAD accepts 2
  electrons and 2 hydrogen)

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Oxidative phosphorylation

• Accounts for most ATP produced during respiration
  (32 to 34)
• Includes electron transport chain made of
  electron carriers molecules built into the inner
  mitochondrial membrane
• Oxygen pulls energized electrons harvested during
  glycolysis and kreb cycle down the electron
  transport chain to a lower energy state.

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• This exergonic slide of electrons is coupled to
  ATP synthesis
• Electron transport accepts electrons from glucose
  during glycolysis and transition reaction and
  kreb cycle usually NAD carries these electrons

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• The electrons then drop off the supply of energy
  needed to pump the hydrogen ions from the matrix
  to the intermembrane space of the mitochondria (
  this is chemiosmosis)
• The NAD and Fad then return to pick up more
  hydrogen ( both reusable)

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• When NADH delivers electrons, it has enough
  energy to make 3 ATP.
• When FADH2 delivers electrons, it has enough
  energy to make 2 ATP
• Cytochrome the molecule that helps with electron
  transport

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• Chemiosmosis ability of some members to use
  hydrogen ion s gradient to drive ATP formation
• Oxidative phosphorylation refers to the
  production of ATP as a result of energy released
  by electron transport system

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Electron Transport Chain of Aerobic Respiration
protons
protons
protons
FADH2
NAD
ADPPhosphate
O2
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Electron Transport Chain of Aerobic Respiration
protons
protons
protons
FADH2
NAD
ADPPhosphate
O2
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Energy Yield of Aerobic Respiration One
glucose can generate up to 38 ATP molecules.
38 x 12 kcal divided by 686 kcal 66
efficiency. About 20 times more efficient
than glycolysis alone. Note a car engine is
only about 25 efficient.
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http//www.sirinet.net/jgjohnso/cellularresp.html
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Photosynthesis and Cellular Respiration
(opposite reactions) The final products of
plant photosynthesis (sugar and oxygen) are used
by animals for the process called cellular
respiration. The products of respiration are
carbon dioxide and water, which plants need for
photosynthesis. Since photosynthesis and
respiration are opposite processes, they form a
cycle that keeps the levels of oxygen and carbon
dioxide fairly constant in the atmosphere.
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Glycolysis
Lactic Acid Fermentation
Alcoholic Fermentation
Krebs Cycle
Electron Transport Chain
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