Cell respiration

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Cell respiration
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Cell Respiration

• How do cells release stored energy?
• How do cells make ATP?
• Glycolysis
• Prep Step
• Krebs Cycle
• Electron Transport Chain
• Alternative Energy Sources of Human Body

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ATP

• Energy must be in a form that can drive thousands
  of life-sustaining reactions.
• Plants make ATP during photosynthesis and use it
  to make glucose and other carbohydrates.
• Every organism on Earth produces ATP by breaking
  down glucose and other carbohydrates, lipids, and
  proteins.

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ATP Reaction

• The ATP reaction releases electrons and H from
  intermediates.
• The H and the electrons are delivered to an
  electron transport chain. An Energy Releasing
  Pathway

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Anaerobic Energy Releasing Pathways

• Energy releasing pathways originated long before
  our oxygen-rich planet evolved about 1 billion
  years ago.
• Early pathways must have been anaerobic. (did not
  use oxygen).
• Many prokaryotics and protistans still live in
  places w/o O2.

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Aerobic Energy Releasing Pathways

• The dominant pathway.
• Each breath you take provides your actively
  respiring cells with a fresh supply of oxygen!

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Both energy pathways start with glycolysis.
Aerobic Respiration (presence of oxygen)
GLYCOLYSIS
Anaerobic Respiration (absence of oxygen)
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What is Glycolysis?
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• The main energy-releasing pathways all start with
  the same reactions in the cytoplasm.
• Glycolysis

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Glycolysis The first stage of
energy- releasing pathways

• Glucose C6H12O6 a simple sugar

Glucose Glucose-6-phosphate
2 Pyruvate
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Glycolysis

• The first step of glycolysis is energy requiring.
• The phosphorylation of glucose
• Two ATP molecules transfer a phosphate group to
  glucose, which raises its energy level up enough
  for the energy-releasing steps.
• \
• The second step, is the beginning of the energy
  releasing steps of glycolysis. The glucose
  cleaves into two molecules of PGAL
  (phosphoglyceraldehyde)
• The next step is when the 2 PGAL are converted to
  an unstable intermediate that gives up the
  phosphate group to ADP to make 2 ATP
• The next intermediate step does the same thing.
  This is called substrate-level phosphorylation
  (substrates transfers P to other group in
  reaction)
• The coenzyme NAD picks up electrons and H
  liberated from each PGAL becoming NADH which have
  roles in the next stage of reactions
• So all together 4 ATP are made. Four out, two in
  2 ATP formed during glycolysis.
• The end product of glycolysis is two molecules of
  pyruvate, 2 ATP and 2 NADH

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Aerobic Pathway

• Next two final steps of breaking down glucose
  takes place in mitochondria.
• In the 2nd stage, glucose is broken down to CO2
  and water. Two ATP form, the transfer of e- and
  H from intermediates to co-enzymes.

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Preparatory Step before Krebs

• In a few preparatory reactions, an enzyme removes
  a carbon from each pyruvate molecule. Coenzyme
  A, an enzyme helper becomes acetyl-CoA by
  combining with the two carbon fragment left after
  the removal. It will be passes to oxaloacetate,
  the entry point of the Kreb Cycle (named for Hans
  Kreb, 1930) Also called the citric acid cycle

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• Electron Transport and Oxidative Phosphorylation
• Inner membrane of the mitochondria contains an
  electron transport system.
•                                                 
                                     

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Electrons from NADH and FADH2 pass through the
protein complexes, and cause protons to be pumped
from the matrix to the inner membrane space.
                                                  
                
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ATP synthase, a protein complex of the inner
membrane, uses the potential energy of the proton
gradient to synthesize ATP.                    
                                         
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Electron Transfer Phosphorylation

• Oxidative Phosphorylation via the Electron
  Transport Chain
• The electron transport chain allows the release
  of the large amount of chemical energy stored in
  reduced NAD (NADH) and reduced FAD (FADH2). The
  energy released is captured in the form of ATP (3
  ATP per NADH and 2 ATP per FADH2).
• NADH H 3 ADP 3 Pi 1/2 O2 ? NAD H2O
  3 ATP
• FADH2 2 ADP 2 Pi 1/2 O2 ? FAD H2O 2
  ATPThe electron transport chain (ETC) consists
  of a series of molecules, mostly proteins,
  embedded in the inner mitochondrial membrane.

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