CELL RESPIRATION

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CELL RESPIRATION
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REACTIONS

• OXIDATION

• REDUCTION

• Removal of oxygen atoms
• Addition of hydrogen atoms
• Addition of electrons to a substance

• Addition of oxygen atoms
• Removal of hydrogen atoms
• Loss of electrons from a substance

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RESPIRATION
GLYCOLYSIS

• IF THE RESPIRATORY SUBSTRATE IS GLUCOSE THEN THE
  
• FIRST STAGE OF CELLULAR RESPIRATION IS
  GLYCOLYSIS
• THIS PATHWAY OCCURS IN THE CYTOPLASM
• LESS AMOUNT OF ENERGY IS PRODUCED
• PARTIAL OXIDATION OF GLUCOSE OCCURS, AND DOES NOT
  REQUIRE OXYGEN
• IT OCCURS IN BOTH AEROBIC AND ANAEROBIC RESPI
  RATION.
• IT OCCURS IN BOTH PROKARYOTES EUKARYOTES

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STEPS INVOLVED IN GLYCOLSIS

• STEP I PHOSPHORYLATION
• 2PO4 groups are added to a GLUCOSE molecule to
  form HEXOSE BIPHOSPHATE.
• 2ATP molecules provide the PO4
• Energy level of the hexose formed is raised by
  phosphorylation and this makes the subsequent
  reactions possible

2 ATP
2 ADP
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• STEP II LYSIS
• Each HEXOSE BIPHOSPHATE splits to form 2
  molecules of TRIOSE PHOSPHATE .

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• STEP III OXIDATION of Triose phosphate

2 NAD
2 NADH H
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• STEP IV ATP formation

4 ADP
4 ATP
Enzymes remove the 2 phosphate groups and
provide them to ADP for ATP formation
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STEPS INVOLVED IN GLYCOLSIS
STEP I PHOSPHORYLATION
STEP II LYSIS
STEP III OXIDATION of Triose phosphate

• STEP IV ATP formation

2 NAD
2 NADH H
2 triose phosphate (3c) molecules
glucose
2 ATP
2 INTERMEDIATE (3c) molecules
2 ADP
4 ADP
Hexose biphosphate (6c)
4 ATP
2 pyruvate molecules
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• The fate of Pyruvate is decided by the
  availability of oxygen.
• This step occurs only if oxygen is not available
  or is in short supply ie . ANAEROBIC
  RESPIRATION

CO2
In plants
In animals
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LINK REACTION
In animals
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LINK REACTION

• Pyruvate passes from the cytosol to the inner
  mitochondrial matrix by active transport
• This step occurs only if oxygen is available
  ie . AEROBIC RESPIRATION

NAD
NADH H
CO2
CoA
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• DeCarboxylation and Oxidation occur
  simultaneously hence the step is called Oxidative
  decarboxylation
• Pyruvate CoA forms Acetyl CoA
• CoA comprises of adenine ribose sugar
  Pantothenic acid
• CoA is a carrier for Acetyl group into the Krebs
  cycle.

NAD
NADH H
CO2
CoA
Link reaction summary
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Oxidation phosphorylation

• The energy stored in NADH is used to generate a
  proton gradient across the inner membrane.
• The energy of the proton gradient is used to make
  ATP (phosphorylate).
• Glucose on oxidation during glycolysis and Krebs
  cycle , the Co-enzymes NAD and FAD are reduced to
  NADH H FADH H

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• In the mitochondrial matrix electrons from NADH
  are transferred to Co Q by NADH DEHYDROGENASE
  energy is released
• As a result the H ions ( protons) are
  transferred to the inter membrane space.

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• Co Q carries the electrons to cytochrome bc1
  complex energy is released
• Electrons are carried forward from cytochrome bc1
  complex to cytochrome c energy is released
• As a result the more and more H ions ( protons)
  are transferred to the inter membrane space.

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• In the mitochondrial matrix electrons from FADH
  are transferred to Co Q energy is released
• As a result the H ions ( protons) are
  transferred to the inter membrane space.

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• Co Q carries the electrons to cytochrome bc1
  complex energy is released
• Electrons are carried forward from Cytochrome C
  to Cytochrome c oxidase energy is released
• As a result the more and more H ions ( protons)
  are transferred to the inter membrane space.

Cytochrome c oxidase ultimately transfers
electrons to Oxygen (terminal e acceptor) and
water is formed as an end product.
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• Transfer of protons to the inter membrane space
  develops a proton motive force across the
  membrane.
• Inner membrane is impermeable to protons so
  protons can pass through into the matrix is only
  through the ATP Synthase enzyme.

Energy derived from the movement of these protons
back into the inner matrix is used to synthesize
ATP from ADP This is oxidative phosphorylation.
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Respiration chemiosmosis

• Involves an electron transport chain in the
  membrane s of the cristae
• Energy is released when electrons are exchanged
  from 1 carrier to another
• Released energy is used to actively pump hydrogen
  ions into the inter-membrane space
• Hydrogen ions come from the matrix
• H ions diffuse back into the matrix through the
  channels of ATP synthase
• ATP synthase catalyses the oxidative
  phosphorylation of ADP to ATP

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PHOTOSYNTHESIS

• 6CO2 12 H2O ? C6H12O6 6 H2O 6 O2.
• Draw and label the chloroplast as seen under the
  electron microscope
• State that photosynthesis contains light
  dependent and light independent reactions.
• Explain light dependent reactions.

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Structure of Chloroplast

• Chloroplast contains a double layered membrane
• Like mitochondria it contains its own DNA
  (plasmid) and 70s ribosomes.
• Stroma- matrix similar to the cytosol of the
  cell it contains enzymes and chemicals
  necessary for dark reaction , some lipid
  molecules and starch granules.
• Grana- contains stacked thylakoids flat
  membranous sacs containing chlorophyll pigment in
  units called photosystems
• Membranes of the grana contain electron carriers
  and hold the pigment enzymes provide a large
  surface area for light dependent reactions to
  occur.

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The overall process

• The reactions on establishing bonds for the
  formation of organic molecules.
• 6CO2 12 H2O ? C6H12O6 6 H2O 6 O2
• Photosynthesis is an anabolic process
• Ocuurs in 2 steps LIGHT DEPENDENT STAGE ( occurs
  in the GRANA) and LIGHT INDEPENDENT STAGE (
  occurs in the STROMA)

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The Light dependent reactions

• Light supplies energy for these reactions to
  occur
• Pigments are arranged on the thylakoid membranes
  in a PHOTOSYSTEM (chlorophyll a , accessory
  pigments and protein matrix and the reaction
  centre (chlorophyll a , primary electron acceptor
  and protein matrix)
• Photosystem 1 is effective at 700 nm
• Photosystem II is effective at 680 nm.
• They work together to bring about non cyclic
  electron transfer.

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The Light dependent reactions

• Light strikes the Photosystem II causing it to
  transfer e to primary electron acceptor at the
  reaction centre.
• Excited e travel down the ETC electron transport
  chain (plastoquinone to cytochrome complex),
  electron loses energy at each exchange.
• Electrons are replaced by splitting water
  molecules, to produce elctrons, H and Oxygen
  atoms, this is photolysis of water.
• Electrons obtained are supplied 1 by 1 to the
  reaction centre.
• Chemiosmosis occurs , H are pumped into the
  thylakoid membrane

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The Light dependent reactions

• The outflow of the H into the stroma via the ATP
  synthase enzyme causes Phosphorylation --- ATP
  generation from ADP and PO4 called NON CYCLIC
  PHOSPHORYLATION.
• Light strikes the Photosystem I causing it to
  transfer e to primary electron acceptor at the
  reaction centre.
• Excited e travel down the ETC electron transport
  chain (INVOLVING FERREDOXIN NADP reductase
  which provides 2 electrons to NADP reduces it
  to NADPH)
• NADPH ATP are the final products of light
  reaction
• oxygen which is a waste product is excreted .

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Photosynthesis chemiosmosis

• Involves an electron transport chain in the
  membrane s of the thylakoids
• Energy is released when electrons are exchanged
  from 1 carrier to another
• Released energy is used to actively pump hydrogen
  ions into the thylakoid space
• Hydrogen ions come from the stroma
• H ions diffuse back into the stroma through the
  channels of ATP synthase
• ATP synthase catalyses the oxidative
  phosphorylation of ADP to ATP

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Cyclic photophosphorylation

• It requires photosystem I, but not photosystem
  II.
• Light-dependent electron transport occurs in the
  thylakoid membranes, where electrons follow a
  cyclic pathway, returning to the photosystem I
  reaction center.
• The energy of this electron transport results in
  a H gradient formation, the energy source for
  ATP synthesis. ATP is formed from ADP and Pi, but
  NADP is not reduced.

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LIGHT INDEPENDENT REACTIONS

• Occurs in the stroma
• It involves Calvins cycle
• Ribulose biphosphate (RuBP) (5c), binds to an
  incoming CO2 ---Carbon fixing catalyzed by enzyme
  RuBP carboxylase,( rubisco) , thus forming an
  unstable 6C compound.
• It breaks down into 2 (3c) compounds
  glycerate-3-phosphate.
• glycerate-3-phosphate are acted upon by ATP
  NADPH from the light reactions to foem 2 more
  compounds called TRIOSE PHOSPHATE (3c), this is
  reduction division.
• TP may go in 2 directions , some leave the cycle
  to become sugar phosphates that become
  CELLULOSE/STARCH while most continue in the
  cycle to form RuBP.
• In order to regain RuBP from TP , the cycle uses
  ATP.