Download Oxidation

CELL RESPIRATION
REACTIONS
OXIDATION
• Addition of oxygen
atoms
• Removal of hydrogen
atoms
• Loss of electrons from
a substance
REDUCTION
• Removal of oxygen
atoms
• Addition of hydrogen
atoms
• Addition of electrons
to a substance
RESPIRATION
GLUCOSE
FATTY ACIDS
AMINO ACIDS
OXIDATION
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
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
GLUCOSE
2 ADP
HEXOSE
BIPHOSPHATE
STEP II:
LYSIS
• Each HEXOSE BIPHOSPHATE splits to form 2
molecules of TRIOSE PHOSPHATE .
HEXOSE
BIPHOSPHATE
2 molecules
TRIOSE
PHOSPHATE
STEP III: OXIDATION of Triose phosphate
2 NAD+
2 molecules of
TRIOSE
PHOSPHATE
2 NADH + H+
3 CARBON
COMPOUND
carrying 2PO4
groups each
STEP IV: ATP formation
4 ADP
Two 3
CARBON
COMPOUND
formed
4 ATP
2 PYRUVATE
MOLECULES
Enzymes remove the 2 phosphate groups and provide them to ADP
for ATP formation
STEPS INVOLVED IN GLYCOLSIS
STEP I: PHOSPHORYLATION
STEP II: LYSIS
STEP III: OXIDATION of Triose phosphate
2 NAD+
STEP IV: ATP formation
2 NADH + H+
2 triose phosphate
(3c) molecules
glucose
2 ATP
2 ADP
2 INTERMEDIATE
(3c) molecules
4 ADP
Hexose
biphosphate (6c)
4 ATP
2 pyruvate
molecules
• 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
In plants
Each molecule of
PYRUVATE
CO2
Ethanol (2 C)
COMPOUND
In animals
Each molecule of
PYRUVATE(3C)
Lactic acid (3 C)
COMPOUND
In animals
Each molecule of
PYRUVATE(3C)
LINK REACTION
Lactic acid (3 C)
COMPOUND
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+
2 CARBON
COMPOUND
ACETYL CoA
Each molecule
of PYRUVATE
CoA
CO2
• 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+
Each molecule of
PYRUVATE
CoA
2 CARBON
COMPOUND
ACETYL CoA
CO2
Link reaction summary
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+
• 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.
• 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.
• 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.
• 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.
• 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.
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
Total Yield
Glycolysis produces 2 ATP; aerobic respiration
produces 34 more ATP
Pathway
Glycolysis
Substrate-Level
Phosphorylation
2 ATP
CoA
Krebs Cycle
2 ATP
TOTAL
4 ATP
Oxidative
Phosphorylation
2 NADH = 4 - 6 ATP
Total
ATP
6-8
2 NADH = 6 ATP
6
6 NADH = 18 ATP
2 FADH2 = 4 ATP
24
32 ATP
36 - 38
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.
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.
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)
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.
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
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 .
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
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.
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.