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CELL RESPIRATION
C6H12O6 + 6O2
---
6H2O + 6CO2 + 36 ATP
Humans use 1,000,000 molecules of ATP/cell/second !!!!
Is this a CATABOLIC or ANABOLIC Reaction?
REACTIONS
OXIDATION
• LOSS of electrons
from a substance
• Addition of oxygen
atoms
• Removal of hydrogen
atoms
REDUCTION
• GAIN of electrons to a
substance
• Removal of oxygen
atoms
• Addition of hydrogen
atoms
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