IB Biology Cell Respiration HL

1. CELL RESPIRATION

2. REACTIONS
OXIDATIONOXIDATION
• Addition of oxygenAddition of oxygen
atomsatoms
• Removal of hydrogenRemoval of hydrogen
atomsatoms
• Loss of electrons fromLoss of electrons from
a substancea substance
REDUCTIONREDUCTION
• Removal of oxygenRemoval of oxygen
atomsatoms
• Addition of hydrogenAddition of hydrogen
atomsatoms
• Addition of electronsAddition of electrons
to a substanceto a substance

5. RESPIRATIONRESPIRATION
GLUCOSEGLUCOSE
FATTY ACIDSFATTY ACIDS
AMINO ACIDSAMINO ACIDS
OXIDATIONOXIDATION
GLYCOLYSISGLYCOLYSIS
•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 REQUIREDOES NOT REQUIRE
OXYGENOXYGEN
•IT OCCURS IN BOTH AEROBIC AND ANAEROBIC RESPI RATION.
•IT OCCURS IN BOTH PROKARYOTES & EUKARYOTES

6. STEPS INVOLVED IN GLYCOLSISSTEPS INVOLVED IN GLYCOLSIS
STEP I PHOSPHORYLATIONSTEP I PHOSPHORYLATION
• 2PO2PO44 groups are added to agroups are added to a GLUCOSEGLUCOSE molecule tomolecule to
formform HEXOSE BIPHOSPHATEHEXOSE BIPHOSPHATE..
• 2ATP2ATP molecules provide themolecules provide the POPO44
• Energy level of the hexose formed is raised byEnergy level of the hexose formed is raised by
phosphorylation and this makes the subsequentphosphorylation and this makes the subsequent
reactions possiblereactions possible
GLUCOSEGLUCOSE
HEXOSEHEXOSE
BIPHOSPHATEBIPHOSPHATE
2 ATP2 ATP 2 ADP2 ADP

7. STEP II: LYSISSTEP II: LYSIS
• EachEach HEXOSE BIPHOSPHATEHEXOSE BIPHOSPHATE splits to formsplits to form 22
molecules ofmolecules of TRIOSE PHOSPHATE .TRIOSE PHOSPHATE .
HEXOSEHEXOSE
BIPHOSPHATEBIPHOSPHATE
2 molecules2 molecules
TRIOSETRIOSE
PHOSPHATEPHOSPHATE

8. STEP III: OXIDATION of Triose phosphateSTEP III: OXIDATION of Triose phosphate
2 molecules of2 molecules of
TRIOSETRIOSE
PHOSPHATEPHOSPHATE
3 CARBON3 CARBON
COMPOUNDCOMPOUND
carryingcarrying 2PO2PO44
groups eachgroups each
2 NAD2 NAD++
2 NADH + H2 NADH + H++

9. STEP IV: ATP formationSTEP IV: ATP formation
TwoTwo 33
CARBONCARBON
COMPOUNDCOMPOUND
formedformed
2 PYRUVATE2 PYRUVATE
MOLECULESMOLECULES
4 ADP4 ADP 4 ATP4 ATP
Enzymes remove the 2 phosphate groups and provide them to ADP
for ATP formation

10. STEP IV: ATPSTEP IV: ATP
formationformation
STEPS INVOLVED IN GLYCOLSISSTEPS INVOLVED IN GLYCOLSIS
STEP III: OXIDATION of Triose phosphateSTEP III: OXIDATION of Triose phosphate
STEP II: LYSISSTEP II: LYSIS
STEP I: PHOSPHORYLATIONSTEP I: PHOSPHORYLATION
glucoseglucose
HexoseHexose
biphosphate (6c)biphosphate (6c)
2 triose phosphate2 triose phosphate
(3c) molecules(3c) molecules
2 pyruvate2 pyruvate
moleculesmolecules
2 ATP2 ATP
2 ADP2 ADP
2 INTERMEDIATE2 INTERMEDIATE
(3c) molecules(3c) molecules
4 ADP4 ADP
4 ATP4 ATP
2 NAD2 NAD++
2 NADH + H2 NADH + H++

11. • The fate of Pyruvate is decided by theis decided by the
availability of oxygen.availability of oxygen.
• This step occurs only if oxygen is notnot available
or is in short supply; ie . ANAEROBIC
RESPIRATION
Each molecule ofEach molecule of
PYRUVATEPYRUVATE
Ethanol (2 C)Ethanol (2 C)
COMPOUNDCOMPOUND
COCO22In plantsIn plants
In animalsIn animals

12. In animalsIn animals
LINK REACTIONLINK REACTION

13. LINK REACTION
• Pyruvate passes from the cytosol to the innerpasses from the cytosol to the inner
mitochondrial matrixmitochondrial matrix by active transport
• This step occurs only if oxygen is available;
ie . AEROBIC RESPIRATION
Each moleculeEach molecule
ofof PYRUVATEPYRUVATE
2 CARBON2 CARBON
COMPOUNDCOMPOUND
ACETYL CoAACETYL CoA
NADNAD++
NADH + HNADH + H++
COCO22CoACoA

14. • DeCarboxylationDeCarboxylation and OxidationOxidation occur
simultaneously hence the step is called OxidativeOxidative
decarboxylationdecarboxylation
• Pyruvate + CoA forms Acetyl CoAAcetyl CoA
• CoACoA comprises of [ adenine + ribose sugar + Pantothenic acid]comprises of [ adenine + ribose sugar + Pantothenic acid]
• CoA is a carrier for Acetyl group into the Krebs
cycle.
NADNAD++
NADH + HNADH + H++
COCO22
CoACoACoACoA
Link reactionLink reaction

15. • The energy stored in NADH is used to generateThe energy stored in NADH is used to generate
a proton gradient across the inner membrane.a proton gradient across the inner membrane.
• The energy of the proton gradient is used toThe energy of the proton gradient is used to
make ATP (phosphorylate).make ATP (phosphorylate).
• Glucose on oxidation during glycolysis andGlucose on oxidation during glycolysis and
Krebs cycle , the Co-enzymes NAD and FAD areKrebs cycle , the Co-enzymes NAD and FAD are
reduced toreduced to NADH + HNADH + H++
& FADH + H& FADH + H++
Oxidation phosphorylationOxidation phosphorylation

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

18. • Co Q carries the electrons to cytochrome bc1Co Q carries the electrons to cytochrome bc1
complex ; energy is releasedcomplex ; energy is released
• Electrons are carried forward from cytochromeElectrons are carried forward from cytochrome
bc1 complex to cytochrome c ; energy isbc1 complex to cytochrome c ; energy is
releasedreleased
• As a result the more and more H+ ionsAs a result the more and more H+ ions
( protons) are transferred to the inter( protons) are transferred to the inter
membrane space.membrane space.

19. • In the mitochondrial matrix electrons fromIn the mitochondrial matrix electrons from
FADH are transferred to Co Q; energy isFADH are transferred to Co Q; energy is
releasedreleased
• As a result the H+ ions ( protons) areAs a result the H+ ions ( protons) are
transferred to the inter membrane space.transferred to the inter membrane space.

21. • Co Q carries the electrons to cytochrome bc1Co Q carries the electrons to cytochrome bc1
complex ; energy is releasedcomplex ; energy is released
• Electrons are carried forward from CytochromeElectrons are carried forward from Cytochrome
C to Cytochrome c oxidase; energy is releasedC to Cytochrome c oxidase; energy is released
• As a result the more and more H+ ionsAs a result the more and more H+ ions
( protons) are transferred to the inter( protons) are transferred to the inter
membrane space.membrane space.
Cytochrome c oxidase ultimately transfersCytochrome c oxidase ultimately transfers
electrons to Oxygen (terminal e acceptor) andelectrons to Oxygen (terminal e acceptor) and
water is formed as an end product.water is formed as an end product.

23. • Transfer of protons to the inter membraneTransfer of protons to the inter membrane
space develops a proton motive force across thespace develops a proton motive force across the
membrane.membrane.
• Inner membrane is impermeable to protons soInner membrane is impermeable to protons so
protons can pass through into the matrix is onlyprotons can pass through into the matrix is only
through the ATP Synthase enzyme.through the ATP Synthase enzyme.
Energy derived from the movement ofEnergy derived from the movement of
these protons back into the inner matrixthese protons back into the inner matrix
is used to synthesize ATP from ADPis used to synthesize ATP from ADP
This is oxidative phosphorylation.This is oxidative phosphorylation.

26. Respiration chemiosmosisRespiration 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

28. PHOTOSYNTHESISPHOTOSYNTHESIS
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.

29. Structure of ChloroplastStructure 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.

31. The overall processThe 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 STAGELIGHT DEPENDENT STAGE ( occurs in the
GRANA) and LIGHT INDEPENDENT STAGELIGHT INDEPENDENT STAGE ( occurs in the
STROMA)

32. The Light dependent reactions: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.

34. The Light dependent reactions: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

35. The Light dependent reactions: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 .

38. Photosynthesis chemiosmosisPhotosynthesis 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

40. Cyclic photophosphorylationCyclic photophosphorylation
• It requires photosystem Iphotosystem I, but not photosystem II.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.

45. LIGHT INDEPENDENT REACTIONSLIGHT 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 form 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.