Stages Aerobic Respiration 1. Stage 1: Glycolysis 2. Stage 2:
Pyruvate Oxidation 3. Stage 3: Krebs Cycle 4. Stage 4: Electron
Transport Chain and Chemiosmosis Glycolysis occurs in cytoplasm
Stage 2 4 occurs in mitochondria - possess double membrane: outer
membrane as well as an inner membrane (highly folded) -
intermembrane space between both membranes (fluid filled) - inner
membrane contains mitochondrial matrix (protein-rich liquid that
fills interior)
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Aerobic cellular respiration: Overview
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Aerobic respiration: An overview A series of enzyme controlled
reactions Oxygen is used to oxidize glucose Glucose is oxidized to
form carbon dioxide Oxygen is reduced to form water During the
oxidation of glucose: Electrons transferred to electron carriers,
NAD+ and FAD+ Glycolysis and Krebs cycle Electrons then passed
through an electron transport chain. The energy from the electrons
will be used to pump protons. The energy from the diffusion of
protons will be used to make ATP.
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Stage 2: Pyruvate Oxidation Recall: reactions of glycolysis
produced TWO pyruvates, TWO ATPs, and 2 NADHs - does not require O
2 ; occurs in cytoplasm Pyruvate Oxidation: chemical pathway that
connects glycolysis to Krebs cycle 2 pyruvate molecules are moved
from the cytoplasm to the matrix of the mitochondria CO 2 is
removed from each pyruvate molecule and released as a waste product
(1/3 of what you exhale)
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Stage 2: Pyruvate Oxidation Cont. The remaining 2-carbon
portions are oxidized by NAD+; As a result, the NAD+ molecule gains
two hydrogen atoms and the remaining 2- carbon molecule becomes
acetic acid Coenzyme A (Co-A) attaches and forms acetyl-CoA
Acetyl-coA enters stage 3 (Krebs cycle) and NADH goes to stage 4
(ETC) 2 CO 2 diffuses out of the mitochondria and cell.
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Stage 3: Krebs Cycle This is an 8 step and cyclic stage cyclic
because one of the products of step 8, is a reactant in step 1 At
the end of the Krebs Cycle, all six carbons have been oxidized to
CO 2 and released from the cell as metabolic waste All that remains
is some free energy in the form of ATP and high energy NADH and
FADH 2 These energy carriers enter the ETC
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Krebs Cycle: The Details 1. Cycle occurs twice for each
acetyl-CoA molecule 2. Acetyl CoA adds 2-carbons to oxaloacetate,
producing citrate 3. Citrate loses a CO 2 molecule, and the
resulting compound is oxidized, reducing NAD+ to NADH 4. Another CO
2 is lost, and the resulting compound is oxidized, reducing NAD+ to
NADH 5. ADP is phosphorylated to ATP 6. Two hydrogen's are
transferred to FAD+ to form FADH 2 Kreb Cycle
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Krebs Cycle Overview 1 Glucose= 2 ATP 6 NADH 2 FADH 2 4 CO 2
EACH pyruvate molecule produced in glycolysis (2) must enter the
Krebs Cycle Therefore the cycle occurs twice for every glucose
molecule
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Stage 4: ETC NADH and FADH 2 : release the electrons they
received during glycolysis and the Krebs cycle to ETC - proteins of
the ETC transfer the electrons and use the energy released to pump
hydrogen ions (protons) Hydrogen ions (protons) are pumped from the
matrix to the intermembrane space Creates a concentration
gradient
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Stage 4: ETC Cont. Oxygen: final electron acceptor at the end
of the ETC - oxygen accepts the electrons, combines with protons
and become water The accumulated hydrogen ions (protons) diffuse
back into the matrix through ATP synthase complex - The energy
released from the diffusion fuels the formation of ATP (by pumping
H+ ions into intermembrane space) ETC: an ongoing process - NADH
delivers electrons continuously - FADH 2 delivers lower energy
electrons in different place than NADH (cannot pump as many H+
ions) Electron Transport Chain animation Electron Transport
Chain
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Stage 4 Cont: Chemiosmosis H+ ions accumulate in intermembrane
space from ETC - creates an electrochemical gradient H+ ions
(protons) move from intermembrane space to ATP synthase complex -
energy in gradient forces them through Energy released as H+ ions
pass through = binds ADP with P i to produce ATP! Energy removed
from 1 NADH = 3 ATPs; 1 FADH 2 = 2 ATPs Oxidative phosphorylation:
Because the energy needed to add the Pi group to ADP is derived
from the oxidation of a glucose molecule aka oxidative ATP
synthesis
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Final Points ATP is now sent to the cytoplasm to be utilized by
the cell All stages are dependent on glycolysis for the production
of pyruvate Last stages are dependent on the availability of
electrons (from food glucose) and oxygen