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Intracellular Respiration
Energy and matter necessary for
metabolism are provided by
Intracellular respiration
C6H12O6 + 6O2 → 6CO2 + 6H2O +36ATP
Photosynthesis
6CO2 + 6H2O
Sunlight
→ C6H12O6 + 6O2
-Matter is always recycled, energy is not
A. Carbohydrates, fats, and proteins can
all be used as fuel
1. catabolism of glucose yields 686
kcal/mole of energy, some is
used to produce ATP, some is
lost as entropy
B. ATP is synthesized with energy of
electrons that are relocated from
food to ATP through a series of
redox reactions
1. oxidation – the loss of electrons
(usually pulled by
electronegative oxygen)
a. in respiration Glucose is
oxidized, releasing energy
b. Oxygen, in turn, is reduced
2.reduction the addition of electrons
3. hydrocarbons, and molecules that
have a lot of Hydrogen(sugars,
fats) are sources of electrons that
can be pulled by Oxygen
4. Glucose is broken down in a series
of steps, each catalyzed by a
specific enzyme
a. hydrogen atoms are transferred
from glucose by Dehydrogenase
enzymes to coenzymes that are
Hydrogen acceptors
1. NAD+ (oxidized)
Nicotinamide adenine
Dinucleotide, accepts
electrons and becomes
2. NADH (reduced)
5. ATP is synthesized as the
electrons carried by NADH lose
their energy when transferred to
oxygen during the ETC (electron
transport chain) (mitochondria)
a. at the end of ETC, Oxygen
combines with the
electrons and Hydrogen to
form water.
C. Respiration occurs in three stages
1.Glycolysis –
2.Krebs Cycle
3.ETC
D. Glycolysis
a. glucose is broken into 2 (3C)
compounds, 2 NADH, and
2ATP
b. occurs in the cytoplasm of both
c.
d.
e.
f.
eukaryotic and prokaryotic
cells.  common to all life
forms, this data to supports
Evolution (common ancestor)
Glucose 6C is oxidized and
splits into two Pyruvates,
which are 3C compounds.
10 steps in process, each with
specific enzymes
Energy Harvest Phase
consumes 2 ATP
4 ATP are synthesized
during the Energy Payoff
Phase by substrate-level
phosphorilation
1. enzymes:
Phosphoglycerokinase and
Pyruvate Kinase, transfer a
phosphate to ADP to form
ATP
2. two ATPs are gained in net
g.
h.
2 NADH molecules are made
through the reduction of
NAD+
1. these go to the ETC, where
each contributes enough
energy to produce 3 ATPs
Summary of molecules
produced:
1. 2 (3C) pyruvates
2. 2 ATPs
3. 2 NADHs
i. 10 steps of Glycolysis
1. These steps occur 2Xs.
Once for each of the two
G3Ps produced per glucose
E. Krebs Cycle
a. occurs in the mitochondrial
matrix, where the specific
Krebs cycle enzymes reside
b.  only occurs in Eukaryotic
cells.
c. Only occurs if Oxygen is
present
d. Pyruvate is oxidized to CO2
e. Cycle turns 2Xs per glucose
f. Per cycle, one ATP is
produced through substratelevel phosphorilation,
2 total ATP per glucose
g. 3 NADHs produced per
cycle,  6 in total per
glucose
h. one FADH2 (Flavin Adenine
Dinucleotide) is produced per
cycle,  2 per glucose
i. prior to cycle, pyruvate
enters the mitochondria
(only if O2 is present)
1. pyruvate is oxidized to an
acetyl CoA molecule
a. a carboxyl group is
removed as CO2
b. a pair of electrons and
H are transferred to
reduce NAD+ to
NADH
j. Cycle’s pathway elucidated
by Hans Krebs in 1930’s
1. He named it the Citric
Acid Cycle. It has 8 steps.
a.cycle starts when acetyl
combines with
Oxaloacetate, a 4C cpd. to
form citrate
b. the acetate is ultimately
degraded into 2 CO2
k. Summary of Krebs Cycle
Cycle turns 2Xs/glucose
(once per pyruvate)
F. ETC The Electron Transport Chain
a. in the cristae, the folded inner
membrane of the mitochondria
b. electrons from NADH & FADH2
move from molecule to molecule
in a series of redox reactions (the
electron transport chain), until
they combine with O2 and H to
form H2O
c. as e- pass along the chain, their
energy is harnessed and used to
power the synthesis of ATP via
oxidative phosphorilation
d. NADH’s electrons are transferred
to the first molecule in the ETC,
a flavoprotein, FMN- flavin
mononucleotide
e. then the electrons pass through a
series of redox reactions through
Q-ubiquinone and the cytochromes
f. the FADH2 electrons enter at a later
point in the chain, into the Fe-S
protein, then to Q, then to the cyt.
g. electrons are passed by increasingly
electronegative molecules in the
chain until the are passed to oxygen,
the most electronegative
h. for every 2 electron carriers (4e-),
one O2 is reduced to 2 H2O
i. Proton Motive Force- a proton
gradient, produced by the
movement of electrons along the
transport chain, as the exergonic flow
of electrons pumps H+ into the
intermembrane space.
1. this creates a proton-motive
force
2. these H+ protons diffuse
through ATP synthase. Their
exergonic energy is used to
power ATP synthesis
j. ATP Synthase- a protein complex
enzyme, on the cristae membrane of
the mitochondria, that makes ATP
from ADP + Pi
k.Chemiosmosis = the process of
coupling the redox reactions of
electron transport to the synthesis of
ATP.
G. Summary of energy gain from
aerobic respiration = 38 ATP
1. each NADH yields 3 ATPs
2. each FADH2 yields 2 ATPs
3. glycolysis:
2 ATP
2 NADH = 6 ATP
Total
= 8 ATP
4. Krebs Cycle per glucose
2 ATP
2 NADH = 6 ATP
6 NADH = 18 ATP
2 FADH2 = 4 ATP
Total
= 30 ATP
H. Efficiency of Intracellular
Respiration
1. the exergonic oxidation of
glucose releases
686 kcal/mole of energy
2. the endergonic synthesis of
ATP requires 7.3 kcal/mole
of energy
3. the efficiency of respiration is
7.3 kcal/mole x
38 ATP/glucose/686kcal/mole
of glucose x 100 = 40%
4. 60% of the energy is lost as heat
I. Fermentation-to produce ATP w/o O2
1. prokaryotes must regenerate
NAD+
AKA Anaerobic Respiration
a. in glycolysis NAD+ is the
oxidizing agent that pulls the
e- from glucose to form:
2 pyruvates derivatives
2 NADH, and
2 ATPs.
2. also occurs in Eukaryotes in the
absence of Oxygen (anaerobic)
to generate 2 ATP through
substrate level phosphorilation
3. 2 types of fermemtations:
a. alcoholic:
pyruvate is converted to:
- ethanol CH3-CH2-OH
- CO2
This pathway used in the production of
wine, beer, and alcoholic beverages
b. lactic acid:
pyruvate is converted to:
- lactate CH3-CHOH-COO
This process used by muscles when
oxygen concentration is low
J. 38 ATP Aerobic Respiration
Vs. 2 ATP Anaerobic from the
oxidation of molecule of glucose
K. Carbohydrates, fats, and proteins
can all be catabolized