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This presentation will discuss the major stages of cellular respiration. Cellular respiration is a set of metabolic reactions and processes that take place in the cells of organisms to convert chemical energy from oxygen molecules or nutrients into adenosine triphosphate and then release waste products.
2.
Mitochondria Parts and
Functions
Mitochondrial Parts Functions in Cellular Respiration
Outer mitochondrial membrane Separates the contents of the mitochondrion
from the rest of the cell
Matrix Internal cytosol-like area that contains the
enzymes for the link reaction & Krebs Cycle
Cristae Tubular regions surrounded by membranes
increasing surface area for oxidative
phosphorylation
Inner mitochondrial membrane Contains the carriers for the ETC & ATP
synthase for chemiosmosis
Space between inner & outer Reservoir for hydrogen ions (protons), the
membranes high concentration of hydrogen ions is
necessary for chemiosmosis
3.
Oxidation and reduction
• Cellular respiration involves the oxidation
and reduction of compounds.
– They occur together because they involve the
transfer of electrons.
• Electron carriers are substances that can
accept and give up electrons as required.
– The main one for cellular respiration is NAD
4.
Oxidation and Reduction
Oxidation Reduction
Loss of electrons Gain of electrons
Gain of oxygen Loss of oxygen
Loss of hydrogen Gain of hydrogen
Results in many C – O bonds Results in many C – H bonds
Results in a compound with Results in a compound with
lower potential energy higher potential energy
A useful way to remember: OIL = Oxidation Is Loss (of electrons)
RIG= Reduction Is Gain (of electrons)
These two reactions occur together during chemical
reactions= redox reactions. One compound’s or element’s
loss is another compound’s or element’s gain.
5.
Cellular Respiration
• 3 Major stages
– Glycolysis
– The citric acid cycle (TCA or Krebbs)
– Oxidative phosphorylation
C6H12O6 + 6O2 <----> 6 CO2 + 6 H20 + e- ---> 36-38 ATP
6.
Respiration
• Glycolysis
– Rearranges the bonds in glucose releasing free energy
in the form of ATP & producing two molecules of
pyruvate
• The citric acid cycle (Krebs Cycle)
– Completes the breakdown of glucose releasing carbon
dioxide; synthesizing ATP & electrons are carried off
by NADH & FADH2
• Oxidative phosphorylation
– Is driven by the electron transport chain
– Generates ATP
7.
Where does all the magic happen?
Electrons Electrons carried
carried via NADH and
via NADH FADH2
Oxidative
Citric phosphorylation:
Glycolsis
Glucos acid electron
Pyruvate cycle
e transport and
chemiosmosis
Cytosol
Mitochondrion
ATP ATP ATP
Substrate-level Oxidative
Substrate-level
phosphorylation phosphorylation
phosphorylation
Figure 9.6
2 ATP 2 ATP 32-34 ATP
8.
Substrate Level
Phosphorylation
• Occurs in both glycolysis & the citric acid cycle
– In order to make an adenosine triphosphate, a phosphate group is
taken from an intermediate compound, referred to as a substrate,
and given to an ADP molecule.
Enzyme Enzyme
ADP
P
Substrate
+ ATP
Product
10.
1) Which of the following statements concerning the metabolic
degradation of glucose (C6H12O6) to carbon dioxide (CO2) and water is
(are) true?
A) The breakdown of glucose to carbon dioxide and water is exergonic.
B) The breakdown of glucose to carbon dioxide and water has a free
energy change of -686 kcal/mol.
C) The breakdown of glucose to carbon dioxide and water involves
oxidation-reduction or redox reactions.
D) Only A and B are correct.
E) A, B, and C are correct.
2) Which of the following statements is (are) correct about an
oxidation-reduction (or redox) reaction?
A) The molecule that is reduced gains electrons.
B) The molecule that is oxidized loses electrons.
C) The molecule that is reduced loses electrons.
D) The molecule that is oxidized gains electrons.
E) Both A and B are correct.
11.
3) Which of the following statements describes the results of this reaction?
C6H12O6 + 6 O2 → 6 CO2 + 6 H2O + Energy
A) C6H12O6 is oxidized and O2 is reduced.
B) O2 is oxidized and H2O is reduced.
C) CO2 is reduced and O2 is oxidized.
D) C6H12O6is reduced and CO2 is oxidized.
E) O2 is reduced and CO2 is oxidized.
4) Which process in eukaryotic cells will proceed normally whether oxygen (O 2) is
present or absent?
A) electron transport
B) glycolysis
C) the citric acid cycle
D) oxidative phosphorylation
E) chemiosmosis
5) Which of the following statements about glycolysis false?
A) Glycolysis has steps involving oxidation-reduction reactions.
B) The enzymes of glycolysis are located in the cytosol of the cell.
C) Glycolysis can operate in the complete absence of O2.
D) The end products of glycolysis are CO2 and H2O.
E) Glycolysis makes ATP exclusively through substrate-level phosphorylation.
12.
Major Stages of Cellular Respiration
Stages Starting End Location Substrate level Energy shuttled
molecule Product phosphorylation to oxidative
phosphorylation
Glycolysis 1 glucose 2 cytosol 2 ATP 2 NADH
pyruvate
Linkage 2 Acetyl Matrix of
None 2 NADH
Reaction pyruvate Co-A, 2 mitochondria
CO2
Krebs Cycle 2 acetyl- 4 CO Matrix of 6 NADH
mitochondria
2 ATP
(CAC) CoA 2
2 FADH2
ETC and Inner
oxidative electrons ATP membrane of none none
phosphorylation mitochondria
By oxidative phosphorylation
32-34 ATP’s are produced
13.
Glycolysis
Glycolysis Citric Oxidative
acid
cycle phosphorylation
• Harvests energy by oxidizing glucose ATP ATP ATP
to pyruvate Energy investment
phase
Glucose
• Glycolysis
– Means “splitting of sugar” 2 ATP + 2 P 2 ATP used
– Breaks down glucose into pyruvate Energy payoff phase
– Occurs in the cytosol of the cell
4 ADP + 4 P 4 ATP formed
• Two major phases 2 NAD+ + 4 e- + 4 2
+ 2 H+
NADH
– Energy investment phase H+
2 Pyruvate + 2
– Energy payoff phase H2O
Glucose 2 Pyruvate + 2 H2O
4 ATP formed – 2 ATP
2 ATP + 2 H+
used
2 NAD+ + 4 e– + 4 2 NADH
Figure 9.8 H+
14.
The First Stage of
Glycolysis
•Glucose (6C) is broken down into 2 PGAL's (3C sugar)
•This requires two ATP's
ENERGY INVESTMENT STAGE
15.
The Second Stage of
Glycolysis
•2 PGAL's (3C) are converted to 2 pyruvates
•This creates 4 ATP's and 2 NADH's (electron shuttlers)
•The net ATP production of Glycolysis is 2 ATP's
STAGE
16.
At the
end you
get these
17.
–Occurs in nearly all organisms
–Probably evolved in ancient prokaryotes before
there was oxygen in the atmosphere
18.
•Cellular respiration Feedback inhibition
Glucose
–Is controlled by Glycolysis
AMP
allosteric enzymes at Fructose-6-phosphate Stimulates
+
key points in
Phosphofructokinase
– –
glycolysis and the
Fructose-1,6-bisphosphate
Inhibits Inhibits
citric acid cycle
–If ATP levels get Pyruvate
too high feedback ATP
Acetyl CoA
Citrate
inhibition will block
the 1st enzyme of the Citric
pathway.
acid
cycle
Oxidative
Figure 9.20 phosphorylation
19.
Before the Krebs cycle
can begin….we have the
link
–Pyruvate must firstreaction
be converted to acetyl CoA,
which links the cycle to glycolysis
CYTOSOL MITOCHONDRION
What is lost
or gained
during this NAD+ NADH + H+
O–
S CoA
2
C O
One carbon atom C O
is lost as CO2 , an C O
electron is given 1 3
CH3
to NADH & a CH3
Acetyle CoA
different 2- Pyruvate CO2 Coenzyme A
carbon chain is
the result. Transport protein
Figure 9.10
20.
Citric Acid Cycle
a.k.a. Krebs Cycle
• Completes the energy-yielding oxidation of
organic molecules
• The citric acid cycle
– Takes place in the
matrix of the mitochondrion
22.
The Krebs Cycle
•6 NADH's are generated
•2 FADH2 is generated
•2 ATP are generated
•4 CO2's are released
Two turns for each molecule of glucose because each
glucose is converted to 2 molecules of acetyl CoA.
23.
Linkage reaction & Krebs's Cycle (citric acid
cycle, TCA cycle)
•Goal: take pyruvate and put it into the Krebs's cycle,
producing FADH2 and more NADH
•Where: the mitochondria matrix
•There are two steps
•The Conversion of Pyruvate to Acetyl CoA
•The Kreb's Cycle proper
•In the Krebs's cycle, all of Carbons, Hydrogens, and
Oxygen in pyruvate end up as CO2 and H2O
•The Krebs's cycle produces 2 ATP's, 6 NADH's, and
24.
If the main purpose of cell respiration is to produce
ATP, why do glycolysis & the Krebs cycle only
make 4 molecules of ATP total by the time glucose
has been converted to carbon dioxide?
Although glycolysis & the Krebs cycle only produce 4
ATP molecules when glucose is converted to CO2 , these
reactions produce 12 shuttle molecules of NADH &
FADH2 which will eventually generate 90% of the total
ATP production during the final phase of cell respiration.
25.
The free energy for the oxidation of glucose to CO2 and water is -686 kcal/mole and the
free energy for the reduction of NAD+ to NADH is +53 kcal/mole. Why are only two
molecules of NADH formed during glycolysis when it appears that as many as a dozen
could be formed?
A)Most of the free energy available from the oxidation of glucose is used in the production
of ATP in glycolysis.
B) Glycolysis is a very inefficient reaction, with much of the energy of glucose released as
C) Most of the free energy available from the oxidation of glucose remains in pyruvate, one
of the products of glycolysis
D) There is no CO2 or water produced as products of glycolysis.
E) Glycolysis consists of many enzymatic reactions, each of which extracts some energy
from the glucose molecule.
26.
In the presence of oxygen, the three-carbon compound pyruvate can be
catabolized in the citric acid cycle. First, however, the pyruvate 1) loses a
carbon, which is given off as a molecule of CO2, 2) is oxidized to form a two-
carbon compound called acetate, and 3) is bonded to coenzyme A. These
three steps result in the formation of:
A)acetyl CoA, O2, and ATP.
B) acetyl CoA, FADH2, and CO2.
C) acetyl CoA, FAD, H2, and CO2.
D) acetyl CoA, NADH, H+, and CO2.
E) acetyl CoA, NAD+, ATP, and CO2.
27.
After the Krebs
Cycle…
•Oxidative phosphorylation=
–electron transport
–chemiosmosis
28.
Electron Transport Chain
-Electrons from NADH and FADH2 lose energy in several steps
-At the end of the chain electrons are passed to oxygen, forming water
29.
ETC
–Electron transfer causes protein complexes to
pump H+ from the mitochondrial matrix to the
intermembrane space
The resulting H+
–Stores energy
–Drives chemiosmosis
in ATP synthase
–Is referred to as a
proton-motive force
30.
• FADH2 enters the ETC at a
lower free energy level than
the NADH.
– Results in FADH2 produces 2
ATP’s to NADH’s 3
• Oxygen is the final electron
acceptor
– The electrons + oxygen + 2
hydrogen ions = H2O
• Important to note that low
amounts of energy is lost at
each exchange along the ETC.
31.
Chemiosmosis
• NADH + H+ supplies pairs of hydrogen atoms to the 1st
carrier. (NAD+ returns to matrix)
• Hydrogen ions are split into 2 electrons which pass
from carrier to carrier in the chain.
• Energy is released as the electrons pass from carrier to
carrier and they are able to transfer protons (H+)across
the inner membrane.
• A concentration of protons build up in the inner-
membrane space results in a store of potential energy.
32.
Chemiosmosis
• To allow electrons to continue to flow, they must be
transferred to a terminal electron acceptor at the
end of the chain.
• Aerobic respiration = oxygen
• Protons pass back through the ATP synthase into the
matrix by way of diffusion and as they pass through
energy is release allowing for the phosphorylation of
ATP.
33.
Chemiosmosis:
The Energy-Coupling Mechanism
INTERMEMBRANE SPACE
H+ A rotor within the
membrane spins
H+ H+
clockwise when
H+ H+ flows past
H+ it down the H+
•ATP synthase H+
H+
gradient.
A stator anchored
–Is the enzyme
in the membrane
holds the knob
stationary.
that actually
makes ATP
A rod (for “stalk”)
extending into
the knob also
spins, activating
catalytic sites in
H+ the knob.
32-34 ATP Three catalytic
sites in the
ADP
stationary knob
+ join inorganic
Pi ATP
Phosphate to ADP
to make ATP.
MITOCHONDRIAL MATRIX
Figure 9.14
34.
Inner
Mitochondrial
Glycolysis
Oxidative
phosphorylation.
membrane
electron transport
and chemiosmosis
ATP ATP ATP
H+
H+
H+
H+
Cyt c
Protein complex
Intermembrane of electron
space carners
Q IV
I III
ATP
Inner II synthase
mitochondrial FADH2 H2O
membrane FAD+ 2 H+ + 1/2 O2
NADH+
NAD+ ADP + Pi ATP
(Carrying electrons
from, food) H+
Electron transport chain Chemiosmosis
matrix ATP synthesis powered by the flow
Electron transport and pumping of protons (H+),
which create an H+ gradient across the membrane Of H+ back across the membrane
Figure 9.15 Oxidative phosphorylation
35.
How does electronegativity play a part in the electron transport chain?
Because each electron acceptor in the chain is more electronegative than the
previous, the electron will move from one electron transport chain molecule to
the next, falling closer and closer to the nucleus of the last electron acceptor.
Where do the electrons for the ETC come from?
NADH and FADH2 which got theirs from glucose.
What molecule is the final acceptor of the electron?
Oxygen, from splitting O2 molecule & grabbing 2 H+ .
What’s consumed
during this process?
O2
What’s gained by
this process?
H+ inside the inner
membrane space
37.
The Case of…
The Seven Deaths
38.
Let’s do a simulation!!
39.
Net Energy Production from
Aerobic Respiration
•Glycolysis: 2 ATP (4 produced but 2 are net gain)
•Kreb's Cycle: 2 ATP
•Electron Transport Phosphorylation: 32 ATP
•Each NADH produced in Glycolysis is worth 2 ATP (2
x 2 = 4) - the NADH is worth 3 ATP, but it costs an
ATP to transport the NADH into the mitochondria, so
there is a net gain of 2 ATP for each NADH produced
in gylcolysis
•Each NADH produced in the conversion of pyruvate
to acetyl COA and Kreb's Cycle is worth 3 ATP (8 x 3
= 24)
•Each FADH2 is worth 2 ATP (2 x 2 = 4)
•4 + 24 + 4 = 32
•Net Energy Production: 36-38 ATP
40.
Is cellular respiration endergonic or exergonic
exergonic?
Is it a catabolic or anabolic process?
If one ATP molecule holds 7.3kcal of potential energy, how much
potential energy does 1 glucose molecule produce in cell respiration?
At its maximum output, 38 x 7.3kcal = 277.4kcal
One molecule of glucose actually contains 686 kcal/mol of potential
energy. Where does the remaining energy go when glucose is reduced?
It’s lost as heat-which is why our bodies are warm right now.
What is the net efficiency of cell respiration if glucose
contains 686kcal and only 277.4kcal are produced?
277.4/ 686 x 100 = 40% energy recovered from aerobic respiration
41.
Is 40% net efficiency of cellular
respiration good or not?
• Let’s first look at the following energy capturing
processes that you see in everyday life.
An incandescent light bulb is about 5% efficient
Electricity generated from coal is about 21% efficient
The most efficient gasoline combustion engine in cars
is about 23% efficient.
So…now what do you think?
42.
OCCURS IN CYTOSOL
OC
MIT CURS
OL OC IN
TO S HO
S IN CY ND
CCUR RIA
43.
Anaerobic Respiration
•Fermentation enables some cells to produce ATP
without the use of oxygen
–Can produce ATP with or without oxygen, in
aerobic or anaerobic conditions
–Couples with fermentation to produce ATP
44.
Anaerobic
Respiration
•Fermentation consists of
–Glycolysis plus reactions that regenerate NAD+,
which can be reused by glyocolysis
•Alcohol fermentation
–Pyruvate is converted to ethanol in two steps, one
of which releases CO2
•Lactic acid fermentation
–Pyruvate is reduced directly to NADH to form
lactate as a waste product
45.
Stage 2: If oxygen is absent-
Fermentation
-Produces organic molecules, including alcohol and
lactic acid, and it occurs in the absence of oxygen.
Cells not getting
enough oxygen, Yeast uses
excess pyruvate alcoholic
molecules are fermentation
converted into lactic for ATP
acid molecules, generation.
raising the pH in the
46.
Wine producers traditionally used their feet to soften and grind the grapes
before leaving the mixture to stand in buckets. In so doing, they transferred
microorganisms from their feet into the mixture. At the time, no one knew
that the alcohol produced during fermentation was produced because of one
of these microorganisms — a tiny, one-celled eukaryotic fungus that is
invisible to the naked eye: yeast.
47.
Red Blood Cells Have No
Mitochondria…How Do They
Produce Energy
• By fermentation, via anaerobic glycolysis of
glucose followed by lactic acid production.
• As the cells do not own any protein coding
DNA they cannot produce new structural or
repair proteins or enzymes and their lifespan
is limited.
48.
Comparing Chemiosmosis in
Respiration vs Photosynthesis
Respiration Chemiosmosis Photosynthesis Chemiosmosis
Involves an ETC embedded in the Involves ETC embedded in the
membranes of the cristae membranes of the thylakoids
Energy is released when electrons are Energy is released when electrons are
exchanged from one carrier to another exchanged from one carrier to another
Released energy is used to actively pump Released energy is used to actively pump
hydrogen ions into the intermembrane hydrogen ions into the thylakoid space
space
Hydrogen ions come from the matrix Hydrogen ions come from the stroma
Hydrogen ions diffuse back into the matrix Hydrogen ions diffuse back into the
through the channels of ATP synthase stroma through the channels of ATP
synthase
ATP synthase catalyses the oxidative ATP synthase catalyses the
phosphorylation of ADP to ATP photophosphorylation of ADP to form
ATP
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