Transcript Cellular Respiration

Water behind a dam represents
_____ energy.
A) Kinetic
B) Electrical
C) Potential
D) Heat
E) Electromagnetic
The “powerhouse of the cell” is
the_________.
A) Nucleus.
B) Mitochondrion.
C) Golgi complex.
D) Ribosome.
E) None of these
Mitochondrial structure review
Cellular respiration provides us
with the energy we use
Slow-twitch muscles have more mitochondria than fast-twitch
Cellular Respiration
All Living Things Require and Consume
Energy
• Ultimate source of
energy for all life on
earth is the sun
• We get our energy
from food
Aerobic respiration of glucose is the most
basic means for cells to acquire energy
C6H12O6(s) + 6O2(g)  6CO2(g)+ 6H2O(l)
This is a combustion reaction
Combustion is a kind of redox reaction
Respiration interacts with
photosynthesis in the recycling of
carbon
Respiration at the cellular level
necessitates our breathing
The more our cells respire, the
more oxygen we need
Although carbohydrates, fats, and proteins
are all consumed as fuel, it is helpful to
trace cellular respiration with glucose:
C6H12O6(s) + 6O2(g)  6CO2(g)+ 6H2O(l) +
Energy (ATP + heat)
Respiration is a REDOX reaction
Oxidation-Reduction Reactions
•
•
•
•
Cellular respiration is a redox reaction
Involves the exchange of electrons
Oxidation- the loss of electrons
Reduction- the gain of electrons (reduction
of charge
• Na + Cl  Na+ + Cl• Which is oxidized? Which is reduced?
Redox does not require complete
loss or gain of electrons
Products
Reactants
becomes oxidized
CH4
2 Oreduced
+becomes
2
CO2
+
Energy
+
2 H2O
becomes reduced
becomes reduced
Methane
(reducing
agent)
Oxygen
(oxidizing
agent)
Carbon dioxide
Water
During cellular respiration,
glucose is oxidized and oxygen is
reduced
becomes oxidized
C6H12O6 + 6O2
6CO2 + 6H2O + Energy
becomes reduced
Electrons bound to more electronegative
atoms are lower in energy
• The energy heirarchy of carbon bonds:
CH4
CH3OH
CH2O
HCOOH
CO2
Electrons in reduced molecules have higher
energy than those in oxidized molecules
Aerobic respiration of glucose is the most
basic means for cells to acquire energy
C6H12O6(s) + 6O2(g)  6CO2(g)+ 6H2O(l)
The cell must control this reaction
Oxidation is the ______, and
reduction is the __________.
A) gain of electrons . . . loss of electrons
B) loss of electrons . . . gain of electrons
C) loss of oxygen . . . gain of oxygen
D) gain of oxygen . . . loss of oxygen
E) gain of protons . . . loss of protons
The Stages of Cellular
Respiration: A Preview
• Cellular respiration has three stages:
– Glycolysis
– The citric acid cycle (a.k.a. the Krebs cycle)
– Oxidative phosphorylation (using the electron
transport chain)
LE 9-6_1
Glycolysis
Pyruvate
Glucose
Cytosol
Mitochondrion
ATP
Substrate-level
phosphorylation
LE 9-6_2
Glycolysis
Pyruvate
Glucose
Cytosol
Citric
acid
cycle
Mitochondrion
ATP
ATP
Substrate-level
phosphorylation
Substrate-level
phosphorylation
LE 9-6_3
Electrons carried
via NADH and
FADH2
Electrons
carried
via NADH
Glycolysis
Pyruvate
Glucose
Cytosol
Citric
acid
cycle
Oxidative
phosphorylation:
electron transport
and
chemiosmosis
Mitochondrion
ATP
ATP
Substrate-level
phosphorylation
Substrate-level
phosphorylation
ATP
Oxidative
phosphorylation
Overview of respiration
• Glycolysis: Glucose is split, 2 pyruvates
are formed, a little ATP is gained (by
substrate-level phosporylation)
• The Citric Acid Cycle: Redox molecules
NAD+ and FAD are charged up, a little ATP
is gained
• Oxidative phosphorylation: Lots of ATP is
made by ATP synthase
Processes important to
respiration
• Substrate-level phosphorylation to form
ATP
• Recycling of the Redox molecules NAD+
and FAD to carry electrons to the etransport chain
• The electron transport chain, which helps
generate much ATP
Substrate-level phosphorylation
Making ATP by taking a phosphate from
something and sticking it onto an ADP
Recycling of NAD+
e
The transport chain
generates a proton gradient
Step 1: Glycolysis
In: 1 glucose, 2 NAD+
Out: 2 ATP (net), 2NADH,
2 pyruvate
Glycolysis converts glucose to
pyruvate
• Glycolysis (“splitting of sugar”) breaks down
glucose into two molecules of pyruvate
• Glycolysis occurs in the cytoplasm and has two
major phases:
– Energy investment phase
– Energy payoff phase
Animation: Glycolysis
Overview of Glycolysis
•
•
•
•
10- step process
Glucose (6C)  2 Pyruvate ( 3 C ea.)
2 ATPs net profit
2 NAD+’s are charged
LE 9-9a_1
Glucose
ATP
Hexokinase
ADP
Glucose-6-phosphate
Glycolysis
Citric
acid
cycle
ATP
ATP
Oxidation
phosphorylation
ATP
LE 9-9a_2
Glucose
ATP
Hexokinase
ADP
Glucose-6-phosphate
Phosphoglucoisomerase
Fructose-6-phosphate
ATP
Phosphofructokinase
ADP
Fructose1, 6-bisphosphate
Aldolase
Isomerase
Dihydroxyacetone
phosphate
Glyceraldehyde3-phosphate
Glycolysis
Citric
acid
cycle
ATP
ATP
Oxidation
phosphorylation
ATP
LE 9-9b_1
2 NAD+
Triose phosphate
dehydrogenase
2 NADH
+ 2 H+
1, 3-Bisphosphoglycerate
2 ADP
Phosphoglycerokinase
2 ATP
3-Phosphoglycerate
Phosphoglyceromutase
2-Phosphoglycerate
LE 9-9b_2
2 NAD+
Triose phosphate
dehydrogenase
2 NADH
+ 2 H+
1, 3-Bisphosphoglycerate
2 ADP
Phosphoglycerokinase
2 ATP
3-Phosphoglycerate
Phosphoglyceromutase
2-Phosphoglycerate
2 H2O
Enolase
Phosphoenolpyruvate
2 ADP
Pyruvate kinase
2 ATP
Pyruvate
Energetics of
Glycolysis
Concept 9.3: The citric acid
cycle completes the energyyielding oxidation of organic
molecules
• Before the citric acid cycle can begin, pyruvate
must be converted to acetyl CoA, which links
the cycle to glycolysis
Before the citric acid cycle,
pyruvate is fastened to
Co-Enzyme A
Step 2: Citric Acid cycle
In: Acetyl CoA, NAD+, FAD, ADP
Out: CO2, NADH, FADH, some
ATP
• In the citric acid cycle, electrons are ripped
from carbon onto the redox molecules
NAD+ and FAD
• All carbon is converted to CO2
• A little bit of ATP is generated
• The citric acid cycle, also called the Krebs
cycle, takes place within the mitochondrial
matrix
• The cycle oxidizes organic fuel derived from
pyruvate, generating one ATP, 3 NADH, and 1
FADH2 per turn
• The citric acid cycle has eight steps, each
catalyzed by a specific enzyme
LE 9-11
Pyruvate
(from glycolysis,
2 molecules per glucose)
CO2
NAD+
Glycolysis
Citric
acid
cycle
ATP
ATP
Oxidation
phosphorylation
CoA
NADH
+ H+
Acetyl CoA
CoA
CoA
Citric
acid
cycle
FADH2
2 CO2
3 NAD+
3 NADH
+ 3 H+
FAD
ADP + P i
ATP
ATP
LE 9-12_4
Glycolysis
Citric
acid
cycle
ATP
ATP
Oxidation
phosphorylation
ATP
Acetyl CoA
NADH
+ H+
H2O
NAD+
Oxaloacetate
Malate
Citrate
Isocitrate
CO2
Citric
acid
cycle
H2O
NAD+
NADH
+ H+
Fumarate
a-Ketoglutarate
FADH2
NAD+
FAD
Succinate
GTP GDP
ADP
ATP
Pi
Succinyl
CoA
NADH
+ H+
CO2
Step 3: Oxidative
Phosphorylation
In which the electron transport
chain generates a proton gradient,
and ATP synthase makes tons of
ATP
Oxidative phosphorylation
• Electron-carrying redox molecules (NADH
and FADH2) transfer their electrons to the
e- transport chain
• The e- transport chain uses the electrons
to create a proton gradient across the
inner mitochondrial membrane
• ATP synthase uses the potential energy
in the proton gradient to convert much
ADP into ATP
LE 9-13
NADH
50
Free energy (G) relative to O2 (kcal/mol)
FADH2
40
FMN
I
Multiprotein
complexes
FAD
Fe•S II
Fe•S
Q
III
Cyt b
30
Fe•S
Cyt c1
Glycolysis
Citric
acid
cycle
ATP
ATP
Oxidative
phosphorylation:
electron transport
and chemiosmosis
IV
Cyt c
Cyt a
Cyt a3
20
10
0
2 H+ + 1/2 O2
H2O
ATP
The electron transport chain uses electrons
to generate a proton gradient
H+
H+
H+
Protein
complex
Intermembrane
space
H+
H+
H+
H+
Electron
carrier
H+
H+
ATP
synthase
Inner
mitochondrial
membrane
FADH2
Electron
flow
NADH
Mitochondrial
matrix
FAD
NAD+
H+
1
2
O2
+ 2 H+
H+
H+
H2O
Electron Transport Chain
OXIDATIVE PHOSPHORYLATION
ADP
+ P
ATP
H+
Chemiosmosis
Some poisons can disrupt e- transport
• The energy stored in a H+ gradient across a
membrane couples the redox reactions of the
electron transport chain to ATP synthesis
• The H+ gradient is referred to as a protonmotive force, emphasizing its capacity to do
work
Animation: Fermentation Overview
LE 9-14
INTERMEMBRANE SPACE
H+
H+
H+
H+
H+
H+
A rotor within the
membrane spins
as shown when
H+ flows past
it down the H+
gradient.
H+
A stator anchored
in the membrane
holds the knob
stationary.
A rod (or “stalk”)
extending into
the knob also
spins, activating
catalytic sites in
the knob.
H+
ADP
+
P
ATP
i
MITOCHONDRAL MATRIX
Three catalytic
sites in the
stationary knob
join inorganic
phosphate to
ADP to make
ATP.
An Accounting of ATP Production
by Cellular Respiration
• During cellular respiration, most energy flows in
this sequence:
glucose NADH electron transport chain
proton-motive force ATP
• About 40% of the energy in a glucose molecule
is transferred to ATP during cellular respiration,
making about 38 ATP
LE 9-16
Electron shuttles
span membrane
CYTOSOL
2 NADH
Glycolysis
Glucose
2
Pyruvate
MITOCHONDRION
2 NADH
or
2 FADH2
2 NADH
2
Acetyl
CoA
6 NADH
Citric
acid
cycle
+ 2 ATP
+ 2 ATP
by substrate-level
phosphorylation
by substrate-level
phosphorylation
Maximum per glucose:
About
36 or 38 ATP
2 FADH2
Oxidative
phosphorylation:
electron transport
and
chemiosmosis
+ about 32 or 34 ATP
by oxidation phosphorylation, depending
on which shuttle transports electrons
form NADH in cytosol
During cellular respiration, NADH
A) is converted to NAD+ by an enzyme
called dehydrogenase.
B) is chemically converted into ATP.
C) is reduced to form NAD+.
D) delivers its electron load to the electron
transport chain.
E) None of the choices are correct.
Oxygen is the final e- resting
place in the chain
Human cells can do glycolysis
faster than human lungs can
take in oxygen
Q: What happens if there is not
enough oxygen?
A: It depends on what kind of
creature you are…
Without O2, yeast make alcohol
Humans make lactic acid
instead of ethanol
Lactic Acid in muscles creates a
burning sensation
• Overworked muscles
can become anoxic
• In low oxygen
environments,
pyruvate is converted
to lactate to
regenerate NAD+
• Lactic acid causes
great suffering
LE 9-17a
2 ADP + 2 P i
Glucose
2 ATP
Glycolysis
2 Pyruvate
2 NAD+
2 Ethanol
Alcohol fermentation
2 NADH
+ 2 H+
2 CO2
2 Acetaldehyde
LE 9-17b
2 ADP + 2 P i
Glucose
2 ATP
Glycolysis
2 NAD+
2 NADH
+ 2 H+
2 CO2
2 Pyruvate
2 Lactate
Lactic acid fermentation
Fermentation and Cellular
Respiration Compared
• Both processes use glycolysis to oxidize
glucose and other organic fuels to pyruvate
• The processes have different final electron
acceptors: an organic molecule (such as
pyruvate) in fermentation and O2 in cellular
respiration
• Cellular respiration produces much more ATP
LE 9-18
Glucose
CYTOSOL
Pyruvate
No O2 present
Fermentation
O2 present
Cellular respiration
MITOCHONDRION
Ethanol
or
lactate
Acetyl CoA
Citric
acid
cycle
The Evolutionary Significance of
Glycolysis
• Glycolysis occurs in nearly all organisms
• Glycolysis probably evolved in ancient
prokaryotes before there was oxygen in the
atmosphere
Glycolysis and the citric acid
cycle connect to many other
metabolic pathways
• Gycolysis and the citric acid cycle are major
intersections to various catabolic and
anabolic pathways
Metabolism can build up, or
break down
LE 6-15
ATP needed to drive biosynthesis
ATP
CITRIC
ACID
CYCLE
GLUCOSE SYNTHESIS
Acetyl
CoA
Pyruvate
G3P
Glucose
Amino
groups
Amino acids
Proteins
Fatty acids
Glycerol
Fats
Cells, tissues, organisms
Sugars
Carbohydrates
The Versatility of Catabolism
• Catabolic pathways funnel electrons from many
kinds of organic molecules into cellular respiration
• Glucose- 4 calories/gram
• Proteins- 4 calories/gram
• Fats- 9 calories/gram
• Which of the following processes produces
the most ATP per molecule of glucose
oxidized?
A) aerobic respiration
B) anaerobic respiration
C) alcoholic fermentation
D) lactic acid fermentation
E) All produce approximately the same
amount of ATP per molecule of glucose