Download L6 Cellular Respiration

2/29/2016
Metabolism
• Consists of ALL OF THE chemical
reactions that take place in a cell
Bio 105: Cellular Metabolism
Lecture 6
Reading: Chapter 3 (Pages 56 – 62)
Metabolism
Cellular Metabolism
• Glycolysis Summary
• 2 kinds
– https://www.youtube.com/watch?v=8Kn6B
VGqKd8
– Aerobic cellular respiration
– Anaerobic fermentation
Summary of Cellular Respiration
Aerobic Cellular Respiration
Electrons
transferred
by NADH
Blood
vessel
Glucose
Cytoplasm
Electrons
transferred
by NADH
– Sugar  CO2 and H2O
– Requires Oxygen
Electrons
transferred
by NADH
and FADH2
Plasma
membrane
Carrier
protein
Citric
Acid
Cycle
Transition
Reaction
Glycolysis
glucose
pyruvate
• Cells take in sugar (glucose)
• Produces energy
Electron
Transport
Chain
– ATP
Oxygen
Mitochondrion
Extracellular fluid
+2 ATP
+2 ATP
+32 ATP

36 ATP
C6H12O6 + 6O2 → 6CO2 +6H2O + Energy
Figure 3.27
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Aerobic Cellular Respiration
• 4 steps
– Glycolysis
– Transition Reaction
– Citric Acid Cycle (Krebs Cycle)
– Electron Transport Chain
NADH and FADH2 are important carriers of electrons
Cellular Respiration - Glycolysis
Glycolysis
Glycolysis (in cytoplasm)
• Phase 1: Glycolysis
– Occurs in cytoplasm
– Splits 1 glucose  2 pyruvate molecules
– Net Gain: 2 ATP and 2 NADH
– Does not require oxygen
Cytoplasm
During the first steps,
two molecules of ATP are
consumed in preparing
glucose for splitting.
Glucose
During the remaining
steps, four molecules
of ATP are produced.
2 ATP
Energyinvestment
phase
2 ADP
4 ADP
4 ATP
The two molecules of
pyruvate then diffuse
from the cytoplasm into
the inner compartment
of the mitochondrion,
where they pass through
a few preparatory steps
(the transition reaction)
before entering the citric
acid cycle.
2 NAD+
2 NADH
2 Pyruvate
Glucose  2 ATP + 2 NADH + 2 pyruvate
Energyyielding
phase
Two molecules of nicotine
adenine dinucleotide
(NADH), a carrier of
high-energy electrons,
also are produced.
Figure 3.23
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Glycolysis Rap
• https://www.youtube.com/watch?v=EfGl
znwfu9U
In Cytosol
Cellular Respiration - Transition
Reaction
Cellular Respiration – Transition
Reaction
• Start with
• Phase 2: Transition Reaction
– 2 pyruvate (3 carbon molecule)
– 2 Coenzyme A
– Occurs in mitochondria
– Coenzyme A combines with pyruvate
– CO2 is removed from each pyruvate
– Forms: 2 acetyl CoA molecules
– Net Gain: 2 NADH
• End with
– 2 CO2
– 2 NADH
– 2 Acetyl CoA (2 carbon molecule)
Cellular Respiration – Citric Acid
Cycle
Transition Reaction (in mitochondrion)
Transition
Reaction
• Phase 3: Citric Acid Cycle
Pyruvate (from glycolysis)
– Occurs in mitochondria
– Acetyl CoA enters
– Releases 2 ATP, 2 FADH2 and 6 NADH, 4 CO2
molecules
– Net Gain: 2 ATP, 2 FADH2 and 6 NADH
– Requires Oxygen
One carbon (in the form
of CO2) is removed
from pyruvate.
A molecule of NADH is
formed when NAD+
gains two electrons
and one proton.
CO2
NAD+
Coenzyme A
NADH
(electron passes
to electron
transport chain)
CoA
Acetyl CoA
The two-carbon
molecule, called
an acetyl group,
binds to
coenzyme A
(CoA), forming
acetyl CoA,
which enters the
citric acid cycle.
• Does not use it
Citric Acid Cycle
Figure 3.24
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Cellular Respiration – Citric Acid
Cycle
• AKA Krebs Cycle
• Start with
Citric Acid
Cycle
Citric Acid Cycle (in mitochondrion)
The citric acid cycle also
yields several molecules of
FADH2 and NADH, carriers of
high-energy electrons that
enter the electron transport
chain.
– 2 Acetyl CoA
Acetyl CoA, the
two-carbon compound
formed during the
transition reaction,
enters the citric acid
cycle.
Acetyl CoA
CoA
CoA
Oxaloacetate
Citrate
• End with
NADH
CO2
leaves
cycle
NAD+
– 4 CO2
– 2 ATP
– 6 NADH and 2 FADH2
NAD+
Citric Acid Cycle
Malate
NADH
FADH2
ADP + Pi
ATP
FAD
-Ketoglutarate
Succinate
CO2 leaves cycle
NAD+
The citric acid cycle yields
One ATP from each acetyl
CoA that enters the cycle,
for a net gain of two ATP.
NADH
Figure 3.25
• https://www.youtube.com/watch?v=JPCs
5pn7UNI
• Remember there are 2 acetyl CoA molecules
for each 1 glucose that entered glycolysis
Cellular Respiration – Electron
Transport Chain
• NADH and FADH2 are important carriers
of electrons
– Donate electrons to ETC
– Oxygen accepts electrons at the end of the
chain
• Produces ATP using ATP synthase protein
molecule
• Produces 32 ATP!!
Cellular Respiration – Electron
Transport Chain
• Phase 4: Electron Transport Chain
– Electrons of FADH2 and NADH are
transferred from one protein to another
– Transferred until they reach oxygen
– Net Gain: 32 ATP
– Requires oxygen
Electron
Transport
Chain
Electron Transport Chain (inner membrane of mitochondrion)
The molecules of NADH and
FADH2 produced by earlier phases
of cellular respiration pass their
electrons to a series of protein
molecules embedded in the inner
membrane of the mitochondrion.
High
NADH
NAD+
As the electrons are transferred
from one protein to the next,
energy is released and used to
make ATP.
2e–
Potential energy
Cellular Respiration – Citric Acid
Cycle
FADH2
Membrane
proteins
2e–
FAD
2e–
2e–
Eventually, the
electrons are
passed to oxygen,
which combines
with two hydrogens
to form water.
2e–
Low
Energy released is used
for synthesis of ATP
H2O
1
2 H+ + 2 O2
Figure 3.26
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Electron Transport Chain
• ATP is made through a series of steps
1) In the mitochondria, NADH and FADH2
donate electrons to the ETC
2) Oxygen is the final electron acceptor
3) ETC uses the energy from electrons to
transport H+ against the concentration
gradient
•
Transporting them from the lumen of the
mitochondria to the intermembrane space
Electron Transport Chain
Electron Transport Chain
• ATP is made, cont’d…
4) ATP Synthase transports the H+ back to
the lumen of the mitochondria
5) H+ falling through the ATP synthase
provides the energy for the ATP synthase
to catalyze the reaction
•
ADP + P  ATP
Cellular Respiration Summary
• Electron Transport Chain
– https://www.youtube.com/watch?v=xbJ0nbzt5
Kw
• ATP Synthase
– https://www.youtube.com/watch?v=3y1dO4n
NaKY&ebc=ANyPxKpaQgOjhUhrwCJplTqYfxSJulZdtyt3Zrb7PwYb20zc
rYe4lJbfCVr6SETniI6Ft21DgQOb0wQXzI3CXdnqwCOUeMRw
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Cellular Respiration Summary
• 1 molecule glucose  36 ATP
• Oxygen
– Used by the electron transport chain
– Accepts electrons from the ETC
• CO2
– Produced by the transition reaction
– Produced by the Citric Acid Cycle (Krebs)
Cellular Respiration - Summary
• Glycolysis
– Starts the process
– Takes in glucose
– Produces 2 ATP
• Transition Reaction
– Produces CO2 and NADH
• Citric Acid Cycle
– Produces 2 ATP
– Produces lots of NADH and FADH2
– Produces CO2.
Cellular Respiration Summary
Complex Carbohydrates
must first be broken
down into glucose
before entering
glycolysis
• Electron Transport Chain
– Takes electrons from NADH and FADH2
– Uses electrons to produce ATP
• ATP synthase molecule
Fats and proteins enter
the process at different
steps
– Requires oxygen
• 1 glucose  36 ATP
Oxygen
• Cellular respiration requires O2
– Aerobic cellular respiration
• What if an organism, including humans,
need energy without using oxygen?
Anaerobic Fermentation
• Breakdown of glucose without oxygen
• Occurs in cytoplasm
• Very inefficient
– Net gain: 2 ATP
– Glycolysys
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Fermentation in Animals
• 2 pyruvic acid + 2 NADH  2 lactate + 2 NAD+
• End Result:
– Lactate
– 2 ATP
– NAD+ is regenerated
Review Questions
• What is the starting molecule of
glycolysis?
• Which stage(s) produces CO2?
• Which stage uses O2?
• Which stage produces the most NADH?
• Which stage produces the most ATP?
Important Concepts
• What are the 4 steps of aerobic cellular
respiration?
– What happens in each step?
– What are the starting molecules?
– What comes out of each step?
– Where in the cell does each step occur?
– How many ATP and NADH/FADH2 are
produced in each step?
Important Concepts
• What is cellular respiration?
• What is anaerobic fermentation?
• What are the differences between
cellular respiration and anaerobic
fermentation?
Important Concepts
• Describe in detail how ATP is made using
the electron transport chain (ETC)
• What is the role of ATP synthase, H+, O2,
NADH and FADH2 and the electron
transport chain in ATP production?
• Know the overall picture of cellular
respiration (summary slides)
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Important Concepts
• What is the role of oxygen in cellular
respiration?
• What steps produce carbon dioxide?
• What is anaerobic fermentation?
– What steps are involved?
– What end products are produced in humans?
– Is oxygen required?
– When is it used?
Definitions
•
•
•
•
Aerobic cellular respiration
Anaerobic fermentation
ATP synthase
Metabolism
The End
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