Transcript Chapter 9

Lesson Overview
Cellular Respiration: An Overview
Chapter 9
The Process of
Cellular Respiration
Lesson Overview
Cellular Respiration: An Overview
THINK ABOUT IT
• Food burns! How does a living cell
extract the energy stored in food
without setting a fire or blowing
things up?
• It is called cellular respiration!
Cellular respiration takes place in
2 stages.
Lesson Overview
Cellular Respiration: An Overview
Glycolysis (the first stage of
respiration)
What happens during the process of
glycolysis?
Lesson Overview
Cellular Respiration: An Overview
Glycolysis
What happens during the process
of glycolysis?
During glycolysis, 1 molecule of
glucose, a 6-carbon compound, is
transformed into 2 molecules of
pyruvic acid, a 3-carbon compound.
Lesson Overview
Glycolysis
Cellular Respiration: An Overview
•
Glycolysis is the first
stage of cellular
respiration.
•
During glycolysis,
glucose is broken down
into 2 molecules of the
3-carbon molecule
pyruvic acid. Pyruvic acid
is a reactant in the
Krebs cycle.
•
ATP and NADH are
produced as part of the
process.
Lesson Overview
Cellular Respiration: An Overview
Cellular Respiration
•Cellular respiration is the step-wise release of
energy from carbohydrates and other
molecules.
•Energy from these reactions is used to
synthesize ATP molecules.
•This is an aerobic process that requires oxygen
(O2) and gives off carbon dioxide (CO2)
•It involves the complete breakdown of glucose
to carbon dioxide and water.
Lesson Overview
Cellular Respiration: An Overview
Reactions
first 5 min
Lesson Overview
Cellular Respiration: An Overview
In organic reactions
oxidation/reduction is:
Oxidation = Loss of H+
Reduction = Gain of H+
Remember: LEO goes GER!
Lesson Overview
Cellular Respiration: An Overview
Remember Photosynthesis?
Oxidation Reaction
The loss of electrons from a
substance. LEO
Or the gain of oxygen.
Oxidation
6CO2
+ 6H2O  C6H12O6
glucose
+
6O2
Lesson Overview
Cellular Respiration: An Overview
Remember Photosyntheis?
Reduction Reaction
The gain of electrons to a
substance. GER
Or the loss of oxygen.
Reduction
6CO2
+
6H2O

C6H12O6
glucose
+
6O2
Lesson Overview
Cellular Respiration: An Overview
The aerobic breakdown of glucose
The oxidation of glucose by removal of
hydrogen atoms involves four phases:
1. Glycolysis – the breakdown of glucose to two
molecules of pyruvate in the cytoplasm
with
no oxygen needed
- yields 2 ATP
2. Transition reaction – pyruvate is oxidized to
a 2-carbon acetyl group carried by CoA, and
CO2 is removed
- occurs twice per glucose molecule
Lesson Overview
Cellular Respiration: An Overview
3. Citric acid cycle – a cyclical series of
oxidation reactions that give off CO2 and
produce one ATP per cycle
- occurs twice per glucose molecule.
4. Electron transport system – a series of
carriers that accept electrons and pass them
from one carrier to the next until they are
passed to the final electron acceptor, O2 , which
is reduced to water.
- water is produced
- energy is released and used to
synthesize 32 to 34 ATP
Lesson Overview
CYU 1
Cellular Respiration: An Overview
Lesson Overview
NAD+
and FAD
Cellular Respiration: An Overview
•Oxidation-reduction reactions use NAD+
or FADH (nicotinamide adenine
dinucleotide, flavinadenine
dinucleotide).UPS and FedX
•When a metabolite is oxidized, NAD+
accepts two electrons plus a hydrogen ion
(H+) and NADH results.
NAD+ is reduced to NADH
•Conversely, NADH can also reduce a
metabolite by giving up electrons.
- NADH is oxidized to NAD+
Lesson Overview
Cellular Respiration: An Overview
Lesson Overview
Cellular Respiration: An Overview
Glycolysis
Glycolysis occurs in the cytoplasm
and is the breakdown of glucose to
two pyruvate molecules. First stage
of Cellular Respiration!
Glycolysis is universally found in all
organisms and likely evolved before
the citric acid cycle and electron
transport system.
Glycolysis does not require oxygen.
Lesson Overview
(Insert Fig. 7.4a)
Cellular Respiration: An Overview
Lesson Overview
Cellular Respiration: An Overview
Glycolysis summary
Inputs:
Glucose
2 NAD+
2 ATP
4 ADP + 2 P
Outputs:
2 pyruvate
2 NADH
2 ADP
2ATP (net gain)
Lesson Overview
Cellular Respiration: An Overview
ATP Production again
• The cell
“deposits” 2
ATP molecules
into its
“account” to get
glycolysis going.
It takes energy
to make energy!
Lesson Overview
Cellular Respiration: An Overview
ATP Production
Glycolysis then
produces 4 ATP
molecules, giving
the cell a net gain
of 2 ATP
molecules for each
molecule of
glucose that
enters glycolysis.
Lesson Overview
Cellular Respiration: An Overview
NADH Production
• During glycolysis,
the electron carrier
NAD+ (nicotinamide
adenine
dinucleotide)
accepts a pair of
high-energy
electrons and
becomes
NADH.(UPS)
• NAD+ is reduced to
become NADH
Lesson Overview
NADH Production
Cellular Respiration: An Overview
• NADH carries the
high-energy electrons to
the electron transport
chain, where they can be
used to produce more
ATP.
• 2 NADH molecules are
produced for every
molecule of glucose that
enters glycolysis.
Lesson Overview
Cellular Respiration: An Overview
The Advantages of Glycolysis
• Glycolysis produces ATP very fast,
which is an advantage when the
energy demands of the cell suddenly
increase.
• Glycolysis does not require oxygen,
so it can quickly supply energy to cells
when oxygen is unavailable. Glycolysis
CYU 2
overview
Lesson Overview
Cellular Respiration: An Overview
The Krebs Cycle
What happens during the Krebs cycle?
During the Krebs cycle, pyruvic acid is
broken down into carbon dioxide in a
series of energy-extracting reactions.
Krebs
cycle
overview
• During the Krebs cycle, The Krebs Cycle
the second stage of
cellular respiration,
pyruvic acid produced in
glycolysis is broken down
into carbon dioxide in a
series of energyextracting reactions.
Lesson Overview
Cellular Respiration: An Overview
• The Krebs cycle is also
known as the citric acid
cycle because citric acid
is the first compound
formed in this series of
reactions.
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Cellular Respiration: An Overview
Citric Acid Production
• Pyruvic acid
from glycolysis
enters the
matrix, the
innermost
compartment of
the
mitochondrion.
Lesson Overview
Cellular Respiration: An Overview
Where does pyruvate go?
When oxygen is available, pyruvate enters the
mitochondria, where it undergoes further
breakdown.
If oxygen is not available, fermentation occurs
and pyruvate undergoes reduction.
- Fermentation is an anaeorbic process
and does not require oxygen.
- In humans, pyruvate is reduced to lactic
acid during fermentation.
Lesson Overview
Cellular Respiration: An Overview
Mitochondria
•A mitochondrion is a cellular organelle that has
a double membrane, with an intermembrane
space between the two layers.
•The transition reaction and citric acid cycle
occur in the mitochondrial matrix.
•The electron transport system is located in
the cristae of the mitochondria.
Lesson Overview
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boxes!
Cellular Respiration: An Overview
Lesson Overview
Cellular Respiration: An Overview
Transition Reaction
The transition reaction connects
glycolysis to the citric acid cycle.(Krebs
cycle)
•Pyruvate is converted to acetyl CoA and
CO2 is released.
•During this oxidation reaction, NAD+ is
converted to NADH + H+
•The transition reaction occurs twice per
glucose molecule.
Lesson Overview
Cellular Respiration: An Overview
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Transition reaction inputs and
outputs from glucose
Inputs:
2 pyruvate
2 CoA
2 NAD+
Outputs:
2 acetyl CoA
2 CO2
2 NADH
Lesson Overview
Cellular Respiration: An Overview
Citric Acid Production again
• Once pyruvic acid is
in the mitochondrial
matrix, NAD+ accepts
2 high-energy
electrons to form
NADH. One molecule
of CO2 is also
produced.
• The remaining 2
carbon atoms react to
form acetyl-CoA.
Lesson Overview
Cellular Respiration: An Overview
Citric Acid Production
Acetyl-CoA
combines with a
4-carbon
molecule to
produce citric
acid.
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Cellular Respiration: An Overview
Energy Extraction
Citric acid is broken
down into a 5-carbon
compound and then a
4-carbon compound.
Two molecules of
CO2 are released.
The 4-carbon
compound can then
start the cycle again
by combining with
acetyl-CoA.
Lesson Overview
Cellular Respiration: An Overview
Energy Extraction
Energy
released by
the breaking
and
rearranging of
carbon bonds
is captured in
the forms of
ATP, NADH,
and FADH2.
Lesson Overview
Cellular Respiration: An Overview
Energy Extraction
• For each turn
of the cycle,
one ADP
molecule is
converted into
ATP. ATP can
directly power
the cell’s
activities.
Lesson Overview
Cellular Respiration: An Overview
• The electron
carriers NAD+ and
FAD each accept
pairs of highenergy electrons to
form NADH and
FADH2. NADH and
FADH2 are used in
the electron
transport chain to
generate ATP.
Energy Extraction
Lesson Overview
Energy Extraction
Cellular Respiration: An Overview
•
Remember! Each molecule
of glucose results in 2
molecules of pyruvic acid,
which enter the Krebs cycle.
So each molecule of glucose
results in two complete
“turns” of the Krebs cycle.
•
Therefore, for each
glucose molecule, 6 CO2
molecules, 2 ATP molecules,
8 NADH molecules, and 2
FADH2 molecules are
produced.
Krebs
click and
Kreb ws
Lesson Overview
Cellular Respiration: An Overview
Electron Transport and ATP Synthesis
How does the electron transport chain use
high-energy electrons from glycolysis and the
Krebs cycle?
• The electron transport chain uses the highenergy electrons from glycolysis and the
Krebs cycle to convert ADP into ATP.
• Review- More Krebs
• Transport
Lesson Overview
Cellular Respiration: An Overview
Electron Transport
• NADH and FADH2 pass their high-energy
electrons to electron carrier proteins in
the electron transport chain.(UPS and
FedEx)
Lesson Overview
Cellular Respiration: An Overview
Electron Transport
• At the end of the electron transport
chain, the electrons combine with H+
ions and oxygen to form water.
Electron Transport
• Energy generated by the electron
transport chain is used to move H+
ions against a concentration gradient
across the inner mitochondrial
membrane and into the
intermembrane space.
Lesson Overview
Cellular Respiration: An Overview
Against
Concentration
Lesson Overview
Cellular Respiration: An Overview
Against the concentration gradient
Lesson Overview
Electron
Cellular Respiration: An Overview
ATP Production
Transport
click and
Ws
• H+ ions pass back across the mitochondrial
membrane through the ATP synthase,
causing the ATP synthase molecule to spin.
With each rotation, the ATP synthase
attaches a phosphate to ADP to produce
ATP. Vid
Lesson Overview
Cellular Respiration: An Overview
The Totals
How much energy does cellular
respiration generate?
Together, glycolysis, the Krebs cycle,
and the electron transport chain
release about 36 molecules of ATP per
molecule of glucose.
Lesson Overview
Cellular Respiration: An Overview
Energy Totals
In the presence of
oxygen, the complete
breakdown of glucose
through cellular
respiration results in the
production of 36 ATP
molecules.
This represents about 36
percent of the total
energy of glucose. The
remaining 64 percent is
released as heat.
Lesson Overview
Cellular Respiration: An Overview
Energy Totals
The cell can generate ATP from just
about any source, even though we’ve
modeled it using only glucose.
Complex carbohydrates are broken
down into simple sugars like glucose.
Lipids and proteins can be broken
down into molecules that enter the
Krebs cycle or glycolysis at one of
several places.
Lesson Overview
Cellular Respiration: An Overview
Fermenation
How do organisms generate energy
when oxygen is not available?
In the absence of oxygen, fermentation
releases energy from food
molecules by producing ATP.
Lesson Overview
Cellular Respiration: An Overview
Fermentation
Fermentation is a process by which energy
can be released from food molecules in the
absence of oxygen. Fermentation occurs in
the cytoplasm of cells.
Lesson Overview
Cellular Respiration: An Overview
Fermentation
Under anaerobic conditions, fermentation
follows glycolysis. During fermentation, cells
convert NADH produced by glycolysis back
into the electron carrier NAD+, which allows
glycolysis to continue producing ATP.
Lesson Overview
Cellular Respiration: An Overview
Alcoholic Fermentation
• Yeast and a few other microorganisms use
alcoholic fermentation that produces ethyl
alcohol and carbon dioxide.
• This process is used to produce alcoholic
beverages and causes bread dough to rise.
Lesson Overview
Cellular Respiration: An Overview
Alcoholic Fermentation
Chemical equation:
Pyruvic acid + NADH  Alcohol + CO2 + NAD+
Lesson Overview
Cellular Respiration: An Overview
Lactic Acid Fermentation
Most organisms, including humans, carry
out fermentation using a chemical
reaction that converts pyruvic acid to
lactic acid.
Chemical equation:
Pyruvic acid + NADH  Lactic acid +
NAD+
Lesson Overview
Cellular Respiration: An Overview
Energy and Exercise
How does the body produce ATP during
different stages of exercise?
For short, quick bursts of energy, the body
uses ATP already in muscles as (glycogen)
well as ATP made by lactic acid fermentation.
For exercise longer than about 90 seconds,
cellular respiration is the only
way to continue generating a supply of ATP.
Lesson Overview
Cellular Respiration: An Overview
Quick Energy
Cells normally contain small amounts of ATP
produced during cellular respiration, enough
for a few seconds of intense activity.
Lactic acid fermentation can supply enough
ATP to last about 90 seconds. However, extra
oxygen is required to get rid of the lactic
acid produced. Following intense exercise, a
person will huff and puff for several minutes
in order to pay back the built-up “oxygen
debt” and clear the lactic acid from the body.
Long-Term Energy
Lesson Overview
Cellular Respiration: An Overview
For intense exercise lasting longer than 90
seconds, cellular respiration is required to
continue production of ATP.
Cellular respiration releases energy more
slowly than fermentation does.
The body stores energy in the form of the
carbohydrate glycogen. These glycogen
stores are enough to last for 15 to 20
minutes of activity. After that, the body
begins to break down other stored molecules,
including fats, for energy.
Lesson Overview
Cellular Respiration: An Overview
Long-Term Energy
Hibernating animals like this brown
bear rely on stored fat for energy
when they sleep through the winter.