Download Cellular Respiration

Cellular Respiration
• The cell obtains most of its energy requirements through the
of glucose (glycogen, glycerol & amino acids may also be
used)
• Releases the energy that is stored in
• Glucose is
(
),
(
to form
) and energy
Releasing Stored Energy
There are 3 ways of releasing the energy stored in food:
1. Aerobic cellular respiration is carried out by organisms that live in
environments(
)
• Examples: fungi, bacteria, plants, animals
2. Anaerobic cellular respiration is carried out by organisms that live in
anaerobic environments(
• Examples: nitrogen fixing bacteria, deep ocean producers
3. Fermentation - modified form of
respiration
• Examples: Yeast, bacteria that cause milk to sour
cellular
)
Aerobic Cellular Respiration
• The controlled process of respiration can be divided into three groups:
• 1. Glycolysis -
process which converts
(
)to
(aka pyruvate)
• 2. Kreb's (
process in which the
acid yields energy in the form of
• 3. Respiratory (
electron transfer system that produces
) cycle of
and
) Chain - an
4
Aerobic Cellular Respiration
Glycolysis
• Anaerobic reaction that occurs
in the
• Occurs in all living cells
• Does not provide enough energy
to sustain life
Stage of Glycolysis Summary
1. Glucose (
) enters
respiration pathway
2. Two
from
provide the activation energy to begin the
reaction (
) which converts
glucose to
(6 carbon molecule)
7
Stages of Glycolysis Summary
3. Glucose phosphate is split into
(phosphoglyceraldehyde) (3 carbon molecule)
4. Each
yield:
forming the
continues through glycolysis to
,
&
8
9
Stage 1 of Glycolysis
10
Stage 2 Glycolysis
11
Energy Gained from Glycolysis
Glycolysis nets:
12
The Fate of Pyruvate
• Pyruvate can proceed to
availability of oxygen:
processes dependent on the
• Aerobic Cellular Respiration
• Pyruvate is transported from the
• Anaerobic Cellular Respiration • Pyruvate remains in the
into the
Preparation for the Kreb’s Cycle Transition Reaction (aka oxidative
decarboxylation)
• Occurs in the
• Pyruvate combines with coenzyme A
(
)
• Loses a carbon atom in the form of CO2
• Remaining 2 carbon molecule
attaches to CoA to form
Coenzyme A “tows”
the acetyl group (2 carbon compound) into
the Krebs cycle
• During the Krebs cycle,
carbon
atoms are fully oxidized to carbon dioxide,
NAD+ and FAD are
to
and
,
and a
is produced.
Krebs Cycle
• The
and
cycle
their
carriers in the electron transport chain.
from the Krebs
to the electron
• As
are passed from one carrier to the
next, the energy that is
is used to pump
hydrogen ions(
) across the mitochondrial inner membrane
into the intermembrane space(
), creating a
concentration(
) gradient.
• The energy stored in the gradient is used to
by
.
Krebs Cycle Citric Acid Cycle
• Occurs in the mitochondria
• Cycle must be completed
glucose molecule
• Net gains per glucose molecule:
• 2 ATP
• 6 NADH
• 2 FADH2
per
Kreb’s Cycle Steps
• The 2 C
combines with a 4 C
called
group from the transition reaction
to produce a 6 C
• Citric acid steps through a number of reactions,
and
5C -
to become a
18
Kreb’s Cycle
• Ketoglutaric acid proceeds through a number of reactions losing CO2
and producing NADH and ATP to become a 4C • Succinyl acid becomes
• Fumeric acid is transformed to
NADH
(4 C) producing FADH
forming
19
Kreb’s Cycle
• The oxaloacetic acid molecule the cycle ends with is not the
same molecule with which the cycle began
[proven using radioactive markers in glucose entering - markers end up in oxaloacetic acid]
20
21
Video – The Kreb’s Cycle
22
Electron Transport
• Provides
during
aerobic cellular respiration
• Electrons are passed down a chain of protein complexes imbedded in the inner membrane
• Energy is pump hydrogen ions, H+, from the matrix into the intermembrane space
• Against concentration gradient
• Requires oxygen to function
• Oxygen is the
producing water
of the electron transport system
Electron Transport System
• Oxidative
has these high energy
electrons being passed step by step to a lower energy acceptor -> oxygen
• In oxidative phosphorylation a series of electron carriers, each holding the
electron at a slightly
energy level, pass the electrons
along the pathway to
• At the top of the energy hill, the electrons are held by
and
24
Cytochromes
• The principle components of the electron transport chain are
• Composed of a protein enclosing an atom of iron each with a different capacity for
holding electrons at different energy levels
• The enclosed iron atom alternately
and
an electron passing it along to the next cytochrome at a slightly lower level of energy
25
Electron Transport System
• At the end of each chain the electrons are
by
which then combines with protons (H+) from the solution
to produce
• For each
of
entering the electron transport chain a yield
is realized
• For each
of
entering the electron transport chain a yield
is realized
26
Role of Oxygen
Video – Oxidative
Phosphorylation
27
C/R - Energy Harvest
28
C/R - Energy Harvest
29
Aerobic Cellular Respiration
• Net gain of
per 1 glucose during
cellular respiration
• Majority of ATP is produced
using Electron Transport
System and Chemiosmosis
Wrap Up
31
Anaerobic Cellular Respiration
• No
available
• Only produces the amount of ATP generated by
• Converts
cycle to
that cannot be processed in the Krebs
or
• Fermentation – pathway taken by pyruvate to produce ATP in anaerobic
conditions
• Two types:
• Lactate Fermentation
• Ethanol Fermentation
Lactate Fermentation
• Occurs in the
• Occurs when energy demands
oxygen supply
• Cells convert pyruvate molecules into
lactate or
• Use
as energy source
• Lactate is stored
• When oxygen levels increase lactate
is converted back to pyruvate
• Pyruvate proceeds to Krebs cycle
Ethanol Fermentation
• Anaerobic process
• Occurs in the
of
cells
• Process in which yeasts and
some bacteria convert
pyruvate to
and
CO2
• Used to produce alcoholic
beverages and aid in the rising
of bread
Anaerobic Respiration
• Both types of fermentation
but free
NAD+ to accept H+ supplying a small amount of energy and preventing
the cell from becoming acidic
• Various other chemical pathways exist which allow some organisms to
thrive in anoxic and hypoxic conditions
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Summary
Cellular Respiration Releases Energy from Organic Compounds - Review
A.
• Three metabolic
pathways make up
aerobic cellular
respiration.
B.
C.
Cellular Respiration Releases Energy from Organic Compounds - Review
• The first set of reactions in aerobic cellular
respiration is called glycolysis.
• It is an anaerobic process.
• During glycolysis, a small amount of ATP is
generated, and NAD+ is reduced to NADH.
Stage 1 of Glycolysis
glucose
↓ (ATP -> ADP) [phosphorylation]
a.
glucose phosphate
↓ [rearranged]
fructose phosphate
b. ↓ (ATP -> ADP) [phosphorylation]
fructose diphosphate
↓ [split]
c.
PGAL  PGAL
d.
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Stage 2 Glycolysis
PGAL
PGAL
↓
NAD -> NADH
DPGA a.
↓
PGA
↓
b.
Pyruvate
↓
NAD -> NADH
DPGA
ADP -> ATP
↓
ADP -> ATP
↓
ADP -> ATP
PGA
ADP -> ATP
Pyruvate
c.
40
Cellular Respiration Releases Energy from Organic Compounds - Review
• The fate of pyruvate, the final product of glycolysis, depends on the
availability of oxygen and on the type of organism.
• When oxygen is available, pyruvate enters the matrix of the mitochondrion.
A series of reactions yield carbon dioxide and acetyl-CoA. NAD+ is reduced
to NADH.
Transition Reaction
Cellular Respiration Releases Energy from Organic Compounds - Review
• Acetyl-CoA enters the Krebs
cycle by combining with a
four-carbon compound.
• During the Krebs cycle, two
carbon atoms are fully
oxidized to carbon dioxide,
NAD+ and FAD are reduced to
NADH and FADH2, and a small
amount of ATP is produced.
citrate
Cellular Respiration Releases Energy from Organic Compounds - Review
• The NADH and FADH2 from the Krebs cycle donate their electrons to the
electron carriers in the electron transport chain.
• As electrons are passed from one carrier to the next, the energy that is
released is used to pump hydrogen ions across the mitochondrial inner
membrane into the intermembrane space, creating a concentration
gradient.
• The energy stored in the gradient is used to generate ATP by
chemiosmosis.
Cellular Respiration Releases Energy from Organic Compounds - Review
• Organisms that carry out anaerobic cellular respiration use inorganic
chemicals other than oxygen as the final electron-acceptor. This
produces ATP for the cell, but not as much as in aerobic respiration.
breakdown of glucose in the
presence of oxygen
36 ATP
breakdown of glucose by lactate
or ethanol fermentation
2 ATP
Cellular Respiration Releases Energy from Organic Compounds - Review
• In muscle that is functioning anaerobically, pyruvate is
converted to lactate and the reduced NADH is reoxidized so
that glycolysis can continue. This process is called lactate
fermentation.
Cellular Respiration Releases Energy from Organic Compounds - Review
• In yeast growing anaerobically, pyruvate is converted to carbon
dioxide and ethanol. This process is known as ethanol
fermentation.
Cellular Respiration Releases Energy from Organic Compounds - Review
• Fermentation is used on an industrial scale to produce
ethanol.
• Ethanol is used as an additive to gasoline to reduce
some environmental contaminants.
Selected Fermentation Products and their Uses
Chapter 5 Concept Organizer
Chapter 5 Summary
• P/S and C/R proceed through many different rxns to produce energy-rich
compounds and break them down to release their stored energy (ATP)
• When the bond to the last phosphate group is broken, leaving ADP and a free
phosphate group, the energy released is available to do cellular work.
• In P/S the CO2 and H2O are involved in two separate sets of reactions:
• H2O is split into hydrogen ions, electrons, and oxygen in the lightdependent reactions
• CO2 is incorporated into carbohydrates in the light-independent reactions.
Chapter 5 Summary
(cont’d)
• light-dependent rxns (thylakoid membranes) capture light energy and use it to
excite electrons to produce ATP and NADPH.
• light-independent reactions (stroma) use the chemical potential energy of ATP
and the reducing power of NADPH to reduce carbon dioxide and form glucose
via the Calvin-Benson cycle.
• Glucose is processed to release energy through glycolysis, the Krebs cycle, and
electron transport
• Glycolysis is an anaerobic process that occurs in the cytoplasm and breaks
down glucose into pyruvate
• Pyruvate enters the mitochondria, where it is broken down into carbon dioxide
and acetyl CoA.
Chapter 5 Summary
(cont’d)
• Acetyl CoA enters the Krebs cycle (matrix) and energy released from
breakdown of compounds in the Krebs cycle is used to reduce NAD -> NADH
and FAD -> FADH
• NADH & FADH donate electrons to the ETC on the inner mitochondrial
membranes
• Energy, released as electrons, is passed along the chain & used to create a
hydrogen ion gradient that powers chemiosmosis, which generates ATP.
• Glycolysis is the only source of energy for some organisms. Pyruvate is broken
down into carbon dioxide and alcohol (ethanol fermentation) or lactate (lactate
fermentation). This process occurs anaerobically.
Chapter 5 Review
• What molecule provides energy for most cellular processes?
• Would photosynthesis and respiration be able to proceed without
enzymes? Why or why not?
• Where are chlorophyll molecules found?
• What happens when a compound is oxidized? Reduced? Which form
contains more energy?
• What occurs during chemiosmosis? Where does it occur?
• What metabolic pathways are involved in cellular respiration? Where do
they occur?