Download Cellular respiration

BIG IDEA II
Biological systems utilize free energy and molecular building blocks
to grow, to reproduce and to maintain dynamic homeostasis.
Enduring Understanding 2.A
Growth, reproduction and maintenance of the organization
of living systems require free energy and matter.
Essential Knowledge 2.A.2
Organisms capture and store free energy for use in biological processes.
PowerPoint® Lecture Presentations for
Biology
Eighth Edition
Neil Campbell and Jane Reece
Lectures by Chris Romero, updated by Erin Barley with contributions from Joan Sharp
Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings
Essential Knowledge 2.A.2: Organisms capture and
store free energy for use in biological processes.
• Learning Objectives:
– (2.4) The student is able to use representations to
pose scientific questions about what mechanisms
and structural features allow organisms to capture,
store and use free energy.
– (2.5) The student is able to construct explanations of
the mechanisms and structural features of cells that
allow organisms to capture, store or use free energy.
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Autotrophs capture free energy from physical sources
in the environment.
• Photosynthetic organisms capture free energy
present in sunlight.
–
6CO2 + 6 H2O + light energy  C6H12O6 + 6 O2 + 6 H2O
–
carbon dioxide + water + light energy  sugar + oxygen + water
• Chemosynthetic organisms capture free energy
from small inorganic molecules present in their
environment, and this process can occur in the
absence of oxygen.
–
6H2S + 6 H2O + 6 CO2 + 6 O2  C6H12O6 + 6 H2SO4
–
hydrogen sulfide + water + carbon dioxide + oxygen  sugar + sulfuric acid
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Autotrophs capture free energy from physical sources
in the environment.
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Heterotrophs capture free energy present in carbon
compounds produced by other organisms.
• Heterotrophs may metabolize carbohydrates,
lipids and proteins by hydrolysis as sources of free
energy.
–
C6H12O6 + 6 O2  6CO2 + 6 H2O + energy (ATP + heat)
–
organic compounds + oxygen  carbon dioxide + water + energy
• Fermentation produces organic molecules,
including alcohol and lactic acid, and it occurs in
the absence of oxygen.
–
C6H12O6  yeast  2 CH3CH2OH + 2 CO2 + heat
–
sugar  yeast  ethanol + carbon dioxide + heat
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Heterotrophs capture free energy present in carbon
compounds produced by other organisms.
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The Role of Electron Acceptors in Energy-Capturing
Processes
• Different energy-capturing processes use different types of
electron acceptors:
–
NADP+ in photosynthesis
–
Oxygen in cellular respiration
• Chemical reactions that transfer electrons between
reactants are called oxidation-reduction reactions, or
redox reactions.
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Catabolic Pathways & ATP Production
• Catabolic Pathways yield energy by oxidizing organic fuels.
• Several processes are central to cellular respiration and
related pathways.
• The breakdown of organic molecules is exergonic:
–
Fermentation is a partial degradation of sugars that occurs
without O2.
–
Aerobic respiration consumes organic molecules and O2
and yields ATP.
–
Anaerobic respiration is similar to aerobic respiration but
consumes compounds other than O2.
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Cellular Respiration
• Cellular respiration includes both aerobic and
anaerobic respiration but is often used to refer to
aerobic respiration
• Although carbohydrates, fats, and proteins are all
consumed as fuel, it is helpful to trace cellular
respiration with the sugar glucose:
• C6H12O6 + 6 O2  6 CO2 + 6 H2O + Energy (ATP + heat)
–
The transfer of electrons during chemical reactions releases
energy stored in organic molecules
–
This released energy is ultimately used to synthesize ATP
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Oxidation of Organic Fuel Molecules During Cellular
Respiration
• During cellular respiration, the fuel (such as glucose)
is oxidized, and O2 is reduced:
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Stepwise Energy Harvest via NAD+ and the Electron
Transport Chain
• In cellular respiration, glucose and other organic molecules
are broken down in a series of steps.
• Cellular respiration in eukaryotes involves a series of
coordinated enzyme-catalyzed reactions that harvest free
energy from simple carbohydrates.
• Electrons from organic compounds are usually first
transferred to NAD+, a coenzyme.
• As an electron acceptor, NAD+ functions as an oxidizing
agent during cellular respiration.
Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings
The Stages of Cellular Respiration: A Preview
• Cellular respiration has three stages:
– Glycolysis (breaks down glucose into two
molecules of pyruvate) – occurs in cytosol
– The citric acid cycle (completes the breakdown
of glucose) – occurs in mitochondrial matrix
– Electron Transport/Oxidative
Phosphorylation (accounts for most of the ATP
synthesis) – occurs across inner membrane of
mitochondria
http://www.sumanasinc.com/webcontent/animations/content/cellularrespiration.html
Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings
Figure 9.16 Review: how each molecule of glucose yields many ATP molecules during
cellular respiration:
http://www.wadsworthmedia.com/biology/0495119814_starr/big_picture/ch07_bp.html
Review Questions from yesterday’s learning:
• How are the equations for photosynthesis and
chemosynthesis different (details)
• What type of reaction is it when organisms break
down sugars?
• What types of reactions transfer electrons?
(Compare the reactions)
• Name the three steps in cellular respiration.
• What is the net ATP production?
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Mitochondria Structure & Function
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Visual Overview of Cellular Respiration
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Term Comprehension: Substrate-Level Phosphorylation
• A smaller amount of
ATP is formed in
glycolysis and the citric
acid cycle by
substrate-level
phosphorylation.
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Glycolysis
http://highered.mcgrawhill.com/sites/0072507470/student_view0/chapter25/animation__how_glycolysis_works.html
• Glycolysis rearranges the bonds in glucose molecules,
releasing free energy to form ATP from ADP and inorganic
phosphate, and resulting in the production of pyruvate.
• Glycolysis harvests chemical energy by oxidizing glucose
to pyruvate – it is the first stage of cellular respiration.
• 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
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Glycolysis
•
Glycolysis occurs WITH or WITHOUT oxygen.
•
The first step is the phosphorylation of glucose (glucose
molecule gains 2 inorganic phosphates) – this ACTIVATES the
glucose to split.
•
The second step is the splitting of glucose – breaking it down
into (2) 3-carbon molecules called pyruvic acid.
–
This process is achieved by stripping electrons and
hydrogens from the unstable 3-C molecules (as well as
the borrowed phosphates).
•
2 ATPs are needed to produce 4 ATPs (energy investment and
energy payoff phases).
•
A second product in glycolysis is 2 NADH, which results from
the transfer of e- and H+ to the coenzyme NAD+.
–
Occurs in the cytoplasm
–
Net of 2 ATPs produced
–
2 pyruvic acids formed
–
2 NADH produced
Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings
10 Steps of Glycolysis
Fig. 9-8
Energy investment phase
Glucose
2 ADP + 2 P
2 ATP
used
4 ATP
formed
Energy payoff phase
4 ADP + 4 P
2 NAD+ + 4 e– + 4 H+
2 NADH + 2 H+
2 Pyruvate + 2 H2O
Net
Glucose
4 ATP formed – 2 ATP used
2 NAD+ + 4 e– + 4 H+
2 Pyruvate + 2 H2O
2 ATP
2 NADH + 2 H+
The “Intermediate” Step
• The pyruvate produced during
glycolysis is transported from
the cytoplasm to the
mitochondrion, where further
oxidation occurs.
• The conversion of pyruvate to
acetyl CoA is the junction
between glycolysis (step 1) and
the Krebs cycle (step 2).
• If oxygen is present, Pyruvate
(3 C each) from glycolysis
enters the mitochondrion.
• Using Coenzyme A, each
pyruvate is converted into a
molecule of Acetyl CoA (2 C
each).
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Fig. 9-10
CYTOSOL
MITOCHONDRION
NAD+
NADH + H+
2
1
Pyruvate
Transport protein
3
CO2
Coenzyme A
Acetyl CoA
The Citric Acid Cycle
http://highered.mcgrawhill.com/sites/0072507470/student_view0/chapter25/animation__how_the_krebs_cycle_works__quiz_1_.html
• In the Krebs cycle, carbon dioxide is released from
organic intermediations ATP is synthesized from ADP
and inorganic phosphate via substrate level
phosphorylation and electrons are captured by
coenzymes.
• The citric acid (Krebs) cycle completes the energyyielding oxidation of organic molecules – and its
events take place within the mitochondrial matrix.
• The cycle oxidizes organic fuel derived from pyruvate,
generating 1 ATP, 3 NADH, and 1 FADH2 per turn.
Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings
Fig. 9-11
Pyruvate
CO2
NAD+
CoA
NADH
+ H+
Acetyl CoA
CoA
CoA
Citric
acid
cycle
FADH2
2 CO2
3 NAD+
3 NADH
FAD
+ 3 H+
ADP + P i
ATP
Term Comprehension: Oxidative Phosphorylation
• The process that generates most of the ATP during cellular
respiration is called oxidative phosphorylation because it is
powered by redox reactions of an electron transport chain.
• Oxidative phosphorylation accounts for almost 90% of the ATP
generated by cellular respiration.
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• What is the literal translation of glycolysis and why
is it an appropriate name?
• How many ATP are used and created from the
process of glycolysis?
• What is the intermediate product made in the citric
acid cycle?
• How many cycles are involved in the completion of
the citric acid cycle?
• What are the electron carriers which are produced
in the first two portions of cellular respiration?
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Chemiosmosis & Electron Transport
http://highered.mcgrawhill.com/sites/0072507470/student_view0/chapter25/animation__electron_transport_system_and_atp_synthesis__quiz_1_.html
• Following the Krebs cycle, the electrons captured by
NADH and FADH2 are passed to the electron transport
chain:
–
The electron transport chain uses the high-energy electrons
from the Krebs cycle to convert ADP to ATP.
–
Every time 2 high energy electrons transport down the ETC,
their energy is used to transport H+ across the inner
membrane of the mitochondria…this creates a + charge on
the inside of the membrane and a – charge in the matrix of
the mitochondria.
–
As a result of this charge difference, H+ ions escape
through channel proteins called ATP synthase causing it to
rotate.
–
Each time it rotates, the enzyme ATP synthase grabs a low
energy ADP and attaches a phosphate, forming highenergy ATP.
Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings
NADH
50
2 e–
NAD+
FADH2
2 e–
40

FMN
FAD
Multiprotein
complexes
FAD
Fe•S 
Fe•S
Q

Cyt b
30
Fe•S
Cyt c1
I
V
Cyt c
Cyt a
Cyt a3
20
10
2 e–
(from NADH
or FADH2)
0
2 H+ + 1/2 O2
H2O
•
The electron transport chain captures free energy from electrons in a series of coupled
reactions that establish an electrochemical gradient across membranes.
•
Electrons delivered by NADH and FADH2 are passed to a series of electron acceptors as
they move toward the terminal electron acceptor, oxygen.
•
The passage of electrons is accompanied by the formation of a proton gradient across
the inner mitochondrial membrane, with the membrane separating a region of high
proton concentration from a region of low proton concentration.
•
The flow of protons back through membrane-bound ATP synthase by chemiosmosis
generates ATP from ADP and inorganic phosphate (Pi).
Fig. 9-14
INTERMEMBRANE SPACE
H+
Stator
Rotor
Internal
rod
Catalytic
knob
ADP
+
P
i
ATP
MITOCHONDRIAL MATRIX
Fig. 9-16
H+
H+
H+
H+
Protein complex
of electron
carriers
Cyt c
V
Q


ATP
synthase

FADH2
NADH
2 H+ + 1/2O2
H2O
FAD
NAD+
ADP + P i
(carrying electrons
from food)
ATP
H+
1 Electron transport chain
Oxidative phosphorylation
2 Chemiosmosis
Fig. 9-17
Electron shuttles
span membrane
CYTOSOL
2 NADH
Glycolysis
Glucose
2
Pyruvate
MITOCHONDRION
2 NADH
or
2 FADH2
6 NADH
2 NADH
2
Acetyl
CoA
+ 2 ATP
Citric
acid
cycle
+ 2 ATP
Maximum per glucose:
About
36 or 38 ATP
2 FADH2
Oxidative
phosphorylation:
electron transport
and
chemiosmosis
+ about 32 or 34 ATP
Fermentation/Anaerobic Respiration
• Fermentation and anaerobic respiration enable cells to
produce ATP without the use of oxygen
•
Most cellular respiration requires O2 to produce ATP
• Glycolysis can produce ATP with or without O2 (in aerobic
or anaerobic conditions)
• In the absence of O2, glycolysis couples with fermentation
or anaerobic respiration to produce ATP
–
Anaerobic respiration uses an electron transport chain with
an electron acceptor other than O2, for example sulfate
–
Fermentation uses phosphorylation instead of an electron
transport chain to generate ATP
Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings
Types of Fermentation
• Fermentation consists of glycolysis plus reactions
that regenerate NAD+, which can be reused by
glycolysis
– Two common types are alcohol fermentation
and lactic acid fermentation
Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings
Fig. 9-18
2 ADP + 2 Pi
Glucose
2 ATP
Glycolysis
2 Pyruvate
2 NAD+
2 NADH
+ 2 H+
2 CO2
2 Acetaldehyde
2 Ethanol
(a) Alcohol fermentation
2 ADP + 2 Pi
Glucose
2 ATP
Glycolysis
2 NAD+
2 NADH
+ 2 H+
2 Pyruvate
2 Lactate
(b) Lactic acid fermentation
Fermentation and Aerobic 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
or acetaldehyde) in fermentation and O2 in cellular
respiration
• Cellular respiration produces 38 ATP per glucose
molecule; fermentation produces 2 ATP per
glucose molecule
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The Anaerobes
• Obligate anaerobes carry out fermentation or
anaerobic respiration and cannot survive in the
presence of O2
• Yeast and many bacteria are facultative
anaerobes, meaning that they can survive using
either fermentation or cellular respiration
– In a facultative anaerobe, pyruvate is a fork in
the metabolic road that leads to two alternative
catabolic routes
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The Versatility of Catabolism
• Glycolysis and the citric acid cycle are major
intersections to various catabolic and anabolic
pathways.
• Catabolic pathways funnel electrons from many
kinds of organic molecules into cellular respiration.
• Glycolysis accepts a wide range of carbohydrates.
• In addition to carbohydrates, heterotrophs may
metabolize lipids and proteins by hydrolysis as
sources of free energy.
Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings
Fig. 9-20
Proteins
Amino
acids
Carbohydrates
Sugars
Glycolysis
Glucose
Glyceraldehyde-3- P
NH3
Pyruvate
Acetyl CoA
Citric
acid
cycle
Oxidative
phosphorylation
Fats
Glycerol
Fatty
acids
Fig. 9-21
Glucose
AMP
Glycolysis
Fructose-6-phosphate
–
Stimulates
+
Phosphofructokinase
–
Fructose-1,6-bisphosphate
Inhibits
Inhibits
Pyruvate
ATP
Citrate
Acetyl CoA
Citric
acid
cycle
Oxidative
phosphorylation
What do you know….
• Glycolysis
• Kreb Cycle
• ETC
• Fermentation Pathways
Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings
Overview of Cellular Respiration
A. Glycolysis –
*takes place in cytosol
*breaks glucose into 2 molecules of pyruvate
*produces a net of 2 ATP’s
B. Krebs cycle -
*takes place in mitochondrial matrix
*makes a derivative of pyruvate into carbon dioxide
*produces a net of 2 ATP’s
C. ETC and Oxidative Phosphorylation –
*takes place in inner membrane of mitochondrion
*accepts e-’s from A and B via NADH
*at end, e-’s are combined with H+ and oxygen to form
water
*forms a net of 34 ATP’s
D. Fermentation Pathways
*takes place in cytosol
*2 types: Alcoholic and Lactic Acid Fermentation
*stores most of the energy in chemical bonds
*no production of ATP
Energy Coupling
H2O
Following cellular respiration or fermentation, free energy becomes
available for metabolism by the conversion of ATPADP, which is
coupled to many steps in metabolic pathways.
Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings