Transcript Unit 3 (ch 6)

BIOLOGY
CONCEPTS & CONNECTIONS
Fourth Edition
Neil A. Campbell • Jane B. Reece • Lawrence G. Mitchell • Martha R. Taylor
CHAPTER 6
How Cells Harvest Chemical
Energy
From PowerPoint® Lectures for Biology: Concepts & Connections
Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings
How is a Marathoner Different from a Sprinter?
• Long-distance runners have many slow fibers in
their muscles
– Slow fibers break down glucose for ATP
production aerobically (using oxygen)
– These muscle cells can sustain repeated, long
contractions
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• Sprinters have more fast muscle fibers
– Fast fibers make
ATP without
oxygen—
anaerobically
– They can contract
quickly and supply
energy for short
bursts of intense
activity
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• The dark meat of a cooked turkey is an example
of slow fiber muscle
– Leg muscles support sustained activity
• The white meat consists of fast fibers
– Wing muscles allow for quick bursts of flight
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Without Oxygen (Anaerobic)
Fermentation occurs when cells do not have
oxygen.
The electron transport chain is stopped.
Glycolysis is the only ATP producing mechanism.
Lactic Acid and Alcoholic fermentation.
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INTRODUCTION TO CELLULAR
RESPIRATION
• Nearly all the cells in our body break down
sugars for ATP production
• Most cells of most organisms harvest energy
aerobically, like slow muscle fibers
– The aerobic harvesting of energy from sugar is
called cellular respiration
– Cellular respiration yields CO2, H2O, and a large
amount of ATP
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6.1 Breathing supplies oxygen to our cells and
removes carbon dioxide
• Breathing and cellular respiration are closely
related
O2
BREATHING
CO2
Lungs
CO2
Bloodstream
O2
Muscle cells carrying out
CELLULAR RESPIRATION
Sugar + O2  ATP + CO2 + H2O
Figure 6.1
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6.2 Cellular respiration banks energy in ATP
molecules
• Cellular respiration breaks down glucose
molecules and banks their energy in ATP
– The process uses O2 and releases CO2 and H2O
Glucose
Oxygen gas
Figure 6.2A
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Carbon
dioxide
Water
Energy
• The efficiency of cellular respiration
(and comparison with an auto engine)
Energy released
from glucose
(as heat and light)
Energy released
from glucose
banked in ATP
Gasoline energy
converted to
movement
About
40%
25%
100%
Burning glucose
in an experiment
“Burning” glucose
in cellular respiration
Figure 6.2B
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Burning gasoline
in an auto engine
6.3 Connection: The human body uses energy from
ATP for all its activities
• ATP powers almost
all cell and body
activities
Table 6.3
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BASIC MECHANISMS OF ENERGY RELEASE
AND STORAGE
6.4 Cells tap energy from electrons transferred
from organic fuels to oxygen
• Glucose gives up energy as it is oxidized
Loss of hydrogen atoms
Energy
Glucose
Gain of hydrogen atoms
Figure 6.4
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6.5 Hydrogen carriers such as NAD+ shuttle
electrons in redox reactions
• Enzymes remove electrons from glucose
molecules and transfer them to a coenzyme
OXIDATION
Dehydrogenase
and NAD+
REDUCTION
Figure 6.5
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6.6 Redox reactions release energy when electrons
“fall” from a hydrogen carrier to oxygen
• NADH delivers electrons to a series of electron
carriers in an electron transport chain
– As electrons move from carrier to carrier, their
energy is released in small quantities
Electron flow
Figure 6.6
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• In an explosion, 02 is reduced in one step
Energy released as
heat and light
Figure 6.6B
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6.7 Two mechanisms generate ATP
• Cells use the energy
released by “falling”
electrons to pump
H+ ions across a
membrane
– The energy of the
gradient is
harnessed to make
ATP by the process
of chemiosmosis
High H+
concentration
Membrane
Electron
transport
chain
ATP
synthase
Energy from
Low H+
concentration
Figure 6.7A
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ATP synthase
uses gradient
energy to
make ATP
Chemiosmosis
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Chemiosmosis
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Chemiosmosis
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Chemiosmosis
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Chemiosmosis
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Chemiosmosis
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Chemiosmosis
H2O
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• ATP can also be
made by
transferring
phosphate groups
from organic
molecules to ADP
– This process
is called
substrate-level
phosphorylation
Enzyme
Adenosine
Organic molecule
(substrate)
Adenosine
New organic molecule
(product)
Figure 6.7B
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STAGES OF CELLULAR RESPIRATION AND
FERMENTATION
6.8 Overview: Respiration occurs in three main
stages
• Cellular respiration oxidizes sugar and
produces ATP in three main stages
– Glycolysis occurs in the cytoplasm
– The Krebs cycle and the electron transport chain
occur in the mitochondria
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• An overview of cellular respiration
High-energy electrons
carried by NADH
GLYCOLYSIS
Glucose
KREBS
CYCLE
Pyruvic
acid
Cytoplasmic
fluid
2
ELECTRON
TRANSPORT CHAIN
AND CHEMIOSMOSIS
Mitochondrion
2
Figure 6.8
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32
6.9 Glycolysis harvests chemical energy by
oxidizing glucose to pyruvic acid
Glucose
Figure 6.9A
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Pyruvic
acid
• Details of
glycolysis
Steps 1 – 3 A fuel
molecule is energized,
using ATP.
Glucose
Step
PREPARATORY
PHASE
(energy investment)
1
Glucose-6-phosphate
2
Fructose-6-phosphate
3
Fructose-1,6-diphosphate
Step 4 A six-carbon
intermediate splits into
two three-carbon
intermediates.
4
Glyceraldehyde-3-phosphate
(G3P)
ENERGY PAYOFF
PHASE
5
Step 5 A redox
reaction generates
NADH.
6
Steps 6 – 9 ATP
and pyruvic acid
are produced.
1,3-Diphosphoglyceric acid
(2 molecules)
7
3-Phosphoglyceric acid
(2 molecules)
8
2-Phosphoglyceric acid
(2 molecules)
2-Phosphoglyceric acid
(2 molecules)
9
Figure 6.9B
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Pyruvic acid
(2 molecules
per glucose molecule)
6.10 Pyruvic acid is chemically groomed for the
Krebs cycle
• Each pyruvic acid molecule is broken down to
form CO2 and a two-carbon acetyl group, which
enters the Krebs cycle
Pyruvic
acid
Acetyl CoA
(acetyl coenzyme A)
CO2
Figure 6.10
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6.11 The Krebs cycle completes the oxidation of
organic fuel, generating many NADH and
FADH2 molecules
Acetyl CoA
• The Krebs cycle
is a series of
reactions in
which enzymes
strip away
electrons and
H+ from each
acetyl group
KREBS
CYCLE
Figure 6.11A
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2
CO2
2 carbons enter cycle
Oxaloacetic
acid
1
Citric acid
CO2 leaves cycle
5
KREBS
CYCLE
2
Malic
acid
4
Alpha-ketoglutaric acid
3
CO2 leaves cycle
Succinic
acid
Step 1
Acetyl CoA stokes
the furnace
Steps 2 and 3
NADH, ATP, and CO2 are generated
during redox reactions.
Figure 6.11B
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Steps 4 and 5
Redox reactions generate FADH2
and NADH.
6.12 Chemiosmosis powers most ATP production
• The electrons from NADH and FADH2 travel
down the electron transport chain to oxygen
• Energy released by the electrons is used to
pump H+ into the space between the
mitochondrial membranes
• In chemiosmosis, the H+ ions diffuse back
through the inner membrane through ATP
synthase complexes, which capture the energy
to make ATP
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• Chemiosmosis in the mitochondrion
Protein
complex
Intermembrane
space
Electron
carrier
Inner
mitochondrial
membrane
Electron
flow
Mitochondrial
matrix
ELECTRON TRANSPORT CHAIN
Figure 6.12
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ATP SYNTHASE
6.13 Connection: Certain poisons interrupt critical
events in cellular respiration
Rotenone
Cyanide,
carbon monoxide
ELECTRON TRANSPORT CHAIN
Figure 6.13
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Oligomycin
ATP SYNTHASE
6.14 Review: Each molecule of glucose yields many
molecules of ATP
• For each glucose molecule that enters cellular
respiration, chemiosmosis produces up to 38
ATP molecules
Cytoplasmic
fluid
Mitochondrion
Electron shuttle
across
membranes
GLYCOLYSIS
2
Glucose
Pyruvic
acid
2
Acetyl
CoA
KREBS
CYCLE
KREBS
CYCLE
ELECTRON
TRANSPORT CHAIN
AND CHEMIOSMOSIS
32 ATP
by substrate-level
phosphorylation
used for shuttling electrons
from NADH made in glycolysis
Maximum per glucose:
by substrate-level
phosphorylation
36 ATP
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by chemiosmotic
phosphorylation
Figure 6.14
6.15 Fermentation is an anaerobic alternative to
aerobic respiration
• Under anaerobic conditions, many kinds of
cells can use glycolysis alone to produce small
amounts of ATP
– But a cell must have a way of replenishing
NAD+
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• In alcoholic fermentation, pyruvic acid is
converted to CO2 and ethanol
– This recycles NAD+ to keep glycolysis working
released
GLYCOLYSIS
Glucose
2 Pyruvic
acid
Figure 6.15A
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2 Ethanol
Figure 6.15C
• In lactic acid fermentation, pyruvic acid is
converted to lactic acid
– As in alcoholic fermentation, NAD+ is recycled
• Lactic acid fermentation is used to make cheese
and yogurt
GLYCOLYSIS
Glucose
2 Pyruvic
acid
Figure 6.15B
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2 Lactic acid
Cellular Respiration
• Cellular Respiration – releases energy from the
bonds of organic molecules
• C6H12O6 + O2  H2O + CO2 + Energy
3 Stages
Glycolysis
Kreb’s (Citric Acid Cycle)
Electron Transport Chain
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Glycolysis
• Glycolysis – sugar breakdown
• Glucose is split into 2 pyruvate molecules
• 2 net ATP are produced (-2 +4 = 2)
• 2 NADH are also produced
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Kreb’s Cycle
• Oxidation of Acetyl CoA
• Each glucose (2 pyruvates) yields
2 ATP
6 NADH
2 FADH2
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Electron Transport Chain and Chemiosmosis
• The electron transport chain is the part of
respiration that produces the most ATP and
requires oxygen.
• The electrons that are carried in NADH and
FADH2 molecules are used to produce ATP
through Chemiosmosis.
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Net Yield of Cellular Respiration
Glycolysis – 2 ATP
Krebs Cycle – 2 ATP
Electron Transport – 32 ATP
Each glucose yields 36 ATP
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Glycolysis (fermentation); ETC
• http://www.youtube.com/watch?v=uTILYYNxxE
• http://www.youtube.com/watch?v=kN5MtqAB
_Yc&feature=related
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