Transcript Cellular Respiration

INTRODUCTION TO CELLULAR
RESPIRATION
• Need Energy for work
• ATP = usable energy
• Cells make ATP by breaking down sugar
– Aerobic cell respiration – uses oxygen
– Anaerobic cell respiration – no oxygen
– Facultative Anaerobe – can use oxygen or not
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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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Cellular respiration banks energy in ATP molecules
• Breakdown sugar to get electrons to use energy
to make ATP
Glucose
Oxygen gas
Figure 6.2A
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Carbon
dioxide
Water
Energy
BASIC MECHANISMS OF ENERGY RELEASE
AND STORAGE
Cells tap energy from electrons transferred from
organic fuels to oxygen
• LEO / GER
• Oxidation: Lose Electrons
Loss of hydrogen atoms
• Reduction:
Gain Electrons
Energy
Glucose
Gain of hydrogen atoms
Figure 6.4
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Electron Transfer
• Sugar has electrons
• Break down sugar to get electrons (sugar gets
oxidized)
• NAD+ gains electrons (becomes oxidized) 
NADH [also FAD + electrons  FADH2]
• Eventually NADH gives electrons to oxygen,
and in process make ATP and water
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STAGES OF CELLULAR RESPIRATION AND
FERMENTATION
Overview: Respiration occurs in three main stages
• Cellular respiration oxidizes sugar and
produces ATP in three main stages
– 1. Glycolysis ( cytoplasm )
– 2. Pyruvate Dehydrogenase Complex PDC
(matrix)
– 3. Krebs Cycle (matrix)
– 4. Electron Transport Chain (cristae)
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• An overview of cellular respiration
High-energy electrons
carried by NADH
GLYCOLYSIS
Glucose
Pyruvic
acid
Cytoplasmic
fluid
Figure 6.8
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KREBS
CYCLE
ELECTRON
TRANSPORT CHAIN
AND CHEMIOSMOSIS
Mitochondrion
Glycolysis harvests chemical energy by oxidizing
glucose to pyruvic acid
Glucose
Figure 6.9A
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Pyruvic
acid
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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The Krebs cycle completes the oxidation of organic
fuel, generating many NADH and FADH2
molecules
Acetyl CoA
• The Krebs
cycle- get more
electrons from
sugar molecule
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.
Chemiosmosis powers most ATP production
• NADH and FADH2 – give electrons to enzymes
in electron transport chain that get passed to
oxygen
• Energy released by the electrons is used to
pump H+ into the space between the
mitochondrial membranes
• 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
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
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
by substrate-level
phosphorylation
2
Acetyl
CoA
used for shuttling electrons
from NADH made in glycolysis
KREBS
CYCLE
by substrate-level
phosphorylation
KREBS
CYCLE
ELECTRON
TRANSPORT CHAIN
AND CHEMIOSMOSIS
by chemiosmotic
phosphorylation
Maximum per glucose:
Figure 6.14
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Event
Location
Substrates
Products
Need
Oxygen
Glycolysis
Cytoplasm
Glucose, 2
ATP
2 Pyruvate, 2
ATP, 2
NADH
No
PDC
Matrix
Pyruvate
Acetyl CoA,
2 NADH,
CO2
No(but need
products
from ETC)
Krebs Cycle
Matrix
Acetyl CoA,
Oxaloacetic
Acid
Electron
Transport
Chain
Inner
membrane –
cristae
10 NADH
2 FADH2
Oxygen
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(must go 2x)
Oxaloacetic
Acid, 3
NADH, 1
ATP, 1
FADH2
NAD, FAD,
ATP, water
No(but need
products
from ETC)
Yes
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