cell respriation chapter 9. 9–1chemical pathways chemical energy and food calorie – amount of...
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CELL RESPRIATIONCHAPTER 9
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9–1 CHEMICAL PATHWAYS
Chemical Energy and Food
Calorie – amount of energy needed to raise1 gram of
water 10 Celcius.
Cells release energy from glucose gotten from food.
Process begins with glycolysis (splitting of a glucose molecule).
If oxygen is present (aerobic), it leads to Kreb’s Cycle & Electron
Transport Chain.
If oxygen is not present (anaerobic), it leads to fermentation.
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Glucose
Glycolysis Krebs cycle
Electrontransport
Fermentation (without oxygen)
Alcohol or lactic acid
CHEMICAL PATHWAYS
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OVERVIEW OF CELLULAR RESPIRATION
Cellular respiration (Rs) – process that releases energy by
breaking down food molecules in the presence of oxygen.
6O2 + C6H12O6 6CO2 + 6H2O + Energy ( 36ATP)
In words:6 oxygen + glucose yields 6 carbon dixoide + 6 waters +
36 ATP
3 stages of cell respiration
Glycolysis
Kreb’s Cycle
Electron Transport Chain
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GlucoseGlycolysis
Cytoplasm
Pyruvic acid
Electrons carried in NADH
Krebs Cycle
Electrons carried in NADH
and FADH2
Electron Transport Chain
Mitochondrion
Figure 9–2 – pg. 222 Cellular Respiration: an Overview – Cell respiration is a process that releases energy by breaking down food molecules in the presence of oxygen. Glycolysis takes place in the
cytoplasm. Krebs cycle and electron transport chain take place inside the mitochondria.
Mitochondrion
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GLYCOLYSIS1st step in Rs
Process in which one molecule of glucose is broken in half
to produce two molecules of pyruvic acid and 2 ATP
molecules.
At the end, 4 ATP are made, however, 2 ATP are used in the
beginning.
Net ATP production during glycolysis is 2 (4-2 = 2)
WHAT DOES GLYCOLYSIS BREAK DOWN?GLUCOSE
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Glucose
To the electron transport chain
2 Pyruvic acid
Figure 9–3 Glycolysis – pg. 223 – Glycolysis is the first stage in cellular respiration. During glycolysis, glucose is broken down
into 2 molecules of pyruvic acid.
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FERMENTATIONNo oxygen after glycolysis, fermantation takes
place (anaerobic)
Fermentation releases energy from food molecules when there is no oxygen available.
Two types of fermentation Alcoholic Lactic Acid
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ALCOHOLIC FERMENTATION
Performed by yeast Produces carbon dioxide and ethyl alcohol as
waste products.
Carbon dioxide causes bread to rise
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LACTIC ACID FERMENTATION
Pyruvic acid is converted to lactic acid
Happens when mucles are used during rapid exercise.
Not enough oxygen available and the body can’t produce
the ATP needed.
Buildup of lactic acid creates the painful burning sensation
during hard exercise.
Reason muscles feel sore after intense activity.
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Glucose Pyruvic acidLactic acid
Figure 9–4 – pg. 225 Lactic Acid Fermentation – Lactic acid fermentation converts glucose into lactic acid. The first part of the equation is glycolysis.
The second part shows the conversion of pyruvic acid to lactic acid.
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9–2 The Krebs Cycle and Electron Transport
Introduction
End of glycolysis, 90% of energy from glucose is unused.
Oxygen – most powerful electron acceptor – required for the remaining steps of cell respiration.
Energy-releasing reactions in the cell require oxygen and this is the reason we “breathe” or “respire”
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KREBS CYCLE
Oxygen is available, glycolysis is followed by
Krebs Cycle.
Named after Hans Krebs an English biochemist.
During Krebs Cycle, pyruvic acid (from
glycolysis) is broken down into carbon dioxide.
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KREB’S CONT’DBegins when pyruvic acid enters the mitochondria
Citric acid is broken down and CO2 is released.
Electrons are transferred to energy carriers (usually proteins)
Each turn of the Krebs Cycle produces 1 ATP molecule.
Krebs turns twice during respiration, producing 2 ATP overall.
CO2 released during Krebs is the source of all the CO2 organisms breath out.
WHY IS THE KREBS, CYCLE ALSO KNOW AS THE CITRIC ACID
CYCLE?
CITRIC ACID IS BROKEN DOWN INTO CO2
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Citric Acid Production
Figure 9–6 The Krebs Cycle – pg. 227 – During the Krebs cycle, pyruvic acid from glycolysis is used too make CO2, NADH, ATP AND
FADH2
Mitochondrion
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ELECTRON TRANSPORT3rd step in cell respiration
Uses high energy electrons from the Krebs cycle to create ATP
from ADP.
Electrons are passed along an electron transport chain.
Passed from 1 carrier protein to the next.
Located on the interior membrane (cristae) of the mitochondria.
At the end the electrons (H+) combine with O to form water.
Waste products of cell respiration.
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Figure 9–7 Electron Transport Chain – pg. 228 – The electron transport chain uses high-energy electrons from the
Krebs cycle to convert ADP into ATP.
Electron TransportHydrogen Ion Movement
ATP Production
ATP synthase
Channel
Inner Membrane
Matrix
Intermembrane Space
Mitochondrion
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THE TOTALSGlycolysis produces 2 ATP.
Kreb’s Cycle produces 2 ATP
Electron Transfer Chain produces 32 ATP
Grand Total of Cell Respiration = 36 ATP
See Fig. 9.8- page 229.
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COMPARING PHOTOSYNTHESIS AND CELLULAR RESPIRATION
Photosynthesis (PS) & Cell Respiration (RS) are opposite chemical reactions
They are the reverse of each other
PS removes CO2 from the atmosphere
RS puts it back
PS releases O2 and RS uses O2 to release energy (ATP) from food.
Products of Ps are the reactants of RS.
Products of RS are the reactants for Ps.
Cell respiration takes place in all eukaryotes and some prokaryotes.
Photosynthesis takes place only in plants, algae and some bacteria.
See Fig. 9-10, page. 232.
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Flowchart – Steps of Cellular Respiration
Glucose(C6H1206)
+Oxygen
(02)
Glycolysis KrebsCycle
ElectronTransport
Chain
Carbon Dioxide
(CO2)+
Water(H2O)
Cellular Respiration