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Active Lecture Questions for
Biology: Concepts & Connections, Sixth EditionCampbell, Reece, Taylor, Simon, and Dickey
Chapter 6 How Cells Harvest ChemicalEnergy
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Answer
Some prokaryotic and all eukaryotic cells use oxygen to harvest
energy from food molecules? In what form is that energyavailable to power cell work?
4) ATP molecules.
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Concept Check
The figure above represents an overview of the different processesof cellular respiration. Which of the following correctly identifies thedifferent processes?
1) 1. Glycolysis; 2. Electron transport chain; 3. Krebs cycle
2) 1. Glycolysis; 2. Krebs cycle; 3. Electron transport chain
3) 1. Krebs cycle; 2. Electron transport chain; 3. Glycolysis
4) 1. Electron transport chain; 2. Glycolysis; 3. Krebs cycle
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Answer
The figure above represents an overview of the different processesof cellular respiration. Which of the following correctly identifies thedifferent processes?
2) 1. Glycolysis; 2. Krebs cycle; 3. Electron transport chain
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Cytoplasm
Glucose
FADH2
Mitochondrion
Maximum per glucose:
OXIDATIVEPHOSPHORYLATION
(Electron Transport
and Chemiosmosis)
CITRIC ACIDCYCLE
Electron shuttleacross membrane
2 NADH
2 NADH
2 NADH
6 NADH 2
(or 2 FADH2)
2 Acetyl
CoA
GLYCOLYSIS2
Pyruvate
About38 ATP
about 34 ATPby substrate-levelphosphorylation
by oxidative phosphorylation
2 ATPby substrate-levelphosphorylation
2 ATP
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6.13 Fermentation enables cells to produce ATP without oxygen
Fermentation is an anaerobic (without oxygen) energy-generating process
It takes advantage of glycolysis, producing two ATP
molecules and reducing NAD+ to NADH
The trick is to oxidize the NADH without passing its
electrons through the electron transport chain to
oxygen
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6.13 Fermentation enables cells to produce ATP without oxygen
Your muscle cells and certain bacteria can oxidize NADHthrough lactic acid fermentation
NADH is oxidized to NAD+ when pyruvate is reduced to
lactate
In a sense, pyruvate is serving as an electron sink, a
place to dispose of the electrons generated by oxidation
reactions in glycolysis
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Animation: Fermentation Overview
http://localhost/var/www/apps/conversion/tmp/scratch_3/06_13FermentationOverview_A.html7/28/2019 Energy From Cell
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Glucose
NADH
NAD+
2
2
NADH2
NAD+2
2 ADP
P
ATP2
2 Pyruvate
2 Lactate
GLYCOLYSIS
Lactic acid fermentation
2
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6.13 Fermentation enables cells to produce ATP without oxygen
The baking and winemaking industry have used alcoholfermentation for thousands of years
Yeasts are single-celled fungi that not only can use
respiration for energy but can ferment under anaerobic
conditions
They convert pyruvate to CO2 and ethanol while
oxidizing NADH back to NAD+
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2 ADP
P
ATP2 GLYCOLY
SIS
NADH
NAD+
2
2
NADH2
NAD+2
2 Pyruvate
2 Ethanol
Alcohol fermentation
Glucose
CO22
released
2
Wine- grapes, water, yeast
Beer- water, malted barley,hops and yeast
Grains make liquors from
mashing and yeast
To Yeast, EtOH is toxic and
secreted to the extracellular
space. If you ferment toomuch, the yeast die and this
limits the proof of what you
are drinking.
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Fermentation vats for wine- have one-way valves to release the CO2 but keep out
the oxygen. Fermentation needs to happen without Oxygen.
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6.14 EVOLUTION CONNECTION: Glycolysis evolved early in the history of life on Earth
Glycolysis is the universal energy-harvesting process ofliving organisms
So, all cells can use glycolysis for the energy
necessary for viability
The fact that glycolysis has such a widespread
distribution is good evidence for evolution
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INTERCONNECTIONS BETWEENMOLECULAR BREAKDOWNAND SYNTHESIS
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6.15 Cells use many kinds of organic molecules as fuel for cellular respiration
Although glucose is considered to be the primary sourceof sugar for respiration and fermentation, there are
actually three sources of molecules for generation of
ATP
Carbohydrates (disaccharides)
Proteins (after conversion to amino acids)
Fats
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Food, such aspeanuts
ProteinsFatsCarbohydrates
Glucose
OXIDATIVEPHOSPHORYLATION(Electron Transportand Chemiosmosis)
CITRIC
ACIDCYCLE
AcetylCoAGLYCOLYSIS
Pyruvate
Amino acidsGlycerolSugars Fatty acids
Aminogroups
G3P
ATP
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Concept Check
1) The electron transport chain is too deeply embedded in themitochondria.
2) The electron transport chain only receives electrons carriedby reduced electron carrier molecules such as NADH.
3) The electron transport chain only receives electrons carriedby oxidized electron carrier molecules such as NAD+.
4) The electron transport chain does not produce ATP.
The figure above represents an
overview of the different entrypathways to cellular respiration when
different macromolecules are digested
for energy production. Why are none
of the digestive products entering the
electron transport chain, directly?
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Answer
2) The electron transport chain only receives electrons carried
by reduced electron carrier molecules such as NADH.
The figure above represents an
overview of the different entrypathways to cellular respiration when
different macromolecules are digested
for energy production. Why are none
of the digestive products entering the
electron transport chain, directly?
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6.16 Food molecules provide raw materials for biosynthesis
Many metabolic pathways are involved in biosynthesis ofbiological molecules
To survive, cells must be able to biosynthesize
molecules that are not present in its foods
Often the cell will convert the intermediate compounds
of glycolysis and the citric acid cycle to molecules not
found in food
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Cells, tissues, organisms
Proteins Fats Carbohydrates
Glucose
ATP needed to drive biosynthesis
CITRICACID
CYCLE
Acetyl
CoA
GLUCOSE SYNTHESIS
Pyruvate
Amino acids Glycerol SugarsFatty acids
Amino
groups
G3P
ATP
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Cytoplasm
GlucoseOxidative
phosphorylation
(Electron Transportand Chemiosmosis)
Citricacid
cycle
Glycolysis
Pyruvate
CO2
ATP
CO2
ATP
NADH and FADH2
Mitochondrion
NADH
ATP
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ATP (a) glucose and
organic fuels
has three stages
producesome
generates
Cellularrespiration
uses
H+ diffusethrough
ATP synthase
by process called
chemiosmosis
energy for
cellular work
uses
(b) (d)
(c)
(f)
(e)
oxidizes
C6H12O6
to pullelectrons down
to
uses pumps H+ to create
H+ gradient
producesmany
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You should now be able to
Explain how photosynthesis and cellular respiration are
necessary to provide energy that is required tosustain your life
Explain why breathing is necessary to support cellularrespiration
Describe how cellular respiration produces energy thatcan be stored in ATP
Explain why ATP is required for human activities
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You should now be able to
Describe the process of energy production frommovement of electrons
List and describe the three main stages of cellularrespiration
Describe the major steps of glycolysis andexplain why glycolysis is considered to be ametabolic pathway
Explain how pyruvate is altered to enter the citricacid cycle and why coenzymes are importantto the process
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You should now be able to
Describe the citric acid cycle as a metabolicpathway designed for generating additionalenergy from glucose
Discuss the importance of oxidativephosphorylation in producing ATP
Describe useful applications of poisons thatinterrupt critical steps in cellular respiration
Review the steps in oxidation of a glucosemolecule aerobically
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