copyright © 2006 pearson prentice hall, inc. intro to biology week 2 energy in cells, capturing...
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Copyright © 2006 Pearson Prentice Hall, Inc.
Intro to BiologyWeek 2
Energy in Cells, Capturing Energy and Harvesting Energy –
Glycolysis, and Cellular Respiration – Athletes.
Chapter 5
• Energy Flow in the Life of a Cell
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What Is Energy?
• From potential energy to kinetic energy
• Potential – energy not yet released
• Kinetic – energy in motion
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Potential Energy
Kinetic Energy
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Laws of ThermodynamicsLaws of Thermodynamics
First Law (ConservationFirst Law (Conservation of Energy)of Energy)Energy is neither created nor destroyed; it Energy is neither created nor destroyed; it is always conserved.is always conserved.
Second LawSecond LawEnergy always tends to go from a more Energy always tends to go from a more usable form to a less usable form, so the usable form to a less usable form, so the amount of energy available to do work amount of energy available to do work decreases (entropy occurs). decreases (entropy occurs).
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Consequence Of Laws Of Thermodynamics For Living
Organisms
Organisms require a constant input Organisms require a constant input of energy to maintain a high level of of energy to maintain a high level of
organization.organization.
““Feed Me Seymour!” Feed Me Seymour!”
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Types of Energy SystemsTypes of Energy SystemsThis Slide is Yellow
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What Is Energy?• Energy Cannot Be Created or Destroyed (1st
Law)• Energy Tends to Become Distributed Evenly
(2nd Law)• Matter Tends to Become Less Organized (2nd
Law)• Living Things Use the Energy of Sunlight to
Create Low-Entropy Conditions– We can see “opposite of entropy” flow when a
tremendous amount of energy is used…
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How Does Energy Flow in Chemical Reactions?
• Exergonic reaction (p. 75)
• “Exit” – energy is released
• Sugar is burned in a flame or consumed in the body, it reacts with oxygen and produces CO2 and H2O + energy
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Exergonic reaction
reactants
products
energyreleased
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The other way…
• Endergonic reaction (p. 75)
• Takes in energy – saves it (“Engender”)
• CO2 + Water + energy = sugar and oxygen
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reactants
products
energyused
Endergonic reaction
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How Does Energy Flow in Chemical Reactions?
• (Again) Exergonic Reactions Release Energy
• The specifics: Burning glucose (sugar)
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Burning glucose
glucose oxygen
carbondioxide
water
energyreleased
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How Does Energy Flow in Chemical Reactions?
• Endergonic Reactions Require an Input of Energy
– The specifics:• Photosynthesis (p. 76)
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Photosynthesis
glucose oxygen
carbondioxide
water
energy
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How Does Energy Flow in Chemical Reactions?
• Important Part: All Reactions Require an Initial Input of Energy– Things don’t burst into flame without some
kick – even exergonic ones– Think of it as a blasting cap or fuse needed
to kick off the stick of dynamite– Energy relations in exergonic and
endergonic reactions (p. 76)
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Burning glucose (sugar): an exergonic reaction Photosynthesis: an endergonic reaction
high
energycontent
of molecules
low
high
energycontent
of molecules
low
progress of reaction progress of reaction
activation energy neededto ignite glucose
activation energy from
light capturedby photosynthesis
glucose
glucose + O2
CO2 + H2O CO2 + H2O
energy releasedby burning glucose
net energy captured bysynthesizing
glucose
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Burning glucose (sugar): an exergonic reaction
high
energycontent
of molecules
low
energy releasedby burning glucose
progress of reaction
activation energy neededto ignite glucose
glucose + O2
CO2 + H2O
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Photosynthesis: an endergonic reaction
high
low
progress of reaction
activation energy from
light capturedby photosynthesis
glucose
CO2 + H2O
net energy captured bysynthesizing
glucose
energycontent
of molecules
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How Does Energy Flow in Chemical Reactions?
• Exergonic Reactions May Be Linked with Endergonic Reactions
• Called a coupled reaction, the exergonic reaction provides the input energy needed for the endergonic reaction:
• An ATP reaction creates energy
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How Is Energy Carried between Coupled Reactions?
• ATP Is the Principal Energy Carrier in Cells adenosine triphosphate
– ATP synthesis: Energy is stored in ATP– It is the ‘big one’ we will hear about again
and again
ENERGY IN!
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ATP synthesis: Energy is stored in ATP
energy
ADP phosphate
ATP
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Energy Out
– ATP breakdown: Energy of ATP is released (p. 77)
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ATP breakdown: Energy of ATP is released
energy
ATP
phosphateADP
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And things can get more complex…
– A coupled reaction (p. 77) (first figure)
Storage and release processes can work together to make the body work!
– Figure 5.4 Coupled reactions give off heat (p. 78) (second figure)
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Exergonic reaction:
Endergonic reaction:
Coupled reaction:
relaxedmuscle
relaxedmuscle
20 unitsenergy
contractedmuscle
100 unitsenergy released
80 units energyreleased as heat
contractedmuscle
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Coupled reaction: glucose breakdown and protein synthesis
glucose
exergonic(glucosebreakdown) endergonic
(ATP synthesis)
exergonic(ATP breakdown)
endergonic(protein synthesis)
net exergonic“downhill” reaction
ADP + heat
protein
aminoacids
CO2 + H2O + heat
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How Is Energy Carried between Coupled Reactions?
• Subtitle- when complex reactions work together…
• Electron Carriers Also Transport Energy within Cells– Electron carriers (p. 78)
– This is just to show you how things begin to build from the microscopic up to the gigantic (your muscles).
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Electron carrier molecules transport energy
endergonicreaction
net exergonic“downhill” reaction
(energizedcarrier)
(depletedcarrier)
exergonicreaction
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How Do Cells Control Their Metabolic Reactions?
(or how to not have spontaneous human combustion)
• The cell is a tiny chemical factory. As it works, this production of chemicals is called it’s metabolism
• Many chemical reactions linked together make up a metabolic pathway
• (next slide) Simplified view of metabolic pathways (p. 79)
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Initial reactant Intermediates Final products
PATHWAY 1
enzyme 1 enzyme 2 enzyme 3 enzyme 4
enzyme 5 enzyme 6
PATHWAY 2
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How Do Cells Control Their Metabolic Reactions?
• At Body Temperatures, Many Spontaneous Reactions Proceed Too Slowly to Sustain Life, something is needed to make them happen easier…
• Catalysts Reduce Activation Energy– Figure 5.7 Catalysts reduce activation
energy (p. 79)
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high
low
energycontent
ofmolecules reactants
products
progress of reaction
activation energywith catalyst
activation energywithoutcatalyst
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How Do Cells Control Their Metabolic Reactions?
• Enzymes Are Biological Catalysts (you’ve heard of enzymes before… now you know what they do)
• The Structure of Enzymes Allows Them to Catalyze Specific Reactions– The cycle of enzyme-substrate interactions
(p. 80)
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substrates
active siteof enzyme
enzyme
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How Do Cells Control Their Metabolic Reactions?
• The Activity of Enzymes Is Influenced by Their Environment
• The 3-D structure (like proteins last year)
• i.e. the salty brine in pickles keeps the enzymes in bacteria working – so they can’t attack and break down the cucumbers.
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Chapter 6
• Capturing Solar Energy: Photosynthesis
• Remember…sunlight is the source of all (>99%)
• (look at solar spectra graph pg 88.)
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• Everything from Gamma rays to Radio waves come out of the sun, but we are most interested in the peak of this energy… which is in the visible light portion of the electromagnetic spectrum
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What Is Photosynthesis?
• Photosynthesis Converts Carbon Dioxide and Water to Glucose (simple sugars)
• Remember – trees/grass etc. are solidified air…CO2 !
• Plant Photosynthesis Takes Place in Leaves– Figure 6.1 An overview of photosynthetic
structures (p. 86) – Stomata (stoma cingular) = holes or breathing– mesophyll where photosynthesis occurs
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internal leaf structure
mesophyllcells
chloroplasts
vein
stoma
channelinterconnectingthylakoids
stroma
outer membrane
inner membrane
thylakoid
chloroplast in mesophyll cell
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internal leaf structure
mesophyllcells
chloroplasts
vein
stoma
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channelinterconnectingthylakoids
stroma
outer membrane
inner membrane
thylakoid
chloroplast in mesophyll cell
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What Is Photosynthesis?• Leaf Cells Contain Chloroplasts – these are the organelles in
which photosynthesis occurs.• Photosynthesis Consists of Light-Dependent and Light-
Independent Reactions – light dependent reactions – thylakoids capture sunlight energy and convert
some of it into chemical energy • these molecules = ATP (adenosine triphosphate (ATP))• and the electron carrier NADPH (nicotinamide adenine dinucleotide
phosphate)• Oxygen is producted
– light independent reactions – enzymes in the stroma use the chemical energy above to make glucose (sugars/starch) or other organic molecules
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LIGHT-DEPENDENTREACTIONS(thylakoids)
depletedcarriers
(ADP, NADP+)
energizedcarriers
(ATP, NADPH)
LIGHT-INDEPENDENTREACTIONS
(stroma)glucoseCO2 + H2O
H2O O2
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How Is Light Energy Converted to Chemical
Energy?• Light, chloroplast pigments, and
photosynthesis (p. 88) • (next image) Chlorophyll strongly absorbs
violet, blue and red light (reflects green -looking green)
• Carotenoids absorb blue and green (reflects orange looking orange –visible in the fall when the leaves die, the green fades first)
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Visible light (“rainbow colors”)
Absorbance of photosynthetic pigments
Gamma rays X-rays UV Infrared Micro-waves
Radiowaves
Visible light
carotenoids
chlorophyll
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Visible light (“rainbow colors”)
Gamma rays X-rays UV InfraredMicro-waves
Radiowaves
Visible light
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Absorbance of photosynthetic pigments
carotenoids
chlorophyll
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How Is Light Energy Converted to Chemical
Energy?• Light Energy Is First Captured by Pigments
in Chloroplasts• The Light-Dependent Reactions Generate
Energy-Carrier Molecules– Light, chloroplast pigments, and photosynthesis
(p. 88) – PS I= photosynthesis process 1– PSII= photosynthesis process 2– ETC = Electron Transport Chain
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thylakoids
chloroplast
within thylakoid membrane
ETCPS IETCPS II
reaction centers
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How Is Light Energy Converted to Chemical
Energy?– Photosystem II Generates ATP (one of our
energy carriers)
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Photosystems – away!
• Photosystem I Generates NADPH (another one of our energy transport chemicals)
• Splitting Water Maintains the Flow of Electrons through the Photosystems
(The electrons that move through the chemical reactions have to be restored somehow…water does it)
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sunlight
ene
rgy
leve
l of
elec
tron
sw
ithin thylak oid
mem
branephotosystem I
photosystemII
synthesisreactioncenter
energy to drive
electron transport chain
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How Is Chemical Energy Stored in Glucose Molecules?• So we have energy now… storage?• Sugars! Starches! Glucose• The Cycle Captures Carbon Dioxide
– In through the stomata (breathing)– Figure 6.4 The C3 cycle of carbon fixation (p. 90) – The output is glucose!– Memorize? No just know it exists. It’s a cycle
that takes in CO2 and outputs glucose (C6H12O6)
• RuBP step = ribulose bisphospate
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6 CO26 H2O
612
RuBPPGA
C3
cycle
6
612
12
12
12
12G3P
glucose(or other organic
compounds)
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What Is the Relationship between Light-Dependent and Light-Independent Reactions?
• Figure 6.5 Two sets of reactions are connected in photosynthesis (p. 91)
• Photo = light capturing part
• Synthesis = light independent part glucose
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energy fromsunlight
chloroplast
glucose
Light-independentreactions(C3 cycle) occurin stroma.
Light-dependentreactions occurin thylakoids.
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CO2 in and out of the forest…
• Forests both consume and emit carbon dioxide (p. 92)
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How Does the Need to Conserve Water Affect
Photosynthesis?• Photosynthesis needs CO2
• But too many pores = water loss!• So stomata can open and close• = Regulation!• But…When Stomata Are Closed to Conserve
Water, Wasteful Photorespiration Occurs– Figure 6.6 Comparison of C3 and C4 plants
(p. 93) RuBP step CAN use O2 when CO2 is not available. Not good for glucose making!
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C3 and C4 Plant primer
• Named by which Carbon cycle they use during photosynthesis.
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C3 plants use the C3 cycle
C4 plants use the C4 pathway
within chloroplast in mesophyll cell
within chloroplast in mesophyll cell
bundle-sheathcells
bundle-sheathcells
glucose
C3
CYCLE
CO2
PGA
G3P
O2
CO2
RuBP
RuBP
C4
Pathway
CO2
CO2
CO2 O2
C3
CYCLE
glucose
PGA
G3P
pyruvate
PEP
4-carbonmolecule
within chloroplast in bundle-sheath cell
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C3 plants use the C3 cycle within chloroplast in mesophyll cell
bundle-sheathcells
glucose
C3
CYCLE
CO2
PGA
G3P
O2
CO2
RuBP
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C4 plants use the C4 pathway within chloroplast in mesophyll cell
within chloroplast in bundle-sheath cell
bundle-sheathcells
RuBP
C4
Pathway
CO2
CO2
C3
CYCLE
glucose
PGA
G3P
pyruvate
PEP
4-carbonmolecule
CO2 O2
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How Does the Need to Conserve Water Affect Photosynthesis?• An Alternative Pathway Reduces Photorespiration in
Plants• C3 and C4 Plants Are Each Adapted to Different
Environmental Conditions• During warm dry weather can make plants open their
stoma but not be able to capture enough energy to live.
• C3 best in low light high water environments (pole-ward forests) and C4 abundant light but water is scarce (deserts)
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Chapter 7 Show me the glucose!
• Harvesting Energy: Glycolysis and Cellular Respiration
• To power chemical reactions in the cell, the most common energy-carrier is ATP (adenosine triphosphate).
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What Is the Source of a Cell’s Energy?
• Glucose Is a Key Energy-Storage Molecule (other chemicals work, but glucose it’s the main player)
• Photosynthesis Is the Ultimate Source of Cellular Energy
• Glucose Metabolism and Photosynthesis Are Complementary Processes– Energy+water+carbon dioxide glucose + oxygen
Photosynthesis– glucose + oxygen energy + water + carbon dioxide
Glucose Metabolism
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How Do Cells Harvest Energy from Glucose?
• An overview of glucose metabolism (p. 101)
• Step 1 = Glycolysis (w/ or w/o oxygen) makes pyruvate (releases chemical energy -ATP)
• Step 2 = Cellular respiration (w/oxygen) or Fermentation (w/o oxygen)
• Step 3 = w/oxygen pyruvate enters the mitochondria CO2 and water + lots of ATP
w/o oxygen, doesn’t enter the mitochondria and is made into lactate or ethanol and no ATP
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(cytoplasm)
glucose
Glycolysis 2
2
2
2 2
2
2
2
lactateor
ethanolFermentation
Cellular respiration
CO2CO2
CO24
32 or 34
acetyl CoA
electroncarriers
Krebscycle
Electrontransport chain
(mitochondrion)
intermembranecompartmentH2O
O2
pyruvate
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What Happens During Glycolysis?
• The essentials of glycolysis (p. 101)
• Glycolysis makes only 2 ATP (energy transporters) and two NADH (energy transporters using the electron carrier)
(NADH = nicotinamide adenine dinucleotide)
• (The next image is a expansion of Step 1 above)
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2 2
2 2
2
4 4
2
glucose fructosebisphosphate
pyruvateG3P
Glucose activation Energy harvest1 2
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7.3 What Happens During Glycolysis?
• Activation Consumes Energy– The first part of the reaction
• Energy Harvest Yields Energy-Carrier Molecules– The second part of the reaction– Essential for life
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What Happens During Cellular Respiration?
• Cellular respiration (p. 103) Step 2 above.
• When you break it down… it is a bit complex
• Look for the parts you recognize…
• (Follow 1 8)
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mitochondrion
innermembrane
outermembrane
intermembranecompartment
matrix
cristae
glucose
2 pyruvate
(cytoplasm)
(intermembranecompartment)
(inner membrane)
coenzyme A
acetyl CoA
(matrix)
Krebscycle
energizedelectroncarriers
depleted carriers(outer membrane)
Electrontransportchain
CO2
CO2
H2O
H+
2 H+
H+
H+
H+
H+
H+
H+
H+
2e–
2e–
1/2 O
Glycolysis
1
8
6
43
5
7
2
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What Happens During Cellular Respiration?
• The Krebs Cycle Breaks Down Pyruvate (from Step 1) in the Mitochondrial Matrix– The reactions in the mitochondrial matrix
(p. 104) – The Krebs cycle is also called the citric-acid
cycle since citrate is formed first…– (More detail than we’ll quiz on)
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Formation ofacetyl CoA
pyruvate
coenzyme Acoenzyme A
Krebscycle
3
3
2 CO2
CO2
acetyl CoA
1
2
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What Happens During Cellular Respiration?
• Energetic Electrons Are Carried to Electron Transport Chains– Table 7.1 Summary of Glycolysis and
Cellular Respiration (p. 105) – Remember, we are looking for ways to
make the life important energy transporters– Figure 7.5 The electron transport chain in
the inner mitochondrial membrane (p. 104)
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(matrix)
(innermembrane)
synthesisenergy to drive
electroncarriers
(intermembrane compartment)
2e–
2e–
H+H+H+
1/2 O2 + 2H+
H2O
2
1
3
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What Happens During Cellular Respiration?
• Notice that there is Hydrogen (freed from the water) moving out at different steps of this respiration process (image back a slide)
• The cell gets more energy from a Hydrogen-Ion Gradient which Is Used to Produce yet more ATP
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What Happens During Fermentation?
• We don’t have oxygen (or enough oxygen) present.
• Some Cells Ferment Pyruvate to Form Alcohol (woo hoo)– Glycolysis followed by alcoholic
fermentation (p. 106) – Don’t get enough oxygen (in bread for
instance) and you get Fermentation (p. 107) byproducts
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Glycolysis followed byalcoholic fermentation
glucose pyruvate ethanol(glycolysis) (fermentation)
2 2 2
2 2
CO2
regeneration
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What Happens During Fermentation?
• Other Cells Ferment Pyruvate to Lactate– You also get lactic acid as a byproduct– Glycolysis followed by lactate fermentation
(p. 106)
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Glycolysis followed bylactate fermentation
glucose pyruvate lactate(glycolysis) (fermentation)
2 2
2 2
regeneration
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Next time…
• Chapters 8,9,10,11,12
• DNA• Gene expression and regulation• How cells reproduce• Patterns of Inheritance• Biotechnology