In This Lesson:
Cellular
Respiration
(Lesson 2 of 3)
Today is Monday,
November 10th, 2014
Pre-Class:
Take a deep breath in and out. No, that’s not
respiration…that’s ventilation. Still, why do we need
oxygen? Exactly what does it do for us?
Also: How do you do?
Today’s Agenda
• Respiration
– Aerobic
•
•
•
•
Glycolysis
Pyruvate Oxidation
Citric Acid Cycle
Oxidative Phosphorylation
– Anaerobic
• Fermentation (Alcohol/Lactic Acid)
• Where is this in my book?
– Chapter 9.
By the end of this lesson…
• You should be able to describe the aerobic
and anaerobic respiration pathways by their
inputs and outputs.
• You should know where the cell gets its ATP.
• You should be able to relate the
mitochondrion’s structure with its function.
So what is it?
• Think of cellular
respiration like a harvest
of chemical energy.
– Like Thanksgiving all the
time.
• This is where cells
actually use the energy
they have available to
them to accomplish
work.
• The goal?
– PRODUCE ATP.
Cell “Work”
Active Transport
Cell “Work”
Movement of Proteins and Molecules
Cell “Work”
Phosphorylation and Molecule Activation, Building Molecules
And ATP is…?
• You know how you can use money for all kinds of
things? Money just facilitates some other activity?
And you need it in the right form for your country?
– The same goes for ATP. It’s used all over the place.
– Glucose is like a foreign currency. It needs to be exchanged.
• ATP is Adenosine Triphosphate.
– It’s a modified nucleotide with 3 phosphates instead of 1.
• ATP = Adenine + Ribose + 3 Phosphate Groups
• ADP = Adenine + Ribose + 2 Phosphate Groups
• AMP = Adenine + Ribose + 1 Phosphate Group
– Adding phosphates is endergonic and requires energy.
– Removing them is exergonic and absorbs energy.
ATP
• What I’d like you to think about when you
hear “ATP” is a giant chocolate bar:
ATP
http://savingmoneyplan.com/wp-content/uploads/2012/11/hersheys.jpg
Chocolate
• Chocolate is high in Calories.
– Therefore it’s got a lot of energy.
• Chocolate is high in sugar.
– It provides you with a boost when you eat it.
• Chocolate bars often are divided into squares
or rectangles that you can eat one-at-a-time.
– You don’t need to destroy the whole bar to get
something out of it.
ATP
• ATP has high-energy bonds.
– Your cell breaks off a phosphate and replaces
those bonds with lower-energy bonds.
• ATP provides free energy when hydrolyzed
and gains free energy.
• ATP can be reused.
– Like putting a square back on the chocolate bar.
• I wish I could do that.
Can chocolate be re-used?
Anyway…
OOOO – P – O O – P – OO
–P–O
Energy
OOO-
• How does ATP actually store energy?
– Each phosphate group added to the adenosine molecule
becomes progressively harder to “hold.”
• Remember, they have a -1 or -2 charge, so that’s a lot of
negativity built up.
– The phosphates can “pop off” easily and release energy.
– This makes ATP a great energy donor.
ATP
Anyway…
OOO – P – OO – P – O
OO-
-OH
OH- O – P – O
O-
• How does ATP transfer energy?
• The hydrolysis of ATP to ADP releases energy.
• ΔG = -7.3 kcal/mol
• Key: The “missing” phosphate is replaced by a
hydroxide from water.
• Key: The formation of this bond releases energy.
• Key: The other hydrogen ion (from water) goes to the
phosphate.
The Catch
• As great as ATP is for energy transfer, it’s a
particularly bad molecule for energy storage.
– It’s quite unstable and transfer its phosphate
group too easily.
• A working muscle recycles over 10,000,000
ATP molecules every second.
ATP Production
H+
• One energy source for
production of ATP is the
enzyme/channel protein
ATP Synthase.
H+
H+
H+
H+
H+
H+
H+
rotor
– Located in the
mitochondrial membrane.
• H+ ions flow down the
channel protein and
power the enzyme like a ADP
hydroelectric dam.
– The question is…how do
we turn it on?
rod
catalytic
head
+
P
ATP
H+
Inquiry Break
• Cellular Respiration – An Overview POGIL
• Go to the second STOP sign.
• IMPORTANT: The POGIL shows the “link
reaction” – more on that later – as occurring
in the intermembrane space. It doesn’t – it
occurs in the matrix.
Back to “harvesting energy…”
• You should know the familiar equation for
respiration:
– C6H12O6 + 6O2  6CO2 + 6H2O + ATP
• [glucose] + [oxygen]  [carbon dioxide] + [water] + [energy]
• Before we really explore this in depth, keep
something in mind:
– Respiration is, almost literally, burning calories.
– It’s like burning a piece of wood, only it happens in a lot
of little steps instead of one big one.
• It even gives off heat, just not as much.
Respiration: Big Ideas
• As big molecules are broken into smaller ones…
• …bonds are broken…
• …and electrons are moved from one molecule to
another…
• …“carrying energy” with them, which is:
– Stored in a new bond OR
– Released as heat OR
– Harvested to make ATP.
Respiration: Big Ideas
• Therefore, quite a bit of respiration is made of redox
(reduction/oxidation) reactions.
• Key: Reduction is a gain of electrons; oxidation is a loss of
electrons.
• Key: The oxidized atom is the reducing agent and vice versa.
• Key: Remember that with “OIL RIG:”
– “Oxidation Is Loss”
– “Reduction Is Gain”
Loss of eGain of eReducing
Agent
e-
+
Oxidizing
Agent
Oxidized
+
Reduced
+
-e
-
Respiration: Big Ideas
• In living systems, electrons are moved with
hydrogen atoms.
– Key: When you see H moving, you’re seeing electrons
move too.
• Consider the overall respiration equation:
Oxidation
The oxygen
has gained
hydrogens.
C6H12O6 + 6O2  6CO2 + 6H2O + ATP
The glucose
will lose
hydrogens.
Reduction
Oxidation and Reduction
• Oxidation:
– Removing H
– Loss of electrons
– Release of energy
– Exergonic
• Reduction:
– Adding H
– Gain of electrons
– Storage of energy
– Endergonic
Coupling Reactions
• I’m sure you remember that exergonic and endergonic
reactions are coupled.
– The energy released by the exergonic reaction is harnessed
for use in an endergonic reaction.
• C-C bonds are broken, but more importantly…
• Key: C-H bonds are broken to strip off H atoms.
– C6H12O6  CO2 = oxidation of glucose fuel.
– O2  H2O = reduction of oxygen.
• Electrons are attracted to the more electronegative
atom, which liberates potential atom.
– In chemistry, F is the most electronegative, but it’s too strong
for living systems. O is the most electronegative for biology.
• Which partly explains why fluoride ions are good in toothpaste.
Okay, let’s go…
• We’re ready to start learning the details of the
respiration “story.”
• We’ll begin with two important “characters:”
– NAD+
• Nicotinamide adenine dinucleotide, AKA niacin or Vitamin B3
– FAD
• Flavin adenine dinucleotide, AKA riboflavin or Vitamin B2
• Key: These are each electron carriers and are
responsible for moving H atoms around.
• I want you to think of these each as batteries.
Electron Carriers/Batteries
• Oxidized: NAD+ and FAD are the “drained” batteries:
• Reduced: NADH and FADH2 are the “charged” batteries:
• I’ll be using these symbols throughout the lesson.
A Closer Look at NAD+ and NADH
http://www.uic.edu/classes/bios/bios100/lectures/NADH01.jpg
Cellular Respiration Overview
• Aerobic Respiration
1.
2.
3.
4.
Glycolysis
Pyruvate Oxidation
Krebs/Citric Acid Cycle
Oxidative Phosphorylation
Cytosol
Mitochondria
• Note: If oxygen is not around, many cells carry
out fermentation following glycolysis.
Warm-Up
• CrashCourse – ATP and Respiration – Part 1
Inquiry Break
• Cellular Respiration – An Overview POGIL
• Stop at the end of Page 4.
Quick Reminder:
Mitochondrial Structure
• They have two bilayer
membranes. From the
outside in:
–
–
–
–
Outer membrane
Intermembrane space
Inner membrane
Matrix
• The inner membrane has
folds called cristae.
• Sketch it like you mean it.
http://course1.winona.edu/kbates/Bio241/images/figure-04-14.jpg
Glycolysis
• The name “glycolysis” literally means “splitting sugar.”
• In this process, glucose (6 carbons) is broken down into
two pyruvate molecules (3 carbons).
• Key: It’s inefficient: 1 glucose molecule results in only
2 net ATP.
– The pyruvates can be broken down further for more energy.
• Glycolysis takes place in the cytosol. Why?
– Energy is needed by all cells, prokaryotic or eukaryotic, so it
had to have evolved a long time ago, before eukaryotes.
Glycolysis: Evolution
• Because early cells had no organelles, and because
the early atmosphere had no oxygen, life had to
find a way to produce ATP anaerobically in the
cytosol.
– Side note: “Cytoplasm” technically extends into the
mitochondria, chloroplasts, and other organelles.
Cytosol is the cytoplasm minus the organelles.
• Since all cells evolved from these early ones,
glycolysis is like a homologous “structure” to us all.
Glycolysis: Input/Output
• Glycolysis is actually
made up of ten (really
9.5) smaller reactions.
• Before we explore them,
let’s get the input and
output straight:
– Input
• Glucose (1)
• ATP (2)
– Output
• Pyruvate (2)
• ATP (4 total, 2 net)
• NADH (2)
The Detailed View
• I do not need you to memorize this.
• However, it’s useful to see the pathway in full at
least once to:
– see why the input/output is so.
– appreciate what’s happening.
• For clarity, enzymes are shown in italics and
inputs/outputs are underlined.
• You are responsible for the inputs and outputs.
Glycolysis: Reactions [Detailed]
1. Hexokinase dephosphorylates ATP and adds the
phosphate to glucose, creating glucose 6-phosphate.
This also prevents glucose from exiting the cell.
– -1 Glucose
– -1 ATP
2. Phosphoglucoisomerase converts glucose 6-phosphate
to fructose 6-phosphate through a shape change.
3. Phosphofructokinase dephosphorylates ATP and adds
the phosphate to fructose 6-phosphate, creating
fructose 1,6-bisphosphate.
– -1 ATP
Glycolysis: Reactions [Detailed]
4. Aldolase converts fructose 1,6-bisphosphate into
glyceraldehyde 3-phosphate (G3P) and
dihydroxyacetone phosphate (DHAP).
– Isomerase converts the DHAP to G3P as well.
– This means there are two G3P molecules and two of every
molecule moving forward.
5. NAD+ oxidizes G3P and then triose phosphate
dehydrogenase adds an inorganic phosphate group to
it, creating 1,3-bisphosphoglycerate (1,3-BPG).
– +2 NADH
6. Phosphoglycerokinase removes the phosphate and
phosphorylates ADP, creating 3-phosphoglycerate.
– +2 ATP
Glycolysis: Reactions [Detailed]
7. Phosphoglyceromutase moves a phosphate group,
creating 2-phosphoglycerate.
– Underachiever.
8. Enolase adds a double bond within the compound,
creating phosphoenopyruvate (PEP).
9. Pyruvate kinase removes a phosphate group and
phosphorylates ADP, creating pyruvate.
– +2 ATP
– +2 pyruvate
Glycolysis
http://cerebraldopamine.files.wordpress.com/2011/09/glycolysis_pathway.jpg
Quick Note
• I know I said you didn’t need
to know the details of
glycolysis, but it’s probably
worth remembering G3P.
• It’s a 3-carbon sugar that will
come up again in
photosynthesis.
Pyruvate Oxidation: Input/Output
• Prior to entering the Citric Acid Cycle, pyruvate has
to be oxidized.
– Your book calls it “pyruvate oxidation” but it is also
known as the “link reaction” (especially by the POGIL).
• As usual, just know the inputs/outputs:
– Input
• Pyruvate (2)
– Output
• Acetyl CoA (2)
• NADH (2)
• CO2 (2) [waste]
Pyruvate Oxidation: Reactions
Matrix 
[Detailed]
• First, the two charged pyruvate molecules enter the
mitochondrion via active transport.
– Both pyruvate oxidation and the citric acid cycle take place
in the matrix (inside the inner membrane).
• Enzyme complex pyruvate dehydrogenase complex:
– Removes CO2, making acetate.
• (6 carbon glucose to 3 carbon pyruvate to 2 carbon fragment now)
• -2 Pyruvate
• +2 CO2 [waste]
– Oxidizes it and reduces NAD+ to NADH.
• +2 NADH
– Adds Coenzyme A (sulfur-containing compound from a B
vitamin), making acetyl CoA.
• +2 acetyl CoA

Pyruvate Oxidation
http://schoolworkhelper.net/wp-content/uploads/2011/02/pyruvate-oxidation.jpg
Citric Acid Cycle: Input/Output
• The products of pyruvate
meaning that it is
oxidation (acetyl CoA)
continuously running like
feed the Citric Acid Cycle, a revolving door.
also known as the Krebs • For both turns:
Cycle.
– Input
• The Citric Acid Cycle is
• Acetyl CoA (2)
made of eight reactions
– Output
but “turns” twice for each
• ATP (2)
• NADH (6)
acetyl CoA input.
• FADH2 (2)
• Importantly, it is a cycle,
• CO2 (4) [waste]
Citric Acid Cycle: Reactions
[Detailed]
1. Acetyl CoA loses its acetyl group to oxaloacetate, forming
citrate.
– Hence the name of the cycle (citrate is ionized citric acid).
– -2 Acetyl CoA after both turns.
2. Citrate is made into isocitrate (isomer) by removing a water
molecule and then adding one.
3. Isocitrate is oxidized by NAD+ and the resulting compound
loses a CO2, becoming α-ketoglutarate.
– +2 NADH after both turns.
– +2 CO2 after both turns.
4. α-ketoglutarate loses another CO2 and is then oxidized by
NAD+, forming succinyl CoA.
– +2 NADH after both turns.
– +2 CO2 after both turns.
Citric Acid Cycle: Reactions
[Detailed]
5. CoA (in succinyl CoA) is replaced by a phosphate group
which is then transferred to GDP (making GTP), which
then is dephosphorylated as ADP becomes ATP.
Meanwhile, succinyl CoA has become succinate.
– +2 ATP after both turns.
6. Succinate is oxidized twice by FAD, making fumarate.
– +2 FADH2 after both turns.
7. Water rearranges bonds in fumarate, making malate.
8. Malate is oxidized by NAD+, making oxaloacetate. The
cycle can repeat as an acetyl group comes from
another acetyl CoA.
– +2 NADH after both turns.
Citric Acid Cycle
http://www.bio.miami.edu/tom/courses/protected/MCB6/ch12/12-10.jpg
So…
•
•
•
•
•
•
•
How’s it going?
I know, phew, right?
Um…
Well how’s your family?
Good, good.
Uh…
Okay let’s just…let’s just keep going…
Review
• We’re about to go to the next step, but let’s
recap a little bit.
– Cue marker joke.
– “Recap”…get it?
• From one glucose molecule:
– 6 CO2 [waste]
– 4 ATP (net)
– And…importantly…?
Review
• We have also built up:
– 10 NADH
– 2 FADH2
• All of that effort (charging the
batteries) is now about to pay off.
• Cue oxidative phosphorylation.
http://fc08.deviantart.net/fs25/f/2008/092/5/f/IMA_FIRIN_MAH_LAZOR_by_Teh_Kenji.gif
Oxidative Phosphorylation
• Oxidative phosphorylation is technically
broken into two phases:
– Electron Transport Chain
• Produces none of the ATP.
– Chemiosmosis
• Produces all of the ATP.
Oxidative Phosphorylation
Electron Transport Chain
• All throughout this process, ΔG has been mostly
positive, meaning our products to this point are high
potential energy and are set to “fall” back down to
lower energy.
• The cell will allow this to happen in short stages.
– Not falling off a building…more like falling down stairs.
• This is called electron transport chain (ETC) and it takes
place primarily within the inner membrane of the
mitochondrion.
– Remember, the inner membrane has lots of folds called
cristae that add surface area and make this even more
efficient.
Electron Transport Chain: Reactions
[Detailed]
1. NADH gives up two electrons to Enzyme Complex I:
– First to FMN (flavin mononucleotide), then to Fe-S, an ironsulfur protein.
– Complex I is an integral membrane protein called NADH
Reductase.
– NADH  NAD+ + H+ + 2 e(remember that H+)
• OR
1. FADH2 gives up two electrons to Enzyme Complex II:
– Directly to Fe-S.
– Complex II, stuck to the inside of the membrane like a G
protein, is called succinate dehydrogenase.
– FADH2  FAD + 2 H+ + 2 e(remember those 2 H+)
Electron Transport Chain: Reactions
[Detailed]
2. Next, the Fe-S passes the electrons to ubiquinone
(abbreviated Q, also known as Coenzyme Q or
CoQ).
– Ubiquinone is not a protein and is hydrophobic, so it
moves around within the inner membrane.
3. Ubiquinone passes its electrons to Enzyme
Complex III, called cytochrome reductase:
– First to Cytochrome b (abbreviated Cyt b)…
– …then to another Fe-S protein…
– …then to Cyt c1…
Electron Transport Chain: Reactions
[Detailed]
4. Complex III (specifically Cyt c1) then passes its
electrons to Cyt c, which passes its electrons to
Enzyme Complex IV, called cytochrome oxidase:
– First to Cyt a…
– …then to Cyt a3.
5. Now, at the end of our giant microscopic hot potato
party, Cyt a3 passes its electrons to oxygen, the final
electron acceptor.
– Oxygen picks up a -2 charge, then two protons, making H2O.
– Oxygen plays this role because it is quite electronegative.
• The electron transport chain has ended, but in the
process we’ve liberated a buttload of potential energy.
– And we have to pee, since we’ve also generated some water.
Oxidative Phosphorylation
http://www.tokresource.org/tok_classes/biobiobio/biomenu/cell_respiration/c8_9x16_chemiosmosis.jpg
Electron Transport Chain: The Catch
• The catch: We haven’t made any ATP.
– “Huhwhat?”
• The cell instead puts that liberated energy to
use engaging in something called
chemiosmosis:
– Making an H+ (proton) gradient across a
membrane, in this case the mitochondrial
membrane, to drive work.
Oxidative Phosphorylaton:
Chemiosmosis
• Enzyme complexes I, III, and IV all pump hydrogen
ions out of the mitochondrial matrix.
• This creates an electrochemical gradient:
– The intermembrane space now has a buildup both of
protons and of positive charge.
• In a specialized form of facilitated diffusion, the cell
lets these protons diffuse back into the matrix
through ATP Synthase.
– ATP Synthase is a membrane protein/enzyme complex.
– As protons diffuse, part of the protein spins (yes, spins),
activating sites that generate ATP from ADP.
ATP Synthase
H+
H+
H+
H+
H+
H+
H+
H+
rotor
rod
ADP
catalytic
head
+
P
ATP
http://upload.wikimedia.org/wikipedia/commons/thumb/0/00/Atp_s
ynthase.PNG/300px-Atp_synthase.PNG
H+
ATP Synthase
• ATP Synthase provides protons the only way
back into the cristae.
• Think of the enzyme much like a waterwheel:
– The water (proton stream) turns the wheel (ATP
Synthase’s rotor), generating power (ATP).
Oxidative vs. Substrate-Level
Phosphorylation
• Notice something. We have now seen ATP
generated both by an enzyme transferring a
phosphate from another molecule, or through
ATP Synthase putting ADP and Pi together.
• Biochemists distinguish these as follows:
– Transferring P from another molecule = substratelevel phosphorylation.
• Krebs Cycle/Glycolysis
– Adding Pi through chemiosmosis = oxidative
phosphorylation.
• Chemiosmosis
Oxidative Phosphorylation:
Input/Output
• After all this, we can look at oxidative
phosphorylation’s inputs and outputs:
– Input
• NADH 10
• FADH2 (2)
• O2 (6)
– Output
• ATP! (realistically 26-28 per glucose, though some sources
say upwards of 34 per glucose. Unlikely.)
• H2O (4) [waste]
• NAD+
• FAD
Did you notice something?
• Glycolysis is an anaerobic step.
• Pyruvate oxidation and the citric acid cycle
don’t use oxygen directly.
• HOWEVER! Because they precede the ETC,
they will not run without oxygen.
– Only the ETC actually needs oxygen.
Cell Respiration Summary
C6H12O6 + 6O2  6CO2 + 6H2O + ATP
• Reactants:
– 1 C6H12O6
• 1 used in Glycolysis
– 6 O2
• 6 used in Oxidative
Phosphorylation
• Products:
– 6 CO2
• 2 from Pyruvate
Oxidation
• 4 from Citric Acid Cycle
– 6 H2O
• 6 from Oxidative
Phosphorylation
– 30 or 32 ATP
[maximum]
• 2 (net) from Glycolysis
• 2 from Citric Acid Cycle
• 26 or 28 from Oxidative
Phosphorylation
Cell Respiration Summary
C6H12O6 + 6O2  6CO2 + 6H2O
Glycolysis and Oxidative
Phosphorylation
Pyruvate Oxidation
and Citric Acid Cycle
Oxidative Phosphorylation
Glycolysis
Closure
• Just kidding! We’re not done yet.
Inquiry Break
• Cellular Respiration – An Overview POGIL
• Stop at the end of Page 5 (STOP sign).
In a world…
• …without oxygen, like the • Furthermore, glycolysis is
world in which glycolysis
not a cycle:
originally evolved, there’s
– Input
an issue:
• Glucose (1)
– We can’t run oxidative
phosphorylation, so the
Krebs Cycle also doesn’t
move.
– Alternatively, if you’re a
prokaryote, you don’t have
mitochondria, so that’s out
too.
• ATP (2)
– Output
• Pyruvate (2)
• ATP (4 total, 2 net)
• NADH (2)
Problems and Solutions
• The Problems:
1. We don’t have oxygen around for the end of the electron
transport chain.
2. NAD+ is ultimately responsible for creating ATP as it oxidizes
G3P. It needs to be restored from NADH.
• The Solutions:
1. Use a different molecule, like something with sulfur, to
accept electrons.
• If so, this is anaerobic respiration.
• In anaerobic respiration, pyruvate oxidation and citric acid cycle
occur in the cytosol, while the membrane used for oxidative
phosphorylation is the cell membrane. Pretty cool.
2. Recycle NADH into NAD+ through fermentation.
Fermentation
• Two types of fermentation:
– Alcohol fermentation oxidizes NADH through the
production of ethanol and CO2.
• Utilized by bacteria and yeast (fungus).
• This explains winemaking, brewing, and bubbles in
pizzas/bread.
– Yeast farts!
– Lactic acid fermentation oxidizes NADH through the
production of…lactic acid.
• Utilized by fungi, bacteria, and animals.
• This explains cheese, yogurt, and not why your muscles are
sore the next day after exercise.
Aside: Alcohol Fermentation in Nature
• BBC – Alcoholic Vervet Monkeys
Aside: Lactic Acid
• You may have heard that lactic acid leads to
muscle soreness.
• Upon resumption of aerobic respiration, your
muscles clear the lactic acid relatively quickly.
– So it’s not lactic acid.
• Some research suggests that short-term
soreness is due to K+ ions, while longer-term
soreness is due to micro-tears in muscle fiber.
Back to Fermentation
• Important stuff to note:
– Fermentation creates no ATP on its own but allows
glycolysis to continue.
– Because the fermentation pathway yields only 2 net ATP,
it’s inefficient for multicellular organisms.
– Obligate anaerobes (prokaryotes that don’t use oxygen)
utilize fermentation regularly, but they’re single-celled.
– Facultative anaerobes (use oxygen only when available)
utilize fermentation regularly as well.
– Humans and other eukaryotes mainly use it as backup
for when the blood can’t deliver enough O2.
• Aside: Brain cells can’t really do it. Strokes = dangerous.
Aside: Athletes
• So here’s a question for you – biomechanically,
how do athletes have higher endurance than
non-athletes?
• The answer, in part, appears to be efficiency of
oxygen use.
– Athletes simply get more oxygen dissolved into
their blood compared to the same volume breath
from a non-athlete.
– This explains why “altitude training” helps make
respiratory pathways even more efficient.
Warm-Up
• CrashCourse – ATP and Respiration – Part 2
Pseudo-Closure
• Whisper Down the Metabolic Pathway
• I have written a short paragraph on respiration, but I’ve
broken it into 31 “cards.”
– So each card has a fragment of a sentence or two.
• Your job, when you receive your card(s), is to arrange yourself
in order with everyone else’s.
– You have to hold onto your card, so get in line.
• This is challenging.
• Hints:
– First figure out what yours is talking about.
– Then think of what comes before and after it – go find those
people first.
– If you’re the beginning or end, tell people so.
Last Topic: Versatility
• Glycolysis accepts a lot of inputs; it doesn’t need to be
glucose.
– Other molecules like starch just get broken down to glucose first.
• Proteins are not efficient sources of energy.
– But when they are used, they must be hydrolyzed back to amino
acids.
– The amino group becomes waste (ammonia, urea, or uric acid – it
goes in yo’ pee).
– The carboxyl group and central carbon become a 2-carbon sugar
and is passed into respiration.
Last Topic: Versatility
• Triglycerides – great energy source that they are – have
an interesting way of getting into the respiration
pathway.
• The glycerol head enters the glycolysis pathway as G3P.
• The fatty acid tails are broken into 2-carbon fatty acids
and enter the citric acid cycle as acetyl CoA.
– Given that only two acetyl CoAs enter for each glucose, one
triglyceride provides a heck of a lot of “bang for your bond.”
Versatility: Fats and Carbs
• Fats generate 2x the ATP compared to
carbohydrates.
– They contain a lot of carbon atoms that are
partially oxidized already.
• On the other hand, carbohydrates are faster to
use.
– They contain oxygen atoms that are partially
oxidized already.
– Less energy released than from fats, though.
Inquiry Break
• Cellular Respiration – An Overview POGIL
• “Finish him!”…I mean…“it.”
Cell Respiration Summary
Cytosol
Glycolysis
Mitochondrial Matrix
Oxygen
Citric Acid
Cycle
Oxidative
Phosphorylation
O
Pyruvate
Oxidation
Citric Acid
Cycle
Oxidative
Phosphorylation
S
No Oxygen
Pyruvate
Oxidation
Fermentation
Real Closure
• Keep in mind that actual people are behind
these myriad facts.
• For example:
?
You?
Hans Krebs
Citric Acid Cycle
http://media-2.web.britannica.com/eb-media/43/21043-004-D206E5D2.jpg
http://www.nobelprize.org/nobel_prizes/chemistry/laureates/1978/mitchell.jpg
Peter Mitchell
Chemiosmosis
Surprise!
• Oxidative Phosphorylation POGIL