In This Lesson:
Respiration
(Lesson 3 of 3)
Today is Tuesday,
November 3rd, 2015
Pre-Class: [choose one of the following]
1. Take a big deep breath in and out. What happened
when you did that? Try to follow the path from your
nose/mouth all the way in…and then all the way out…
2. What is your body’s overall respiration rate called? If
you don’t know what respiration is, choose #1.
Today’s Agenda
• Respiration (in outline form)
• Respiration (in specific form)
• And maybe Gaboon Vipers
http://www.kostich.com/gaboon%20viper%20snake.JPG
By the end of this lesson…
• You should be able to identify reactants and
products of the detailed steps of each
respiration reaction.
By the end of this lesson…
• You should be able to identify the general
input and output of the respiration reactions.
A brief note…
• Since we’re talking about respiration, we’re
basically talking about food.
• 1 calorie is the amount of energy needed to heat
1 gram of water by 1 degree Celsius.
• Food calories are actually measured as Calories.
– 1 Calorie = 1000 calories.
• Your body needs a certain amount of calories to
function properly, so that all your cells can have
the energy needed to do their jobs.
Aside: High Calorie Foods
• Recommended daily intake of Calories is 2000 for
an adult woman, 2500 for an adult male
(average).
– White Castle: Chocolate Shake [Large]
• 1680 Calories.
– Outback Steakhouse: Bloomin’ Onion
• 2210 Calories.
– Uno Chicago Grill: Classic Deep Dish Pizza
• 2310 Calories
– and 162g Fat, 123g Carbs, 4470mg Sodium.
– Cheesecake Factory: Bistro Shrimp Pasta
• 3120 Calories
Let’s start with the basics…
• Where is this in my book?
– P. 90 and following…
• So what is respiration?
– Cellular respiration is the process by which cells use energy to
carry out life functions.
– BOTH PLANTS AND ANIMALS UNDERGO CELLULAR
RESPIRATION!
• Plants do it during the day and night.
• Overall rate of respiration?
– Metabolism
• Gaboon vipers have a VERY low rate of respiration.
• Where does it take place?
– The mitochondria, whether it’s an animal cell or a plant cell, as
well as the cytoplasm.
The Magic Respiration Machine
?
INPUT
YE OLDE
Respiration
MACHINE
?
OUTPUT
Respiration: An Outline
• Respiration is basically this:
• C6H12O6 + 6O2  6CO2 +6H2O
– In other words, it’s a conversion of chemical energy to
chemical energy
– Using glucose to make ATP
• What you should do is this:
– Write down the chemical formula.
– Write down the formula in English
– Draw the formula in mini-diagrams.
• (2 minutes to work)
Respiration: An Introduction
• Respiration occurs in plant and animal cells.
• Two kinds:
– Aerobic
– Anaerobic
• Before we get any further, let’s start with a
flowchart.
– That kinda rhymes.
Two Basic Steps
• The first step is called glycolysis. That one
always happens, and it happens in the
cytoplasm.
– That means that even those cute little prokaryotes
can do it, too!
• From there, either aerobic or anaerobic
respiration takes place.
– Let’s start by looking at glycolysis.
Cell Respiration
• Glycolysis is the breakdown of glucose. It
makes 4 ATP molecules, but costs 2 ATP
molecules.
– Net gain of 2 ATP (produces 4, costs 2).
– Anaerobic process.
Steps of Respiration
• Glycolysis is the first step in respiration.
– Remember, it’s anaerobic.
• The second step in respiration can be either
aerobic or anaerobic.
– We’ll start with the aerobic version.
If it’s aerobic…
• …it’s called the Krebs Cycle (sometimes called
the Citric Acid Cycle), followed by the Electron
Transport Chain.
• These two steps make LOTS of ATP.
– Krebs Cycle: 2 ATP.
– Electron Transport Chain: 34 ATP.
• Both steps happen in the mitochondria.
• The ETC “resets” the process and allows
glycolysis to start again.
Anaerobic Respiration
• Without oxygen, the Krebs
Cycle does not function, so
neither can the ETC.
• Another process must occur.
– Hint?
http://125.164.208.76/how/b
Fermentation!
• Mostly a prokaryote thing, but it happens in humans
and other animals too (under not-so-ideal
conditions).
• Fermentation is a “reset button” for glycolysis,
allowing it to continue running.
– Does not make any ATP on its own.
• Where do we see fermentation?
– Fermentation by yeast or prokaryotes.
• Beer, wine, and bread (rises from CO2 release).
– Alcohol fermentation creates ethanol, which kills yeast
when it rises above a 12% concentration.
• So, naturally-fermented wine has how much alcohol?
Fermentation for Us
• Lactic Acid Fermentation
– As in some prokaryotes, it does not allow the
Krebs Cycle or anything aerobic to continue.
• What are the side effects?
– Let’s experience ‘em ourselves!
Fermentation for Us
• What do you feel immediately after running a long
distance, or maybe lifting a lot of weights, or after what we
just did?
– Most of us call it “muscle soreness.”*
– Biologists call it lactic acid.
• *Note: This is NOT the muscle soreness you feel the next day.
• **Note: Some research suggests that what you feel is due to K+ ions.
• Builds up in muscles when they’re not getting enough
oxygen.
– Why do athletes have better endurance, then?
– Why do our bodies do this even though it’s so inefficient?
Fermentation Summary
• In prokaryotes and some eukaryotes:
– Alcohol fermentation.
– Metabolize sugars into ethanol.
• In eukaryotes and prokaryotes:
– Lactic acid fermentation.
– Muscles can continue to work without oxygen, but
lactic acid builds up.
One last thing…
• Anaerobic Respiration produces:
– 2 ATP (from glycolysis)
• Aerobic Respiration produces:
– 2 ATP (from glycolysis)
– 36 ATP (!!!) (from Krebs Cycle and ETC combined)
• 38 total!
• Which one do most cells “want” to use?
• BIG HUGE IMPORTANT THING TO REMEMBER:
– These numbers are all “ideal.”
– In reality, many conditions, including intermediate
molecules that move stuff from the cytoplasm to the
mitochondrion, affect these numbers.
• Typically they’re actually lower.
RapidTrivia!
• Grab a whiteboard and talk to your partner
(quickly) about each of the questions.
– That means you need to write FAST!
• There will still be an off-topic question today.
Question #1
• Is glycolysis aerobic or anaerobic?
– Anaerobic.
Question #2
• Where does glycolysis take place?
– The cytoplasm.
Question #3
• What substance builds up in muscles during
fermentation?
– Lactic Acid
Question #4*
• What’s a female peacock called?
– Peahen
http://www.mayanmajix.com/ma.jpg
*Off-topic
Question #5
• How much combined ATP do the Krebs Cycle
and ETC produce?
– 36 ATP molecules!
Now let’s test it…
• Log onto Quia and find the quiz labeled, “Cell
Energy Cycle Gizmo.”
• That quiz will give you instructions for opening
a gizmo in another tab from the
ExploreLearning website.
• [Log-in Instructions]
Comparing Photosynthesis & Respiration
Photosynthesis
Cellular
Respiration
Function
Energy Storage
Energy Release
Location
Chloroplasts
Mitochondria
Reactants
CO2 and H2O
C6H12O6 and O2
Products
C6H12O6 and O2
CO2 and H2O
Equation
6CO2 + 6H2O  C6H12O6 +
6O2
C6H12O6 + 6O2
6CO2 + 6H2O
Cellular Respiration
• Cellular respiration, as you might remember,
works in three stages.
– Only two stages if there’s no oxygen.
• First, we have glycolysis.
Glycolysis
• Costs 2 ATP molecules
• Makes 4 ATP molecules
– Net gain of 2 ATP.
• Uses NAD+.
– (Plants use NADP+, remember?)
• Makes two pyruvate molecules.
– Pyruvate is an intermediate
molecule that still holds some
energy
• Glycolysis also transfers protons
to NAD+ and makes it into NADH
as an electron carrier.
http://content.answers.com/main/content/img/oxford/Oxford_Sports/0199210896.glycolysis.1.jpg
Summarizing Glycolysis
• Glycolysis:
–
–
–
–
Anaerobic
Costs 2 ATP
Happens in the cytoplasm
Ingredients:
• Glucose
• NAD+
• ATP
– Products:
•
•
•
•
Pyruvate (temporary energy-storer)
Makes 4 ATP (Net gain of 2 ATP)
NADH (byproduct used later)
CO2
Now then…
• Remember that after glycolysis, assuming
there’s some oxygen around, the cell begins
to use the Krebs Cycle.
• The Krebs Cycle occurs inside the
mitochondria.
Aerobic Respiration
• The Krebs Cycle
– Sometimes called the
Citric Acid Cycle.
– Named for Hans Krebs.
• Not as goofy a name as
Melvin Calvin.
Hans Krebs
http://media-2.web.britannica.com/eb-media/43/21043-004-D206E5D2.jpg
Krebs (Citric Acid) Cycle
http://www.transtutors.com/Uploadfile/CMS_Images/22583_KREBS-CYCLE.JPG
The Krebs Cycle
• The Krebs Cycle always needs to repeat twice.
– In doing so, it breaks down pyruvate into CO2.
• Products from 1 molecule of glucose (2 turns):
– 4 CO2 (you exhale this part)
– 6 NADH (Electron Carrier)
– 2 FADH2 (yet another Electron Carrier)
– 2 ATP
Summarizing the Krebs Cycle
• Krebs Cycle:
– Sometimes called the Citric Acid Cycle.
– Aerobic.
– Happens in the mitochondrial matrix.
• There is no spoon.
– Ingredients:
• Pyruvate
– Products:
•
•
•
•
4 CO2
2 ATP
6 NADH
2 FADH2
After the Krebs Cycle
• An Electron Transport Chain (ETC)!
– Uses NADH and FADH2 (electron carriers like
NADPH in photosynthesis).
• Occurs in inner membrane of mitochondria.
http://www.sp.uconn.edu/~terry/images/anim/ETS_slow.html
Electron Transport Chain
• Electrons power a pump which moves protons out of the
innermost space, from what is called the mitochondrial
matrix).
– Where did the electrons come from?
• From the electrons carriers charged in the Krebs Cycle!
– How is this different from photosynthesis?
• Protons are pumped out, not in.
• ATP Synthase makes ADP into ATP.
• Hydrogen ions (H+) and electrons combine with O2 to make
H2O.
– How is this different from photosynthesis?
• Photosynthesis split water!
An Animation of the ETC
http://www.sp.uconn.edu/~terry/images/anim/ETS_slow.html
Summarizing the
Electron Transport Chain
• Electron Transport Chain:
– Sometimes called Oxidative Phosphorylation.
– Happens in the mitochondrial membrane.
– Electrons move from NADH and FADH2 to oxygen
atoms.
– Ingredients:
• NADH and FADH2
– Products:
• 34 ATP (in ideal conditions)
• NAD+ (which is recycled to restart glycolysis) and FAD
• ATP Produced from the overall aerobic
respiration process from 1 glucose molecule:
– 38!!!
Cell Respiration Summary
C6H12O6 + 6O2  6CO2 + 6H2O
Glycolysis and
Electron Transport Chain
Glycolysis and Krebs Cycle
Electron Transport Chain
Glycolysis
One last thing (not on the test)…
• We already know that the ATP numbers I’ve
given you so far are for ideal circumstances.
• Some textbooks will even tell you that aerobic
respiration produces only 36 ATP maximum
(not 38).
– This is due to how the electrons are “shuttled”
into the ETC.
– NADH tends to contribute more ATP than does
FADH2.
Fermentation: The Anaerobes
• Fermentation occurs in one of two situations:
– In prokaryotes – normal conditions.
– In eukaryotes – stressful conditions (no oxygen!)
• Just like glycolysis except:
– NADH needs to be recycled to NAD+.
• Normally, where does this happen?
– The Electron Transport Chain!
• Since there’s no oxygen around, the ETC doesn’t run.
– Fermentation provides the recycling step
necessary to make NADH into NAD+.
Fermentation
• In essence, you can think of fermentation as
glycolysis happening without the Krebs Cycle
starting later.
• In many prokaryotes, like yeast, fermentation
produces ethanol.
• In many eukaryotes, like us, fermentation
produces lactic acid.
– Causes muscle soreness…maybe.
– Not fun, but at least it allows your muscles to keep
working.
The Grand Summary
• And now…(drum roll please)…a
comprehensive summary of photosynthesis
and respiration from start to finish.
• Remember, the goal is to make ATP (and lots
of it).
– Autotrophs make their own glucose to make ATP.
– Heterotrophs can’t make their own glucose, so
they skip the photosynthesis step and go straight
for someone else’s glucose.
The Grand Summary
• Morning. Light from the glow of sunrise
strikes a leaf, still coated in the dew of a
springtime night.
• Light specifically strikes the plant cells
responsible for photosynthesis, and within
them it strikes the chloroplasts.
• Even more specifically, light strikes the
chlorophyll within the chloroplasts.
The Grand Summary
Start of Photosystem II
• The chlorophyll is located in the membrane of the
thylakoid, a disk arranged in multiple stacks
within the innermost space of the doublemembraned chloroplast.
• Chlorophyll molecules lose some electrons, which
go bounding down the thylakoid membrane.
• At the same time, an enzyme tears two water
molecules to pieces, generating O2 as waste and
freeing up electrons and protons (H+).
The Grand Summary
Photosystem II
• Remember those electrons that bounded off?
• They power a proton pump, which brings H+ ions
into the thylakoid.
– Don’t forget about those electrons; they’ll come back
later.
• The protons – and thus a positive charge – builds
up inside the thylakoid, creating an
electrochemical gradient.
• Protons want to diffuse back out of the thylakoid,
but they can’t go through the membrane directly
so they use facilitated diffusion.
The Grand Summary
End of Photosystem II
• Protons diffuse through the specialized
protein channel called ATP Synthase.
– Why specialized? Because, like the name
suggests, it’s both a channel and an enzyme.
• The passage of protons through ATP Synthase
causes the enzyme to make ATP from ADP.
• This part is the end of Photosystem II, which is
the first phase of the Light-Dependent
Reactions of Photosynthesis.
The Grand Summary
Photosystem I
• But wait! Photosystem I begins with those
same electrons that powered the proton
pump of Photosystem II.
• Those electrons now move to an electron
carrier molecule called NADP+.
• They, along with protons, activate the
molecule into its high-energy form: NADPH.
• NADPH will power the next step of
photosynthesis.
The Grand Summary
Calvin Cycle (AKA Dark/Light-Independent Reactions)
• The Calvin Cycle begins with the ATP and
NADPH made from the light-dependent
reactions (Photosystems II and I).
• The chloroplast – this process is happening in
the stroma by the way – uses CO2 and the
power contained in NADPH and ATP to build
up glucose molecules.
• No light is needed for the Calvin Cycle to
occur.
The Grand Summary
Respiration
• Photosynthesis is great in that we get glucose
from the power of the Sun, but it doesn’t do
much for our cells.
• For our cells to do their jobs, they use energy
based in a different form.
– Not a carbohydrate like glucose, but a nucleotide
like ATP.
• So how do we get ATP? Respiration.
The Grand Summary
Start of Glycolysis
• Respiration starts with the breakdown of
glucose, called glycolysis.
– If you’re an autotroph, you’ll use the glucose
made during photosynthesis.
– If you’re a heterotroph, you’ll eat something that
has organic molecules that can be broken down
into glucose and use that.
• Glycolysis takes place in the cytoplasm of the
cells and therefore even prokaryotes do it.
The Grand Summary
End of Glycolysis
• Glycolysis costs 2 ATP to run.
• During the process, a 6-carbon glucose molecule
is broken down into two 3-carbon molecules
called pyruvate.
– Pyruvate still has more energy that can be given off if
we could just break it down further.
– That’ll happen in the next step.
• 4 ATP are made (thus net gain of 2) and we are
able to charge up NAD+ into NADH.
– NADH is an electron carrier just like NADPH.
• CO2 is given off as waste.
The Grand Summary
Aerobic Respiration: Krebs Cycle
• The Krebs Cycle (AKA Citric Acid Cycle) is a
complex cyclical series of reactions that take
place inside the mitochondria.
– It serves to further break down those pyruvates.
• In all, the Krebs Cycle generates 2 ATP, more
NADH, and another electron carrier known as
FADH2.
– FADH2 functions similarly to NADH.
• More CO2 is given off as waste.
The Grand Summary
Aerobic Respiration: Start of Electron Transport Chain
• For the final step, electrons are pulled from the
electron carriers FADH2 and NADH and are fed
into another electron transport chain.
– This one occurs in the inner membrane of the
mitochondria.
• Electrons power a proton pump again this time,
which brings protons from the innermost part of
the mitochondrion (the matrix) into the
intermembrane space.
• The protons diffuse back into the intermembrane
space through ATP Synthase, generating more
ATP.
The Grand Summary
Aerobic Respiration: End of Electron Transport Chain
• The electron transport chain has now reset
NADH and FADH2 to their low-energy forms
(NAD+ and FAD).
• The electrons removed from the carriers are
combined with protons and oxygen in order to
make H2O.
• The ingredients for glycolysis are now reset.
The Grand Summary
Anaerobic Respiration: Fermentation
• On the other hand, if the organism in question is
an anaerobe, a prokaryote, or if no oxygen is
available, the Krebs Cycle cannot run.
– Which means NADH made in glycolysis can’t be
returned to NAD+ and will eventually run out, stopping
ATP production.
• Instead, the cell must employ fermentation.
• Fermentation is a process that generates no ATP
but does allow for NADH to be recycled to NAD+.
The Grand Summary
Anaerobic Respiration: Fermentation
• In prokaryotes and some simple eukaryotes,
fermentation produces ethanol (alcohol).
• In more complex eukaryotes, fermentation
produces lactic acid.
• Though both substances are toxic,
fermentation allows glycolysis, and thus ATP
formation, to continue.
Closure
• To your lab tables!
• With your lab table, write down four
questions that each are one of two types.
– You can either write a possible test question and
its answer.
– OR you can write a question you have (don’t
include the answer for this, since, uh, you don’t
know it).