Chapter 7: Cellular
Respiration
Pp 202-233
Cellular Respiration
 Process through which we use
energy for cellular activity
 A bunch of chemical reactions
to break down glucose to use
it as energy
 Energy is stored in a molecule
called ATP
 Cellular respiration occurs in
all Eukaryotic organisms
 Start with glucose, oxygen, and water to get
carbon dioxide, water, and ENERGY
 But what is happening in the middle (those 16
enzmatic reactions)
 In the middle, we have products that include
NADH, FADH2, and ATP
Why does a cell even need
energy?
 Many cellular processes require large amounts of
energy to work
 Active Transport: movement of substances against
concentration gradient using membrane-bound carrier
proteins  this requires ATP
 Example: sodium-potassium pump works against
concentration gradients using ATP to help nerve and
muscle cells work
ATP and Energy Storage
 Recall Laws of Thermodynamics:
1. Energy cannot be created or destroyed, only transferred
2. As energy is converted, less useful forms of energy result
and heat is produced
 Cell resp. banks energy as ATP by breaking down glucose
 36% of glucose energy is stored as ATP (very high energy
compound)
 64% of glucose energy is lost as heat (how we maintain our
body temperature
 Analogy:
 Glucose is like a $100 bill
 ATP is like a loonie
 Smaller denominations are easier for us to
use (ie in a vending machine)
 In the same way, ATP is easier for the cell to
use, so it must convert glucose into ATP
 Recall the numbers from the last
slide…36% of glucose turns into ATP. That
would be like $36 loonies from a $100 bill.
Is this really efficient?
 Compare to high-performance racecar engines
 They use only 30-34% of energy from fuel combustion
and the remaining is lost as thermal energy (which
helps no one)
 For living organisms, the 64% lost to heat is NOT a
waste – we need it to maintain body temperature!
NADH and FADH2
 Intermediate products
 Undergo oxidation and reduction
 Recall:
 LEO the lion says GER
 LEO: Losing electrons oxidation
 GER: Gaining electrons reduction
 Oxidation: Na  Na+ + e-
 Reduction: Na+ + e-  Na
 NADH and FADH2 serve as electron carriers
(which serves as transfer of energy)
 Transfer of electrons from one reactive atom to
another produces more stable ions or
compounds
 Energy released to create these stable
ions/compounds is stored as ATP (ie
oxidation/reduction reactions makes energy
available for the cell to make ATP)
+
NAD /NADH
 NAD+ attracts electrons
 NAD+ + 2e- + H+  NADH
 NAD+ is reduced
 NADH is an electron carrier and can also lose its
electrons
 NADH  NAD+ + 2e- + H+
 NADH is oxidized when it comes in contact with a
molecule that has a strong attraction for electrons
 NAD+ is reused and is reduced again
Where does Cell Resp
Occur?
 In the Cytoplasm and Mitochondria
 Mitochondrion matrix and inner membrane play roles in
cell resp
Cellular Respiration
 2 Types:
 Aerobic: takes place in the presence of Oxygen
 Anaerobic: takes place in the absence of Oxygen
Aerobic Cellular Respiration
 Occurs in 4 steps
1. Glycolysis: cytoplasm (anaerobic – occurs in both
processes)
2. Pyruvate Oxidation (Krebs Cycle Preparation):
mitochondria matrix (aerobic only)
3. Krebs Cycle: mitochondria matrix (aerobic only)
4. Electron Transport Chain and Chemiosmosis:
inner mitochondrial membrane (aerobic only)
1. Glycolysis
 Glycolysis = Greek for “sugar splitting”
 Occurs in the cytoplasm
 Anaerobic process (occurs in both aerobic and
anaerobic processes)
 Glucose is broken down into two pyruvate molecules
1 Glucose (6-Carbon)  2 Pyruvate (3-Carbon)
1. Glycolosis
 2 ATP molecules are needed to begin the process
 4 ATP molecules are produced (net gain of 2)
 2 NADH molecules are also produced
 Glucose is oxidized
 NAD+ is reduced
*Note: You do not need to
know what PGAL or fructose
diphosphate are
*Note: Pyruvic acid is
Pyruvate
What Happens Next?
 Pyruvate enters the next phase:
Pyruvate Oxidation
 NADH is saved for chemiosmosis
and electron transport chain (step 4)
 ATP used by the cell as energy
2. Pyruvate Oxidation
 Pyruvate is transported from cytoplasm (where
glycolysis occurs) to the mitochondrial matrix
 Here:
 One CO2 is lost to form a acetyl molecule
 Acetyl joins to a coenzyme carrier called Coenzyme A to
form Acetyl Co-A
 One NADH forms
 These are the products for one pyruvate
 How many pyruvates per glucose??
 2 – this means if we are talking about how much is
made per glucose, we double these numbers
 Glycolysis
Net tally so far
 2 ATP per glucose
 2 NADH per glucose
 Pyruvate Oxidation
 1 NADH per
pyruvate
(2 NADH per
glucose)
3. Krebs Cycle
 AKA citric acid cycle
 Occurs in the matrix of the mitochondria
 Starts with Acetyl-CoA(2 per glucose)
 Cycle goes around twice for every glucose
molecule (because it
cycles once for
every Acetyl-CoA,
and there is 2
produced for every glucose)
 Acetyl Co-A is oxidized
 NAD+ and FAD are reduced
3. Krebs Cycle
 2 Carbons enter as AcetylCoA
 2 Carbons leave as CO2
 3 NAD+ are reduced to NADH
 1 FAD is reduced to FADH
 1 ATP is formed
 REMEMBER: this is doubled
for a glucose molecule
4. Electron Transport Chain
 Occurs in the inner membrane of the
mitochondria using proteins called
cytochromes
 Take electrons from NADH and FADH2
 Where did these molecules come from?
 Glycolysis and Krebs
Cycle!
 NAD+ and FAD
are reused in
more glycolysis
and Krebs cycles
4. Electron Transport Chain
 As the electrons move down the chain, a small amount of
energy is released
 This energy is used to move H+ ions into the intermembrane
space
 OXYGEN




Final electron acceptor
Is reduced to form WATER
2 H+ + ½ O2  H2O
What if there is NO OXYGEN??
 System backs up all the way to glycolysis and anaerobic respiration
will occur
4. Chemiosmosis
 This produces most of the ATP
 32 ATP produced per glucose
 Requires
 Concentration gradient of H+ ions
 ATP synthase channel (inner membrane of mitochondria)
4. Chemiosmosis
 H+ ions are built up in the intermembrane space and
cannot diffuse back into the matrix
 The ATP synthase channel is the only place permeable
to H+
 As H+ flows into the matrix from the intermembrane
space, energy is released, which is turned into ATP
http://www.science.smith.edu/departmen
ts/Biology/Bio231/etc.html
Total ATP
 2 ATP – Glycolysis
 2 ATP – Krebs
 32 ATP – Electron Transport Chain and Chemiosmosis
 EQUALS 36 ATP per Glucose
Review of ETC: http://highered.mcgrawhill.com/olc/dl/120071/bio11.swf
DO NOW
 Why is Cellular Respiration important??
 Write down the 4 steps in Cellular Respiration, and
include the following
 What is the reactant (what goes in) and what are the
products (what is left in the end)?
 Total ATP produced at each step
Review: http://www.youtube.com/watch?v=2f7YwCtHcgk
REDOX
 REDOX = Reduction and
Oxidation
LEO the lion says GER
LEO = Losing electrons is
OXIDATION
GER = Gaining electrons is
REDUCTION
REDOX
 Electrons are passed from a higher-energy electron
donor to a lower-energy acceptor
 Electron Donor:
 Oxidation: NADH  it will give up it’s H-atom and 2
electrons to form NAD+ + H+ + 2e-
 Reduction: NAD+  it will gain 2 electrons and a H-atom
to form NADH (ie electron carrier)
Mitochondria Review
 Organelles in the cell – scattered around
the cytoplasm
 Produce large amounts of ATP (which
step of Cell Resp produces the most
ATP?)
 Can only make ATP with oxygen
 Has a double membrane
 Smooth outer membrane
 Folded inner membrane
 Folded inner membrane creates 2
compartments
 Mitochondrial matrix (protein filled)
 Intermembrane space (between inner and
outer membrane)
Mitochondria Review
Assignment
MASTER STUDY SHEET
 Create a master study sheet of aerobic cellular respiration
on a piece of 11X17 paper
 Your study sheet must include the following things. Be
creative and add in anything extra that will help you
understand aerobic respiration
 4 steps of Cellular Respiration
 Where these steps occur
 What the reactants and products are for each step
 Net tally of ATP
DUE: Tuesday (after Easter)
DO NOW
 What is the function of NAD+ and FAD in aerobic
respiration?
 What is the final electron acceptor and how does this
differ from an electron carrier?
 Aerobic respiration will stop if there is no oxygen
present. Why is this?
Today
 Anaerobic Respiration Notes
 Some notes about tomorrow’s lab
 Work on homework
 Cell Resp study sheet (due Tuesday)
 If you finish, you may begin the next assignment (will be
due later next week)
Anaerobic Respiration
 Recall that aerobic respiration occurs when oxygen is
present
 Anaerobic respiration occurs when there is no oxygen
present
 The Electron Transport Chain (step 4) cannot work
without oxygen
 Why??
 A: O2 is the final electron acceptor and creates water
 Without oxygen, cells need to reuse the NAD+ in
another way
 Eukaryotic organisms prefer to carry out cellular
respiration in aerobic conditions, but have evolved
ways to cope in anaerobic conditions
 The two we are going to talk about are:
 Alcohol Fermentation
 Lactic Acid Fermentation
 Both occur in two steps
Alcohol Fermentation
1. Glycolysis
 This is identical to step one of
aerobic respiration
1 Glucose (C6H12O6)
2 Pyruvate + 2 ATP + 2 NADH
Alcohol Fermentation
2. Alcohol Formation
2 Pyruvate
2 H2O
2 CO2
2 acetaldehyde
2 ethanol
NADH (from
glycolosis)
OXIDIZES. This
creates NAD+,
which gets reused
in glycolysis
Alcohol Fermentation Summary
1 Glucose (C6H12O6)
2 Pyruvate + 2 ATP + 2 NADH
2 H2O
2 CO2
2 acetaldehyde
2 NADH
NAD+ + H+ + e-
2 ethanol
Back to
glycolysis
Why Use Alcohol
Fermentation?
 Humans have learned you use this in food/beverage
making through the use of other organisms
 Most done through YEAST (fungi) and microbes
 Ex: Alcohol fermentation through yeast
Bread leavening by yeast
Chocolate is made through microbial fermentation
of cacao beans
Lactic Acid Fermentation
1. Glycolysis
1 Glucose (C H O )
6
12
6
2 Pyruvate + 2 ATP + 2 NADH
Lactic Acid Fermentation
2 Pyruvate
NADH (from
glycolosis)
OXIDIZES. This
creates NAD+,
which gets reused
in glycolysis
2 Lactic Acid
Alcohol Fermentation Summary
1 Glucose (C6H12O6)
2 Pyruvate + 2 ATP + 2 NADH
2 NADH
NAD+ + H+ + e-
2 lactic acid
Back to
glycolysis
When do we use Lactic Acid
Fermentation?
 Happens in humans after strenuous
exercise
 Muscle demands more ATP than
can be supplied by aerobic
respiration alone (lack of oxygen)
 If an oxygen source is found, cells
will resume aerobic respiration (like
what happens when you pant to get
your breath back – you are paying
back the oxygen debt)
Exercise Physiology
 Exercise Physiology: branch of biology dealing with
body’s biological responses
 Most common question: shortage of energy by athletes
 Athletic fitness
 Measure of ability of heart, lungs,and bloodstream to
supply O2 to cells of body
 Other factors to athletic fitness:
 Muscular strength, muscular endurance, flexibility, body
composition (ratio of fat to bone to muscle)
Maximum Oxygen
Consumption (VO MAX)
2
 A measure of body’s capacity to generate E required
for physical activity
 Treadmill exercise test is used to measure VO2 max
 10 – 15 minute test
 Animal is forced to move faster and faster on a treadmill
 Expired air is collected and measured by a computer
 VO2 max measures:
 Volume of O2 (mL) that cells of body can remove from
bloodstream in 1 minute per kg of body mass while body
experiences maximum exertion
Values
 VO2 max values:
 Average: 35 mL/kg/min.
 Athletes: 70 mL/kg/min.
 VO2 max
 Can be increased with more exercise
 Genetic variation is also a factor
 Decreases with age
Lactic Acid Thresholds
 Value of exercise intensity at which blood lactic acid
concentration begins to increase sharply
 Exercising beyond threshold may limit duration of exercise
 Due to pain, muscle stiffness, and fatigue
 Athletic training improves blood circulation and efficiency of
O2 delivery to body cells
 Result:
 Decrease in lactic acid production
 Increase in lactic acid threshold
 Untrained individuals reach a lactic acid threshold at 60 %
VO2 max
 Elite athletes reach threshold at or above 80 % VO2 max
Supplements and Toxins
 Creatine phosphate
 May serve as an E source by donating its phosphate to




ADP
Occurs naturally in body and many foods
Athletes consume compound to produce more ATP in
muscles
Compound may also buffer muscle cells and delay onset
of lactic acid fermentation
Potential harmful side – effects are possible
Metabolic Poisons
 Some poisons interfere with the electron
transport chain
 Causes death quickly because electron flow
stops, which stops all stages of cellular
respiration
 Examples:
 Cyanide
 Hydrogen sulfide