"Everyone has the ability of
making someone happy, some by
entering the room, others by
leaving it."
---Unknown
Ch 9 reading quiz
1.
2.
3.
4.
5.
What is your muscle cell’s alternative to
cellular respiration?
If you GAIN an electron, you have just
been _______.
What is the first step in cellular
respiration?
Which step of cellular respiration receives
all of the reduced coenzymes?
What does it mean to be “phosphorylated”?
1.
1.
2.
3.
4.
Diagram energy flow through the
biosphere.
Energy flows into most ecosystems as sunlight
Photosynthetic organisms trap some and
transform it into chemical bond energy of
organic molecules. O2 released.
Cells use the chemical bond energy in organic
molecules to make ATP – the energy source for
cellular work
Energy leaves living organisms as it dissipates as
heat 
2. Write the overall summary equation for
cellular respiration.
Food + Oxygen  carbon dioxide + water
+energy
C6H12O6 + 6 O2  6CO2 + 6H2O + Energy
(glucose)

(oxygen)
(carbon dioxide) (water) (heat &ATP)
3. Briefly describe how cells recycle the ATP
they use for work.
• Cells tap stored energy in ATP by
transferring the terminal phosphate groups
to other compounds
- energy is released & the new compound
is more reactive
- loses phosphate as cellular work is
performed
- cells need to replenish ATP supply to
continue work  cell respiration provides
the energy to regenerate ATP 
4. Distinguish between oxidation and
reduction, and describe why they are
referred to as “redox” reactions.
Oxidation – partial or complete LOSS
of electrons
Reduction – partial or complete GAIN
of electrons
“LEO GER”
“Redox” refers to ‘reduction-oxidation’
reactions where compounds trade
electrons 
5. Explain how redox reactions are involved in
energy exchanges.
• Involve a partial or complete transfer
of electrons
• Release of energy when electrons
move closer to electronegative atoms
(ex: O)
Xe- + Y  X + Ye-
6. Define coenzyme and list those involved in
respiration.
Coenzyme  small nonprotein organic
molecule that is required for certain
enzymes to function
NAD+(nicotinamide adenine dinucleotide)  found in all
cells that assists electron transfer
NADH  reduced coenzyme
FADH2  reduced coenzyme
FAD(flavin adenine dinucleotide)
 without electrons 
7. Describe the role of NAD+ during
respiration.
• NAD+ acts as an electron ‘carrier’, a
coenzyme
• Enzymes called ‘dehydrogenases’ remove a
pair of hydrogen atoms (electrons) from
the substrate
• The enzyme delivers these electrons to
NAD+, and then NADH is neutral, and
carrying electrons to the electron
transport chain where they then make
their ‘fall’ towards O2, creating ATP 
8. Describe the role of ATP in coupled
reactions.
9.
1.
2.
3.
List the three steps of cellular respiration.
Glycolysis (sugar-splitting)
Krebs Cycle (makes coenzymes & ATP)
Electron Transport Chain (makes ATP) 
10. Distinguish between substrate-level
phosphorylation and oxidative
phosphorylation.
Phosphorylation
• A compound receiving the phosphate group from
ATP is said to be ‘phosphorylated’ and becomes
more reactive
Substrate-Level
• ATP production by direct enzymatic transfer of a
phosphate from an intermediate substrate in
catabolism to ADP
Oxidative
• ATP production that is coupled to the exergonic
transfer of electrons from food to oxygen 
11. Describe how the carbon skeleton of glucose
changes as it proceeds through glycolysis, and what
it looks like after glycolysis.
1.
2.
3.
4.
5.
6.
Starts as a 6 carbon sugar, carbon 6 is
phosphorylated
It rearranges from glucose-6-phosphate to
fructose-6-phosphate
Carbon 1 becomes phosphorylated
The 6-carbon molecule is cleaved into 2 isomeric
3 carbon sugars
The phosphate on carbon 3 is transferred to
carbon 2
Glucose has now been oxidized into two
‘pyruvates’. 
12. Identify where in glycolysis that sugar
oxidation, substrate-level phosphorylation
and reduction of coenzymes occur.
Sugar oxidation  step 5 energy yielding phase
occurs after glucose is split into 2 3carbon sugars
and ATP and NADH are produced
Substrate-level phosphorylation  last step – this
is how ATP is produced; it is a highly exergonic
process
Reduction of coenzymes  step 6 – where
glyceraldehyde phosphate is oxidized and NAD+ is
reduced to NADH+ and H+ 
13. Write a summary equation for glycolysis
and describe where it occurs in the cell.
• Glycolysis occurs in the cytosol of the
cell
14. Describe where pyruvate is oxidized to
acetyl CoA, what molecules are produced and
how it links glycolysis to the Krebs cycle.
• Pyruvate is oxidized in the mitochondria
• The Krebs cycle completes glucose
oxidation by breaking down a pyruvate
derivative (acetyl CoA) into CO2
• Junction between glycolysis and the Kreb’s
cycle is the oxidation of pyruvate to acetyl
coA
• Molecules produced: CO2, NADH, FADH2,
and ATP 
15. Describe the location, molecules in and
molecules out for the Krebs cycle.
•
•
1.
2.
3.
4.
5.
Kreb’s occurs in the mitochondria
For every turn of the Kreb’s cycle:
2 carbons enter in the acetyl fragment of acetyl
coA
2 different carbons are oxidized and leave as
CO2
Coenzymes are reduced; 3 NADH and 1 FADH2
are produced
1 ATP molecule is produced by substrate-level
phosphorylation
Oxaloacetate is regenerated 
16. Explain at what point during cellular
respiration glucose is completely oxidized.
•
In the Krebs cycle, pyruvate’s fate
depends on the presence of O2.
1. If O2 is present, pyruvate enters the
mitochondrion where it is completely
oxidized by a series of enzyme-controlled
reactions (moved by a carrier protein in
the mitochondrial membrane)
2. Oxidizing of the remaining acetyl
fragments of acetyl coA to CO2. Energy is
released and used for ATP and reducing
coenzymes 
17. Explain how the exergonic “slide” of electrons
down the electron transport chain is coupled to the
endergonic production of ATP by chemiosmosis.
• It is the mechanism that couples the electron flow (exergonic)
to oxidative phosphorylation (endergonic) 
18. Describe the process of chemiosmosis.
• It is the coupling of
exergonic electron
flow down an electron
transport chain to
endergonic ATP
production by the
creation of a proton
gradient across a
membrane. The proton
gradient drives ATP
synthesis as protons
diffuse back across
the membrane 
19. Explain how membrane structure is
related to membrane function in
chemiosmosis.
• The existing proton gradient across the inner
mitochondrial membrane helps to power ATP
synthesis
• Cristae, or infoldings of the inner mitochondrial
membrane, increase the surface area available for
chemiosmosis to occur
• Proton gradients across membranes are maintained
because the phospholipid bilayer is impermeable to
H+ ions and prevents diffusion  it is this
potential energy that is used to make ATPs 
20. Summarize the net ATP yield from the oxidation of a
glucose molecule by constructing an ATP ledger (chart) which
includes coenzyme production during the different stages of
glycolysis and cellular respiration.
Process
ATP produced directly
by substrate-level
phosphorylation
Reduced
Coenzyme
ATP produced by
oxidative
phosphorylation
Total ATP
Glycolysis
Net 2 ATP
2 NADH
4 – 6 ATP
6 – 8 ATP
Krebs cycle None
2 NADH
6 ATP
6 ATP
Electron
Transport
Chain
6 NADH
2 FADH2
18 ATP
4 ATP
24 ATP
2 ATP
36 – 38
ATP
21. Describe the fate of pyruvate in the
absence of oxygen.
•
•
1.
2.
•
Pyruvate is reduced,
and NAD+ regenerated
Fermentation converts
pyruvate to ethanol in 2
steps:
Pyruvate loses CO2 and
is converted to the 2C
compound acetyldehyde
NADH is oxidized to
NAD+ and
acetylaldehyde is
reduced to ethanol
Oxidizing agent is not
O2 but NAD+ 
22. Explain why fermentation is necessary.
• When O2 is scarce, ATP can still be produced
• Example: human muscle cells switch from aerobic
to anaerobic respiration (lactic acid fermentation)

23. Distinguish between aerobic and
anaerobic metabolism.
Aerobic  existing in
the presence of
oxygen
- cell respiration –
yields 18x more ATP
Anaerobic  existing in
the absence of free
oxygen
- fermentation 
24. Describe how food molecules other than
glucose can be oxidized to make ATP.
Glycolysis  can accept a wide range of carbs for
catabolism
• Starch is hydrolyzed to glucose in the digestive
tract
• Liver hydrolyzes glycogen to glucose
• Enzymes in the small intestine break down
disaccharides into glucose
• Proteins are hydrolyzed to amino acids
enzymatically – converted to intermediates
(pyruvate, acetyl CoA)
• Fat is digested into glycerol or fatty acids, then
to the intermediates of glycolysis 
25. Describe evidence that the first
prokaryotes produced ATP by glycolysis.
1.
Glycolysis does not require oxygen, and
the oldest known bacteria fossils date
back to 3.5 billion years
2. It is the most widespread metabolic
pathway, so it probably evolved early on
3. Glycolysis occurs in the cytosol and does
not require membrane-bound organelles
(mitochondria). Eukaryotic cells with
organelles probably evolved about 2
billion after prokaryotic cells 
26. Explain how ATP production is controlled by the
cell and what role the allosteric enzyme,
phosphofructokinase, plays in this process.
• Cells respond to changing metabolic needs by
controlling the reaction rates
• Most common method is feedback inhibition
• Glycolysis/Krebs, catabolic pathways, are
controlled by regulating enzyme activity at
strategic points
• Phosphofructokinase catalyzes the 3rd step of
glycolysis
- it is sensitive to changes in the ratios of ADP
& ATP
- helps to control reaction rates 