1. Cellular Respiration

3. the atoms of glucose together. When those
I. Introduction
NRG is stored in the chemical bonds that hold
the atoms of glucose together. When those
bonds are broken, the NRG can be captured
and used to do work
One of the major types of work done is the
synthesis of ATP. Coupled RXNS play an
important role (FIGURE 1)
The ATP will provide energy for a variety of
biochemical rxns in the cell.

5. Breakdown of any other phosphate ester releases less
than half the NRG of what ATP releases (7.3 Kcal)

6. The process that involves the breakdown of
Cellular Respiration
The process that involves the breakdown of
glucose to produce ATP. Occurs anaerobically
(when oxygen is NOT present) or aerobically
(when oxygen IS present).
It can be summarized by the equation:
C6H12O O2  6CO H2O + ATP

7. II. Understanding Glucose Breakdown
REDOX reaction (a.k.a. oxidation-reduction rxn) –
a chemical rxn in which one molecule is OXIDIZED
(i.e. losses e-) and another molecule is REDUCED
(i.e. gains e-)
These terms also apply to the gain/loss of H atoms
b/c that involves the transfer of e-
Example: next slide

9. Each half of the rxn has specific characteristics
1. Oxidation half
a. Releases a pair of e-, becomes oxidized
b. Releases NRG, thus is exergonic
2. Reduction half
a. Accepts a pair of e-, becomes reduced
b. Gains NRG, thus endergonic

10. Coenzymes whose sole purpose is to carry
D. NAD+ and FAD
Coenzymes whose sole purpose is to carry
H atoms to the E.T.C. to produce high
amounts of ATP
In the process:
NAD+ is reduced to (NADH + H+)
FAD is reduced to FADH2
FIGURE 2

11. III. Overview of glucose breakdown (NRG release)
A. The breakdown occurs in several stages
Glycolysis (stage 1): Universal
2. Aerobic Respiration (if oxygen IS present)
 Transition Reaction
 Kreb’s Cycle (stage 2)
 Electron Transport Chain
3. Anaerobic Respiration (if no oxygen)
 Lactic Acid Fermentation
 Alcoholic Fermentation

12. IV. The breakdown of glucose (FIGURE 3)
Glycolysis (1st stage):
(a.k.a. Substrate-level phosphorylation)
1. Occurs in the cytoplasm of your cells
2. Anaerobic – no oxygen is required
3. Steps:
a. Two molecules of ATP are broken down in
order to begin this process
b. The P group from each is added to glucose
(6C)
At this point, there’s an NRG debt of 2 ATP

13. c. The glucose is split in half forming two molecules,
each w/ 3-C and 1 P group (this is the “substrate”)
d. 2 P groups enter from cytoplasm and are attached to
each molecule (now have 2 molecules, each w/ 3 C &
2 P groups). This also causes 2 H atoms from each
molecule to be transferred to NAD+ to form
(NADH + H+) (2 TOTAL)  they will go to E.T.C
e. Each molecule transfers both P groups to an ADP to
form 2 ATP (4 TOTAL). Left with 2 molecules of
pyruvate (3C)
f. So, 4 ATP have been produced, but 2 are used to
repay NRG debt, thus 2 NET ATP are produced

14. http://highered. mcgraw-hill

16. One of two things can now happen:
a. Aerobic respiration – if oxygen is present
b. Anerobic respiration – no oxygen available

17. B. Aerobic Respiration (requires oxygen)
REMEMBER: The following steps happen twice,
once for each pyruvate from glycolysis
Transition Reaction (takes place in mitochondria)
*** (requires 2 ATP)
a. Pyruvate (3C) from glycolysis enters the
mitochondria – double membrane organelle
1. Matrix – gel-like material; site of Krebs cycle
2. Cristae – The internal folds;
the site of E.T.C.

18. combine w/ CoEnzyme-A to form Acetyl Co-A (2C)
b. One of the C is released as CO2, the other 2 C
combine w/ CoEnzyme-A to form Acetyl Co-A
(2C)
 This produces one molecule of (NADH + H+)
which goes to E.T.C.

19. 2. Krebs Cycle (Citric Acid Cycle)
a. The Acetyl Co-A (2C) enters the Kreb’s cycle and
combines w/ a 4C molecule to form Citric Acid
(1st molecule made in cycle)
b. The rest of the cycle is a series of rxns
 One turn of the cycle produces:
-- 2 CO2 molecules
-- 3 (NADH + H+)  goes to E.T.C.
-- 1 FADH2  goes to E.T.C.
-- 1 ATP
REMEMBER, this is for ONE pyruvate molecule; happens 2x)

21. The Transition RXN & Kreb’s cycle occur for each
REMEMBER:
The Transition RXN & Kreb’s cycle occur for each
pyruvate that was made during glycolysis.
So now, every C from the original glucose molecule
has been utilized (turned into CO2)
You get twice as many products as stated in the notes

22. 3. Electron Transport Chain – Oxidative Phosphorylation
Each (NADH + H+) and FADH2 that was created
will release their e- into the chain
Chemiosmosis:
e- pass from molecule to molecule in the chain. As
that happens, H+ protons are pumped into the
intermembrane space of the mitochondria (proton
motive force). They diffuse back into the matrix
thru ATP Synthase channels, producing ATP.
When the e- reaches the end of the chain, they are
picked up by O2 (the final e- acceptor) to form H2O
 NAD+ and FAD are now reoxidized
FIGURE 4

25. NOTE:
Every pair of e- from (NADH + H+) = 3 ATP
Every pair of e- from FADH2 = 2 ATP
Thus, 34 ATP (32 NET) are produced from
co-enzymes NAD and FAD in E.T.C.
*** 2 ATP used to get NADH made during glycolysis
from cytoplasm into mitochondria

26. C. Summary of ATP production (FIGURE 5)
-- To start glycolysis:
-- From glycolysis directly:
-- From (NADH + H+) made
during glycolysis:
from transition rxn:
-- From Krebs cycle directly:
during Krebs cycle:
-- From FADH2 made during Krebs cycle:
_______
-- TOTAL
-2 ATP
4 ATP {2 NET}
6 ATP {4 NET}
6 ATP
2 ATP
18 ATP
4 ATP
38 ATP (36 NET}

28. 4 CO2
2 CO2
H2O

29. ANIMALS
BACTERIA

32. Anaerobic Respiration (Fermentation)
*** Energetically less efficient!!!
The E.T.C. can fxn properly as long as O2 is present
to act as the last e- acceptor. If no O2, the Kreb’s
cycle & E.T.C. can’t be utilized  no ATP produced
If O2 supply is cut off, the result is death for cells
(b/c they don’t reoxidize NADH or FADH2, thus they
can’t produce ATP from glycolysis (EX: brain cells)
However, some cells (ex. muscle cells) have special
enzymes allowing them to use fermentation to
reoxidize NADH into NAD+; this allows more
glucose break down in glycolysis, producing
minimal ATP, but enough for the cell to live

33. 1. Lactic Acid (FIGURE 6)
After glycolysis, (NADH + H+) will pass e- to pyruvate
This will regenerate NAD+ and produce:
Lactic acid and 4 ATP (NET of 2 ATP)
c. Muscles feel sore (strenuous exercise, no oxygen present)

34. 2. Alcoholic (FIGURE 7)
Single-celled organisms (e.g. yeast) can ferment glucose
After glycolysis, (NADH + H+) will pass e- to pyruvate
This will regenerate NAD+ and produce:
Ethanol and CO2 and ATP
d. This is responsible for beer, wine, bread rising

35. FIGURE 8 (Processes combined)
V. The Metabolic Pool
Describes all the rxns involved in cell.resp.
Catabolic rxns – Those that degrade
molecules and release NRG (exergonic)
B. Anabolic rxns – Those that require NRG to
synthesize molecules (endergonic)