Cellular Respiration
Using food to make energy
All cells do this
Occurs in the Mitochondria
I. The body uses energy in a form called ATP
A. The cell needs ATP to do several different kinds of work
1. Mechanical work (muscles contracting)
2. Transport work (any kind of active transport)
3. Chemical work (enzymes, reactions)
B. ATP = Adenosine Tri-Phosphate
1. It is a nucleotide
2. Contains Adenine (nitrogen base)
Ribose sugar (5 carbon sugar)
3 Phosphate groups
3. Energy is stored in the phosphate bonds
a. when a phosphate bond breaks off, energy is released
ATP  ADP + P + energy
C. Respiration vs. Cellular Respiration
1. Respiration: When you breath you exchange O2 and CO2
2. Cellular Respiration: you use O2 to “burn” sugar which
gives off CO2 as waste.
D. General equation of cellular respiration:
C6H12O6 + 6O2 ---> 6CO2 + 6H2O + ATP
1. The process is divided into 3 parts:
a. Glycolysis = “sugar splitting”
b. Krebs cycle = named after Hans Krebs
c. Electron Transport Chain
2. Only get 40% of glucose’s potential energy. The rest is
converted to heat.
3. Organic molecule is not always glucose (can be fats and
protein too)
II. Glycolysis – “sugar splitting”
A. occurs in the cytoplasm
B. The Process:
Glucose
2ATP  2ADP + 2P
G3P
G3P
2ADP + 2P  2ATP
2ADP + 2P  2ATP
NAD+  NADH
NAD+  NADH
Pyruvic
Acid
Pyruvic
Acid
Energy Harvest Phase
G3P
Small amounts of ATP are made by “Substrate level
phosphorylation” – an enzyme transfers a phosphate group
from a substrate molecule to ADP.
The substrate molecule is a glucose “intermediate” as it is
broken down.
III. Pyruvic acid grooming
A. Right inside the mitochondria, pyruvic acid loses a Carboxyl
group (as CO2) and NADH forms. This molecule
becomes acetic acid.
Pyruvic Acid
-CO2
NAD+  NADH
Acetic Acid
B. Acetic acid bonds with coenzyme A, now becoming
“acetyl-coA”
Acetic Acid + coenzyme A  Acetyl-coA
C. Acety-coA enters the Kreb’s cycle
IV. Krebs Cycle = named after Hans Krebs
A. carboxyl groups on the acetyl-coA molecule are lost as CO2
and NADH molecules are produced
NADH
6 Carbon
(Citric Acid)
Acetyl-coA
-CO2
NADH
5 Carbon
4 Carbon
-CO2
NADH
ATP
FADH2
V. Electron Transport Chain
A. All the NADH’s produced in glycolysis, grooming, and
Kreb’s cycle go to the cristae of the mitochondria
B. The “chain” is a collection
of molecules embedded in
the inner membrane of
the mitochondria.
1. Cristae increases this
surface area
(structure/function)
2. Most components of
the chain are proteins.
3. The final electron
acceptor in the chain
is O2
C. Electrons removed during glycolysis, grooming and Krebs
cycle are transferred by NADH to the first molecule of the
chain
D. The chain does not make ATP directly. Its function is to
break a large energy drop into a series of smaller steps so
energy is released in manageable amounts.
E. How does the mitochondria couple electron transport and
energy release to making ATP? Chemiosmosis
F. Chemiosmosis
1. Definition: Using the energy of H+ gradient across a
membrane to phosphorylate ADP to make ATP.
2. The flow of electrons through the chain produces energy
that is used to pump H+ ions across the membrane
(from matrix to intermembrane space). This produces
a concentration gradient.
a. The carriers are arranged in the membrane so that
H+ is accepted from the matrix and deposited in the
intermembrane space.
3. How ATP is made from this gradient:
a. ATP Synthase is the enzyme that makes ATP. It is
located in the inner membrane of the mitochondria.
Made of three main parts:
a clinder within the inner mitochondrial membrane
a knob protruding into the mitochondrial matrix
an internal rod connecting the two.
b. ATP Synthase uses the energy from the gradient to
make ATP.
c. When H+ ions flow through the cylinder, with their
gradient, they cause the cylinder and the attached rod to
rotate.
d. The spinning rod causes the knob to change shape.
This activates sites on the enzyme to bond ADP and P to
make ATP.
e. For every NADH that enters the ETC, 3 ATPs result
f. For every FADH2 that enters the ETC, 2 ATPs result
VI. Anaerobic Respiration – When oxygen is NOT available
There are 2 chemical pathways depending on the type of
cell.
A. Lactic Acid Fermentation
1. Starts with Glycolysis
2. Pyruvic acid  Lactic Acid
a. no additional ATP is formed
b. muscles cramp, burn, sore due to lactic acid.
3. Food spoilage (botulism)
4. use process to make yogurt and sauerkraut
Lactic Acid Fermentation
B. Alcoholic Fermentation
1. Starts with glycolysis
2. Pyruvic acid  Ethyl alcohol + CO2
a. no additional ATP is made
3. Use process to make wine and beer
4. yeast cells go through this process, bread rises.
VII. Differences
A. Fermentation = Anaerobic
Respiration =Aerobic
B. Fermentation final e- acceptor= pyruvic acid
Respiration final e- acceptor = oxygen
C.Fermentation generates 2 ATP
Respiration generates 34--38 ATP
Alcohol Fermentation