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**Food provides life with the
chemical building blocks need to
grow and reproduce.**
Calorie
The amount of
energy needed to
raise the
temperature of 1
gram of water 1oC.
On food labels,
“Calorie” is a
kilocalorie of 1000
calories.
It is the beginning process of our
food “burning” to release energy.
Begins process of respiration and
releases a small amount of energy
that leads to 2 other processes that
release A LOT of energy.
What is Cellular Respiration?
The process that releases energy by
breaking down glucose and other food
molecules in the presence of oxygen.
There Are 3 Steps: Glycolysis, Kreb’s
Cycle, Electron Transport
6 O2 + C6H12O6
6 CO2 + 6 H2O + ATP
It is a process in which one
molecule of glucose is
broken in half, producing
two molecules of pyruvic
acid, a 3 – carbon sugar.
The process releases energy,
but needs a boost to get
started.
It takes 2 ATP’s to start glycolysis.
4 ATP’s are produced at the end.
NET ATP after glycolysis = __________
One of the reactions of
glycolysis removes four high
energy electrons and passes
them to NAD+.
NADH then holds those
electrons with their energy.
Energy Output of Glycolysis
The process is so fast, it can produce
thousands of ATP in milliseconds.
Glycolysis doesn’t require oxygen,
so it can supply chemical energy
to cells when oxygen is not
available.
PROBLEM:
All the NAD+ becomes filled up with
electrons and cells run out.
Step 1
Two phosphates are
added to glucose with
an ATP investment of
2 molecules.
Step 2
The 2 phosphate sugar molecule is
then split to form 2, 3 carbon
molecules.
Step 3
The two phosphate, 3 carbon
molecules are then converted to 2
pyruvate (pyruvic acid). As this
occurs, electrons are transferred to
NAD+ to form NADH. ATP is also
formed.
Result
Two Pyruvates (with a lot of stored
energy left)
A net of 2 ATP’s 
Kreb’s Cycle
After glycolysis, 90% of of the chemical energy
from glucose is still left.
For the Kreb’s Cycle, oxygen is necessary.
The pyruvic acid will be further broken down
into CO2 in a series of energy extracting steps.
Step 1 (Citric Acid Production)
The pyruvic acid enters the mitochondria and
loses a CO2 molecule.
The 2 carbons left attach to coenzyme A to from
Acetyl CoA.
The Acetyl CoA is actually what enters the Krebs
Cycle.
Step 1 -contThe 2 C acetyl CoA then joins with a 4
carbon molecule to make Citric Acid.
Step 2
The citric acid is broken down, releasing more
CO2.
One ATP is produced. ⌘
3 NADH and 1 FADH is converted to FADH2
There is now a 4 carbon molecule left.
The Krebs Cycle must occur
2 times in order to break
down both of the pyruvic
aicds that were created
during glycolysis.
NADH & FADH2
Both these molecules are electron carriers that
trap most of the energy from the Krebs cycle.
Electron Transport
Occurs in inner Membrane of Mitochondria
First Step
The electrons from the original glucose
molecule are moved to an electron
transport chain using NADH.
(Electrons move to carriers that they have
a stronger attraction for.)
Step 1 – cont. –
These transfers along the chain release energy.
This energy is used to pump H+ ions into the
inner membrane of the mitochondria.
The electrons in the chain are “pulled” toward
oxygen and once there the oxygen, electrons
and hydrogen combine to form water.
Those H+ ions then rush
back out of the
membrane through ATP
synthases.
This energy is used to
then to convert ADP to
ATP.
Up to 36 ATP’s can be
made from one glucose
molecule.
Step 2
36 ATP Molecules For 1 Glucose Molecule