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Cellular Respiration
**Food provides life with the chemical building blocks need to
grow and reproduce.**
CalorieThe amount of
energy needed to raise the
temperature of 1 gram of water 1oC.
On food labels, “Calorie” is a
kilocalorie of 1000 calories.
Glycolysis
Begins process of respiration and releases a small amount of energy
that leads to 2 other processes that release A LOT of energy.
It is the beginning process of our food “burning” to release 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
Equation
6 O2 + C6H12O6 6 CO2 + 6 H2O + ATP
Glycolysis
It is a process in which one molecule of glucose is
broken in half, producing two molecules of pyruvic
acid and a 3 – carbon sugar.
ATP & Glycolysis
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 = __________
NADH ProductionOne 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.
Steps of Glycolysis
Step 1
Two phosphates are added to glucose to
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 -cont-
The 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 TransportOccurs in inner Membrane of Mitochondria
First StepThe 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.
Step 2Those 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.
Total ATP’s Produced 36 ATP Molecules For 1 Glucose
Molecule