Download Glycolysis is the first stage of cellular respiration

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The following information on cellular respiration is not all accurate I want you to read it and
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We eat a potato which is full of the polysaccharide glycogen which is digested by salivary
amylase. The polysaccaride is broken down to monosaccarides glucose which are absorbed into
the blood through the wall of the small intestine. As the blood glucose level rises the hormone
glucagon is released by the alpha cells of the pancreas which bind to receptor lipids on numerous
target cells initiating the uptake of glucose by those cells from the blood. The movement of
glucose into a cell is a type of passive transport. The digested glucose molecules move into the
cytoplasm where the four stages of cellular respiration digest them further into water, ATP and
oxygen. Glycolysis is the first stage of cellular respiration: In the cytoplasm a series of
enzymatic reactions act on glucose breaking it down to four pyruvate molecules, generating a net
gain of 4 ATP, and 2 NADH. (Note: the enzymes responsible for glycolysis are produced by
free ribosomes in the cytoplasm). The four ATP molecules produced in glycolysis are made by
the process of chemiosmosis. The enzymes responsible for converting ADP to ATP during the
process of glycolysis are generally referred to as dehydrogenases. The production/conversion of
NAD+ to NADH is the result of redox reactions usually catalized by kinase enzymes. The
glucose molecule is being reduced and the NAD+ molecule is being oxidized. Thus, the
reducing agent NAD+ loses energy/electrons while the oxidizing agent glucose gains
energy/electrons. The breakdown of a mole of glucose is a nonspontaneous reaction and the cell
must invest 2870kj of energy to overcome the EA. During the first few steps of glycolysis the
glucose molecule is phosphorlyated by endergonic/anabolic hydrolysis of ATP. The
phosphorlated intermediate is more reactive and more likely to breakdown.
Before the 2 pyruvate molecules from glycolysis are able to enter the Krebs cycle which is a
group of enzymes located in the cistae of the mitochondria, they are converted to Acetyl ACO.
During the conversion of pyruvate to Aceytl ACO a CO2 and FADH2 molecule are produced.
The Krebs cycle the second stage of cellular respiration: a series of reactions catalyzed by
enzymes located in the mitochondria matrix (remember the mitochondria has it’s own DNA,
therefore it is able to produce its own enzymes). The final products of the Krebs cycle: 6NADH,
4FADH2, 4ATP & 6CO2. The ATP molecules from the Krebs cycle can be used directly to
provide 8 kcal/mol of energy for both endergonic and exergonic reactions. The CO2 diffuses out
of the mitochondria, then out of the cell, where it binds to red blood cells and is carried to the
lungs and inhaled.
The 2NADH from glycolysis, 6NADH & 2FADH2 from the Krebs cycle, and 2NADH from the
conversion of pyruvate to Acetyal COA move to the outer membrane of the mitochondria where
the ETC is located. The ETC the third stage of cellular respiration: it is a series of lipids
found in the outer mitochondrial membrane. The protons are passed from the electron
carriers/coenzymes NAD+ and FADH to the cytochromes. A series of Redox reactions occur as
the protons are passed down the lipid chain. The energy being released from the redox reactions
is used to produce an electron gradient in the outer membrane space. At the end of the ETC a
hydrogen acts as the final proton acceptor forming water. Why do these reactions take place the
oxygen at the end of the ETC is the driving force, its attraction (high electronegativity) for
electrons pulls all the other reactions forward.
The concentration of protons in the inner membrane space creates a proton gradient. Energy
from the gradient is used to produce ATP. The protons want to diffuse back into the
mitochondrial matrix the only way to get through the inner membrane is through ADP synthase.
As the protons move through the ADP synthase ATP is converted to ADP. Substrate level
phosphroylation is the process of producing ATP in the ETC.
For each NADH molecule that drops off electrons four protons are pumped into the inner
membrane space resulting in the production of three ATP molecules. For every FADH2
molecule that drops off electrons one proton is pumped into the inner membrane space resulting
in the production of one ATP.
Total production of ATP in cellular respiration:
Glycolysis:
Produces 2 ATP directly
2NADH ------------------> 6 ATP
Krebs:
Produces 4 ATP directly
6 NADH ------------------> 24 ATP
2 FADH2 -----------------> 4 ATP
Plus:
2 Pyruvate ---------------- Acetyal COA
Produces 2 NADH ------------------------------- 6 ATP
Total Production: 40 ATP