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3 Cellular respiration
June 26
20
Biology
Undergraduate 2
06/26/2015

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Term
Why do we need to breath?
Definition
to make water
2 H2 + O2 → 2 H2O + energy
Term
What is cellular respiration?
Definition
Making water, the productive way
Term
What are the three parts of cellular respiration?
Definition
Glycolysis
Citric Acid Cycle
Oxidative phosphorylation
Term
What are the two parts of glycolysis?
Definition
Energy investment
Energy Payoff
Term
What does the citric acid cycle require before the cycle?
Definition
Pyruvate oxidation
Term
What is glycolysis?
Definition
◦ Glucose is oxidized to pyruvate
 NADH and ATP are formed
sugar splitting
◦ Two phases:
 Energy investment
 IN: Glucose, 2ATP
 OUT: 2G3P
 Energy payoff
 IN: 2G3P
 OUT: 4 ATP, 2 NADH,
2 Pyruvate
◦ Ten enzyme-mediate steps
◦ All intermediates are phosphorylated
Term
What is the citric acid cycle?
Definition
◦ Pyruvate derivative is oxidized to CO2
 NAD, FADH2 and ATP are formed
Term
What is the oxidative phosphorylation?
Definition
◦ Electron transport chain creates proton gradient
 Gradient used to form ATP
Term
What comes in and out of energy investment?
Definition
 Energy investment
 IN: Glucose, 2ATP
 OUT: 2G3P
Term
What comes in and out of energy payoff?
Definition
 Energy payoff
 IN: 2G3P
 OUT: 4 ATP, 2 NADH,
2 Pyruvate
Term
What enzymes are used in glycolysis?
Definition
 Kinase
 Isomerase
 Dehydrogenase
Term
Describe energy investment
Definition
Step 1
The step one in glycolysis is phosphorylation. This step glucose is phosphorylated by the enzyme hexokinases. In this process, ATP molecule is consumed. A phosphate group from the ATP is transferred to the glucose molecules to produce glucose-6-phosphate.

Glucose (C6H12O6) + Hexokinase + ATP → Glucose-6-phosphate (C6H11O6P1) + ADP

Step 2
The second stage of glycolysis is an isomerization reaction. In this reaction the glucose-6-phosphate is rearranged into fructose-6-phosphate by the enzyme glucose phosphate isomerase. This is a reversible reaction under normal conditions of the cell.

Glucose-6-phosphate (C6H11O6P1) + Phosphoglucoisomerase → Fructose-6-phosphate (C6H11O6P1)

Step 3
In the third step of glycolysis is a phosphorylation reaction. In this step the enzyme phosphofructokinase is transfers phosphate group to form fructose 1,6-bisphosphate. Another ATP molecule is used in this step.

Fructose 6-phosphate (C6H11O6P1) + phosphofructokinase + ATP → Fructose 1,6-bisphosphate (C6H10O6P2) + ADP

Step 4
This step in glycolysis is a destabilization step, where a the action of the enzyme aldolase splits fructose 1,6-bisphosphate into two sugars. These sugars are isomers of each other, they are dihydroxyacetone phosphate and glyceraldehyde phosphate.

Fructose 1,6-bisphosphate (C6H10O6P2) + aldolase → Dihydroxyacetone phosphate (C3H5O3P1) + Glyceraldehyde phosphate (C3H5O3P1)

Step 5 of glycolysis is an interconversion reaction. Here, the enzyme triose phosphate isomerase interconverts the the molecules dihydroxyacetone phosphate and glyceraldehyde phosphate.

Dihydroxyacetone phosphate (C3H5O3P1) → Glyceraldehyde phosphate (C3H5O3P1)
This step marks the end of the preparatory or the investment phase of glycolysis. So at the end here, the 6-carbon glucose molecule is split into two three-carbon molecules with the expense of two ATP molecules.
Term
Describe Energy Payoff
Definition
The second phase of glycolysis is known as the pay-off phase of glycolysis. This phase is characterized by gain of the energy-rich molecules ATP and NADH.

Step 6
This step of glycolysis is a dehydrogenation step. The enzyme triose phosphate dehydrogenase, dehydrogenates glyceraldehyde 3-phosphate and adds an inorganic phosphate to form 1,3-bisphosphoglycerate. Firstly, the enzyme action transfers a H- (hydrogen) from glyceraldehyde phosphate to the NAD+ which is an oxidizing agent to form NADH. The enzyme also adds a inorganic phosphate from the cytosol to the glyceraldehyde phosphate to form 1,3-bisphosphoglycerate. This reaction occurs with both the molecules produced in the previous step.

2 Glyceraldehyde phosphate (C3H5O3P1) + Triose phosphate dehydrogenase + 2H- + 2P + 2NAD+ → two 1,3-bisphosphoglycerate
(C3H4O4P2) + 2NADH + 2H+

Step 7
Step 7 of glycolysis is a substrate-level phosphorylation step, where the enzyme phosphoglycerokinase transfers a phosphate group from 1,3-bisphosphoglycerate. The phosphate is transferred to ADP to form ATP. This process yields two molecules of 3-phosphoglycerate molecules and two molecules of ATP. There are two moleculesof ATP synthesized in this step of glycolysis.

2 molecules of 1,3 bisphophoglycerate (C3H4O4P2)+ phosphoglycerokinase + 2 ADP → 2 molecules of 3-phosphoglycerate (C3H5O4P1) + 2 ATP

Step 8
This step of glycolysis is a mutase step, occurs in the presence of the enzyme phosphoglycerate mutase. This enzyme relocates the phosphate from the 3-phosphoglycerate molecule ar third carbon position to the second carbon position, this results in the formation of 2-phosphoglycerates.

2 molecules of 3-phsophoglycerate (C3H5O4P1) + phsosphoglyceromutase → 2 molecules of 2-Phosphoglycerate (C3H5O4P1)

Step 9
This step of glycolysis is a lyase reaction, which occurs in the presence of enolase enzyme. In this reaction the enzyme removes a molecule of water from 2-phosphoglycerate to form phosphoenolpyruvic acid (PEP)

2 molecules of 2-phosphoglycerate (C3H5O4P1) + enolase → 2 molecules of phosphoenolpyruvic acid (PEP) (C3H3O3P1) + H2O

Step 10
This is the final stage of glycolysis which is a substrate-level phsophorylation step. In the presence of the enzyme pyruvate kinase, there is transfer of a inorganic phosphate molecule from phosphoenol pyruvate molecule to ADP to form pyruvic acid and ATP. This reaction yields 2 molecules of pyruvic acid and two molecules of ATP.

2 molecules of PEP (C3H3O3P1) + pyruvate kinase + 2 ADP → 2 molecules of pyruvic acid (C3H4O3) + 2 ATP
This reaction marks the end of glycolysis, hereby producing two ATP molecules per glucose molecule.
Term
What is substrate level phosphorylation?
Definition
◦ Phosphate transferred directly from substrate to
ADP to form ATP
Term
What is pyruvate oxidation?
Definition
◦ Pyruvate is imported into mitochondria and oxidized,
forming Acetyl CoA
 NADH and CO2 are produced
Term
Describe the steps of pyruvate oxidation
Definition
◦ Step 1 – transfer pyruvate into mitochondria
 Facilitated diffusion across outer membrane
 Active transport into matrix – pyruvate translocase

-OH antiporter, using energy in proton gradient

◦ Several linked enzymatic reactions
 Stripping CO2
 Attachment of remaining Acetate to
Coenzyme A
 Transfer of electrons to NADH
Term
What come in and out of pyruvate oxidation?
Definition
 IN: Pyruvate (cytoplasm)
 OUT: Acetyl-CoA (matrix),
CO2
, NADH
 (reduction of gradient by 1 H+)
 (everything x2 if starting from 1
glucose)
Term
What occurs during the citric acid cycle?
Definition
◦ Acetyl CoA is added to Oxaloacetate, then oxidized,
producing CO2
 NADH, FADH2 and ATP are formed
Term
How was the citric acid cycle characterized and why is it cyclical?
Definition
Citric acid cycle
◦ Characterized by Hans Krebs
 formerly called Krebs cycle
◦ Cyclical
 First step produces citric acid
 Begins and ends with
oxaloacetate
Term
What comes in and out of the citric acid cycle?
Definition
IN: Acetyl CoA
OUT: 3 NADH, 1 FADH2
1 GTP (or ATP),
2 CO2
 (everything x2 if
starting from glucose)
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