Topic 8.2 - Respiration Flashcards
NAD
Nicotinamide adenine dinucleotide is the main electron carrier in respiration
Phosphorylation
Phosphorylation involves adding a PO₄³⁻ to a biological molecule, making it less stable.
For many biological reactions, the purpose of phosphorylation is to make a molecule less stable and therefore more likely to react.
Exergonic
Energy releasing. For example the hydration of ATP (adenosine triphosphate)
Endergonic
Energy-absorbing. Most reactions in the body are endergonic.
Metabolic
Since endergonic reactions need energy, they cannot occur spontaneously. Only in combination with an exergonic reaction can reactions occur spontaneously.
ie glucose -> glucose-6-phosphate is endergonic and ATP hydrolysis is exergonic so these reactions are coupled up.
Phosphorylation in glycolysis
Glucose + ATP -> Glucose-6-phosphate + ADP
Glucose-6-phosphate -> fructose-6-phoshate
Fructose-6-phosphate + ATP -> fructose-1,6-bisphopshate + ADP
Net reaction:
Glucose + 2 ATP -> Fructose-1,6-bisphosphate + 2 ADP
Formation of pyruvate
Fructose-1,6-bisphosphate -> 2 trios phosphate
2 trios phosphate oxidised and phosphorylate 2 ADP -> 2 glycerate-3-phosphate + 2 NADH + 2 ATP
2 glycerate-3-phosphate phosphorylates 2 ADP -> 2 pyruvate + 2 ATP
Net reaction:
Fructose-1,6-bisphosphate + 2 NAD⁺ 4 ADP -> 2 pyruvate + 4 ATP + 2NADH +2H
Pyruvate in aerobic respiration
Two molecules of pyruvate are produced per every glucose molecule. With oxygen present, pyruvate is pulled into the mitochondria.
Pyruvate (CH₃COCOOH) is then fully oxidised to form carbon dioxide and water.
Net reaction for glycolysis:
Glucose + 4 ADP + 2 ATP -> 2 pyruvate + 4 ATP + 2 ADP
Link reaction
Occurs twice per glucose, in the matrix of mitochondria
Pyruvate (3C) is oxidised and decarboxylated -> Acetate (2C), CO₂, and NADH + H⁺
Acetate (2C) + CoA -> CoA acetate
Net reaction ->
2 Pyruvate + 2 CoA + NAD⁺ -> 2 CoA acetate + 2 reduced NAD + 2 CO₂
Krebs cycle
Occurs twice per glucose, in the matrix of mitochondria
acetyl CoA (2C) -> Citrate (6C) by combining with Oxaloacetate (4C)
Citrate (6C) is decarboxylated and oxidised -> 5C compound, CO₂ + reduced NAD + H⁺
5C is decarboxylated and oxidised -> 4C compound, CO₂ + reduced NAD + H⁺
4C has a structure change + ADP -> another 4C compound + ATP
4C is oxidised -> FADH₂ + another 4C compound
4C is oxidised -> reduced NAD + H⁺ + Oxaloacetate
Net reaction ->
2 acetyl CoA (2C) + 2 Oxaloacetate (4C) -> 2 Oxaloacetate (4C) + 2x2CO₂ + 2x3 reduced NAD + 2x1 reduced FAD + 2x1 ATP
Oxidative phosphorylation
Formed of two parts: electron transport chain and chemiosmosis
Electron transport chain
NADH and FADH₂ are the main electron carriers and they donate their electrons at electron transporter proteins in the cristae. They then leave and go back into the matrix to be reduced during the krebs cycle.
Passing electrons through these electron transporter carriers releases energy, this energy pushes hydrogen into the intermembrane space. The electrons reach the end of the carriers, where they reach Oxygen atoms and reduce these atoms to 2•O⁻.
Chemiosmosis
Hydrogens in the intermembrane space build up and they can only leave through ATP synthase. Leaving through ATP synthase generates enough energy to create ATP from ADP + P.
Role of oxygen
After hydrogens are pushed out through ATP synthase and oxygen radicles are generated through the electron transport chain, they react with O₂ to make 2H₂O.
If there was no oxygen present, the electrons would have no place to be released, the NADH/FADH₂ would not be oxidated and they would build up and krebs cycle would not be possible to continue on a loop.
Structure of the mitochondria
The mitochondria contains the following parts to it: Matrix, Crista, Outer mitochondrial membrane, Inner mitochondrial membrane, Intermembrane space, Ribosomal DNA.
