Week 1 Flashcards
ATP & pathways of ATP resynthesis
What is the process of hydrolysis(of ATP)? What for?
ATP + H₂O → ADP + Pi + Energy
Water breaks the bond between 2nd and 3rd phosphate of Adenosine Triphosphate (ATP) forming Adenosine diphosphate (ADP) and an inorganic phosphate, releasing energy from the bond, to be used as currency for other processes.
Types of ATP Resynthesis ?
Substrate level phosphorylation =
Creatine-phosphate system
Glycolysis
Oxidative phosphorylation = oxidative metabolism of carbs or fats.
Process of the Creatine-Phosphate system?
1) ATP is broken down to ADP during exercise to provide energy
2) To replenish this ATP, phosphocreatine stored in the muscle transfers a phosphate group to ADP forming ATP and Creatine
3) This is catalysed by creatine kinase
Describe the Creatine-Phosphate system?
Quickest method for ATP production
Lasts short period of time =
< 10 seconds.
Used for short explosive movements
Stores are limited so must be replenished during recovery periods
Process of Creatine-phosphate system in terms of Adenylate Kinase?
1) Adenylate kinase (AK) works alongside creatine kinase to maintain ATP level
2) AK catalyses conversion of 2 ADP molecules into 1 ATP and AMP
3) AMP then signals energy is low therefore activating other ATP resynthesis pathways such as Glycolysis or OP for longer activities.
Process of Glycolysis?
1) Glucose Transport: Glucose enters the cytosol from the blood via GLUT4.
2) Phosphorylation: Glucose is phosphorylated and rearranged, using 2 ATP, by hexokinase and phosphofructokinase.
3) Splitting: The 6-carbon molecule splits into two 3-carbon molecules.
4) Oxidation: Both 3-carbon molecules are oxidized, losing electrons and becoming phosphorylated.
5) Electron Transfer: Electrons are transferred to NAD+, forming NADH.
6) ATP Formation: Phosphate groups are transferred from the molecules to ADP, forming ATP.
Glycolysis with Fats?
1) Fats/Triglycerides are broken down into fatty acids and glycerol through lipolysis
2) Glycerol is converted 3 carbon molecule which can enter glycolysis the same as glucose
3) Fatty acids are broken down into Acetyl-CoA via beta oxidation, and enters the krebs cycle to provide for OP.
Glycolysis with Proteins?
1) Proteins are broken down into amino acids via proteolysis
2) Amino acids undergo deamination - removal of amino group
3) Some amino acids converted to pyruvate or intermediates like oxaloacetate and can enter glycolysis or krebs. depending on the specific amino acid.
What pathways can pyruvate follow?
Anaerobic (Fermentation):
- Lactic acid fermentation: In muscles or bacteria, pyruvate is reduced to lactate by lactate dehydrogenase, regenerating NAD+ for glycolysis.
- Alcoholic fermentation: In yeast or some bacteria, pyruvate is decarboxylated to acetaldehyde, which is reduced to ethanol by alcohol dehydrogenase, regenerating NAD+ but not producing ATP (only ethanol and CO2).
Aerobic (Krebs/Citric Acid Cycle and Oxidative Phosphorylation):
- Pyruvate is transported to the mitochondria, where it’s decarboxylated by the pyruvate dehydrogenase complex into Acetyl CoA.
- Acetyl CoA enters the Krebs cycle, producing NADH, FADH2, and ATP.
- These molecules then enter the electron transport chain (ETC) to generate ATP through oxidative phosphorylation.
Pyruvate oxidation process?
Location: Pyruvate oxidation occurs in the matrix of the mitochondria, where pyruvate is transported from the cytosol after glycolysis(uf oxygen is present).
Decarboxylation: Pyruvate dehydrogenase removes a carbon from pyruvate, releasing CO2 and oxidizing the remaining two-carbon fragment to form an acetyl group and produce NADH.
Formation of Acetyl CoA: The acetyl group attaches to Coenzyme A, forming Acetyl CoA.
Entry into Krebs Cycle: Acetyl CoA enters the Krebs cycle, where it contributes to the production of NADH, FADH2, and ATP, which are used in the electron transport chain (ETC) for oxidative phosphorylation (OP).
Process of Krebs/Citric acid cycle?
1) Acetyl CoA from pyruvate oxidation combines with Oxaloacetate forming citrate (6c molecule) catalysed by citrate synthase
2) Citrate is rearranged to isocitrate by aconitase
3) Isocitrate is oxidised and decarboxylised into alpha-ketoregulate (5c) releasing Co2 and reducing NAD+ to NADH, catalysed by Isocitrate dehydrogenase
4) Alpha-ketoglutarate is further oxidised producing NADH/Co2 and forming Succinyl-CoA (4c), catalysed by Alpha-ketoglutarate dehydrogenase
5) Succinate is formed from SUccinyl-CoA by Succinyl-CoA synthetase, and ATP is formed from ADP + P
6) Succinate is oxidized to fumarate, reducing FAD to FADH2, catalysed by Succinate dehydrogenase.
7) Fumarate is hydrated to form malate, catalysed by Fumarase
8) Malate is oxidized to regenerate oxaloacetate, producing NADH, catalysed by Malate dehydrogenase
9) Overall leaving net gain of 3 NADH, 1 FADH2, 1 ATP and oxaloacetate regeneration to repeat, with 2 Co2 as waste, everything is doubled as it is per pyruvate.
Process of the Electron Transport Chain (ETC)?
1) NADH and FADH2 from Krebs donates electrons
2) Complex I (NADH dehydrogenase) recieves electrons from NADH, which transfers ubiquinone(Q), which also pumps protons from matrix to intermembrane space.
3) Complex II (Succinate dehydrogenase) receives electrons from FADH2 which also goes to Q but does not pump protons.
4) Q carries electrons to Complex III to transfer to cytochrome c, this also pumps protons.
5) Cytochrome c is a small protein that shuttles electrons from Complex III to Complex IV
6) Complex IV transfers electrons from cytochrome c to oxygen (O₂), the final electron acceptor. Oxygen combines with protons to form water (H₂O). It also pumps protons into the intermembrane space.
Process of Oxidative Phosphorylation?
Refers to the whole process = ETC and OP
7) This different protons pumped via Complexes I - IV creates an electrochemical proton gradient between the matrix and intermembrane space
8) Protons flow down the gradient through ATP synthase complex which allows synthesising of ATP from ADP and Pi.
9) The O2/H2O formed in the ETC is crucial because it acts as the final electron acceptor and removes electrons from the chain, allowing the process to continue.
Where do ATP processes occur?
Phosphocreatine system: Cytoplasm
Glycolysis: Cytoplasm
Pyruvate Oxidation: Mitochondrial matrix
Krebs Cycle: Mitochondrial matrix
Electron Transport Chain (ETC): Inner mitochondrial membrane
Oxidative Phosphorylation (OP): Inner mitochondrial membrane/Cristae
Beta Oxidation: Matrix
Process of Fat Oxidation?
1) Lipolysis: Breakdown of triglycerides into glycerol and fatty acids.
2) Esterification: Fatty acids are activated = Fatty acid + Coenzyme A (CoA) = fatty acyl-CoA in the cytoplasm.
3) Beta-Oxidation: Fatty acyl-CoA is broken down into acetyl-CoA in the mitochondrial matrix, generating FADH₂, NADH, and acetyl-CoA.
4) This can then enters Krebs and ETC
