Carbohydrate metabolism Flashcards
what happens when a substrate is oxidised (hydrogen)
- gives up 2 hydrogen atoms
- a hydride ion (H- ) (hydrogen with extra electron) to NAD+ (to make neutral NADH) or FADH (to make FADH2)
- a proton (H+) to the aqueous environment (lowers pH)
glycolysis
- where does it take place
- high/low energy yield
- reactant
- products
- free energy change from start to finish
- what are the 2 phases and what happens during
- cytosol
- low
- glucose
- 2 (3C) pyruvates, 4 ATP (net gain 2), 2 NADH
- -31.9 kcal.mol-1
- Investment Phase (top half) - 2 ATP Molecules phosphorylate glucose as it requires energy (thermodynamically favours catabolism in the next phase: -∆G)
- Pay-Off Phase (bottom half) - phosphorylated glucose split into 2 3C molecules, then through another phosphorylation reaction reducing 2 NAD+ and releasing 2 H+. 2 molecules of ATP reformed by dephosphorylation from each 3C molecule (4 created).
how can exercise increase the glycolytic rate (4)
- Substrate availability – glycogenolysis forming more glucose
- Physiological factors – greater blood flow of glucose to active muscle during exercise
- Cellular factors – increased glucose uptake by glucose transporters which are integrated into the CSM during exercise, such as GLUT4
- Molecular factors – allosteric activation of pyruvate kinase (break down pyruvate) and phosphofructokinase (break down glucose) involved with glycolysis, due to decreasing ATP and phosphocreatine and increasing ADP levels.
pyruvate oxidation
- how does pyruvate get from the cytosol to the mitochondria
- what enzyme oxidised pyruvate
- what activates this enzyme
- 1 Pyruvate can be oxidised to 1 acetyl coA via pyruvate dehydrogenase (PDH) and generates 1 NADH each pyruvate.
- pyruvate dehydrogenase
- Low ATP, increasing ADP and AMP levels
how does NADH enter the mitochondria even though its impermeable to its membrane
- transfers its electrons to FADH reducing it to FADH2 via an enzyme in the mitochondria membrane
krebs/citric acid cycle
- aerobic/anaerobic
- high/low energy yield
- where
- what is its purpose
- reactant
- products
- free energy change
- the cycle
- how does exercise change metabolites and activate enzymes to increase cycle
- aerobic
- low
- mitochondrial matrix
- reduce electron carriers for the ETC
- 2 acetyl coa
- 2 ATP, 6 NADH and 2 FADH2, 8 H+
- -44.8 kcal.mol-1
- 2C Acetyl CoA reacts with 4C oxaloacetate producing 6C citrate. A series of 9 reactions oxidise citrate to reform oxaloacetate (for next cycle-metabolites recycled) and produce NADH, FADH2 and ATP. Citrate is also decarboxylated twice at reaction 4, then 5 producing 2 CO2 and remaking the 4C compound
- ↓ ATP/ADP and ↑ Ca2+
what happens to gibbs free energy during carb metaolism
reduces during formation of fadh nadh2 and atp
oxidative phosphorylation
- aerobic or anaerobic
- energy yield
- where
- reactants
- products
- change in free energy
- aerobic
- high
- mitochondrial intermembrane space and matrix
- 8 NADH (20 ATP) and 4 FADH2 (6 ATP)
- 26 ATP + 6 CO2 + 6 H2O
- -643 kcal.mol-1 (lots of energy yield to produce ATP
the electron transport chain process
- The ETC re-oxidises reduced coenzymes NADH and FADH2 back to NAD+ and FADH – releasing H- (2 electrons and 1 proton)
- These 2 electrons are then passed down a series of 4 haem proteins embedded in the mitochondrial membrane.
- oxygen (aerobic) is the final electron acceptor and H2O is produced (end product)
- NAD+ and FADH are then recycled back to the cytosol and mitochondrial matrix
the oxidative phosphorylation process
- The electron flow down ETC releases energy (-∆G) which pumps free protons across the membrane from the matrix to the intermembrane space, creating a proton concentration gradient
- Total of 10 H+ are pumped per 2 e- transferred from NADH to oxygen
- 6 H+ for FADH2 – because it enters at complex 2
impact of exercise on the proton gradient formed
- Exercise can increase the proton gradient 1000 fold as more NADH, so more H+ and the charge generated drives ATP resynthesis
ATP synthase
- process
- where is ATP synthase
- ATP synthesis is directly related to …. (2)
- The enzyme binds ADP + Pi when 4 protons are present and travel back through, yielding 1 ATP molecule
- cristae of the inner mitochondrial membrane
- supply of ADP and Pi, and the proton gradient
how many protons and ATP does 1 NADH and 1 FADH2 make
- 1 NADH - - - 10 protons - - - 2.5 ATP produced
- 1 FADH2 - - - 6 protons - - - 1.5 ATP produced
how much ATP does each stage make and what is the net ATP at the end from 1 glucose
2, 2, 26 = 30 ATP per 1 glucose
what is the limiting factor for aerobic metabolism
regeneration of NAD+ for glycolysis and krebs
