metabolism overview

• Glycolysis, the breakdown of glucose, occurs in the cytosol and is a decarboxylic reaction that converts glucose into acetyl-CoA, which then enters the TCA (Krebs) cycle to form the high energy intermediate that goes through the electron transport chain to produce ATP.
• Metabolism refers to enzyme reactions that allow synthesis, breakdown and interconversions of essential biomolecules.
• Catabolism is the metabolic breakdown of complex substances into smaller products including the breakdown of carbon compounds with liberation of energy for use by the cell or organism.
• At the liver, glutamate can be reformed from glutamine with the loss of NH4+ where deamination can take place.
• Anabolism is the energy requiring part of metabolism in which similar substances are transformed into more complex ones as in growth or other biosynthetic processes.
• Catabolism names end in 'lysis', such as glycolysis, lipolysis, glycogenolysis, and generate ATP & NADH.
• Most metabolic reactions occur in the mitochondria.
• Anabolism names end in 'genesis', such as gluconeogenesis, lipogenesis, glycogenesis, and use ATP, GTP, UTP.
• Most anabolic reactions occur in the cytosol.
• The breakdown of sugar in a non-living system, such as sugar+O2= carbon dioxide and water, involves a large activation energy overcome by the heat from fire and releases all free energy as heat.
• The stepwise oxidation of sugar in a cell, such as sugar + O2= carbon dioxide and water, involves small activation energies overcome by enzymes that work at body temperature and stores some free energy in activated carrier molecules to be used later.
• Instead of having enzymes to be irreversibly used, a mixture of reversible and irreversible reaction conducted by specific enzymes can be used to allow specific products to be used.
• Activated carriers include ATP, NADH, NADPH, FADH2, Acetyl CoA, Uridine Diphosphate glucose.
• ATP, adenosine triphosphate, can be recognised by specific proteins or enzymes.
• Hydrolysis gives ADP+ inorganic phosphate + H+ + energy.
• The breakdown of ATP to ADP involves the break of phosphoanhydride bonds which can be broken with water.
• A negative gibbs energy allows a spontaneous reaction.
• The hydrolysis of ATP is energetically so favourable due to the relief of electrostatic repulsion between phosphate groups and the resonance stabilisation of the released phosphate ion.
• Pyrophosphate, with 2 phosphate groups, is used in motor proteins and active transport systems.
• ATP is used in cell motility and muscle contraction, active transport systems, metabolic control, and metabolism to add Pi to metabolic intermediates.
• Glucose can be trapped inside the cell by adding a negative phosphate group which prevents movement across the membrane.
• Other 'high energy' nucleotide carriers are used to drive specific biosynthetic reactions: UTP drives the synthesis of complex sugars, GTP drives the synthesis of proteins.
• NAD, nicotinamide adenine dinucleotide, and NAD+, nicotinamide adenine dinucleotide phosphate, are used in metabolic control and metabolism to add Pi to metabolic intermediates.
• Flavin adenine dinucleotide, FAD, does not release as much ATP and acts as a hydrogen acceptor.
• Acetyl CoA is an acetyl group which is connected to S (thioester bond) by a high energy bond and then is attached to the coenzyme A.
• The acetyl CoA has 2 carbons.
• The thioester bond can be broken for it to react.
• Some of the energy from oxidation of glucose and fatty acids are stored within the bond.
• Metabolic reactions require: fuel molecules (substrates and intermediates) and enzyme catalysts and cofactors (activating ions: Mg2+, Zn2+, cl- and coenzymes with specific prosthetic groups).
• Enzyme cofactor can be ATP because it is high energy and allows for kinase enzymes.
• Fatty acids can easily pass through the membrane.
• Fatty acids enter the cytosol and taken into the mitochondria to be converted into acetyl CoA by fatty acid B oxidation which then enters the krebs cycle.
• Glucose needs a transporter.
• Glucose reaches the cytosol through the transporter then to enter the mitochondria it needs to be converted into pyruvate.
• Pyruvate dehydrogenase allows the conversion of pyruvate into acetyl CoA which enters the krebs cycle.
• All the high energy intermediates goes into the electron transport chain.
• Glucose is oxidised into 2 molecules of pyruvate in a pathway known as glycolysis.
• Glucose is trapped in the cell by phosphorylation to glucose-6-phoshate.
• The negative charges on the phosphate group prevents the molecules diffusion across the lipid membrane.
• A series of enzymatic reactions can oxidise glucose-6-phosphate to pyruvate.