1.5 - 1.8

• The genome of an organism is its entire hereditary information encoded in DNA.
• A genome is made up of genes and other DNA sequences that do not code for proteins.
• In genomic sequencing the sequence of nucleotide bases can be determined for individual genes and entire genomes.
• Computer programs can be used to identify base sequences by looking for sequences similar to known genes. To compare sequence data, computer and statistical analysis (bioinformatics) of individual genomes is required.
• An individual’s genome can be analysed to predict the likelihood of developing certain diseases.
• Pharmacogenetics is the use of genome information in the choice of drugs.
• An individual’s personal genome sequence can be used to select the most effective drugs and dosage to treat their disease (personalised medicine).
• Metabolic pathways are integrated and controlled pathways of enzyme-catalysed reactions within a cell.
• Metabolic pathways can have reversible steps, irreversible steps and alternative routes.
• Anabolic reactions build up large molecules from small molecules and require energy.
• Catabolic reactions break down large molecules into smaller molecules and release energy.
• Metabolic pathways are controlled by the presence or absence of particular enzymes and the regulation of the rate of reaction of key enzymes.
• Induced fit occurs when the active site changes shape to better fit the substrate after the substrate binds.
• The substrate molecule(s) have a high affinity for the active site and the subsequent products have a low affinity allowing them to leave the active site.
• Some metabolic reactions are reversible and the presence of a substrate or the removal of a product will drive a sequence of reactions in a particular direction.
• The sum of all the anabolic and catabolic reactions that occur within a living cell is collectively known as a cells metabolism.
• Enzymes lower the activation energy for a reaction to occur.
• Competitive inhibitors bind at the active site preventing the substrate from binding. Competitive inhibition can be reversed by increasing substrate concentration.
• Non-competitive inhibitors bind away from the active site but change the shape of the active site preventing the substrate from binding. Non-competitive inhibition cannot be reversed by increasing substrate concentration.
• Feedback inhibition occurs when the endproduct in the metabolic pathway reaches a critical concentration. The end-product then inhibits an earlier enzyme, blocking the pathway, and so prevents further synthesis of the end-product.
• to function effectively enzymes require an adequate supply of substrate. If the substrate concentration is low, the rate of reaction is low (rate of release of product). This improves as the substrate concentration increases.
• Phosphorylation is the addition of phosohate molecules. ATP is used to transfer energy to cellular processes. It does so by phosphorylation of other molecules, making them more reactive.
• Glycolysis is the first stage of cellular respiration and is the breakdown of glucose into two molecules of pyruvate and does not require oxygen.
• In glycolysis, 2 ATP is required for the phosphorylation of intermediate molecules during the energy investment stage of glycolysis. 4 ATP are produced during the energy pay-off phase producing a net gain of 2 ATP.
• During glycolysis hydrogen ions and electrons are removed from glucose and bind to the co-enzyme NAD+ to form NADH and transported to the electron transport chain. This is controlled by the enzyme dehydrogenase.
• The citric acid cycle occurs in the matrix and in aerobic conditions pyruvate is broken down to an acetyl group that combines with co-enzyme A forming acetyl co-enzyme A.
• In the citric acid cycle the acetyl group from acetyl coenzyme A (2c) combines with oxaloacetate (4c) to form citrate (6c). During a series of enzyme-controlled steps, citrate is gradually converted back into oxaloacetate which results in the generation of ATP and release of carbon dioxide.
• Dehydrogenase enzymes remove hydrogen ions and electrons and pass them to the coenzyme NAD, forming NADH. This occurs in both glycolysis and the citric acid cycle.
• The hydrogen ions and electrons from NADH are passed to the electron transport chain on the inner mitochondrial membrane.
• In the electron transport chain, the electrons are passed along in the inner membrane, releasing energy. This energy allows hydrogen ions to be pumped across the inner mitochondrial membrane through ATP synthase resulting in the production of ATP.
• In the electron transport chain, the hydrogen ions and electrons combine with oxygen to form water.
• During Vigouris exercises, the muscle cells do not get sufficient oxygen from the blood stream for the electron transport chain to continue to produce ATP.
• When oxygen is not present pyruvates are converted into lactic acid. This involve the transport of hydrogen from NADH to produced during glycolysis from pyruvate in order to produce lactate. This regenerates the NAD needed to maintain ATP production through glycolysis.
• Lactate accumulates and muscle fatigue occurs. The oxygen debt is repaid when exercise is complete. This allows respiration to provide the energy to convert lactate back to pyruvate and glucose in the liver.
• Slow-twitch muscle fibres contract relatively slowly, but can sustain contractions for longer. They are useful for endurance activities such as long-distance running, cycling or cross-country skiing.
• Slow-twitch muscle fibres rely on aerobic respiration to generate ATP and have many mitochondria, a large blood supply and a high concentration of the oxygen-storing protein myoglobin. The major storage fuel of slow-twitch muscle fibres is fats.
• Fast-twitch muscle fibres contract relatively quickly, over short periods. They are useful for activities such as sprinting or weightlifting.
• Fast-twitch muscle fibres can generate ATP through glycolysis only and have fewer mitochondria and a lower blood supply compared to slow-twitch muscle fibres. The major storage fuel of fast-twitch muscle fibres is glycogen.
• Most human muscle tissue contains a mixture of both slow-twitch and fast-twitch muscle fibres. Athletes show distinct patterns of muscle fibres that reflect their sporting activities.