Cellular Metabolism refers to the sum of thousands of chemical reactions that occur constantly in each living thing. 2 Types: Anabolic: atoms or molecules are joined together to make a more complex molecule. Energy is required (endothermic). Catabolic: Break down complex molecules into simpler substances, releasing energy (exothermic).

ATP = energy molecule Adenosine triphosphate (ATP) is the universal energy carrier for cells. It is similar to a nucleotide, composed of adenine, ribose and three phosphate groups. The phosphate groups are joined by high energy covalent bonds. H H H H OH OCH 2 N CH C C N C N CH NH 2 N OP O O-O- O-O- OP O O-O- OP O O-O- Phosphate groups Adenine Ribose The chemical structure of adenosine triphosphate (ATP), and a space filling molecule (right). Phosphate groups Ribose Adenine

The Role of ATP in Cells ATP (a high energy molecule) can release its energy by releasing a single phosphate group to become ADP (a low energy molecule) ADP returns to the mitochondria where it gains more energy through cellular respiration to reattach a free phosphate group. ATP PiPiPiPi ATPase Inorganic phosphate P ADP +

Metabolism = Redox Reactions Oxidation – the substance that loses electrons (fuels, fats, sugars, etc.) to become CO 2 Reduction – the substance that gains electrons (an electronegative atom, eg. oxygen) to become H 2 O Once the fuel breaks its (C-H) bonds and transfers its electrons to oxygen, energy is released in the form of heat In a fire (combustion), fuels are oxidized rapidly to produce water and carbon dioxide.

Cellular Respiration & Redox C 6 H 12 O O 2 --> 6 CO H 2 O + energy reduction oxidation In biological systems, it’s not useful to produce only heat energy from the oxidation of glucose

Cellular Respiration & Redox It’s not 100% efficient, creating some body heat The oxidation of glucose is performed in a series of controlled steps to avoid combustion Instead of the electrons reducing oxygen in one step, they are being used elsewhere to perform useful work (ie. make ATP) Electron carriers (eg. NAD+) are used to transfer electrons which help to generate ATP

NAD + and NADH NAD + (nicotinamide adenine dinucleotide) is a coenzyme used in cellular respiration. NAD + is an electron acceptor, carrying electrons from one reaction to another. E.g. When glucose molecules are broken down (oxidized) they lose electrons, these are then picked up by the NAD + which is reduced to form NADH. The NADH then transports the electrons to where they are needed. (high energy)

Aerobic Respiration Cell cytoplasm Mitochondrion 4. Electron transport chain Location: mitochondrial cristae Process: H 2 is oxidised to water using oxygen. Energy is released as ATP. Electron transport chain Krebs Cycle 3. Krebs cycle Location: mitochondrial matrix Process: A series of reactions producing carbon dioxide, ATP and hydrogens. 2. Transition reaction Location: mitochondrial matrix Process: Formation of acetyl coenzyme A from pyruvate. Transition Reaction Glycolysis 1. Glycolysis Location: cytoplasm Process: Glucose is broken down into two molecules of pyruvate. Aerobic respiration can be separated into 4 stages.