Metabolic Processes – V1b Metabolism describes all the chemical reactions in an organism that transform matter and energy. Metabolic reactions can break down molecules, synthesize compounds, eliminate waste and repair damage.

Metabolism Examples include the reactions that: - allow plant cells to capture sunlight and produce glucose in photosynthesis - absorb nutrients in the digestive system - synthesize polymers from monomers - allow all plant and animal cells to break glucose into carbon dioxide and water in cellular respiration and release the energy for other metabolic processes.

Anabolic and Catabolic Reactions All metabolic reactions belong to two categories: 1. Anabolic reactions are endergonic reactions where free energy from the surroundings is stored in newly formed chemical bonds. The most crucial anabolic reaction is photosynthesis which stores sunlight energy in glucose bonds for use by cells.

Photosynthesis chemical equation: 6 CO2 + 6 H2O C6H12O6 + 6 O2  G= +2870 kJ/mol of glucose formed sunlight

Anabolic and Catabolic Reactions 2. Catabolic reactions are exergonic reactions where bonds are broken and energy is released to the surroundings. The crucial catabolic reaction is cellular respiration which releases chemical bond energy in glucose as ATP energy for cellular reactions.

Cellular respiration chemical equation: C6H12O6 + 6 O2  6CO2 + 6 H2O + 36 ATP (energy)  G= -2870 kJ/mol of glucose oxidized

Adenosine Triphosphate (ATP) All cells use ATP as energy currency. The Gibbs free energy from the phosphorylation of ADP to ATP is  G = +30.5 kJ/mol. The hydrolysis of ATP back to ADP is exergonic with a free energy of  G = - 30.5 kJ/mol.

Adenosine Triphosphate (ATP) This amount of energy is just right to power many biochemical reactions in the cell. The three major ways ATP is used in cells is: 1. Chemical Work – energy to synthesize and catabolize macromolecules 2. Mechanical Work – provide energy for movement of muscles, moving cilia 3. Transport Work – energy to actively transport molecules across membranes.

Redox Reactions and Electron Carriers Electrons are essential not only to forming bonds between atoms but also for reduction – oxidation (redox) reactions. Electrons are often transferred between molecules in a coupled reaction. The substance that lost electrons is oxidized and the substance that gains the energized electrons is reduced. (LEO goes GER). The oxidized substance has less energy and the reduced substance that received the electrons is energized.

Energy Carrier Molecules The energy carrier molecules NAD+ and FAD are vital in the process of moving energy from the bonds in glucose to the bonds in ATP during cellular respiration.   Oxidized (low energy) Reduced (high energy) Nicotinamide Adenine Dinucleotide NAD+ NADH Flavin Adenine Dinucleotide FAD FADH2

Metabolism Summary