ATP, water, inorganic ions

• All organisms require a constant supply of energy to maintain their cells and stay alive
• Energy is required in anabolic reactions to build larger molecules from smaller ones and to move substances across the cell membrane or within the cell
• In animals, energy is needed for muscle contraction, coordination of movement at the whole-organism level, conduction of nerve impulses, and many other cellular processes
• ATP (Adenosine Triphosphate) is a nucleotide and the energy-carrying molecule that drives many processes inside living cells
• ATP is structurally similar to the nucleotides that make up DNA and RNA, and it is a phosphorylated nucleotide
• Adenosine can be combined with one, two, or three phosphate groups, forming AMP, ADP, and ATP respectively
• The hydrolysis of ATP to ADP and an inorganic phosphate group is catalyzed by the enzyme ATP hydrolase, also known as 'ATPase'
• The hydrolysis of ATP can be coupled to energy-requiring reactions within cells, such as active transport of ions, enzyme-controlled reactions, muscle contraction, and DNA synthesis
• Removal of one phosphate group from ATP releases 30.8 kJ mol of energy, forming ADP
• Removal of the third and final phosphate group from AMP releases 14.2 kJ mol of energy, forming adenosine
• The inorganic phosphate released during the hydrolysis of ATP can be used to phosphorylate other compounds, making them more reactive
• ATP can be made in two different ways: substrate-linked phosphorylation and chemiosmosis
• Water is of great biological importance, being the medium for all metabolic reactions in cells and composing a significant portion of cell mass
• Water is a polar molecule with hydrogen bonds forming between its molecules, contributing to its many essential roles in living organisms
• Water is considered a universal solvent due to its polarity
• Water's specific heat capacity is 4200 J/kg°C, meaning a relatively large amount of energy is required to raise its temperature
• The high specific heat capacity of water is due to the many hydrogen bonds present, which stabilize its temperature
• Water's high specific heat capacity is vital for living organisms as it provides suitable habitats and maintains a constant temperature, crucial for optimal enzyme activity
• To change state from liquid to gas, water requires a large amount of thermal energy to break hydrogen bonds and evaporate, providing a cooling effect for living organisms
• Hydrogen bonds between water molecules allow for strong cohesion, enabling water columns to move through plants' xylem and blood vessels in animals
• Water's adhesion property allows it to hydrogen bond to other molecules like cellulose, aiding in water movement up the xylem through transpiration
• Inorganic ions play a crucial role in essential cellular processes, occurring in solution in the cytoplasm and body fluids of organisms
• Inorganic ions have specific roles depending on their properties, with some occurring in high concentrations and others in low concentrations
• Hydrogen ions (H+), iron ions (Fe2+/Fe3+), sodium ions (Na+), phosphate ions (PO43-), and calcium ions (Ca2+) are essential inorganic ions with specific roles in the body
• Hydrogen ions determine pH levels in solutions, affecting enzyme-controlled reactions and metabolic processes within cells
• Iron ions are essential for oxygen binding in proteins like hemoglobin, myoglobin, and cytochromes, playing a key role in energy generation
• Sodium ions (Na+) are crucial for transporting glucose and amino acids across cell membranes and for nerve impulse transmission
• Phosphate ions (PO43-) are essential components of DNA, RNA, and ATP, storing and releasing energy for cellular processes
• Calcium ions (Ca2+) regulate impulses transmission in synapses, stimulate muscle contraction, and are necessary for blood clot formation