The Chemical Basis of Life

Atomic Structure and Electrons

• Atomic number refers to the number of protons in the nucleus of an atom, determining the element's identity.
• Mass number is the total number of protons and neutrons in an atom’s nucleus.
• Valence electrons are the outermost electrons involved in chemical bonding and reactions.
• Silicon (Si) and carbon (C) are examples of elements with 4 valence electrons.
• Carbon is the most abundant element in living organisms, essential for life's molecular structures.

Subatomic Particles

• Protons have a positive charge and are located in the nucleus.
• Neutrons are electrically neutral and also found in the nucleus.
• Electrons have negligible mass relative to protons and neutrons, found in orbitals outside the nucleus.

Chemical Bonds and Reactions

• Covalent bonds involve the sharing of electron pairs between atoms.
• Ionic bonds involve the complete transfer of electrons from one atom to another.
• Covalent bonds are generally the strongest type of chemical bond.
• Chemical potential energy is stored in the bonds linking atoms to form molecules.
• Adenosine triphosphate (ATP) is the primary energy currency for cells.

Energy and Metabolism

• Exothermic reactions release energy during the process.
• Increasing temperature and concentration are two methods to accelerate reaction rates.
• Metabolism encompasses the entirety of biochemical processes occurring within a living organism.

Water Properties

• Energy and matter primarily enter the biosphere through photosynthesis and nutrient cycling.
• Water's polarity allows it to dissolve polar and charged molecules, acting as a solvent.
• Ice floats due to its lower density compared to liquid water.
• Cohesion leads to the formation of a meniscus when water meets a solid surface.
• Surface tension prevents light objects from sinking in water due to cohesive forces among water molecules.
• Capillary action enables water to travel in biological systems, such as within plant roots and leaves.

pH and Cellular Response

• pH measures the concentration of H+ and OH- ions in a solution, affecting biological and chemical processes.
• Buffers help cells maintain stable pH levels, protecting against damaging fluctuations in acidity or alkalinity.

Organic Chemistry

• The functional behavior of a molecule in organic chemistry is determined by its structure and functional groups.
• Amino acids are the building blocks of proteins, linked by peptide bonds.
• Carbon's tetravalency allows it to form diverse molecular shapes and combinations of bonds.
• Water's high specific heat capacity allows it to absorb and retain substantial amounts of energy, regulating temperature in environments.