BackStudy Guide: Basic Chemistry for Biology
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Basic Chemistry in Biology
Major Elements in Living Things
Living organisms are primarily composed of a few key elements that are essential for life processes.
Most Common Elements: The four elements most abundant in living things are carbon (C), hydrogen (H), oxygen (O), and nitrogen (N).
Trace Elements: These are elements required by an organism in only minute quantities, such as iron (Fe), iodine (I), and zinc (Zn).
Importance: These elements are fundamental for building biological molecules like proteins, nucleic acids, carbohydrates, and lipids.
Structure of the Atom
An atom is the smallest unit of matter that retains the properties of an element.
Subatomic Particles:
Proton: Positively charged particle found in the nucleus.
Neutron: Neutrally charged particle found in the nucleus.
Electron: Negatively charged particle orbiting the nucleus.
Atomic Number: Number of protons in the nucleus; defines the element.
Atomic Mass: Sum of protons and neutrons in the nucleus.
Electron Distribution in Atoms
Electrons are arranged in energy levels or shells around the nucleus.
Valence Shell: The outermost electron shell; determines chemical reactivity.
Octet Rule: Atoms tend to fill their valence shell with 8 electrons (except for hydrogen and helium).
Example: Carbon has 6 electrons: 2 in the first shell, 4 in the second (valence shell).
Chemical Bonds
Chemical bonds are forces that hold atoms together in molecules and compounds.
Covalent Bonds: Atoms share pairs of electrons.
Single Bond: One pair of electrons shared (e.g., H2).
Double Bond: Two pairs of electrons shared (e.g., O2).
Polar Covalent: Electrons shared unequally, leading to partial charges (e.g., H2O).
Nonpolar Covalent: Electrons shared equally (e.g., O2).
Ionic Bonds: Electrons are transferred from one atom to another, creating ions (e.g., NaCl).
Hydrogen Bonds: Weak attractions between a hydrogen atom (already covalently bonded to an electronegative atom) and another electronegative atom (e.g., between water molecules).
Van der Waals Interactions: Weak, transient interactions due to temporary shifts in electron density.
Molecular Shape and Its Importance
The shape of a molecule is determined by the arrangement of its atoms and the bonds between them. This shape is crucial for the molecule's function in biological systems.
Example: The shape of an enzyme determines which substrate it can bind.
Application: Drug design often relies on matching the shape of a drug molecule to its target protein.
Chemical Reactions
Chemical reactions involve the making and breaking of chemical bonds, resulting in the transformation of substances.
Reactants: Starting materials in a chemical reaction.
Products: Substances formed as a result of the reaction.
General Equation:
Example: Photosynthesis:
Key Vocabulary
Matter: Anything that has mass and takes up space.
Element: A substance that cannot be broken down into other substances by chemical means.
Atom: The smallest unit of an element.
Neutron: Neutrally charged subatomic particle.
Proton: Positively charged subatomic particle.
Electron: Negatively charged subatomic particle.
Atomic Number: Number of protons in an atom.
Atomic Mass: Total number of protons and neutrons.
Valence Shell: Outermost electron shell.
Isotope: Atoms of the same element with different numbers of neutrons.
Compound: Substance formed from two or more elements in a fixed ratio.
Molecule: Two or more atoms held together by covalent bonds.
Molecular Formula: Shows the types and numbers of atoms in a molecule (e.g., H2O).
Ion: Atom or molecule with a net electric charge.
Cation: Positively charged ion.
Anion: Negatively charged ion.
Electronegativity: Atom's ability to attract electrons in a bond.
Reactants: Substances that start a chemical reaction.
Products: Substances produced by a chemical reaction.
