Biology Basic Chemistry

Biology Introduction

• Biology is the scientific study of life.
• Living things are composed of the same chemical elements as nonliving things.
• Living things obey the same physical and chemical laws that govern everything in the universe.

Characteristics of Life

• Living things are organized, from atom to biosphere.
• Life requires materials and energy, with the sun being the source of energy and metabolism referring to all chemical reactions in a cell.
• Living things maintain homeostasis, which is the maintenance of internal conditions.
• Living things respond to stimuli, reproduce and develop, and have adaptations that may lead to evolution.

Chemical Elements

• Matter refers to anything that has mass and occupies space.
• Matter exists in four states: solid, liquid, gas, and plasma.
• All matter, both living and nonliving, is composed of basic substances called elements.
• An element is a substance that cannot be broken down into simpler substances by ordinary chemical means.
• Each element has its own unique properties, such as density, solubility, melting point, and reactivity.
• Ninety-two elements are naturally occurring, and six elements (CHNOPS) make up 95% of the body weight of organisms.

Atoms

• An atom is the smallest part of an element that displays the property of the element.
• Atoms are composed of subatomic particles: protons, neutrons, and electrons.
• The central nucleus of an atom contains protons and neutrons.
• Protons are positively charged, neutrons have no charge, and electrons are negatively charged.
• Electrons revolve around the nucleus in energy shells.

Atomic Number and Mass Number

• The atomic number is equal to the number of protons in each atom of an element.
• The mass number of an atom is equal to the sum of the number of protons and neutrons in the atom's nucleus.
• The atomic mass is approximately equal to the mass number.

Isotopes

• Isotopes are atoms of the same element that differ in the number of neutrons.
• Some isotopes are unstable or radioactive.
• Isotopes can spontaneously decay.

Periodic Table

• The periodic table is a table of elements arranged horizontally by increasing atomic number in rows called periods.
• Atoms of an element are arranged in vertical columns called groups.
• The atomic number increases by 1 from left to right in a period.
• Atoms within the same group share the same chemical binding characteristics.
• Group VIII are the noble gases and are inert.

Electrons and Energy

• Electrons are attracted to the positively charged nucleus.
• It takes energy to hold electrons in place and push them away.
• Electrons have energy due to their relative position (potential energy).
• Electrons determine the chemical behavior of atoms.

The Distribution of Electrons

• The Bohr model is a useful way to visualize electron location.
• Electrons revolve around the nucleus in energy shells.
• The first energy shell can hold up to 2 electrons, and each additional shell can hold up to 8 electrons.
• Each lower shell is filled first before electrons are placed in the next shell.

Valence Electrons

• The outermost energy shell of any atom is called the valence shell.
• The valence shell determines many of an atom's chemical properties.
• The octet rule states that the outermost shell is most stable when it has eight electrons.

Chemical Bonding

• Chemical bonds contain energy.
• Organisms are directly dependent on chemical-bond energy.
• Bonds between atoms are caused by the interactions between electrons in outermost energy shells.
• The process of bond formation is called a chemical reaction.

Types of Bonds

• Ionic bonds form when electrons are transferred from one atom to another.
• Covalent bonds result when two atoms share electrons.
• In a nonpolar covalent bond, electrons are shared equally between atoms.
• In a polar covalent bond, electrons are shared unequally.
• Electronegativity is the ability of an atom to attract electrons towards itself in a chemical bond.

Chemistry of Water

• Water is a polar molecule.
• The shape of a water molecule and its polarity make hydrogen bonding possible.
• Hydrogen bonds are weak attractions between a slightly positive hydrogen atom and a slightly negative atom.
• Hydrogen bonds help maintain the proper structure and function of complex molecules.

Properties of Water

• Water molecules cling together because of hydrogen bonding.
• Water has a high heat capacity.
• Water has a high heat of evaporization.
• Water is a good solvent because of its polarity.
• Water molecules are cohesive and adhesive.

Acids and Bases

• pH is a measure of hydrogen ion concentration in a solution.
• Acids are substances that dissociate in water, releasing hydrogen ions.
• Bases are substances that either take up hydrogen ions or release hydroxide ions.
• The pH scale is used to indicate the acidity or basicity of a solution.
• Buffers are chemicals or combinations of chemicals that keep pH within normal limits.

Buffers and pH

• The body has built-in mechanisms to prevent pH changes.
• Buffers, such as the carbonic acid buffer, help maintain a stable pH.
• The pH of body fluids must be maintained within narrow limits to ensure health