CHAPTER 2 Biochemistry

Copyright Pearson Prentice Hall 2-1: The Nature of Matter Photo Credit: © John Conrad/CORBIS Copyright Pearson Prentice Hall

ATOMS Atom – is the basic unit of matter Ex. Democritus – breaking a piece of chalk, when is it not chalk anymore? Until atomos “unable to be cut” An atom is very small. 100 million atoms make up about 1 cm.

Atoms are made of smaller subatomic particles: protons, neutrons and electrons. Protons have a positive charge, neutrons a neutral charge and together they make up the nucleus of an atom Electrons are negatively charged and much smaller than protons Atoms have a neutral charge, equal number of electrons and protons

ELEMENT An element is a pure substance made up of just one type of atom Elements have a one or two letter symbol The number of protons equals the atomic number of the element

Atoms of the same element that differ in the number of neutrons they contain are known as isotopes. Isotopes are identified by their mass number Isotopes of an element are similar because they have the same number of electrons; all isotopes of an element have the same chemical properties. Radioactive isotopes are important to use for dating and labels to follow the movement of substances within organisms.

CHEMICAL COMPOUNDS A chemical compound is a substance formed by the chemical combination of two or more elements in definite proportions. Written in shorthand known as a chemical formula

The physical and chemical properties of a compound are usually very different from those of the elements from which it is formed. Ex. Sodium Chloride – Sodium and Chlorine

CHEMICAL BONDS The main types of chemical bonds are ionic bonds and covalent bonds. An ionic bond is formed when one or more electrons are transferred from one atom to another. Positively and negatively charged atoms are known as ions.

A covalent bond is formed when one or more pairs of electrons are shared between two atoms. Can be a single, double or triple bond

A molecule is the smallest unit of most compounds. Ex. Water – H2O Doesn’t usually share electrons equally between the two atoms

INTERMOLECULAR INTERACTIONS Van der Waals forces are a type of intermolecular interaction in which when molecules are close together, a slight attraction develops between the oppositely charged regions of nearby molecules. Ex. Tokay gecko

2-2: Properties of Water

THE WATER MOLECULE Water is one of the only few compounds that naturally occur as a liquid Polarity Oxygen’s 8 protons vs. Hydrogen’s 1 proton = Oxygen with a greater pull on electrons So, the Oxygen end is slightly negative and Hydrogen slightly positive “Polar” molecules behave like poles of magnets

Hydrogen Bonding - The attraction between a hydrogen atom on one molecule and the oxygen atom of another Because water is a polar molecule, it is able to form multiple hydrogen bonds, which account for many of water’s special properties.

Cohesion – an attraction between molecules of the same substance. Ex: Surface Tension Adhesion – an attraction between molecules of different substances. Ex: Water meniscus Ex: Capillary Action

Heat Capacity It takes a large amount of energy to have water molecules move faster to raise the temperature of water Ex: Ocean temperature Ex: Cell Processes

SOLUTIONS AND SUSPENSIONS Mixture – is a material composed of two or more elements or compounds that are physically mixed together but not chemically combined. Ex: Saline Solutions

Solutions – a mixture in which all materials are evenly distributed throughout the solution. Solute – The substance dissolved Solvent – The substance in which the solute dissolves Water’s polarity gives it the ability to dissolve both ionic compounds and other polar molecules. Water is the universal solvent with some limitations - Ex: Salt Water

Suspensions – mixtures of water and non-dissolved material Ex: Human Blood

ACIDS, BASES, AND pH Water does split apart into ions every 1 in 550 million molecules Remember though, the number of H+ ions is equal to OH- ions therefore water is neutral

The pH Scale – a system of measurement that indicates the concentration of H+ ions in a solution. Ranges from 0-14 7 is neutral (equal H+ and OH-) <7 Acidic (more H+ than OH-) >7 Basic (more OH- than H+) Each step represents a factor of 10

Acid – a compound that forms H+ ions in a solution. Ex: Hydrochloric acid for stomach digestion Base – a compound that produces hydroxide (OH-) ions in a solution. Ex: Lye (NaOH – Sodium Hydroxide) for soap making

Buffer – a weak acid or base that can react with strong acids or bases to prevent sharp, sudden changes in pH. The human body needs to maintain a pH of a 6.5 to 7.5 to maintain homeostasis Buffers dissolved in life’s fluids play and important role in maintain homeostasis in organisms.