Concepts of Matter and Energy

We shall begin with a pun… A neutron walked into a diner and asked, "How much for a coke?" How did the waiter reply? "For you, no charge."

Matter Anything that occupies space and has mass 3 states (that we are concerned with) – Solid – definite shape and volume – Liquid – definite volume, conform to the shape of the container they are in – Gas – neither definite shape nor volume Matter can change! – Physical change – does not alter the basic nature of the substance – Chemical change – alter the composition of the substance

Composition of Matter Composed of elements – unique substances that cannot be broken down into simpler substances by ordinary chemical methods Importance in the body: – 4 elements make up 96% of our body’s mass O – breathing, oxidation reactions that produce ATP C – primary component of biomolecules H – ionic, determines pH N – important in structure of proteins and nucleic acids

Atoms! Smallest particle that still retains the properties of the element – Protons – positively charged subatomic particle, found in the nucleus, mass of 1 AMU – Neutrons – neutral subatomic particle, found in the nucleus, mass of 1 AMU – Electrons – negatively charged subatomic particle, found in the electron cloud; mass is negligible Planetary Model – atom is a miniature solar system in which the protons and neutrons are clustered at the center of the atom in the nucleus; the electrons orbit the nucleus like planets orbit the sun in our solar system Orbital Model – depicts the general location of electrons outside the nucleus as a haze of negative charge

Atoms cont’d Atomic Number – the number of protons in the nucleus Atomic Mass Number (AMU) – the sum of the protons and neutrons contained in an atom’s nucleus Atomic Weight – the exact mass of an element – Isotopes – atoms with different numbers of neutrons in the nucleus Radioisotopes – isotopes that are unstable and tend to decompose to become more stable Radioactivity – process of spontaneous atomic decay

Molecules Two or more atoms chemically combined Compound: two or more DIFFERENT atoms, chemically combined form a molecule of a compound. Molecules are the smallest particles of a compound that still retain the properties of that compound – Compounds have different properties than their atomic constituents! Formed by bonds

Chemical Reactions Whenever atoms combine with or dissociate from other atoms Bonds: energy relationship involving interactions between electrons of reacting atoms

Types of Bonds Ionic Bonds – formed between a metal and a nonmetal; in an ionic bond, metals donate their electrons to non-metals resulting in a positive charge on the metal and a negative charge on the non-metal. The ionic “bond” forms as a result of the attraction between these opposite charges Covalent Bonds – formed between two non-metals; in covalent bonds electrons are shared – Polar covalent bond – electrons are shared unequally – Non-polar covalent bond – electrons are shared equally – Hydrogen Bonds – weak covalent bond important in biomolecules. In water, H-bonds are responsible for: Polarity Surface Tension Role in biomolecules

3 Types of Reactions Synthesis Reactions – Occur when two or more atoms or molecules combine to form a larger, more complex molecule – Bond formation – Require energy – Examples: growth, formation of amino acid chains, repair of damaged tissues – A + B  AB

Decomposition Reactions Occur when a molecule is broken down into smaller molecules, atoms, or ions Bonds are broken Energy is released Examples: Digestion, breakdown of glycogen AB  A + B

Exchange Reactions Involves other two types Bonds are formed AND broken A “switch” is made between molecular parts Example: ATP and Glucose AB + CD  AD + BC

Biochemistry! Inorganic Compounds: – Lack carbon – Small, simple Organic Compounds: – Contain carbon – Biomolecules Carbohydrates, Lipids, Proteins, Nucleic Acids

Inorganic Compounds Water is the most important inorganic compound in the body – High heat capacity (resists changes in temperature) – Universal solvent (polarity) – Chemical reactivity (reactions in the body do not occur unless reactants are dissolved in water) – Cushioning Salts – source of ions in the body – Electrolytes – substances that conduct an electrical current in solution Acids and Bases

pH – concentration of H+ ions in solution Acids: proton donors (pH<7) Bases: proton acceptors (pH>7) Acid-Base reactions: products are always salt and water Buffers – act to maintain pH stability by taking up excess hydrogen or hydroxyl ions in the body

Organic Compounds Carbohydrates – Monosaccharides – simplest sugars; characteristic sweet taste; predominant source of cellular energy – example is glucose – Disaccharides – made up of two monosaccharide subunits; sweet in taste – Polysaccharides – many monosaccharide subunits; most complex carbohydrates; example is starch; not sweet in taste Lipids – Triglycerides – fatty acids; made of a glycerol backbone and three fatty acid tails – Phospholipids – form membranes within the body; polar, hydrophyllic head group and a non-polar hydrophobic tail group – Steroids Cholesterol

Organic Compounds Cont’d Proteins – carry out most cellular functions (made of 20 common amino acids) – Fibrous (structural) – Globular (functional) – Enzymes – increase the rate of chemical reaction in the body Nucleic Acids – genetic material – Made of Nucleotides (contain a phosphate group, a simple sugar, and a nitrogenous base); Adenine, Thymine, Cytosine, Guanine, Uracil – DNA/RNA

Fin.