The Chemical Level of Organization Chapter 2

Atoms and Molecules  Atoms are the smallest units of matter, they consist of protons, neutrons, and electrons

Structure of an Atom  An element consists entirely of atoms with the same number of protons.  Within an atom, an elecron cloud surround the nucleus.  An element consists entirely of atoms with the same number of protons.  Within an atom, an elecron cloud surround the nucleus.

 The atomic mass of an atom is equal to the total number of protons and neutron in its nucleus.  Isotopes are atoms of the same element whose nuclei contain different number of neutrons.  The atomic weight of an element takes into account the abundance of its various isotopes.  The atomic mass of an atom is equal to the total number of protons and neutron in its nucleus.  Isotopes are atoms of the same element whose nuclei contain different number of neutrons.  The atomic weight of an element takes into account the abundance of its various isotopes.

 Electrons occupy a series of electron shells around the nucleus.  The number of electrons in the outer shell determine an atom’s chemical properties.  Electrons occupy a series of electron shells around the nucleus.  The number of electrons in the outer shell determine an atom’s chemical properties.

Chemical bonds and chemical compounds  An ionic bond results from the attraction between ions: atoms that have gained or lost electrons.  Cations are positively charged  Anions are negatively charged.  An ionic bond results from the attraction between ions: atoms that have gained or lost electrons.  Cations are positively charged  Anions are negatively charged.

 Atoms can combine to form a molecule  Combinations of atoms of different elements form a compound  Some atoms share electrons to form a molecule held together by covalent bonds.  Atoms can combine to form a molecule  Combinations of atoms of different elements form a compound  Some atoms share electrons to form a molecule held together by covalent bonds.

 Sharing one pair of electron creates a single covalent bond  Sharing two pairs forms a double covalent bond  Unequal sharing of electrons creates a polar covalent bond.  Sharing one pair of electron creates a single covalent bond  Sharing two pairs forms a double covalent bond  Unequal sharing of electrons creates a polar covalent bond.

 A hydrogen bond is the attraction between a hydrogen atom with slight positive charge and a negatively charged atom in another molecule or within the same molecule  Hydrogen bond can affect the shaes and properties of molecules  A hydrogen bond is the attraction between a hydrogen atom with slight positive charge and a negatively charged atom in another molecule or within the same molecule  Hydrogen bond can affect the shaes and properties of molecules

Chemical Notation  Chemical notation allows us to describe reactions between reactant tha generate one or more products.

Chemical Reactions  Metabolisms refers to all the chemical reaction in the body. Our cells capture, store and use energy to maintain homeostasis and support essential functions.

Basic energy concepts  Work involves movement of an object or a change in its physical structure.  Energy is the capacity to perform work.  There are two major types of energy: knetic and potential.  Work involves movement of an object or a change in its physical structure.  Energy is the capacity to perform work.  There are two major types of energy: knetic and potential.

 Kinetic energy is the energy of motion.  Potential energy is stored energy that results from the position or structre of an object.  Conversions from potential to kinetic energy are not 100% efficient.  Every energy exchange produces heat.  Kinetic energy is the energy of motion.  Potential energy is stored energy that results from the position or structre of an object.  Conversions from potential to kinetic energy are not 100% efficient.  Every energy exchange produces heat.

Types of Reactions  A chemical reaction may be classified as  Decomposition  Synthesis  Exchange  A chemical reaction may be classified as  Decomposition  Synthesis  Exchange

 Exergonic reaction release heat  Endergonic reactions absorb heat  Cells gain energy to power their functions by catabolism: the breakdown of complex molecules  Much of this energy supports anabolism, the synthesis of new organic molecules  Exergonic reaction release heat  Endergonic reactions absorb heat  Cells gain energy to power their functions by catabolism: the breakdown of complex molecules  Much of this energy supports anabolism, the synthesis of new organic molecules

Reversible Reactions  Reversible reactions consist of simultaneous synthesis and decomposition reactions.  At equilibrium the rates of these two opposing reactions are in balance.  Reversible reactions consist of simultaneous synthesis and decomposition reactions.  At equilibrium the rates of these two opposing reactions are in balance.

Acids and Bases  A acid releases hydrogen ions  A base removes hydrogen ions from a solution  A acid releases hydrogen ions  A base removes hydrogen ions from a solution

pH  The pH of a solution indicates the concentration of hydrogen ions it contains.  Solutions can be classified as neutral (pH of 7)acidic (pH 7) on the basis of pH  The pH of a solution indicates the concentration of hydrogen ions it contains.  Solutions can be classified as neutral (pH of 7)acidic (pH 7) on the basis of pH

 Buffers maintain pH within normal limits ( in most body fluids) by releasing or absorbing hydrogen ions.

Inorganic Compounds  Nutrients and metabolites can be broadly classified as organic or inorganic compounds  Living cells in the body generate carbon dioxide and consume oxygen.  Nutrients and metabolites can be broadly classified as organic or inorganic compounds  Living cells in the body generate carbon dioxide and consume oxygen.

Water and it Properties  Water is the most important inorganic component of the body  Water is an excellent solvent, has a high heat capacity, and participates in the metabolic reactions of the body.  Many inorganic compounds will undergo ionization, or dissociation in water to form ions.  Water is the most important inorganic component of the body  Water is an excellent solvent, has a high heat capacity, and participates in the metabolic reactions of the body.  Many inorganic compounds will undergo ionization, or dissociation in water to form ions.

Inorganic Acids and Bases  Inorganic acids found in the body include hydrochloric acid carbonic acid, sulfuric acid and phosphoric acid.  Sodium hydroxide is an inorganic base that may form within the body.  Inorganic acids found in the body include hydrochloric acid carbonic acid, sulfuric acid and phosphoric acid.  Sodium hydroxide is an inorganic base that may form within the body.

Salts  A salt is an ionic compound whose cation is not H + and whose anion is not OH -  Salts are electrolytes, compounds that dissociate in water and conduct an electrical current.  A salt is an ionic compound whose cation is not H + and whose anion is not OH -  Salts are electrolytes, compounds that dissociate in water and conduct an electrical current.

Organic Compounds  Organic compounds contain carbon and hydrogen, and usually oxygen as well.  Large and complex organic molecules include carbohydrates, lipids proteins and nucleic acids.  Organic compounds contain carbon and hydrogen, and usually oxygen as well.  Large and complex organic molecules include carbohydrates, lipids proteins and nucleic acids.

Carbohydrates  Carbohydrates are most important as an energy source for metabolic process.  The three major types are monosaccharides (simple sugars), dissacharides and polysaccharides.  Carbohydrates are most important as an energy source for metabolic process.  The three major types are monosaccharides (simple sugars), dissacharides and polysaccharides.

 A. the straight - chain formula for glucose  B. The ring form that is most common in nature.  An abbreviated diagram fo the ring form.

Lipids  Lipids are water-insoluble molecules that include fats, oils, and waxes.  There are four important classes of lipids: fatty acids, fats, steroids, and phospholipids.  Lipids are water-insoluble molecules that include fats, oils, and waxes.  There are four important classes of lipids: fatty acids, fats, steroids, and phospholipids.

 Triglycerides (fats) consists of three fatty acid molecules attached to a molecule of glycerol  Cholesterol is a precursor of steroid hormones and is a component of cell membranes  Triglycerides (fats) consists of three fatty acid molecules attached to a molecule of glycerol  Cholesterol is a precursor of steroid hormones and is a component of cell membranes

 Phospholipids are the most abundant components of cell membranes.

Proteins  Proteins perform a great variety of function in the body.  Important types of protein include structural proteins, contractile proteins, transport proteins, enzymes, hormones and antibodies.  Proteins perform a great variety of function in the body.  Important types of protein include structural proteins, contractile proteins, transport proteins, enzymes, hormones and antibodies.

 Proteins are chains of amino acids linked by peptide bonds.  The sequence of amino acids and the interactions of their R groups influence the final shape of the protein molecules.  Proteins are chains of amino acids linked by peptide bonds.  The sequence of amino acids and the interactions of their R groups influence the final shape of the protein molecules.

 The shape of the protein determines its function.  Each protein works best at an optimal combination of temperature and pH.  The shape of the protein determines its function.  Each protein works best at an optimal combination of temperature and pH.

 Activation energy is the amount of energy required to start a reaction. Proteins called enzymes control many chemical reaction within our bodies. Enzymes are catalysts--substances that accelerate chemical reaction without themselves being permanently changed.  Activation energy is the amount of energy required to start a reaction. Proteins called enzymes control many chemical reaction within our bodies. Enzymes are catalysts--substances that accelerate chemical reaction without themselves being permanently changed.

 The reactants in an enzymatic reaction, called substrates, interact to form a product by bonding to the enzyme at the active site.

Nucleic Acids  Nucleic acids store and process information at the molecular level.  There are two kinds of nucleic acids: DNA and RNA  Nucleic acids are chains of nucleotides.  Each nucleotide contains a sugar, a phosphate group and a nitrogen base.  Nucleic acids store and process information at the molecular level.  There are two kinds of nucleic acids: DNA and RNA  Nucleic acids are chains of nucleotides.  Each nucleotide contains a sugar, a phosphate group and a nitrogen base.

 The sugar is always ribose or deoxyribose.  The nitrogenous bases found in DNA are adenine, guanine, cytosine, and thymine. In RNA uracil replaces thymine.  The sugar is always ribose or deoxyribose.  The nitrogenous bases found in DNA are adenine, guanine, cytosine, and thymine. In RNA uracil replaces thymine.

High-Energy Compounds  Cells store energy in high-energy compounds.  The most important high-energy compound is ATP  When energy is available, cells make ATP by adding a phosphate group to ADP  When energy is needed ATP is broken down to ADP and phosphate.  Cells store energy in high-energy compounds.  The most important high-energy compound is ATP  When energy is available, cells make ATP by adding a phosphate group to ADP  When energy is needed ATP is broken down to ADP and phosphate.