Chapter 2 - Chemistry Comes Alive
INTRODUCTION - Why study chemistry in an Anatomy and Physiology Class?
- body function depend on cellular functions
- cellular functions result from chemical changes
- biochemistry helps to explain physiological processes, and develop new drugs and method for treating diseases
DEFINITIONS OF CONCEPTS: Matter and Energy
- Matter is anything that occupies space and has mass
- Mass is equal to the amount of matter in the object.
- Mass remains constant regardless of gravity.
- Matter exists in one of three states: solid, liquid, or gas.
- Energy
- Energy is the capacity to do work, and it exists in two forms.
- Kinetic energy is the energy of motion.
- Potential energy is stored energy.
- Forms of Energy
- Chemical energy is energy stored in chemical bonds.
- Electrical energy results from the movement of charged particles.
- Mechanical energy is energy directly involved with moving matter.
- Radiant energy is energy that travels in waves.
- Energy is easily converted from one form to another. During conversion, some energy is "lost" as heat
COMPOSITION OF MATTER: Atoms and Elements
- Basic Terms
- Elements are unique substances that cannot be broken down into simpler substances by ordinary chemical means.
- Four elements that make up roughly 96% of body weight _____________________________.
- Lesser Elements________________________________________________________
- Trace Elements - required in minute amounts, and are found as part of enzymes
- Atoms are the smallest particles of an element that retain the characteristics of that element.
- Atomic symbols to know are _________________________________________________
- Atomic Structure
- Each atom has a central nucleus with tightly packed protons and neutrons.
- Protons have a positive charge and weigh 1 atomic mass unit (amu).
- Neutrons do not have a charge and weigh 1amu.
- Electrons are found moving around the nucleus, have a negative charge, and are weightless (0 amu).
- Atomic Number
- equal to the number of protons of an element.
- unique for each element.
- Atomic mass
- the number of protons plus the number of neutrons in one atom
- electrons do not contribute to the weight of the atom
- Isotopes are structural variations of an atom.
- They have the same number of protons but differ in the number of neutrons the atom has.
- Atomic mass is an average of the relative weights of all isotopes of an element, taking into account their relative abundance in nature.
- Radioisotopes are heavier, unstable isotopes of an element that spontaneously decompose into more stable forms
- The time required for a radioactive isotope to lose one-half of its radioactivity is called the half-life. Example I131
- Periodic Table
HOW MATTER IS COMBINED: Molecules and Mixtures
- Molecules and Compounds
- A combination of two or more atoms is called a molecule.
- If two or more atoms of the same element combine it is called a molecule of that element.
- If two or more atoms of different elements combine it is called a molecule of a compound.
- Molecular formulas depict the elements present and the number of each atom present in the molecule
- H2 C6H12O6 H2O
- Mixtures
- Mixtures are substances made of two or more components mixed physically.
- Solutions are homogeneous mixtures of compounds that may be gases, liquids, or solids.
- The substance present in the greatest amounts is called the solvent.
- Substances present in smaller amounts are called solutes.
- Colloids or emulsions are heterogeneous mixtures that do not settle out.
- Suspensions are heterogeneous mixtures with large, often visible solutes that tend to settle out.
- Distinguishing Mixtures and Compounds
- The main difference between mixtures and compounds is that no chemical bonding occurs between molecules of a mixture.
- Mixtures can be separated into their chemical components by physical means; separation of compounds is done by chemical means.
- Some mixtures are homogeneous, while others are heterogeneous; all compounds are homogeneous.
CHEMICAL BONDS an energy relationship between the electrons of the reacting atoms
- Electron shells, or energy levels, surround the nucleus of an atom
- Bonds are formed using electrons in outermost energy level (valence shell)
- Octet rule - except for the first shell which is full with two electrons, atoms interact in a manner to have eight electrons in their valence shell
- Inert elements have their outermost energy level fully occupied by electrons
- Reactive elements do not have outermost energy level fully occupied by electrons
- Types of Chemical Bonds (ionic, covalent, hydrogen)
- Ionic Bonds
- Ions are charged atoms resulting from the gain or loss of electrons
- Anions have gained one or more electrons
- Cations have lost one or more electrons
- Ionic bonds form between atoms by the transfer of one or more electrons
- Ionic compounds form crystals instead of individual molecules
- Example: NaCl (sodium chloride)
- Covalent bonds formed when atoms share electrons
- Some atoms are capable of sharing two or three electrons between them, resulting in double covalent or triple covalent bonds.
- Polar Molecule - results when electrons are not shared equally in covalent bonds
- water is an important polar molecule
- molecule with a slightly negative end and a slightly positive end - dipole
- soluble in water
- Nonpolar Molecule - electrons shared equally (insoluble in water)
- Hydrogen bonds are weak attractions that form between partially charged atoms found in polar molecules.
- Too weak to bind atoms together
- Important as intramolecular bonds, gives molecule a three-dimensional shape
- Formed between water molecules
- Important for protein and nucleic acid structure
- Review
- Chemical reactions occur whenever bonds are formed, rearranged, or broken.
- A chemical equation describes what happens in a reaction.
- Are written in symbolic form using chemical equations
- Chemical equations contain:
- Number and type of reacting substances, and products produced
- Balanced in accordance with the conservation of matter
- Evidenced by - temp change; color change; new products
- Rate is regulated by- temperature, concentration, particle size and catalysts
- Patterns of Chemical Reactions
- In a synthesis(combination) bonds are formed
- In a decomposition reaction bonds are broken
- Exchange (displacement) reactions involve both synthesis and decomposition reactions.
- Reversible Reaction - the products can change back to the reactants
- Energy Flow in Chemical Reactions
- Exergonic reactions release energy as a product, while endergonic reactions absorb energy.
INORGANIC COMPOUNDS
- Electrolytes - Acids, Bases, and Salts (substances that release ions in water (dissociate))
- Acids - proton donors (H+)
- electrolytes that release hydrogen ions in water
- pH less than 7 (acidic)
- Bases - proton acceptors or OH-
- substances that release ions that can combine with hydrogen ions
- pH greater than 7 (alkaline)
- Salts- no H+ or OH-
- pH scale - indicates the concentration of hydrogen ions in solution
- Buffers - prevent abrupt changes in pH that would be damaging to living
- Weak acids (example - acetic acid); proteins
- Physiological pH - 7.35
- pH above -->alkalosis
- pH below -->acidosis
- Carbonic acid-bicarbonate system
- Carbonic acid dissociates, reversibly releasing bicarbonate ions and protons
- The chemical equilibrium between carbonic acid and bicarbonate resists pH changes in the blood
- Water - most abundant compound in living material
- Acts as a lubricant and shock absorber
- important role in transporting chemicals in the body
- two-thirds of the weight of an adult human
- major component of all body fluids
- medium for most metabolic reactions
- can absorb and transport heat - maintains body temperature
- high heat of vaporization
- high specific heat
- Oxygen (O2 )
- used by organelles to release energy from nutrients
- necessary for survival
- Carbon dioxide (CO2)
- waste product released during metabolic reactions
- must be removed from the body
- Inorganic salts - abundant in body fluids
- sources of necessary ions (Na+, Cl-, K+, Ca ++, etc.)
- play important roles in metabolic processes
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