Anatomy and Physiology Chapter 2: The Chemistry of Life

Biochemistry

The study of molecules that compose living organisms (carbohydrates, fats, proteins, nucleic acids)

Element

Simplest form of matter to have unique chemical properties

Atomic Number

Number of protons in its Nucleus

6 Elements that make up 98.5% body weight

Oxygen, Carbon, Hydrogen, Nitrogen, Calcium, Phosphorus

Trace Elements

Present in minute amounts, but play vital roles in physiology (on demand/varies based on need)

Minerals

Inorganic elements that extracted from the soil by plants and passed up the food chain to humans and other organisms (3/4 Ca,P + ¼ Cl, Mg, K, Na, S = 4% body weight)

Minerals function for the body

Contributes to body structure (bone, nucleic acids, ATP, cell membranes) and enables enzymes and organic molecules to function

Electrolytes

Mineral salts needed for nerve and muscle function; substance that that ionize in water and forms solutions capable of conducting electric current; important for their chemical, physical, and electrical effects of the body

Democritus

Reasoned that matters are made of particles so small that nothing can cut them apart and called them atoms

Dalton

Developed an atomic theory

Neil Bohr

Proposed planetary model of atomic structure in 1913

Nucleus Components

At the center of an atom composed of Protons (single positive charge p+) and Neutrons (no charge n)

Atomic Mass Unit (amu)

The mass of an atom and their subatomic particles; each proton or neutron weigh approximately 1

Atomic Mass

Approximately equals its total number of protons and neutrons

Electrons

Single negative charge; goes around the nucleus made up of one or more concentric clouds. Function is to determine the chemical properties of an atom.

Concentric Clouds (electron shells)

The more energy an electron has, the farther away from the nucleus its orbit lies (1st shell= 2, 2nd shell= 8)(only 4 shells exist in the human body)

Valence Electrons

Electrons of the outermost shell and determine the chemical bonding properties of an atom

Isotopes

Varieties of an element that differ only in the number of neutrons

Atomic Weight (relative atomic mass)

Accounts for the fact that an element is a mixture of isotopes

Radioscope

Unstable isotopes that decay into more stable isotopes and give off radiation

Radioactivity

Process of decaying

Ionizing Radiation

The higher the energy, the more electrons are ejected; converting atoms to ions; destroys molecules and produced dangerous free radicals/ions in human tissue

Sievert (Sv)

Measurement/standard unit of radiation dosage

Physical half-life of radioisotopes

Time required for 50% to decay to a stable state

Biological half-life of radioisotopes

Time required for 50% to disappear from the body

Madame Curie

First women in the world to receive a PhD, coined the term radioactivity, discovered radioactivity of polonium +radium, trained physicians in use of x-rays + pioneered radiation therapy for cancer treatment

Ions

Charged particle (atom or molecule) with unequal number of protons and electrons

Ionization

Transfer of electrons from one atom to another (one gains and one loses)

Anion

Particle that has a net negative charge (due to gain of electrons)

Cation

Particle that has a net positive charge (due to loss of electrons)

Salts

Electrically neutral compounds of cations/anions. They readily dissociate in water into their respective ions, and act like electrolytes

Electrolyte Importance

Chemical reactivity, osmotic effects, electrical excitability of nerve + muscle (one of the most important balances consideration inpatient care)

Free Radicals

Unstable, highly reactive chemical particles with odd number of electrons. represented with a dot. Produced by normal metabolic reactions, radiation, certain chemicals

Antioxidant

Chemical that neutralizes free radicals

Molecules

Chemical particles composed of 2 or more atoms united by a covalent chemical bond

Compounds

Molecules composed of 2 or more different elements

Molecular Formula

Identifies constituent elements and how many atoms of each are present

Structural Formula

Identifies location of each atom

Isomers

Molecules with identical molecular formulae but different arrangements of atoms

Molecular Weight (MW)

The sum of the atomic weights of its atoms

Chemical Bonds

Hold atoms together within a molecule, or attract one molecule to another

Ionic Bond

Attraction of a cation to an anion and is easily broken by water (weak bond) (giving an electron up/gaining one)

Covalent Bond

Atoms share one or more pairs of electrons

Singular Covalent Bond

Nuclei share 1 pair of electrons

Double Covalent Bond

Nuclei share 2 pairs of electrons

Non-Polar Covalent Bond

The electrons of the 2 atoms share equal time around each nucleus; strongest of all chemical bonds

Polar Covalent Bonds

Electrons spend unequal time around the nuclei, resulting in slightly positive and negative regions in the molecule

Hydrogen Bond

Weak attraction between a slightly positive hydrogen atom in one molecule and a slightly negative oxygen or nitrogen atom in another atom (Water molecules are attracted to each other by hydrogen bonds)

Van der Waals Forces

Weak, brief attraction due to random disturbances in the electron clouds of adjacent atoms

Mixture

Consist of substances that are physically blended but not chemically combined

Water

50-75% of body weight, atoms are joined by polar covalent + hydrogen bonds, molecule is V shaped

Solvency

The ability to dissolve other chemicals; universal solvent (dissolves a broad range of substances). Function is to carry out metabolic reactions and transport substances

Hydrophilic

Substances that dissolve in water, these molecules are polarized or charged

Hydrophobic

Substances that do not dissolve in water, these molecules are nonpolar or neutral

Adhesion

Tendency of one substance to cling to another (Water adheres to large membranes reducing friction around organs/lubrication)

Cohesion

Tendency of molecules of the same substance to cling to each other: water is very cohesive due to its hydrogen bonds: surface film on surface of water is due to molecules being held together by surface tension

Chemical Reactivity

Waters ability to participate in chemical reactions (ionize); hydrolysis and dehydration synthesis

Thermal Stability

Helps to stabilize the internal temperature of the body

Heat Capacity

Amount of heat needed to raise the temperature of 1 g of a substance by 1 °C

Calorie (cal)

Base unit of heat (amount of heat that raises the temperature of 1 g of water 1 °C)

Solution

Consists of particles called the solute mixed with a more abundant substance (usually water) called the solvent

Solution defining properties

• Solute particles under 1 nm

• Solute particles do not scatter light

• Will pass through most membranes

• Will not separate on standing

Colloid

Colloids in the body are often mixtures of protein and water, many can change from liquid to gel state within and between cells

Colloid defining properties

• Particles range from 1–100 nm in size

• Scatter light and are usually cloudy

• Particles too large to pass through semipermeable membrane

• Particles remain permanently mixed with the solvent when mixture stands

Suspension

Blood cells in our blood plasma

Suspension defining properties

• Particles exceed 100 nm

• Too large to penetrate selectively permeable membranes

• Cloudy or opaque in appearance

• Separates on standing

Emulsion

Suspension of one liquid in another

Acid

Proton donor (releases H+ ions in water)

Base

Proton acceptor (accepts H+ ions or releases OH− ions)

pH

Measure of acidity derived from the molarity of H+ (Maintaining normal (slightly basic) pH of blood is crucial for physiological functions)

pH Scale

Ranges from 1-14. a pH of 7 is neutral, pH below 7 is acidic, pH above 7 is basic (alkaline)

Buffer

Chemical solutions that resist change (pH regulation)

Weight Per Volume

Weight of solute in a given volume of solution

Percentage

Might be weight of solute (solid) per volume

Might be volume of solute (liquid) per volume of solution

Molarity (M)

Number of moles of solute per liter of solution. The physiological effect of a chemical depends on how many molecules of it are present in a given volume, not weight of chemical

Energy

The capacity to do work (move something)

Potential Energy

Energy contained in an object because of its position or internal state, but not doing work at the time

Chemical Energy

Potential energy in molecular bonds (when chemical reaction occurs energy is released)

Electrical Energy

Can be both potential and kinetic

P: when charged particles have accumulated at a point

K: when particles starting from their potential state begin to move and create an electrical current

Kinetic Energy

Energy in motion and is doing work at the time

Heat Energy

Kinetic energy; Molecular motion; temp of a substance is a measure of rate of this molecular motion (increased heat=increased rate)

Electromagnetic Energy

Kinetic energy of moving “packets” of radiation called photons

Chemical Reaction

Process in which a covalent or ionic bond is formed or broken

Chemical Equation

Symbolizes the course of a chemical reaction; reactants on left, products on right

Decomposition Reactions

Large molecule breaks down into two or more smaller ones (AB → A + B)

Synthesis Reactions

Two or more small molecules combine to form a larger one (A + B → AB)

Exchange Reactions

Two molecules exchange atoms or group of atoms (AB + CD → ABCD → AC + BD)

Reversible Reactions

Can go in either direction under different circumstances; symbolized with double-headed arrow (CO2 + H2O ↔ H2CO3 ↔ HCO3− + H+)

Law of Mass Action

Direction of reaction determined by relative abundance of substances on either side of equation

Equilibrium

when ratio of products to reactants is stable

Reactions

Occur when molecules collide with enough force and correct orientation

Concentration effect on Reactions

Increased concentration = increased rate of reaction rate (crowded, therefore collide with increased frequency)

Temperature effect on Reactions

Increased temp = increased rate or reaction rate (heat will increase motion of molecules, therefore collide with increased force+frequency)

Catalysts effect on Reaction

substance that temporarily binds to reactant & holds them in favorable position to react with each other, may change shape of reactant in ways more likely to react (increased catalyst = increased rate of reaction rate)

Metabolism

All chemical reactions in the body

Catabolism

Energy-releasing (exergonic) decomposition reactions. Function is breaking covalent bonds and producing smaller molecules from larger ones

Anabolism

Energy-storing (endergonic) synthesis reactions. Requires energy input

Oxidation

Any chemical reaction in which a molecule gives up electrons and releases energy

Oxidizing Agent

“Electron acceptor” whatever molecule takes the electrons (mostly oxygen)

Reduction

Any chemical reaction in which a molecule gains electrons and energy