Anatomy & Physiology - Chapter 2

Chemistry of Life

Atoms

Atoms are so small they can be observed only with sophisticated equipment. For example, tunneling microscopes and atomic force microscopes (AFMs) can produce pictures of individual atoms. Atoms are composed of several kinds of subatomic particles: protons, electrons, neutrons.

Nucleus

At the core of each atom. Composed of positively charged protons and uncharged neutrons.

Atomic number

The number of protons in the nucleus.

Atomic mass

The number of protons and neutrons combined.

Electrons

Negatively charged electrons surround the nucleus at a distance. If an atom is neutral (carries no electrical charge), there is one electron for every proton. Electrons do not stay still. Instead, electrons keep darting about within certain limits called orbitals.

Proton

Positively charged particle in nucleus

Neutron

Noncharged particle in nucleus

Electrolytes

Compounds that form ions when dissolved in water.

Covalent bonds

Form when atoms share their outer energy to fill up

and thus become stable

Do not ordinarily easily dissociate

in water

Water and Aqueous Solution

Water is the solvent in which most other compounds or solutes are dissolved. When water is the solvent for a mixture (a blend of two or more kind of molecules), the mixture is called an aqueous solution.

Water

an inorganic compound, essential to life. Found in and around each cell, water is the most abundant compound in the body. It’s slightly glue like properties help to hold the tissues of the body together.

PH

Mathematical expression of relative H+

concentration in an aqueous solution

• pH 7 is neutral (neither acid nor base)

• pH values above 7 are basic; pH values below 7 are

acidic

Acids

Substance that shifts the H+/OH− balance

in favor of H+; opposite of base

Base

Substance that shifts the H+/OH− balance

against H+; also known as an alkaline; opposite

of acid

Buffer

A third way to adjust the body’s PH is by using buffers- chemicals in the blood that maintain PH. Buffers maintain PH balance by preventing sudden changes in the H+ ion concentration.

Types of Organic Compounds

Organic compounds are much more complex than inorganic compounds. The major types of organic compound found in the body: Carbohydrates, lipids, proteins and nucleic acids.

Carbohydrate Example

Monosaccharide (glucose, galactose, fructose)

Disaccharide (sucrose, lactose, maltose)

Polysaccharide (glycogen, starch)

Carbohydrate Functions

Used as a source of energy. Unit used to build other carbohydrates.

Lipid Example

Triglyceride (fat)

Phospholipid

Steroid

Lipid Component

One glycerol head, three fatty acid tails

Lipid Functions

Forms cell membrane

Protein Example

Structural proteins (fibers)

Functional proteins (enzymes, hormones)

Protein Components

Amino acids

Protein Functions

Form structures of the body

Facilitate chemical reactions

Carry signals

Regulate functions

Cholesterol

an important steroid lipid that performs several critical functions in the body. For example, it is embedded within cell membranes to help stabilize the bilayer structure. The body uses cholesterol as a starting point in making steroid hormones such as estrogen, testosterone, and cortisone (cortisol).

Enzymes

Catalysts: Help chemical reactions occur

Lock-and-key model: Each enzyme fits a particular

molecule like a key fits into a lock

Adenosine triphosphate (ATP)

A modified nucleotide used

to transfer energy from nutrients to cellular processes, thus

acting as an energy-transfer “battery”