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A & P Ch. 2: Chemical Basis of Life

Hole's Anatomy & Physiology 10th Edition
by

Cynthia Boylan

on 27 September 2018

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Transcript of A & P Ch. 2: Chemical Basis of Life

Ch. 2:
Chemical Basis of Life

A. Study of chemistry essential for study of physiology; body functions depend on cellular functions that, in turn, result from chemical changes.
Compounds are chemical combinations.
Elements needed in lg amts are called
bulk
elements
Bulk element E.g.: carbon, hydrogen, oxygen, nitrogen, sulfur, & phosphorus
Elements needed in sm. amts are called
trace
elements
Trace elements used for parts of enzymes
Ultratrace
elements are needed in very sm. amts, & toxic in lg amounts

Elements are composed of particles called atoms
Atoms that make up elements are chemically identical to one another, but they differ from the atoms that make up other elements
B. Atomic Structure
Central portion of an atom =
nucleus
Nucleus contains protons & usually neutrons
Electrons
= negative charge; located around nucleus
Protons
= positive charge
Neutrons
= electrically neutral
Nucleus
= positively charged
Complete atom is electrically neutral
II. Structure of Matter
A & P Chapter 2: Chemical Basis of Life
I. Introduction
B. Biochemistry=study of chemistry in living organisms.
A. Elements & Atoms
Matter is anything that has mass and takes up space
All matter is composed of elements
E.g. iron, copper, silver, gold, aluminum, carbon, hydrogen, & oxygen
Atoms of different
elements have different #'s
of protons
Atomic #
=the # of protons in atoms of a particular element
Carbon has atomic # of 6
Carbon atom contains 6 protons
Weight of atom primarily due to weight of protons & neutrons
Atomic weight
of atom =# of protons + # of neutrons in each of element's atoms
Atomic weight of carbon=12
Carbon atom=6 protons
+ 6 neutrons
Isotopes
Atoms of the same element can vary
in atomic weights because of their # of neutrons
An oxygen atom (atomic weight of 16) w/an atomic weight of 17 has 8 protons and 9 neutrons
Atoms have same atomic #'s but different atomic weights
# of electrons in an atom equals the # of protons
Isotopes (cont.)
Radioactive isotopes release atomic radiation
E.g. isotopes of oxygen (O), iodine (I), iron (Fe), phosphorus (P), & cobalt (Co)
3 common forms of atomic radiation are
alpha
=made of particles from atomic nuclei (2 protons & 2 neutrons)
beta
=consists of electrons
gamma
=most penetrating type of atomic radiation
Molecules & Compounds
2 or more atoms combine to form molecules
Molecular formula depicts the #'s & kinds of atoms in a molecule
Subscripts in molecular formula indicate # atoms of each element
Atoms of diff elements combine molecules of substances to form compounds
Bonding of Atoms
Bonds form when atoms combine
Electrons of an atom are in energy shells
1st electron shell can hold 2 electrons
2nd shell can hold 8 electrons
3rd shell of an atom w/atomic number 18 will hold 8 electrons
Innermost shells filled first
Atom Diagram
5. Formulas
A. Molecular formula represents the #'s & types of atoms in a molecule
B. Structural formula depicts arrangement of atoms within a molecule.
6. Chemical
Reactions
A. Breaks or forms bonds between atoms, ions, or molecules
B. Three types of chemical reactions:
synthesis
A + B = AB
decomposition
AB = A + B
exchange
AB + CD = AD + CB
Chemical reactions (cont.)
C. Many reactions are reversible. Direction of the reaction depends on proportions of reactants & end products, energy available, & presence of catalysts.
III. Chemical Constituents of Cells
Molecules that have carbon & hydrogen atoms are organic & are usually nonelectrolytes. Other molecules are inorganic & are usually electrolytes.
1. Inorganic substances
A.
Water
= most abundant compound in cells & solvent in which chemical reactions occur; water transports chemicals & heat.
Inorganic Substances (cont.)
B.
Oxygen
releases energy from glucose and other nutrients; this energy drives
metabolism
.
C.
Carbon dioxide
is produced when metabolism releases energy.
D.
Salts
provide a variety of ions that metabolic processes require.
2. Organic
substances
A. Carbohydrates provide much of energy that cells require & also contribute to cell structure; basic building blocks are simple sugar molecules.
B. Lipids, such as fats, phospholipids, & steroids, supply energy & build cell parts. Basic building blocks of fats-the most common lipid-are molecules of glycerol & fatty acids.
2. Organic
substances (cont.)
C. Proteins serve as structural materials, energy sources, hormones, cell surface receptors, & enzymes.
1.
Enzymes
speed chemical reactions w/out being consumed.
2.
Amino acids
are building blocks of proteins.
3. Proteins vary in #'s, types, & sequences of their amino acids.
2. Organic
substances (cont.)
4.
Amino acid chain
of a protein molecule folds into a complex shape (conformation) that is maintained largely by hydrogen bonds.
Excessive heat, radiation, electricity, altered pH, or various chemicals can
denature
proteins (lose structure & function).
D.
Nucleic acids
are genetic material & control cellular activities.
1. Nucleic acid molecules are composed of nucleotides.
2. Two types of nucleic acids are RNA & DNA.
3.
DNA
molecules store info. that cell parts use to construct specific protein molecules;
RNA
molecules help synthesize proteins.
Full transcript