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A & P Ch. 2: Chemical Basis of Life
Transcript of A & P Ch. 2: Chemical Basis of Life
Chemical Basis of Life
A. The study of chemistry is essential for the study of physiology because body functions depend on cellular functions that, in turn, result from chemical changes.
Compounds are chemical combinations.
Elements needed by the body in large amounts are called bulk elements
Bulk element examples: carbon, hydrogen, oxygen, nitrogen, sulfur, & phosphorus
Elements needed by the body in small amounts are called trace elements
Trace elements are used by the body for parts of enzymes
Ultratrace elements are elements needed
by the body in very small amounts &
are toxic in large 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
The central portion of an atom is the nucleus
Nucleus contains protons and usually neutrons
Electrons have a negative charge
Electrons are located around the nucleus
Protons have a positive charge
Neutrons are electrically neutral
Nucleus of an atom is positively charged
Complete atom is electrically neutral
II. Structure of Matter
A & P Chapter 2: Chemical Basis of Life
B. Biochemistry is the 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
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
Atoms of the same element can vary
in atomic weights because their # of neutrons may vary
An oxygen atom (atomic weight of 16) w/an atomic weight of 17 has 8 protons and 9 neutrons
Atoms that have the same atomic #'s but different atomic weights
# of electrons in an atom equals the # of protons
Radioactive isotopes release atomic radiation
E.g. isotopes of oxygen, iodine, iron, phosphorus, & cobalt
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 may combine to form a molecule
Molecular formula depicts the #'s & kinds of atoms in a molecule
Subscripts in molecular formula indicate how many atoms of each element are present
Atoms of different 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
A. A molecular formula represents the #'s & types of atoms in a molecule
B. A structural formula depicts the arrangement of atoms within a molecule.
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
is most abundant compound in cells & is a solvent in which chemical reactions occur; water transports chemicals & heat.
Inorganic Substances (cont.)
releases energy from glucose and other nutrients; this energy drives
is produced when metabolism releases energy.
provide a variety of ions that metabolic processes require.
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.
C. Proteins serve as structural materials, energy sources, hormones, cell surface receptors, & enzymes.
speed chemical reactions w/out being consumed.
are building blocks of proteins.
3. Proteins vary in #'s, types, & sequences of their amino acids.
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
proteins (lose structure & function).
are genetic material & control cellular activities.
1. Nucleic acid molecules are composed of nucleotides.
2. Two types of nucleic acids are RNA & DNA.
molecules store info. that cell parts use to construct specific protein molecules;
molecules help synthesize proteins.