Chapter 2 - The Chemical Basis of Life Flashcards
anything that occupies space and has mass
matter
amount of matter in an object
Mass
gravitational force acting on an object of a given mass
weight
international unit for mass
kilogram (kg)
simplest type of matter, having unique chemical properties
element
About 96% of the body’s weight results
from the elements __
oxygen
carbon
hydrogen
nitrogen
majority of the body’s weight is from __, it is also the most abundant element in the earth’s crust
oxygen (65%)
plays an especially important role in the chemistry of the body, due in part to
its propensity to form covalent bonds with itself and other molecules
carbon
(T/F) Elements can have multiple roles
and exist in different states in the body.
true (ex. mineralized calcium contributes to the solid matrix of bones, while dissolved calcium helps regulate enzyme activities and nervous system signaling)
the smallest particle of an element that has the chemical characteristics of that element.
atom
composed of atoms of only one kind
element (ex. element carbon is composed of only carbon atoms)
(T/F) Atoms are composed of subatomic
particles, some of which have an electrical charge.
true
three major types of subatomic particles
neutrons
protons
electrons
has no electrical charge
neutron
has one positive charge
proton
has one negative charge
electron
Things to remember:
- The positive charge of a proton is equal in magnitude to the negative charge of an electron.
- The number of protons and the number
of electrons in each atom are equal - Individual charges cancel each other, therefore, each atom is electrically neutral.
what forms the nucleus at the center of the atom?
Protons and neutrons
what moves charge moves around the nucleus?
Electron
accounts for 99.97% of an atom’s mass but only 1 ten-trillionth of its volume
nucleus
Most of the volume of an atom is occupied by
electrons
region where electrons are most likely to be found
electron cloud
equal to the number of protons in each atom
atomic number (because the number of electrons is equal to the number of
protons, the atomic number is also the number of electrons
there are how many naturally occurring elements?
90
responsible for most of the mass of atoms
Protons and neutrons (have about the same mass)
the number of protons plus the number of neutrons in each atom
mass number
how to find the number of neutrons?
subtract the number of protons from the mass number
are two or more forms of the same element
that have the same number of protons and electrons but a different number of neutrons
Isotopes
three isotopes of hydrogen (have 1 proton
and 1 electron, but hydrogen has no neutrons in its nucleus)
hydrogen
deuterium
tritium
have the same atomic number but different mass numbers
Isotopes
can be denoted using the symbol of the element preceded by the mass number (number of protons and neutrons)
Isotopes
unified atomic mass unit (u)
dalton (Da)
the average mass of its naturally
occurring isotopes, taking into account the relative abundance of each isotope.
atomic mass
value of Avogadro’s number, or 1 mole (abbreviated mol).
6.022 × 10^23
mass of 1 mole of a substance expressed
in grams is called the
molar mass
The chemical behavior of an atom is dependent on its
electrons
concentric rings around the nucleus
electron shells
maximum number of electrons a shell can hold:
The innermost shell (the shell closest to the nucleus) - maximum of 2 electrons
remaining shells - maximum of 8 electrons
outermost, valence shell - 8
(T/F) The number of electrons in the valence shell determines an atom’s chemical nature.
true
full valence shell
inert and does not form chemical bonds with other atoms
not fill valence shell
atom is chemically reactive and forms chemical bonds with other atoms to achieve a full valence shell, called an octet.
tendency of atoms to combine
with other atoms until each has 8 electrons (2 electrons for hydrogen) in its valence shell
octet rule
what determines the type of chemical bond?
The fate of electrons as being either transferred or shared
2 types of chemical bond
ionic or covalent
The decision whether an electron is transferred or shared between two atoms is determined by __
Electronegativity
ability of an atom’s nucleus to attract electrons.
Electronegativity
what atoms have a strong
electronegativity?
atoms that lack only 1 or 2 electrons from having an octet in their valence shell
what atoms have a weak electronegativity
atoms that lack 6 or 7 electrons from
having an octet in their valence shell
lacks only 1 electron from its valence shell to be full
hydrogen
(T/F) Hydrogen’s pull on electrons is less than
that of other atoms with more protons (low electronegativity)
True
How are covalent bonds formed?
When the electronegativities of two atoms
forming a chemical bond are similar, the atoms tend to share
How are ionic bonds formed?
when electronegativities are
very different, the atoms tend to transfer electrons
forms when atoms share one or more pairs of
electrons.
covalent bond (ex. two hydrogen atoms to form
a hydrogen molecule)
sharing of one pair of electrons by two atoms
single covalent bond.
results when two atoms share 4 electrons,
2 from each atom
double covalent bond
When electrons are shared equally between atoms, as in a hydrogen molecule, the bonds are called
nonpolar covalent bonds
atoms bound to one another by a covalent bond do not always share their electrons equally because in these situations the
electronegativity of one atom is stronger than the electronegativity of the other atom. Bonds of this type are called
polar covalent bonds
composed of two or more atoms chemically combined to form a structure that behaves as an independent unit.
molecule
substance resulting from the chemical combination of two or more different types of atoms.
compound
can be determined by adding up the atomic masses of its atoms (or ions)
molecular mass
are the weak electrostatic attractions
that exist between oppositely charged parts of molecules, or between ions and molecules
Intermolecular Forces
are much weaker than the forces producing
chemical bonding (include hydrogen bonds
and the properties of solubility and dissociation)
Intermolecular forces
results from the attraction of the
positive end of one polar molecule to the negative end of another
polar molecule
Intermolecular forces
If the positively charged hydrogen of one molecule is attracted to the negatively charged oxygen, nitrogen, or fluorine
of another molecule, a __ forms
hydrogen bond
ability of one substance to dissolve in another
Solubility
Four representations of picturing molecules
Chemical Formula
Electron-Dot Formula
Bond-Line Formula
Models
Cations and anions that dissociate in water that have the capacity to conduct an electric current
electrolytes
a recording of electric
currents produced by the heart
electrocardiogram (ECG)
Molecules that do not dissociate form solutions that do not conduct electricity
nonelectrolytes
A complete transfer of electrons between
two atoms results in separate positively
charged and negatively charged ions.
Ionic Bond
An unequal sharing of electrons
between two atoms results in a slightly
positive charge (δ+) on one side of the
molecule and a slightly negative charge
(δ−) on the other side of the molecule
Polar Covalent Bond
An equal sharing of electrons
between two atoms results in an
even charge distribution among
the atoms of the molecule.
Nonpolar Covalent Bond
The attraction of oppositely charged
ends of one polar molecule to another
polar molecule holds molecules or
parts of molecules together
Hydrogen Bond
occurs when atoms, ions, molecules, or
compounds interact either to form or to break chemical bonds
chemical reaction
substances that enter into a chemical reaction
reactants
substances that result from the chemical reaction
products
three important points about chemical reactions
- less complex reactants are combined to form a larger, more complex product.
- a reactant can be broken
down, or decomposed, into simpler, less complex products. - atoms are generally associated
with other atoms through chemical bonding or intermolecular forces; therefore, to synthesize new products or break down reactants, it is necessary to change the relationship between atom
when two or more reactants chemically
combine to form a new and larger product.
synthesis reaction
The synthesis reactions occurring in the body are collectively referred to as
anabolism
These reactions produce the molecules
characteristic of life, such as
ATP
proteins
carbohydrates
lipids
nucleic acids
the product of amino
acids bound together
water
Synthesis reactions in
which water is a product are called
dehydration reactions
How is ATP formed?
ATP, which is composed of adenosine and three phosphate groups, is synthesized from adenosine diphosphate (ADP), which has two phosphate groups, and an inorganic phosphate (H2PO4)
a larger reactant is chemically broken down into two or more smaller products.
decomposition reaction
decomposition reactions occurring in the body are collectively called
catabolism
All of the anabolic and catabolic reactions in the body are collectively defined as
metabolism
Reactions that use water in this manner are called
hydrolysis reactions
the reaction can run in the opposite direction, so that the products are converted back to the original reactants
reversible reaction
the amount of reactants relative to the amount of products remains constant.
equilibrium
Chemical reactions that result from the exchange of electrons between the reactants
oxidation-reduction reactions
The loss of an electron by an atom
oxidation
the gain of an electron
reduction
the capacity to do work
Energy
stored energy that could do work but is not doing so
Potential energy
is the form of energy that is
actually, doing work and moving matter
kinetic energy
results from the position or movement of
objects
Mechanical energy
a form of potential energy stored within
the chemical bonds of a substance.
Chemical energy
a form of energy that flows from a hotter object
to a cooler object
Heat energy
a measure of how hot or cold a
substance is relative to another substance
Temperature
(T/F) A chemical reaction occurs only when molecules with sufficient kinetic energy collide with each other.
true
the minimum amount of energy that the reactants must have to start a chemical reaction
Activation energy
are substances that increase the rate of chemical reactions
Catalysts
proteins that act as catalysts and increase
the rate of chemical reactions by lowering the activation energy necessary for the reaction to begin
Enzymes
generally deals with substances that do not
contain carbon, with lack of carbon-hydrogen bonds
Inorganic chemistry
the study of carbon-containing substances, with a few exceptions. (Carbon monoxide (CO), carbon dioxide (CO2), and bicarbonate ions (HCO3−)
Organic chemistry
formed when an atom of oxygen forms polar covalent bonds with two atoms of hydrogen.
water
attraction of water to another water molecule
Cohesion (ex. surface tension exhibited when water bulges over the top of a full glass without spilling over)
the same attractive force of
hydrogen bonds of water that will also attract other molecules.
Adhesion
combination of two or more substances physically blended together, but not chemically combined
mixture
any mixture in which the substances are uniformly distributed
solution
mixture containing materials that separate
from each other unless they are continually, physically blended together
suspension (ex. blood)
a mixture in which a dispersed substance
or particle is unevenly distributed throughout the mixture.
colloid
indicate the number of particles in a solution.
osmoles
reflects the number, not the type, of particles
in a solution
osmolality
1/1000 of an osmole
milliosmole
can alter body functions by releasing and binding protons
acids and bases
maintained by homeostatic mechanisms involving buffers, the respiratory system,
and the kidneys
normal balance of acids and bases
defined as a proton donor
acid
defined as a proton acceptor
base
dissociate almost completely when dissolved in water
Strong acids or bases
only partially dissociate in water
Weak acids or bases
a means of referring to the H+ concentration in a solution
pH scale
has equal concentrations of H+ and OH−;
neutral solution
Solutions with a pH less than 7
acidic
Solutions with a pH greater than 7 a
alkaline or basic
results if blood pH drops below 7.35, in which case the nervous system becomes depressed and the individual may become disoriented and possibly comatose
Acidosis
results if blood pH rises above 7.45. Then the nervous system becomes overexcitable, and the individual may become extremely nervous
or have convulsions.
Alkalosis
a compound consisting of a cation other than H+ and an anion other than OH−.
salt
are chemicals that resist changes in pH when either acids or bases are added to a solution.
buffers
Buffers prevent large changes in pH values by acting as
conjugate acid-base pairs
(T/F) The greater the buffer concentration, the more effectively it can resist a change in pH
true
an inorganic molecule consisting of two oxygen atoms bound together by a double covalent bond.
oxygen
consists of one carbon atom bound to two
oxygen atoms.
Carbon dioxide
four major groups of organic molecules essential to living organisms
carbohydrates
lipids
proteins
nucleic acids
organic molecules composed primarily of carbon, hydrogen, and oxygen atoms and range in size from small to very
large.
carbohydrates
Large carbohydrates are composed of numerous, relatively simple
building blocks called
monosaccharides
molecules that have the same number and types of atoms but differ in their three-dimensional arrangement
isomers (ex. glucose, fructose, galactose)
are composed of two
monosaccharides bound together through a dehydration reaction.
Disaccharides
glucose and fructose combine to form a disaccharide called
sucrose
glucose combined with galactose
Lactose
two glucose molecules joined together
Maltose
are long chains of monosaccharides
Polysaccharides
a multibranched polysaccharide
composed of many glucose molecules
Glycogen
main storage form of glucose in humans that is also an important energy-storage molecule.
Glycogen
two important polysaccharides
found in plants
Starch and cellulose
is an important
structural component of plant cell walls
cellulose
can be broken down and used as an energy
source when humans ingest
plants
Starch
can be broken down and used as an energy
source when humans ingest
plants
eliminated in the feces, where it provides bulk as humans, do not have the digestive enzymes necessary to break down such
Cellulose
a major group of organic molecules that are relatively insoluble in water.
Lipids
broken down by hydrolysis reactions in cells
to release energy for use by those cells.
fats
constitute 95% of the fats in l
the human body.
Triglycerides
Triglycerides consist of two different types of
building blocks:
one glycerol and three fatty acids
3-carbon molecule with a hydroxyl group attached to each carbon atom
Glycerol
consists of both an oxygen atom
and a hydroxyl group attached to a carbon atom
carboxyl group
contains only single covalent bonds between
the carbon atoms
saturated fatty acid
one or more double
covalent bonds between carbon atoms (
unsaturated fatty acid
one double covalent bond
between carbon atoms
Monounsaturated fats
two or more double covalent
bonds between carbon atoms
Polyunsaturated fats
unsaturated fats that have been chemically altered by the addition of hydrogen
Transfats
similar to triglycerides,
except that one of the fatty acids bound to the glycerol is replaced by a phosphate-containing region
Phospholipids
water-loving
hydrophilic
water-fearing
hydrophobic
composed of carbon atoms bound together into
four ringlike structures
steroid
an especially important steroid because other steroid molecules are synthesized from it.
Cholesterol
organic macromolecules that contain carbon,
hydrogen, oxygen, and nitrogen bound together by covalent bonds
Proteins
The basic building blocks for proteins
20 amino acid
Covalent bonds formed between amino acid molecules during protein synthesis
peptide bonds
determined by the sequence of the amino acids bound by peptide bonds
primary structure
results from the folding or bending of the polypeptide chain caused by the hydrogen bonds between amino acids
secondary structure
change in shape caused by the breaking of
hydrogen bonds.
denaturation
results from large-scale folding of
the protein driven by interactions within the protein and with the immediate environment
tertiary structure
results from the association of two
or more proteins to form a functional unit
quaternary structure
a protein catalyst that increases the
rate at which a chemical reaction proceeds without the enzyme being permanently changed
Enzymes
region of the enzyme that binds reactants and catalyzes their conversion
to products.
active site
an enzyme that catalyzes the breakdown of lipids
lipase
an enzyme that breaks down proteins
protease
are large molecules
composed of carbon, hydrogen, oxygen, nitrogen, and phosphorus
Nucleic Acids
genetic material of cells
Deoxyribonucleic acid (DNA)
contains the
information that determines the structure of proteins
DNA
play important roles in protein synthesis.
Ribonucleic acid (RNA)
The basic building blocks of DNA and RNA
nucleotides
Each nucleotide is composed of a
a __ to which a nitrogenous base and a phosphate
group are attached
monosaccharide
5-carbon monosaccharide for DNA; for RNA
deoxyribose; ribose
Consist of carbon and nitrogen atoms organized into rings.
Nitrogenous
bases
nitrogenous bases (5)
cytosine
thymine
uracil
guanine
adenine
two strands of nucleotides joined together to form a twisted, ladderlike structure
double helix
. Single-ringed bases
pyrimidines
double-ringed bases
purines
nucleotide of DNA
adenine
thymine
cytosine
guanine
e bases held together by
hydrogen bonds
Complementary base pairs
Complementary base pairs
Adenine and thymine
Cytosine and guanine
A sequence of DNA bases that directs the synthesis of proteins or RNA molecules
gene
nucleotide of RNA
thymine is replaced by uracil and can only be paired with adenine
an especially important molecule for storing and providing energy
in all living organisms. I
Adenosine triphosphate
