1.1 Fundamental Chemistry of Life Flashcards
Element definition
An element is a pure substance that cannot be broken down into simpler substances using ordinary chemical or physical techniques.
The smallest particle of an element is an ____.
atom
Chemical compound definition
A chemical compound is a stable combination of
different elements that are held together by chemical bonds.
Which four elements make up
96% of the weight of a living organism?
Carbon, hydrogen, oxygen and nitrogen
Definition of trace elements
Elements that are required by organisms and are found in such small amounts
A deficiency in any trace element can lead to _________ _________.
health problems
Why does an atom have no net charge?
An atom has no net charge because the number of protons is equal to the number of electrons.
Isotope definition
Isotopes are different forms of the
same element, with different atomic masses.
Because isotopes of the same element
have the same number of protons and electrons, they behave _______ ______ _____ in a
chemical reaction.
exactly the same
Radioisotope definition
A radioactive isotope of an element
Radioactive decay continues at a ______ rate, with a constant proportion of radioisotope atoms breaking down during a given time interval.
steady
The rate of decay of a radioisotope is _________ of chemical reactions or environmental conditions,
such as ________ or _______.
independent; temperature; pressure
Radioisotopes generally behave the _______ way in cells as non-radioactive isotopes of the same element.
same
True or false:
Radioisotopes are used to study many biochemical reactions and to perform basic
techniques, such as DNA sequencing.
true
How does the arrangement of electrons determine the chemical properties of an atom?
Only electrons are usually directly involved in a chemical reaction.
Orbital definition
A region of space that is occupied by electrons located around the nucleus of an atom
True or false:
Even though one or two electrons may occupy a given orbital, the least stable and balanced condition occurs when the orbital contains two electrons.
False
The MOST stable and balanced condition occurs when the orbital contains 2 electrons
Electron orbitals are grouped into energy levels, which are sometimes called ________ ______.
energy shells
The lowest energy shell of an atom is
______ to the nucleus.
closest
True or false:
The second and third energy shells hold up to eight and 18 electrons, respectively.
True
The farther away the electron is from the nucleus, the ________ its energy.
greater
Valence electrons definition
Valence electrons are the electrons in an atom’s outermost energy shell, or valence shell.
Atoms with an outermost energy shell that is not completely filled with electrons tend to be chemically __________ atoms.
reactive
Atoms with a completely filled outermost
energy level are chemically ________.
inactive (inert)
Atoms can also become more _______ when they share electrons in such away that their
_________ orbitals are filled.
stable; valence
The _______ of electrons in the valence shells of atoms creates what are called _________ electron orbitals.
sharing; hybridized
In a hybridized electron orbital, there is a
direct ________ of the valence electron orbitals of the two atoms, so the orbital is a __________ of two different orbitals.
overlap; combination
Sharing electrons is the most common way for atoms to _______ and form __________ molecules.
bond; biological
Atoms of reactive elements combine with each other to form compounds, these atoms form a _______ attraction to one another called a _________ ________.
stable; chemical bond
Ionic bond definition
a bond that results from the attraction between two oppositely charged atoms or molecules
Cation vs. Anion
Cation - an ion that has a positive charge
Anion - an ion that has a negative charge
Ions are very strongly attracted to ______ molecules. As a result, ionic compounds tend to __________ and dissolve in water, forming ___________ ions.
water; dissociate; hydrated
True or false:
Covalent bonds form when atoms share two or more pairs of valence electrons.
False
Covalent bonds form when atoms share ONE or more pairs of valence electrons
The strength of a covalent bond
depends on the _____________ of the atoms involved in the sharing of the electron pair.
electronegativity
Electronegativity definition
Electronegativity is the measure of an atom’s attraction for additional electrons.
The number of covalent bonds that an atom can form is usually equal to the number of additional _________ needed to fill its __________ shell.
electrons; valence
True or false:
The number and tetrahedral arrangement of the bonds around a carbon atom allow carbon atoms to link together in more complicated biological compounds.
True
You can predict the arrangement of the bond angles around an atom using the ___________________________ theory
valence shell electron pair repulsion (VSEPR)
The VSEPR theory states that because electrons
are _______ charged, valence electron pairs ______ one another and move as far apart
from one another as possible.
negatively; repel
The more electronegative an atom is, the more
___________ it attracts electrons.
strongly
Electronegativity _________ as the distance between the electrons and the nucleus ___________.
increases; decreases
The unequal sharing of electrons between two atoms with different electronegativity
results in a _______ ________ bond.
polar covalent
The atom that attracts the valence electrons more strongly carries a partial ________ charge, which results in the other atom carrying a partial ______ charge.
negative; positive
True or false:
The more electronegative oxygen pulls the electrons closer, so the oxygen atom has a partial positive charge.
False
The oxygen atom has a partial NEGATIVE charge
Polar molecules _________ and align themselves to other polar molecules and tend to be _______ in water.
attract; soluble
Intermolecular force definition
The force of attraction between two molecules
Van der Waals forces definition
Very weak attractions between two molecules, or
parts of molecules, when they are close together
Hydrogen bond definition
The attractive force between a partially positively charged hydrogen atom and a partially negatively charged atom in another molecule
True or false:
Hydrogen bonds are the strongest and most biologically significant form of van der Waals forces.
True
Although most of the strongest bonds in living organisms are covalent, weaker hydrogen bonds
are crucial to the function of _____ and __________ __________
cells; cellular processes.
The weaker attractive force of hydrogen bonds makes them much easier to _____ than covalent or ionic bonds, especially when there is an increase in __________, which increases the __________ of the molecules.
break; temperature; movement
Long linear ______ molecules have numerous OH functional groups and are able to form very _______ solid fibres.
cellulose; strong
Globular shaped molecules such as ________ have fewer accessible atoms for van der Waals forces and therefore tend to form less ______ solids.
starches; rigid
All chemical reactions involve the _______ and formation of chemical bonds, thereby changing the ________ of atoms and ions.
breaking; arrangements
What are the four major types of chemical reactions that are common in biological processes?
Dehydration, hydrolysis, neutralization, and redox reactions.
Dehydration reaction
Also called condensation reactions, consist of the removal of an -OH and an -H from two reactant molecules
The -OH and -H form a water molecule, while the two reactant molecules are joined together
Dehydration reactions are the most common method used by cells to _____ smaller molecules and assemble extremely large _____________, such as complex carbohydrates and proteins.
join; macromolecules
Hydrolysis reaction definiton
A chemical reaction in which water is used as a reactant to split a larger molecule into smaller
subunits
Neutralization reaction definition
A reaction in which an acid and a base combine to create a salt and water
Redox reaction definition
During a redox reaction (named for “reduction” and “oxidation”), electrons are lost from one atom and gained by another atom.
Oxidation refers to the ______ of electrons. The result is an ________ molecule or atom.
loss; oxidized
The oxidation of one molecule is always linked to the _________ of another molecule.
reduction
The term reduction refers to the _____ of electrons. In a redox reaction, the oxidizing
agent is the molecule or atom being ________.
gain; reduced
What is the reducing agent in a redox reaction?
The reducing agent is the molecule
or atom being oxidized.
The term “oxidation” also refers to the transfer of entire _______ atoms (and their electrons) from ______ electronegative atoms to _____
electronegative atoms.
hydrogen; less; more
True or false:
During oxidation reactions in biological systems, the electrons involved are more strongly attracted to the oxidizing agent.
True
Redox reactions involve electrons moving from where they are ______ held to where they are
more ______ held.
weakly; strongly
Redox reactions are responsible
for most of the _______ _______ within cells.
energy transfer
Differences in electronegativity result in _______ ________.
bond polarity
Hydrolysis occurs when a bond in a large molecule is _______, and ______ is added to the resulting subunits.
broken; water
How do bonding arrangements in a molecule affect the shape of the molecule?
To minimize their energy, electron pairs in atoms move as far away from each other as possible, which causes the bonds to be at different angles from one another.
Compare ionic bonds with covalent bonds.
Ionic bonds form when an electron is transferred from one atom to another, and the resulting ions are attracted to each other.
Covalent bonds form when atoms share electrons to fill their valence shell.
How can the atomic composition of a molecule affect its polarity?
For a molecule to be polar it must contain atoms that differ in electronegativity and the resulting electronegative bonds must be arranged asymmetrically in the molecule.
How can the shape of a molecule affect its polarity?
The asymmetrical shape of a molecule containing polar bonds can result in an overall unbalanced
distribution of charge, making the molecule as a whole polar.
What effect do the polarity, size, and shape of a
molecule have on the physical properties of the
molecule?
Polarity, size, and shape can affect the solubility, melting and boiling points, and brittleness
of molecules.
How does polarity, size, and shape of a
molecule influence intermolecular forces?
Larger molecules have greater number of intermolecular forces, so the molecule is held more tightly to another molecule.
Linear molecules also have greater intermolecular forces than globular molecules because of their ability to get closer together.
Polar molecules have stronger forces of attraction between them.
How do polar covalent bonds and non-polar
covalent bonds differ?
Electrons are not shared equally in a polar covalent bond while electrons are shared relatively equally in non-polar covalent bonds
In a bond between nitrogen and hydrogen (N-H),
which atom will the electrons be closer to?
Nitrogen has a higher electronegativity than hydrogen, so the electrons will be closer to the
nitrogen atom
Oxygen plays a major role in biological molecules. Explain how oxygen plays a role in polarity, bond shape, and redox reactions.
Oxygen has a very high electronegativity, so it strongly attracts electrons of other elements and forms polar bonds.
Oxygen has two pairs of non-bonding electrons in its out orbital and therefore forms two bonds that are not aligned—oxygen produces
“bent” molecules.
Oxygen also plays a role in redox reactions. It is frequently the oxidizing reagent because of its strong electronegativity in a reaction.
In what ways do hydrogen bonds produce
attractive forces between molecules?
Hydrogen bonds produce attractive forces by lining up partially positively charged hydrogen atoms with a partially negative charged atoms of different molecules.
How do hydrogen bonds influence the physical
properties of water?
Hydrogen bonds give water a high heat capacity, high melting and boiling points, and high
surface tension, cohesion and adhesion.
Describe dehydration and hydrolysis. How are these two types of reactions related?
Dehydration is the removal of –OH and –H from two reactant molecules, which allows the
reactant molecules to form a bond, as well as creating water.
Hydrolysis is the breaking of a bond between two subunits and the addition of water in the form of –OH and –H to the subunits.
Dehydration is the reverse of hydrolysis, and vice versa.
Can a reduction reaction occur independently
of an oxidation reaction, or vice versa? Why or
why not?
The reduction or oxidation of one molecule always implies the oxidation or reduction of
another molecule; they cannot occur independently.
All organic compounds inside of living organisms are made of _ _ _ _
C, H, O, N
Matter is made up of small units called ______ which combine to form more complex structures called __________
atoms; molecules
elements are _____________ that can’t be broken down into simpler substances
pure substances
all organic compounds contain _______ atoms and may also contain ________ and ________
carbon, hydrogen, oxygen
which elements are included in the 96% composition of living things?
carbon, oxygen, hydrogen and nitrogen
which elements are included in the 4% composition of living things?
calcium, phosphorus, potassium, sulphur, sodium, chlorine, magnesium
which elements are trace elements?
iodine and iron
what does the number of protons determine?
the type of element
why are atoms neutral?
they have the same number of protons as electrons
atomic mass
the weight of protons and neutrons (electrons are so small we ignore their mass)
isotope
a form of an element that has the same number of protons but different number of neutrons
(behave exactly the same in chemical reactions)
radioisotopes
unstable isotope that decays giving off radiation
-transforms into an atom of another element
example of a radioisotope
14C is unstable and one neutron splits into an electron
and a proton.
When this happens 14C decays into 14N
radioactive decay
occurs at a steady and
measurable rate
can be used to determine the
age of rocks and fossils.
radioactive tracers
radioisotopes can be used
to trace the path of atoms throughout the body.
ionic bonds
bond that forms between two oppositely charged atoms/molecules
-positive cation and negative anion
covalent bonds
when atoms share valence electrons
electronegativity
the measure of an atom’s attraction to shared electrons
high electronegativity= _____ attraction of electrons
strong
low electronegativity= _____ attraction of electrons
weak
why is oxygen slightly more negative in an H2O molecule?
oxygen has a stronger pull on electrons and becomes slightly more negative
why is hydrogen slightly more positive in an H2O molecule?
hydrogen has a weaker pull on electrons and becomes slightly more positive
polar covalent bond
an unequal sharing of electrons
_____ molecules are generally water soluble
polar
_____ molecules are generally NOT water soluble
non-polar
intermolecular forces
forces of attraction between molecules
hydrogen bonds
attractive force between slightly positive hydrogen atoms and a slightly negative atom in another molecule
-e.g. water
dipole dipole force
attractive force between slightly positive atoms (not hydrogen) and a slightly negative atom in another molecule
van der Waal forces
very
weak attractions between two
molecules, or parts of molecules
when they are close together
Larger molecules have larger
forces of attraction than smaller
molecules
how do van der Waal forces form
Form from the momentary
attractions of electrons to nuclei
of other molecules
dehydration rxn is also known as …
condensation rxn
dehydration rxn
Involves the joining of two molecules through the
removal of water
In which reaction does one molecule lose a Hydrogen atom while the other loses an –OH group?
dehydration/condensation rxn
hydrolysis rxn
involves splitting a larger
molecule apart by adding a water molecule
Which reaction involves adding an –OH group to one molecule and a
Hydrogen atom to the other?
hydrolysis rxn
neutralization rxn
a reaction in which
an acid and a base combine to create a salt and
water
redox rxn
electron transfer rxn
reduction
gaining of electrons
oxidation
loss of electrons
