Bio 1 ch 2-3

Molecular mimics

can produce similar effects as the naturally occurring molecules

What are the four most abundant elements found in living systems?

Hydrogen, oxygen, nitrogen, and carbon

The behavior of an atom depends on the

valence electrons in the outermost electron shell

The fact that oxygen is an atom that is strongly electronegative means that

it more strongly pulls shared electrons toward itself when forming a covalent bond with a less electronegative atom

Weak chemical bonds such as hydrogen bond

form when a hydrogen atom that is covalently bonded to an electronegative atom like oxygen or nitrogen is attracted to another electronegative atom

The molecular shape of a biological molecule is important because

it determines how biological molecules recognize and respond to one another

Which statement is true of all atoms that are anions?

The atom has more electrons than protons.

Trace elements

are required by an organism in minute quantities

When one or more pairs of valence electrons are shared by two neutral atoms, what type of bond is formed?

A covalent bond

Which of the following subatomic particles has appreciable mass and lacks a charge?

Neutron

Radioactive tracers

are important tools in biological research and medicine

Which of the following statements is true about chemical reactions?

They involve the making and breaking of chemical bonds.

A covalent bond

is the sharing of a pair of valence electrons by two atoms

In a process called radiometric dating, scientists measure the __________ of an isotope to determine the age of the Earth

half-life

Orbitals are best described as

a three-dimensional space where an electron spends most of its time with no more than 1 other electron, forming a pair

In ionic interactions

the transfer of valence electrons results in a completed valence shell for each ion

A covalent bond is likely to be polar if

one of the atoms sharing electrons is much more electronegative

When a very electronegative atom strips a valence electron away from its partner, __________ form.

ions

The number of protons in an uncharged atom

equals the number of electrons

When the proton number and electron number are unequal, the atom or molecule

is an ion

In chemical reactions, the __________ are the starting materials that are converted into the __________.

reactants; products

Nonpolar covalent bonds are always formed from atoms that are

equal in their electronegativity

Isotopes of an element will always differ in

atomic mass

Hydrogen bonds occur when

partial opposite charges on molecules come close enough to attract each other

Which of the following four statements, if any, is true regarding essential elements and living organisms?

Although all forms of life require iron, other elements are required only by certain species.

The reactivity of an atom arises from

the existence of unpaired electrons in the valence shell

The difference between a stable isotope and an unstable isotope of an element is that

the unstable isotope has a nucleus that decays spontaneously, is radioactive, and can be transformed into an atom of another element

Ionic bonds form as a result of

attraction between ions that have opposite charges

Which of the following has negligible mass?

electron

An acid is

a compound that donates hydrogen ions to a solution (1-6)

A substance that reduces the hydrogen ion concentration of a solution is

a base

The amount of heat required to change the temperature of 1 g of any substance by one °C is defined as

the specific heat of that substance

When ice forms, the __________ are farther apart than in liquid water, allowing the ice to form an organized crystal structure and float.

hydrogen bonds

Water is a polar molecule. This means that

the opposite ends of the molecule have opposite electrical charges

Glucose has a molecular mass of 180 daltons. To make a 2-molar (2 M) solution of glucose,

stir 360 g of glucose in water to dissolve the sugar, and then add enough water to bring the total volume of the solution up to 1 L

The specific heat of a substance is

the amount of heat that must be absorbed or lost for 1 g of that substance to change its temperature by 1°C

Adding a base tends to __________ of a solution

lower the hydrogen ion concentration and increase the pH

Buffers are

substances that minimize changes in the concentration of H+ and OH- in a solution

Water molecules have __________ than molecules of similar size, such as ammonia and methane, reflecting its capacity to absorb large amounts of heat.

a higher boiling point

Adhesion is best described as

the clinging of one substance to another substance

When the pH of a solution shifts from 3 to 7, the hydrogen ion concentration has changed, and

it has decreased by 10,000 times

Many mammals control their body temperature by sweating. Which property of water is most directly responsible for the ability of sweat to lower body temperature?

The absorption of heat by the breaking of hydrogen bonds.

The ability of water molecules to form hydrogen bonds with other water molecules and water's ability to dissolve substances that have charges or partial charges are

both caused by water's partial charges

Nonpolar molecules that cluster away from water molecules are called __________ molecules.

hydrophobic

Sweating has a cooling effect because of water's high

heat of vaporization

__________ is an emergent property of water that allows insects like the raft spider to walk on water.

surface tension

Hydrophobic molecules

are uncharged, nonionic substances that seem to repel water

You can fill a glass of water to just slightly above the rim without it spilling over the glass. What property of water best explains this phenomenon?

surface tension

The partial charges on a water molecule occur because of

the unequal sharing of electrons between the hydrogen and the oxygen atoms of a water molecule

A solution at pH 10 contains __________ than the same amount of solution at pH 8.

100 times less H+

Hydrophilic molecules

are charged molecules that are attracted to the partial charge of the water molecule

The absorption of human-generated CO2 by the oceans

All of the listed responses are correct

Water moves up a plant because of hydrogen bonds by a process called _

cohesion and adhesion

A mole of methanol (CH3OH) weighs 32 g. The number of grams of methanol that are needed to produce 1 L of a 1 millimolar solution is

0.032 g

All of the following are hydrogen bonding properties except

nonpolar covalent bonding

The amount of heat required to convert 1 g of any substance from the liquid to the gaseous state is defined as

the heat of vaporization of that substance

Urine, at pH 6, contains __________ H+ as household bleach, at pH 13.

10,000,000 times as much

The phenomenon responsible for maintaining the upward movement of water through a vessel is

cohesion