Biology 1100 Clemson Chapter 2

Entropy

A quantitative measure of the amount of disorder of any system, such as a group of molecules.

Space filling models

A representation of a molecule where atoms are shown as balls that are color coded and scaled to indicate to atom's identity and volume. Depicts spatial relationships between atoms more accurately than ball and stick models.

Ball and stick models

A representation of a molecule where atoms are shown as balls-colored and scaled to indicate the atom's identity-and covalent bonds are shown as rods or sticks connecting the balls in the correct geometry.

Hydrogen ion (H+)

A single proton with a positive electric charge of +1; typically, one that is dissolved in solution or that is being transferred from one atom to another in a chemical reaction.

Functional group

A small group of atoms bonded together in a precise configuration and exhibiting particular chemical properties that it imparts to any organic molecule in which it occurs.

Element

A substance consisting of atoms with a specific number of protons. Elements preserve their identity in chemical reactions.

Free radicals

A substance containing one or more atoms with at least one unpaired valence electron, which makes it unstable and highly reactive.

Molecule

A substance made up of two or more atoms held together by covalent bonds.

Buffer

A substance that, in solution, acts to minimize changes in the pH of that solution when acid or base is added.

Structural Formula

A two dimensional notation in which the chemical symbols for the constituent atoms are joined by straight lines representing single, double, or triple covalent bonds.

Covalent Bond

A type of chemical bond in which two atoms share one or more pairs of electrons.

Dalton (Da)

A unit of mass approximately equal to the mass of one proton or one neutron.

Radioactive Isotope

A version of an element that has an unstable nucleus, which will release radiation energy as it decays to a more stable form. Decay often results in the radioisotope losing protons and becoming a different element.

Hydrogen bond

A weak interaction between two molecules or different parts of the same molecule resulting from the attraction between a hydrogen atom with a partial positive charge and another atom with a partial negative charge.

Isotopes

Any of several forms of an element that differ in the number of neutrons contained in their nuclei.

Product

Any of the final materials formed in a chemical reaction.

Reactant

Any of the starting materials in a chemical reaction.

Chemical reaction

Any process in which substances combine or are broken down into other substances; involves the making and or breaking of chemical bonds.

Compounds

Any substance that consists of more than one element chemically bonded together.

Catalyst

Any substance that increases the rate of a chemical reaction without itself undergoing any permanent chemical change.

Solute

Any substance that is dissolved in a liquid.

The proton concentration of a pH 8.5 solution is 1.0x10^-8.5M, or 3.2x10^-9M. This is about 32 times less concentrated that a solution with pH 7.0 (1.0x10^-7).

If you were given a solution that has a pH of 8.5, what would be its concentration of protons? What is the difference between this solution and one that has a pH of 7.0?

Hydrophilic

Interacting readily with water. Hydrophilic compounds are typically polar compounds containing partially or fully charged atoms.

Prebiotic Soup Model

Model of chemical evolution whereby small molecules present in Earth's early atmosphere reacted and condensed into the early oceans, where they combined to form larger organic molecules.

Surface Metabolism Model

Model of chemical evolution whereby small molecules reacted with one another to form larger organic molecules through catalytic activity associated with a surface, such as the mineral deposits found in the deep sea hydrothermal vents.

Relative electronegativities would be F>O>H>Na. One bond would form with sodium and it would be ionic.

Predict Fluorine's relative electronegativity compared to hydrogen, sodium, and oxygen. State the number and type of bonds it would from if it reacted with sodium.

hydrogen bonds between surface water molecules resist being stretched.

Water has surface tension because ... there is positive pressure inside the water mass. cohesion forces are weaker at the surface. molecules at the surface make more hydrogen bonds. water tends to evaporate from the surface. hydrogen bonds between surface water molecules resist being stretched.

Atomic Weight

The average mass of an element that is based on the relative proportions of all its naturally occurring isotopes.

Energy

The capacity to do work or to supply heat. May be stored or available in the form of motion.

Surface tension

The cohesive force that causes molecules at the surface of a liquid to stick together, thereby resisting deformation of the liquid's surface and minimizing its surface area.

Both (a) and (b)

Water is a source of ______________ for chemical reactions in cells. (a) hydrogen atoms (b) oxygen atoms (c) energy Both (a) and (b) (a), (b), and (c).

Hydrophobic interactions

Very weak interactions between nonpolar molecules, or nonpolar regions of the same molecule, when exposed to an aqueous solvent. The surrounding water molecules support these interactions by interacting with one another and encapsulating the nonpolar molecules.

Aqueous

Water-based

Hydrophobic

Water-fearing. Typically nonpolar molecules.

Potential energy and entropy

What factors determine whether a chemical reaction is spontaneous or not?

Both (a) and (b).

Which statement helps to explain why ice is less dense than liquid water? (a) Water molecules make hydrogen bonds at definite angles. (b) Cold molecules move less than warm molecules. (c) Hydrogen bonds lengthen in the cold. All of the above. Both (a) and (b).

c) They consist of weak acids and weak bases.

Which statement is true of pH buffers? (a) They consist of strong acids and strong bases. (b) They keep the pH of the blood constant. (c) They consist of weak acids and weak bases. Both (a) and (b). Both (b) and (c).

(a), (b), and (c).

Which statement is true of water's tensile strength? (a) It results from hydrogen bonding. (b) It helps to pull water through plants. (c) It involves both cohesion and adhesion. Both (a) and (b). (a), (b), and (c).

Polar groups attract one another.

Which statement must be mentioned in explaining why amphipathic molecules line up at a water surface? Polar groups repel water. Nonpolar groups attract one another. Nonpolar groups repel water. Polar groups attract one another. All of the above.

(c) Polar molecules attract one another.

Why doesn't oil mix with water? (a) Nonpolar molecules repel water molecules. (b) Polar molecules repel nonpolar molecules. (c) Polar molecules attract one another. (d) Nonpolar molecules attract one another. Both (a) and (d).

Cation

A positively charged ion.

(b) A- reacts with H+ to become HA.

A buffer consists of undissociated acid (HA) and the ion made by dissociating the acid (A-). How does this system buffer a solution against decreases in pH? (a) HA dissociates and releases H+ and A- into solution. (b) A- reacts with H+ to become HA. (c) As the solution loses H+, HA replaces the lost H+. Both (a) and (c). None of the above.

Ionic Bonds

A chemical bond that is formed when an electron is completely transferred from one atom to another. Resulting ions remain associated due to their opposite electric charges.

Nonpolar covalent bond

A covalent bond in which electrons are equally shared between two atoms of the same or similar electronegativity.

Polar Covalent Bond

A covalent bond in which electrons are shared unequally between atoms differing in electronegativity, resulting in the more electronegative atom having a partial negative charge and the other atom having a partial positive charge.

Photons

A discrete packet of light energy; a particle of light.

Chemical Equilibrium

A dynamic but stable state of a reversible chemical reaction in which the forward reaction and reverse reactions proceed at the same rate, so that the concentrations of reactants and products remain constant.

Electron shells

A group of electron orbitals with similar energies. Electron shells are arranged in roughly concentric layers around the nucleus of an atom, and electrons in outer shells have more energy that those in inner shells. Electrons in the outermost shell, the valence shell, often are involved in chemical bonding.

Organic Compounds

A group of molecules that include at least one carbon atom; most have carbon-hydrogen bonds and carbon-carbon bonds. Organic compounds are widely used by living organisms.

Solution

A liquid containing one or more dissolved solids or gases in a homogenous mixture.

Electronegativity

A measure of how strongly an atom pulls shared electrons toward itself in a bond.

pH

A measure of the concentration of protons in a solution and thus of how acidic or basic the solution is. Defined as the negative of the base 10 logarithm of the proton concentration. pH=-log[H+].

Temperature

A measurement of thermal energy present in an object or substance, reflecting how much the constituent matter is moving.

Anion

A negatively charged ion.

Molecular Formula

A notation that indicates only the numbers and types of atoms in a molecule, such as H2O for the water molecule.

Solvent

Any liquid in which one or more solids or gases can dissolve.

Ion

An atom or a molecule that has lost or gained electrons and thus carries a full electric charge, either positive (cation) or negative (anion).

Chemical bond

An attractive force binding two atoms together. Covalent bonds, ionic bonds, and hydrogen bonds are types of chemical bonds.

Valence electrons

An electron in the outermost electron shell, the valence shell, of an atom. Valence electrons tend to be involved in chemical bonding.

Hydroxide ion (OH-)

An oxygen atom and a hydrogen atom joined by a single covalent bond and carrying a negative electric charge of -1.

Bases

Any compound that acquires protons or gives up electrons during a chemical reaction or accepts hydrogen ions when dissolves in water.

Acid

Any compound that gives up protons or accepts electrons during a chemical reaction or that releases hydrogen ions when dissolved in water.

about half of the buffer molecules are dissociated.

Buffers work best when ... about half of the buffer molecules are dissociated. the ratio of H+ to OH- is close to 1.0. nearly all of the buffer molecules are undissociated. 5% nearly all of the buffer molecules are dissociated. the pH is nearly neutral.

Polar

Carrying a partial positive charge on one side of a molecule and a partial negative charge on the other. Polar molecules are typically hydrophilic.

A.

If a reaction is exothermic, then which of the following statements is always true? A. The products have lower potential energy than the reactants. B. Energy must be added for the reaction to proceed. C. The products have lower entropy (are more ordered) than the reactants. D. It occurs extremely quickly.

a mingling of molecules and/or ions.

Dissolving is best described as ... a separation of molecules into neutral atoms. molecules breaking into ions. a change from a solid to a liquid. breaking covalent bonds. a mingling of molecules and/or ions.

Potential energy

Energy stored in matter as a result of its position or the position of electrons that form chemical bonds between atoms.

Exothermic

Heat that is released.

Endothermic

Heating from within.

It's the same reaction running backward or forward.

How does the way a buffer stabilizes pH during addition of acid differ from the way the same buffer stabilizes pH during addition of base? The same buffer can't work for both acid and base. It's the same reaction running backward or forward. In one case it adds H+; in the other case it adds OH-. In one case the buffer is strong; in the other case it's weak.

6.78 μCi

Radioactive decay occurs exponentially. The equation A = Ao e(−0.693t/T1/2) where Ao is the initial amount of radioactivity, t is the time between the initial and final measurement, and T1/2 is the half-life. You purchased 10 microcuries (10 μCi) of radioactive phosphorus, 32P. The half-life of 32P is 14.29 days. You use the phosphorus 8 days later to label DNA. How many μCi of 32P did you use? Hints 6.78 μCi 3.22 μCi 16.78 μCi 0.68 μCi 0.0039 μCi

Mole

The amount of a substance that contains 6.022 x 10^23 of its elemental entities (atoms, ions, or molecules). This number of molecules will have a mass equal to its molecular weight expressed in grams.

Specific heat

The amount of energy required to raise the temperature of 1 grams of a substance by 1C; a measure of the capacity of a substance to absorb energy.

699

The annual growth rate (r) of a population is 0.02. The initial population has 550 individuals. How many individuals would be in the population after 12 years? Hints 209 699 784 549 956

Homeostasis

The array of relatively stable chemical and physical conditions in an organism's cells, tissues, and organs.

Kinetic energy

The energy of motion.

Heat of vaporization

The energy required to change 1 gram of a liquid into a gas.

LUCA

The last universal common ancestor of cells. This theoretical entity is proposed to be the product of chemical evolution and provided characteristics of life that are shared by all living organisms on Earth today.

Molarity

The number of moles of a solute present in 1 liter of solution.

Atomic Number

The number of protons in the nucleus of an atom, giving the atom its identity as a particular chemical element.

Valence

The number of unpaired electrons in the outermost electron shell of an atom; when an atom is involved in covalent bonding, valence often determines how many covalent bonds the atom can form.

(a) aquatic life to exist at the North Pole.

The open spaces in water's crystal structure make it possible for ... (a) aquatic life to exist at the North Pole. (b) water to have a low boiling point. (c) life to occur in hot springs. Both (b) and (c). (a), (b), and (c).

Valence Shell

The outermost electron shell of an atom.

3.89 × 10−8 M

The pH of a solution is 7.4. What is the concentration of protons (H+) in the solution? Hints 3.89 × 10−7 M 2.51 × 10−7 M 3.89 × 10−8 M 2.00 M 2.51 × 107 M

Chemical energy

The potential energy stored in chemical bonds between atoms.

First Law of Thermodynamics

The principle of physics that energy is conserved in any process. Energy can be transferred and converted into different forms, but it cannot be created or destroyed.

Second Law of Thermodynamics

The principle of physics that the entropy of the universe or any closed system always increases.

Orbital

The region of space around an atomic nucleus in which an electron is present most of the time. Orbitals are grouped into electron shells.

Molecular weight

The sum of the atomic weights of all the atoms in a molecule; roughly, the total number of protons and neutrons in the molecule.

Adhesion

The tendency of certain dissimilar molecules to cling together due to attractive forces.

Cohesion

The tendency of certain like molecules to cling together due to attractive forces.

Chemical Evolution

The theory that simple chemical compounds in the early atmosphere and ocean combined via chemical reactions to form larger, more complex substances, eventually leading to the origin of life and the start of biological evolution.

Thermal energy

The total kinetic energy of a system that includes the motion of matter and is measured as temperature.

Mass Number

The total number of protons and neutrons in the nucleus of an atom.

Heat

Thermal energy that is transferred from an object at higher temperature to one at lower temperature.

it takes energy to break hydrogen bonds.

Though you add heat, the temperature of boiling water remains constant because ... water has a constant boiling temperature. it takes energy to break covalent bonds. it takes energy to circulate water. it takes energy to break hydrogen bonds. None of the above. The temperature rises during boiling.

(d) have a weak acid or a weak base half ionized in water.

To make a buffer, you need to ... (a) combine equal amounts of a strong acid and a strong base in water. (b) put either a strong acid or a strong base in water. (c) adjust the pH to 7.0. (d) have a weak acid or a weak base half ionized in water. Both (a) and (c).

B.

When H2 and CO2 react, acetic acid can be formed spontaneously while the production of formaldehyde requires and input of energy. Which of the following conclusions can be drawn from this observation? A. More heat is released when formaldehyde is produced compared the production of acetic acid. B. Compared to the reactants that it is formed from, formaldehyde has more potential energy than does acetic acid. C. Entropy decreases when acetic acid is produced and increases when formaldehyde is produced. D. The mineral catalyst involved in acetic acid production provides energy to make the reaction spontaneous.

Amino acid side chains have many carboxyl and amino groups.

Which answer helps to explain why all living cells need pH buffers? Amino acid side chains have many carboxyl and amino groups. Nucleic acids must have positive charges to form double helices. Hydrogen bonds only form at medium pH values. ATP will not deliver energy if it is ionized.

(a), (b), and (c).

Which factor is important in making it possible to cool yourself by sweating? Think carefully! (a) Molecules collide with varied angles and speeds. (b) Hydrogen bonds are relatively weak. (c) Water has more energy at the body surface. Both (a) and (b). (a), (b), and (c).

(a) A water molecule can make 4 hydrogen bonds.

Which of the following helps most to explain why water has a high specific heat? (a) A water molecule can make 4 hydrogen bonds. (b) The water molecule has exceptionally strong covalent bonds. (c) Water temperature is exceptionally sensitive to heat. Both (a) and (b). Both (b) and (c).

C.

Which of the following is most likely to have supplied the energy needed for the formation of acetic acid in deep-sea hydrothermal vents? A. heat from volcanoes. B. Photons from solar radiation. C. Chemical energy stored in the reactants. D. Kinetic energy released by the products.

C. Acetic acid has more highly electronegative oxygen atoms than the other molecules. When oxygen is bonded to carbon or hydrogen, a polar covalent bond forms.

Which of the following molecules would you predict to have the largest number of polar covalent bonds based on their molecular formulas? A. C2H6O (ethanol) B. C2H6 (ethane) C. C2H4O2 (acetic acid) D. C3H8O (propanol)

B.

Which of the following occurs when a covalent bond forms? A. Electrons in valence shells are transferred from one atom to another. B. Electrons in valence shells are shared between atoms. C. Partial charges on polar molecules interact. D. Nonpolar molecules are pushed together by surrounding water molecules.