Chapter 1 Flashcards
What are the two different classes of molecules?
biological macromolecules and metabolites
What are biological macromolecules?
large molecules such as proteins and nucleic acids
What are metabolites?
low-molecular-weight molecules such as glucose and glycerol
What is the main function of DNA?
store genetic information in all cellular organisms
Proteins
the macromolecules that are key participants in most biological processes that are built from 20 building blocks of amino acids
What are the three domains of organisms?
Eukarya, Archaea, Bacteria
Eukarya
comprise all multicellular organisms; well-defined nucleus
Prokaryotes
unicelluar organisms lacking a nucleus
Archaea
organisms having diverged from bacteria
DNA
deoxyribonucleic acid: a linear polymer made up of four different types of monomers
DNA is polar or nonpolar?
polar
What are the four bases of DNA?
Adenine, Guanine, Cytosine, Thymine
The bases of DNA are held together by what bond interactions?
covalent bonds
Are hydrogen bonds stronger or weaker than covalent bonds?
weaker
The structure of the double helix proposed what two properties of central importance to DNA as hereditary material?
1) the structure is compatible wit any sequence of bases 2) because of base-pairing, the sequence of bases along one strand completely determines the sequence along the other strand
What forces cause two strands of DNA to bind to each other?
Covalent bonds, noncovalent bonds
What are the strongest bond types?
covalent
How is a covalent bond formed?
by the sharing of a pair of electrons between adjacent atoms
T/F. A molecule that can be written as several resonance structures of approximately equal energies has greater stability than does a molecule without multiple resonance structures.
True
What are the four fundamental noncovalent bond types?
1) electrostatic interactions 2) hydrogen bonds 3) van der Waals interactions 4) hydrophobic interactions
Electrostatic interactions
a charged group on one molecule can attract an oppositely charged group on another molecule
The energy of an electrostatic interaction can be given by what law?
Coulomb’s Law: E=kq1q2/Dr^2
An attractive interaction has a ____ energy.
negative
hydrogen bonds
responsible for specific base-pair formations in the DNA double helix
In a hydrogen bond, what is the hydrogen atom shared by?
Two electronegative atoms
Hydrogen bond donor
group that includes both the atom to which the hydrogen bond is more tightly linked and the hydrogen atom itself
hydrogen bond acceptor
the atom less tightly linked to the hydrogen atom
The strongest or weakest hydrogen bonds tend to be straight?
strongest
van der Waals interactions
the distribution of electronic charge around an atom fluctuates with time
Explain the energy of the van der Waals interaction as two atoms approach each other.
the energy is most favorable at the van der Waals contact distance. Due to electron-electron repulsion, the energy rises rapidly as the atoms approach closer than this distance.
When the surfaces of two large molecules come together, a larger number or a smaller number of atoms are in van der Waals contact?
larger
Water is polar or nonpolar?
polar
The molecule is bent or straight?
bent
Due to the polar and bent water molecule, what is the distribution of charge in the molecule?
asymmetric
What are the two properties of water that are essential to the formation of macromolecular structures an the progress of chemical reactions?
1) Water is a polar molecule 2) Water is highly cohesive
What is the dielectric constant of water?
80
What makes water a versatile solvent?
the formation of hydrogen bonds and ionic interactions
What is the hydrophobic effect?
a final fundamental interaction that is a manifestation of the properties of water: the aggregation of nonpolar groups in water leads to the release of water molecules, initially interacting with the nonpolar surface, into bulk water. The release of water molecules into solution makes the aggregation of nonpolar groups favorable.
Which molecules show an increased tendency to associate with one another in water compared with other, less polar and less self-associating solvents?
nonpolar molecules
Explain the electrostatic interactions in DNA.
Each unit within the double helix includes a phosphate group that bears a negative charge. The unfavorable interactions of one phosphate (phosphoryl group) with several others are repulsive interactions that oppose the formation of a double helix.
Explain the hydrogen bond interactions in DNA.
When two single strands of DNA come together, the hydrogen bonds with water are broken and new hydrogen bonds form between the bases.
Explain the van der Waals interactions in DNA.
The base pairs are parallel and stacked nearly on top of one another. The separation distances between the most closely approaching atoms responds nicely to the van der Waals contact distance.
Explain the hydrophobic interactions in DNA.
The hydrophobic effect contributes to the favorable base stacking and moves the nonpolar surfaces of the bases out of water into contact with each other.
What occurs when complementary surfaces meet in DNA?
hydrogen bond donors align with hydrogen bond acceptors and nonpolar surfaces come together to maximize van der Waals interactions and minimize nonpolar surface area exposed to the aqueous environment
system
refers to the matter within a defined region of space
surroundings
the rest of the universe
1st Law of Thermodynamics
the total energy of a system and its surroundings is constant; energy can neither be created nor destroyed
2nd Law of Thermodynamics
the total entropy of a system plus that of its surroundings always increases
entropy
the degree of randomness or disorder in a system
heat
a manifestation of kinetic energy
How is the local decrease in entropy accomplished?
By a release of heat, which increases the entropy of the environment
enthalpy
heat content
What does the precise change in the entropy of the surroundings depend on?
temperature
The change in entropy is ____ when heat is added to cold surroundings that when heat is added to warm surroundings that are already in a high degree of disorder.
greater
When and only when is there free energy change?
when the overall entropy of the universe is increased
What does free energy represent?
a single term that takes into account both the entropy of the system and the entropy of the surroundings
