Chapter 2 Flashcards by Alina Azmat

The structure and function of cells are stabilized by ______ interactions that have a fraction of strength of ______ bonds

weak; covalent

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True or False: Stabilization is possible because many weak bonds result in large stable structures

True

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True or False: We experience life at a distance of 5 Angstrom

False. We experience life at a distance of 4 Angstrom, similar to the typical length of noncovalent bonds

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What are chemical bonds?

Chemical bonds are transient (short) chemical interactions that are key to the formation of biochemical compounds and the molecular interactions that are essential for life

Essentially, they are short chemical interactions that help with the formation of biochemical compounds and molecular interactions

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What is the correct order of the types of chemical bonds from weakest to strongest?

a) van der Waals, dipole, hydrogen, covalent, ionic
b) dipole, van der Waal, hydrogen, ionic, covalent
c) covalent, ionic, hydrogen, van der Waals, dipole
d) van der Waals, dipole, hydrogen, ionic, covalent

d) van der Waals, dipole, hydrogen, ionic, covalent

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What is the Brownian Motion?

The random movement of gasses and liquids powered by the background thermal energy
Water and gas molecules are bouncing randomly at a rate determined only by temp
Water is the most common medium for thermal noise

Botanist Robert Brown observed pollen granules suspended in water. Noted that granules darted randomly, thought he was observing life force inherent. Dismissed idea when he observed same behavior w/ dye particles in water and dust particles in air. Movement of particles he observed are referred to as Brownian Motion – vital energy source for life

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Humans are ____% water

65%

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A typical cell is about _____% water

70%

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Important properties of water are because ______ is an electronegative atom

Oxygen

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True or False: Electrons of the hydrogen to oxygen bonds spend more time near hydrogen

False: Although bonds joining hydrogen to oxygen atoms are covalent, electrons of bonds spend more time near the oxygen atom

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Charge distribution is not uniform, resulting in the water molecule being _____

Polar

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True or False: Oxygen atom is slightly positive charged, while hydrogen atoms are slightly negative charged

False: Oxygen atom is slightly negative charged, while hydrogen atoms are slightly positive charged

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True or False: Hydrogen bonds are unique in water

True

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When do hydrogen bonds take place?

Whenever a hydrogen is covalently bonded to an electronegative atom

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True or False: Hydrogen bonds are stronger than covalent bonds, but are shorter in length

False: Hydrogen bonds are weaker than covalent bonds and longer in length

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Describe a hydrogen bond

When a partially positively charged Hydrogen atom of one molecule of water can interact with a partially negatively charged Oxygen atom of another molecule of water

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What rises by _______. This water is maintained by hydrogen bonds between water and molecules

Transpiration

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The strength of hydrogen bonds play limiting role in the ultimate height attained by tall trees. When bonds break, an _______ forms, preventing water flow to the top of the tree

Embolism (air bubbles)

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What are the two most common electronegative atoms in hydrogen bonds?

Oxygen and Nitrogen

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What distance range separates two non-hydrogen atoms in a hydrogen bond?

a) 2.4 - 3.5 A
b) 2.5 - 3.0 A

a) 2.4 - 3.5 A

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True or False: Hydrogen bonds between two molecules will be disrupted by water, inasmuch as water itself forms hydrogen bonds w/ the molecules

True

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True or False: Hydrogen bonding between two molecules is weaker in absence of water

False. Hydrogen bonding between two molecules is stronger in absence of water

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Describe electrostatic interactions (ionic bonds)

Weak interactions between ions having opposite charges; interactions between distinct electrical charges on atoms

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True or False: Water weakens electrostatic interactions because of its polar characteristics

True

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True or False: Electrostatic Interactions are minimized in an uncharged environment

False: Electrostatic Interactions are maximized in an uncharged environment

True or False: Electrostatic interactions are weak in a non-polar solvent

False: Electrostatic interactions are strongest in a non-polar solvent; thus weakened by polar solvents (water)

Electrostatic Interactions' energy is measured by which law?

Coulomb’s law: E = Kq1q1 / Dr E = energy q1 and q2 = charges on the two atoms (in units of electrical charge) r = distance between the two atoms D = dielectric constant k = proportionality constant

True or False: Electrostatic interactions are strongest in a vacuum, where D = 1

True

For electrostatic interactions, the distance for maximum bond strength is about 2 angstrom

False: For electrostatic interactions, the distance for maximum bond strength is about 3 angstrom

True or False: Electrostatic interaction between 2 ions with opposite charges separated by 3 A in water has energy of -5.8 kJ mol-1, whereas the same 2 ions separated by 3 A nonpolar solvent (ex. hexane) has an energy of -231 kJ mol -1

True

How much does 1 KJ equal in Joules?

1000 J

What is a Joule?

The amount of energy needed to apply to a 1 Newton over 1 meter

If a grain of salt (NaCl) is added to water, salt dissolves, and the _____ bond between _____ and ____ is destroyed because the individual ions now bind to the _______ rather than to each other

If a grain of salt (NaCl) is added to water, salt dissolves, and the ionic bond between Na+ and Cl- is destroyed because the individual ions now bind to the water molecules rather than to each other

True or False: Water can dissolve any molecule that has sufficient partial or complete charges on the molecule to interact with water

True

Van der Waals distance is _____ angstrom, depending on participating atoms

3-4 A

True or False: Energies associated with van der Waals interactions are quite large

False: Energies associated with van der Waals interactions are quite small

Hydrogen bonds between base pairs stabilize the _________ and keep the coding information inside the helix, away from potential harmful reactions

double helix

______ interactions are strong enough to stabilize and protect the DNA but _____ enough to allow access to the information of the base sequence under appropriate circumstances

Weak; weak

Hydrophobic forces arise when _____ molecules come in contact with _____ and are unable to form _______

non-polar; water; hydrogen bonds

What does the second law of thermodynamics state?

The total entropy of a system always increases in a spontaneous process

A molecules with two distinct personalities (hydrophobic and hydrophilic) are called an ______ or ______ molecule

amphipathic; amphiphilic

True or False: Under the right conditions, hydrophobic forces can form membranes

True

Hydrophobic Interactions form spontaneously because.... a) when they form, the entropy of water decreases b) when they form, the entropy of water increases

b) when they form, the entropy of water increases

Change in entropy ______ when a system becomes more disordered _____ when the system becomes more ordered/less random

increases; decreases

Describe the hydrophobic effect?

It is where nonpolar molecules in an aqueous solution are driven together no primarily because they have high affinity for each other, but because when they associate, they release water molecules Essentially, nonpolar molecules in aqueous solution are driven together because of the resulting increase in entropy of water molecules

What is pH?

A measure of the hydrogen ion concentration of a solution, values ranging from 0 – 14

Important reactions are those that include releasing or binding of _____

H+ (proton)

On a pH scale, the smaller number are ________ and the larger numbers are _______

acidic environments; basic environments

Human blood has a pH of ______. A deviation of +/- 0.5 can result in ______

7.4; death

How can loss of function occur with regards to pH?

Alterations in pH drastically affect the internal electrostatic environment of an organism, which can alter the weak bonds that maintain the structure of biomolecules Altered structure = loss of function

Very small amounts of pure water dissociate and form _______ and _________, with the concentration ion of each being _________

hydronium (H3O+); hydroxyl (OH) ion; 10^-7 M

Describe acids

- Donates hydrogen ions (protons) into a solution (proton donor) - Increases hydrogen ion concentration in a solution - Dissociates into proton and "conjugate base"

Describe bases

- accept hydrogen ions (protons) from solutions (proton acceptor) - lowers hydrogen ion concentration in solutions

Organic acids ionize to produce a ______ and a ______

proton; base

True or False: The larger the Ka value, the stronger the acid

True

Ionization of a weak acid is given by ____________

H = (H+) + (A-)

The equilibrium constant for H = (H+) + (A-) is _______

Ka = [H+] [A-] / [HA]

The handerson-hassbalch equation is ____________

pH = pKa + log ([A-] / [HA]) When [A-] = [HA]...... log ([A-] / [HA] ) = 0 and pH = pKa

True or False: An acid-base conjugate pair resists changes in the pH of a solution

True

True or False: Buffers resist changes to pH

True

True or False: A buffer is least effective at a pH near its pKa value

False: A buffer is most effective at a pH near its pKa value

pH of blood is buffered by the conjugate acid-base pair of ______ and ______

carbonic acid and bicarbonate (H2CO3 / HCO3)

pH > pKa indicates that the ______ form is dominant

base form

pH < pKa indicates that the _______ form is dominant

acid form

Which of the following is NOT example of a noncovalent interaction a) nonionic bond b) hydrogen bond c) van der waals interactions d) electrostatic interactions

a) nonionic bond

What are examples of noncovalent bonds?

ionic bonds, hydrogen bonds, van der waals interactions

What are examples of covalent bonds

Single, double, or triple bonds between atoms in polar and nonpolar molecules

In an electrostatic interaction, the strength of the bond is ________ proportional to the charges of the ________

inversely; two interacting atoms

Nonpolar molecule in water results in the ______ in the entropy of water

Decrease