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BIO 101 > Topic 2 - The Nature Of Molecules And Water > Flashcards

Topic 2 - The Nature Of Molecules And Water Flashcards

1
Q

Atom

A

The smallest unit of matter that has the properties of an element

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2
Q

Isotope

A

One or more forms of an element that have a different number of neutrons

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3
Q

Atomic number

A

Number of protons

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4
Q

Mass number

A

Protons + neutrons

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5
Q

Where are the protons and neutrons located in an atom?

A

In the nucleus

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6
Q

Where are the electrons located in an atom?

A

In orbitals/clouds around the nucleus

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7
Q

True or false: in a neutral atom, protons = electrons

A

True

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8
Q

What determines the chemical behavior of atoms?

A

Electrons

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9
Q

What is the octet rule?

A

Atoms are most stable if their valence shell is full of electrons.

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10
Q

When is an atom reactive?

A

When it does not have the maximum number of electrons in its energy level.

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11
Q

Electronegativity

A

The tendency of an atom to attract electrons towards itself.

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12
Q

True or false: oxygen has the highest electronegativity

A

True

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13
Q

List the electronegativities of the following elements: O, N, C, H

A

O: 3.5
N: 3.0
C: 2.5
H: 2.1

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14
Q

Ionic bond

A

The attraction of 2 oppositely charged ions; a bond in which electrons are transferred from one ion to the other

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15
Q

Ions

A

Atoms that have an unequal number of protons and electrons

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16
Q

Cations

A

Positively charged ions

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17
Q

True or false: cations lose electron(s)

A

True

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18
Q

Anions

A

Negatively charged ions

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19
Q

True or false: anions gain electron(s)

A

True

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20
Q

Ionic bonds are strong as a crystal, but weak in water. Why?

A

Water is polar and interferes with the electrical charge holding ions together.

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21
Q

Covalent bonds

A

Bonds between two atoms sharing electrons

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22
Q

True or false: covalent bonds are strong bonds

A

True

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23
Q

What is the strongest type of covalent bond?

A

Triple bond

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24
Q

Polar covalent bond

A

Type of covalent bond that forms as a result of unequal electron sharing, resulting in creating slightly positive and negative charged molecule regions.

In other words, polarity is caused by atoms with different electronegativities sharing electrons in a covalent bond.

Intramolecular

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25
Q

Is a polar covalent bond intramolecular or intermolecular?

A

Intramolecular

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26
Q

Hydrogen bonds

A

Bonds that occur between two molecules that have polar covalent bonds.

The slightly positively charged atom (hydrogen) in one polar covalent bond is attracted to the slightly negatively charged atom in a second polar covalent bond.

Intermolecular

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27
Q

Are hydrogen bonds strong or weak?

A

Weak

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28
Q

Why are hydrogen bonds biologically important?

A

They can be easily broken and reform.
1. They hold proteins together at secondary and tertiary structure, allowing them to be flexible.
2. They hold the strands of DNA together in the double stranded helix, allowing it to break apart and reform easily for replication or protein synthesis.
3. They hold water together, essential for all life.

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29
Q

Van der Waals interactions

A

Fleeting interactions between atoms due to the movement of electrons

30
Q

List bonds from strongest to weakest

A

Covalent, polar covalent, ionic, hydrogen, van der Waals

31
Q

Why is water a unique substance?

A

Its polarity and hydrogen bonding give it special properties that tie to the processes of life.

32
Q

What are the special properties of water?

A

High heat capacity, high heat of vaporization, ability to dissolve polar molecules (solvent), cohesion and adhesion, and dissociation into ions that generates pH

33
Q

True or false: all the properties of water are due to its polarity.

A

True

34
Q

Explain how water is polar and why it forms hydrogen bonds.

A

The hydrogen and oxygen within water form polar covalent bonds. Water molecules attract other water molecules (also polar covalent), creating hydrogen bonds.

35
Q

Hydrophilic

A

“Water loving”
Polar substances that interact readily with or dissolve in water

36
Q

Hydrophobic

A

“Water fearing”
Nonpolar substances that do not interact well with water

37
Q

Water’s high heat capacity

A

Water has a high specific heat, meaning it can absorb or release a large amount of heat with only a slight change in its own temperature. It has the highest heat capacity of any liquid.

38
Q

Heat

A

The measure of the total amount of kinetic energy due to molecular motion

39
Q

Temperature

A

The intensity of heat due to the average kinetic energy of molecules

40
Q

Kinetic energy

A

The energy of motion

41
Q

Water’s high heat of vaporization

A

Water has a high heat of vaporization, the amount of energy required to change one gram of liquid to a gas.

42
Q

Explain why water’s high specific heat is biologically important.

A
  1. Moderated temperature of organisms
  2. Moderated global temperatures
  3. Evaporative cooling
43
Q

True or false: water acts as a heat sink/reservoir.

A

True

44
Q

Why is water less dense in its solid form?

A

When water cools, water molecules lose kinetic energy. Hydrogen bonds become more stable, trapping pockets of air between water molecules.

45
Q

True or false: water molecules push farther apart when water freezes and form a lattice structure.

A

True

46
Q

Solvent

A

A substance capable of dissolving other polar molecules and ionic compounds; the dissolving agent of a solution

47
Q

Solution

A

A liquid that is a mixture of substances

48
Q

Solute

A

Substance that is dissolved

49
Q

Why is water a versatile solvent?

A

Its polarity allows it to form hydrogen bonds with other polar (hydrophilic) substances easily. This allows water to dissolve these substances, facilitating their transport and interaction with other polar molecules (i.e. chemical reactions.)

50
Q

True or false: nonpolar substances do not mix well with water

A

True. Nonpolar substances are hydrophobic.

51
Q

Cohesion

A

Water molecules are attracted to each other because of hydrogen bonding

52
Q

Adhesion

A

The attraction between water molecules and other molecules

53
Q

Surface tension

A

The capacity of a substance to withstand rupturing when placed under tension or stress

54
Q

Why are cohesion and adhesion biologically important?

A

They help the transport of water through xylem against gravity in plants via capillary action.

55
Q

pH

A

“potential of hydrogen”
The measure of [H+] in a solution

56
Q

Hydrogen ion

A

H+

57
Q

Hydronium ion

A

H3O+

58
Q

Hydroxide ion

A

OH-

59
Q

Acid

A

Any substance that increases the H+ concentration of a solution

60
Q

Base

A

Any substance that reduces the H+ concentration of a solution

61
Q

True or false: as [H+] increases, [OH-] decreases, and vice versa

A

True

62
Q

How is pH calculated?

A

pH is calculated as the negative of the base 10 logarithm of the concentration of H+

Ex. log10 of 1 x 10^-7 moles/liter of H+ is -7. The negative of this number yields a pH of 7.

63
Q

Where on the pH scale are acids

A

<7 pH

64
Q

Where on the pH scale are bases

A

> 7 pH

65
Q

True or false: pure (distilled water) is neutral at a pH of 7

A

True

66
Q

True or false: most living cells remain close to pH 7

A

True

67
Q

True or false: human blood has a pH of 7.4, making it slightly basic; changes to 7.1 or 7.7 are fatal

A

True

68
Q

Buffers

A

Substances that minimize changes in concentrations of H+ and OH- in a solution. Most buffers consist of an acid-base pair that reversibly combines with H+

69
Q

What is the key buffer in human blood?

A

The acid-base pair of carbonic acid (H2CO3) and bicarbonate (HCO3-)

70
Q

Explain how human blood is maintained at a narrow pH.

A

Water combines with carbon dioxide in the blood to produce carbonic acid, which then becomes a bicarbonate ion and H+. If the blood becomes too basic, carbonic acid will form making the blood more acidic. If the blood becomes too acidic, bicarbonate will form making the blood more basic.

71
Q

Show the carbonic acid-bicarbonate buffer system.

A

CO2 + H2O ⇌ H2CO3 ⇌ HCO3- + H+

72
Q

Explain how an increase in atmospheric CO2 leads to the acidification of oceans.

A

CO2 + H2O ⇌ H2CO3 (carbonic acid)

BIO 101 (15 decks)

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