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Biochemistry & Molecular Biology > 2. Why Water is Essential for Life > Flashcards

2. Why Water is Essential for Life Flashcards

1
Q

What is Electronegativity?

A
  1. A measure of the affinity of an atoms nucleus for its outermost electrons
  2. (i.e. How strongly a nucleus holds on to its electrons)
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2
Q

What atoms have high electronegativity values?

A
  1. Atoms who’s nuclei hold on tightly to its outermost electrons
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3
Q

What 2 elements have the highest electronegativities?

A
  1. Florine
  2. Oxygen
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4
Q

How does electronegativity change on the Periodic Table?

A
  1. As you move right to left, electronegativity tends to decrease, with the exception of Hydrogen
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5
Q

Why does water have only one Oxygen atom and 2 Hydrogen atoms?

A
  1. Because Oxygen has a higher electronegativity than Hydrogen.
  2. In other words, it likes electrons more, so doesn’t want to share equally
  3. Because of this, Oxygen keeps its electrons closer to the nucleus than Hydrogen
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6
Q

What results from Oxygen keeping it’s electrons closer to its nucleus than hydrogen does?

A
  1. The Oxygen acquires a partial negative charge
  2. The Hydrogen atoms acquire a partial positive charge
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7
Q

What is the shape of a water molecule?

A
  1. A relaxed V
  2. The Oxygen is at the bottom, with a partial negative charge
  3. The Hydrogen atoms are at the top, with a slightly positive charge, making it polar
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8
Q

What is a polar molecule?

A
  1. A molecule with an uneven distribution of charge, like water.
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9
Q

Why are water molecules in close proximity to one another?

A
  1. The partial positive charges on the Hydrogen atoms are attracted to the partial negative charge on the other molecules’ Oxygen atom
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10
Q

What is a Hydrogen Bond?

A

An interaction arising from partial charges like in 2 water molecules

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11
Q

What 4 elements are usually involved in Hydrogen Bonds?

A
  1. Oxygen
  2. Nitrogen
  3. Sulfur
  4. Hydrogen
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12
Q

What 2 of the most important structures in our cells rely on Hydrogen Bonds for stability?

A
  1. The complex folded structure of proteins
  2. The double strands of DNA
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13
Q

What allows water to remain liquid at room temperature?

A
  1. The Hydrogen Bonds between the molecules
  2. They attract and allow the molecules to hold on to each other instead of turning to a gas
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14
Q

Why does it take so much heat to break water molecules apart to create steam?

A
  1. The water molecules are constantly breaking and making hydrogen bonds with their neighbors, swapping partners, but always staying connected
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15
Q

What happens when temperatures drop in water?

A
  1. Thermal motion is minimal
  2. Each water molecule forms a Hydrogen Bond with 4 other water molecules, creating the highly ordered structure of an ice crystal
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16
Q

Why is frozen water less dense than liquid water?

A
  1. Because frozen water is in crystal form, causing it to expand
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17
Q

What force allows Amino Acids to interact within Proteins?

A
  1. Electronegativity within and around the molecule, similar to electronegativity around water molecules
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18
Q

What is the primary requirement for a Hydrogen Bond to form?

A
  1. A large electronegativity difference between Hydrogen and another atom
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19
Q

What kinds of bond does every Amino Acid contain?

A
  1. Nitrogen-Hydrogen bonds
  2. Carbon-Oxygen double bonds
  3. Hydrogen Bonds between the Hydrogen and Oxygen atoms of each molecule

(Same as in Nucleotides)

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20
Q

What kind of bond does every Nucleotide in DNA and RNA contain?

A
  1. Nitrogen-Hydrogen bonds
  2. Carbon-Oxygen double bonds
  3. Hydrogen Bonds between the Hydrogen and Oxygen atoms of each molecule

(Same as in Amino Acids)

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21
Q

What relationship do Nucleotides and Amino Acids have with water?

A
  1. They all have Hydrogen Bonds that attract each other
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22
Q

What makes water an effective medium and solvent for the molecules important to life?

A
  1. Its Hydrogen Bonds
23
Q

What is a solvent?

A
  1. A liquid that dissolves something
24
Q

How does water dissolve compounds?

A
  1. By using its partial charges to break apart molecules
25
Q

Why do many organic compounds dissolve in water?

A
  1. Because the partial charges of their own Hydrogen Bonds can mingle directly with the Hydrogen Bonds in water
26
Q

How does Sodium Chloride get ionized in water?

A
  1. Sodium has a low affinity for electrons
  2. Chlorine has a high affinity for electrons
  3. Because Sodium then has a fully positive charge and Chlorine has a fully negative charge.
  4. No Hydrogen bonds exists, so it does not mingle with the water molecules like organic compounds
27
Q

Why don’t oil and fat molecules dissolve or mix in water?

A
  1. They have long chains of Carbon-Hydrogen bonds that do not ionize or form hydrogen bonds
  2. The electronegativities of Hydrogen and Carbon are so similar that they are almost equally shared
  3. The bond is therefore effectively non-polar
28
Q

Why can’t we pull fat molecules apart from each other in the body?

A
  1. They can neither ionize nor form Hydrogen Bonds
29
Q

What does Hydrophobic Mean?

A
  1. “Water-fearing”
  2. Molecules that do not dissolve in water
30
Q

What does Hydrophilic mean?

A
  1. “Water-loving”
  2. Molecules that dissolve in water
31
Q

What does Amphiphilic mean?

A
  1. Molecules that are ambivalent about water
  2. They fall somewhere between soluble and nonsoluble
32
Q

What is a Micelle?

A
  1. A spherical, bubble like structure made of a hydrophilic head and a hydrophobic tail, with the heads lining the outside and the tails on the inside.
33
Q

What is The Hydrophobic Effect?

A
  1. The chemical property of nonpolar parts of molecules to associate with each other to the exclusion of water.
34
Q

Why is The Hydrophobic Effect important?

A
  1. It enables the creation of cellular membranes
35
Q

What is an example of an amphiphilic compound?

A
  1. Soap
  2. The hydrophilic end interacts with water readily
  3. The hydrophobic end does not
  4. Its micelluar structure allows it to remove grease when you wash your hands
36
Q

How common is it for a water molecule to ionize?

A

About 1 in over 5,000,000

37
Q

What happens when water ionizes?

A
  1. It breaks into a positively charged hydrogen ion, called a proton, and a negatively charged hydroxide ion
38
Q

Why does water ionize?

A
  1. Because when the molecule splits, the Oxygen takes the unequally shared electron all for itself because of its higher electronegativity, leaving the positively charged proton with no electron
39
Q

What is the difference between an acid and a base?

A
  1. An acid can donate a proton
  2. A base can receive a proton
40
Q

How can water be both an acid and a base?

A
  1. When water ionizes, it releases a proton, acting as an acid
  2. Simultaneously, it releases a Hydroxide ion, which can accept a proton to act as a base
41
Q

Why is water not a very strong acid or base?

A
  1. Only a minuscule amount of it ionizes
  2. The proton joins to a water molecule to form H3O+, so the concentration of H30+ and Hydroxide ions is equal, keeping the solution overall neutral
42
Q

What is the concentration of protons (hydrogen ions) in pure water?

A

1 X 10 ^-7 M

43
Q

What does the H in pH represent?

A
  1. The Hydrogen proton
44
Q

What is the negative logarithm of 10^-7?

A
  1. 7, or the pH of pure water
45
Q

What happens to the pH of water if the hydrogen ion concentration goes down to 10^-6M by the addition of an acid?

A
  1. The pH goes down to 6
46
Q

How much of a difference in proton concentration does a change in 1 pH unit represent?

A
  1. 10x
47
Q

Why is the pH of cellular and extracellular fluids so important?

A
  1. All cellular processes involve water
48
Q

What happens if the pH in blood drops below 6.8 or rises above 7.8?

A
  1. Bonds holding together critical proteins can get destroyed, resulting in death
49
Q

“_____ _____ act as buffering agents to keep pH constant.”

A
  1. Weak Acids
50
Q

What is a pKa?

A
  1. The specific pH of an acid at which 1/2 of its carboxyl groups (COOH) are protonated
51
Q

What is “Buffering”

A
  1. The range of pH values on either side of a pKa, within which there is a stubborn reluctance to change.
  2. Resistance to change in pH
52
Q

Why is Buffering so important to living organisms?

A
  1. They have the maintain the pH of cellular and extracellular fluids within very narrow ranges
53
Q

Can diets, such as the Alkaline Diet, change the pH in our blood or cells?

A
  1. No. The body’s buffering systems keep the pH where it needs to be.
  2. If they did, it would almost certainly be detrimental

Biochemistry & Molecular Biology (4 decks)

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