Chemical Structures and Properties of Biologically Important Molecules Flashcards

1
Q

What are key characteristics of organic molecules?

A
  • have C-H bonds
  • generally have covalent bonds
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2
Q

What are key characteristics of inorganic molecules?

A
  • may contain C, but lack H
  • usually contain metals
  • generally have ionic bonds
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3
Q

When do covalent bonds form?

A
  • covalent bonds form when electrons are shared
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4
Q

What are the two types of covalent bonds?

A
  1. Nonpolar (pure) covalent bonds: electrons are shared equally
  2. Polar covalent bonds: electrons are shared unequally
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5
Q

When do ionic bonds form?

A
  • form when electrons are transferred
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6
Q

What is the distinction between a cation and an anion?

A
  • cations lose electrons and are positively-charged
  • anions gain electrons and are negatively-charged
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7
Q

What elements can participate in hydrogen bonding?

A
  • Occurs only between polar molecules with hydrogen atoms bonded directly to F, O, or N
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8
Q

Why is carbon such an important element for biological molecules? Why are carbon-containing compounds so diverse and stable?

A
  • valence of four - carbon forms four covalent bonds w/other atoms, which gives it diversity in structure and function
  • covalent bonds - carbon covalent bonds have high bond energies, which makes them stable
  • diverse - carbon-containing compounds are extremely diverse (ie many functional groups)
  • tetrahedral - b/c carbon has a tetrahedral geometry, it can form stereoisomers
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9
Q

What are key characteristics of water?

A
  • polar
  • excellent solvent
  • high specific heat
  • high heat of evaporation
  • strong cohesive/adhesive forces
  • less dense as solid than liquid
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10
Q

What is the most important characteristic of water?

A
  • its polarity, b/c this accounts for all of its other characteristics
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11
Q

How is water polar?

A
  • water has a bent geometry (104.50)
  • oxygen = highly electronegative = draws electrons towards it = partial negative charge
  • hydrogen = electropositive = electrons are drawn from it = partial positive charge
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12
Q

Why is water considered an excellent solvent?

A
  • b/c it is polar, it can dissolve many polar/ionic solutes
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13
Q

Why is the high specific heat of water important?

A
  • it takes a lot of energy to raise the temperature of water by a degree
  • this helps keep the surrounding environment temperature regulated/consistent
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14
Q

Why is the high heat of vaporization of water important?

A
  • it takes a lot of energy to change water from liquid to a gas
  • this helps cool down organisms via evaporative cooling
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15
Q

Why are the strong cohesive forces of water important?

A
  • water molecules have a strong attraction to other water molecules b/c H-bonds
  • this creates surface tension and enables fluid transport of substances
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16
Q

Why are the strong adhesive forces of water important?

A
  • water molecules have a strong attraction to other non-water molecules because of partial charges
  • this allows it to stick to other substances besides itself and enables fluid transport of substances
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17
Q

Why is it important that water is less dense as a solid than as a liquid?

A
  • this causes ice to float and keeps ponds/lakes/oceans from freezing solid during the winter, which allows life to continue below the surface
18
Q

What are the 4 macromolecules?

A
  1. proteins
  2. carbohydrates
  3. nucleic acids
  4. lipids
19
Q

What is the basic structure of an amino acid?

A
  • an alpha carbon surrounded by:
    • carboxyl group (-COOH)
    • amino group (-NH2)
    • hydrogen atom
    • side-chain (r-group)
20
Q

What determines the chemical characteristics of a specific AA?

A
  • the side-chain chemistry
21
Q

How do peptide bonds form?

A
  • peptide bonds form between adjacent AA in a chain via a dehydration synthesis reaction between the carboxyl group of one AA and the amino group of the second AA, releasing water
  • this reaction is not easily reversible b/c it is catalyzed by enzymes and the peptide bond is extremely stable
22
Q

What determines the primary structure of a protein?

A
  • the linear sequence of the AA in a polypeptide chain
23
Q

What determines the secondary structure of a protein?

A
  • local interactions between AAs via hydrogen bonds between the carbonyl oxygen and the amino nitrogen
24
Q

When do alpha helices form?

A
  • secondary structures that form via hydrogen bond interactions between AAs four residues apart on the same chain
25
Q

When do beta-sheets form?

A
  • form via hydrogen bond interactions between AAs on separate chains
26
Q

What determines the tertiary structure of proteins?

A
  • determined by long-range hydrophobic/hydrophilic interactions between the R-groups of AAs on separate
27
Q

When do proteins have quaternary structure?

A
  • only when the protein contains more than one subunit
28
Q

What is the general structure of a monosaccharide?

A
  • general formula = (CH2O)n [n determines the specific type]
  • ~3-7 carbons
  • carbonyl group
  • hydroxyl group
29
Q

How are glycosidic bonds formed?

A
  • glycosidic bonds are formed between two monosaccharides via an oxygen atom after a dehydration reaction that releases water
30
Q

What are the two most abundant storage polysaccharides?

A
  • starch (plant cells)
  • glycogen (animal cells)
31
Q

What are the two types of starch?

A
  1. amylose: straight-chain polymer of glucose, ~20% of starch content
  2. amylopectin: branched-chain polymer of glucose, ~80% of starch content
32
Q

What are the two most abundant structural polysaccharides? What are the differences between the two?

A
  1. Cellulose:
    • Polymer of glucose
    • Plant/algae cell walls
  2. Chitin:
    • Polymer of glucosamine (contains N)
    • Arthropod exoskeletons and fungi cell walls
33
Q

What is the basic structure of a fatty acid? What is the most key characteristic of fatty acids?

A
  • long hydrocarbon chain (non-polar)
  • carboxyl group at one end (polar)

Amphipathic: both polar and nonpolar

34
Q

What is the distinction between saturated fatty acids and unsaturated fatty acids?

A
  • Saturated fatty acids: no double-bonds in tails; long, straight chains that pack together well
  • Unsaturated fatty acids: one or more double-bonds; result in a kink in a chain that prevents tight packing
35
Q

What is a triacylglycerol?

A
  • Composed of a glycerol molecule with 3 fatty acids linked to it
  • Ester bonds link fatty acids to glycerol
  • Main function = store energy
36
Q

What is a phospholipid?

A
  • Composed of one glycerol, two fatty acids, and phosphorus
  • Main function = bilayer of membrane
37
Q

What is the basic structure of nucleotides?

A
  • Nitrogen-containing base
  • Pentose
  • One or more phosphate groups
38
Q

What are the two types of nucleotide bases?

A
  • pyrimidine: one-carbon/nitrogen ring: uracil, cytosine, thymine
  • purine: two-carbon/nitrogen rings: guanine, adenine
39
Q

What are the two types of pentose sugars?

A
  • ribose: has a hydroxyl group on 2’C
  • deoxyribose: lacks a hydroxyl group on 2’C
40
Q

How are nucleotides linked to one another?

A
  • phosphodiester (covalent) bonds between the phosphate group of one nucleotide and the C’3 of the pentose sugar
  • creates an alternating backbone of sugar-phosphate-sugar
41
Q

How do bases pair?

A
  • purines and pyrimidines pair up
    • A forms two H-bonds w/T (or U)
    • G forms three H-bonds with C