Size, Scale & Bonding
What is a covalent bond?
Atoms sharing electrons
What type of bond holds water molecules together?
Hydrogen bonds
What are the monomers of carbohydrates called?
Monosaccharides
What type of bond links amino acids together?
Peptide bond
What are the main components that make up a triglyceride?
1 glycerol and 3 fatty acids
What determines whether a covalent bond is polar or nonpolar?
Electronegativity difference; greater than 0.5 is polar, less than 0.5 is nonpolar
How many hydrogen bonds can a single water molecule form?
4
What type of reaction breaks a polymer down into its monomers, and is water a reactant or a product in that reaction?
Hydrolysis; water is a reactant
Besides the R group, what are the three other main parts of an amino acid's structure?
Amino group, carboxylic acid group, alpha carbon
What type of bond links the glycerol backbone to the fatty acid chains in a triglyceride?
Ester bond
Arrange the following in ascending order by size (smallest to largest): eukaryotic cell, atom, virus, macromolecule, prokaryotic cell
Atom → macromolecule → virus → prokaryotic cell → eukaryotic cell
At a pH of 4, is the concentration of protons higher or lower than at a pH of 7, and by how much?
1000 times higher
If you're building a polysaccharide out of 12 glucose monomers, how many glycosidic bonds (linkages) would be formed?
11 (n monomers require n-1 linkages)
What base is different in DNA and RNA? How is it different? (Specify the letters)
Why do saturated fatty acids tend to be solid at room temperature, while unsaturated fatty acids tend to be liquid?
Saturated fatty acids have straight chains that pack tightly together; unsaturated fatty acids have kinks (from double bonds) that prevent tight packing
An atom has 4 protons, 5 neutrons, and 5 electrons. What is its net electrical charge?
-1
Are polar molecules hydrophilic or hydrophobic, and why?
Hydrophilic; they can interact with and dissolve in water since water is also polar
Starch and cellulose are both polysaccharides made of glucose. What's the key structural difference that makes only one of them digestible by humans?
Alpha vs beta glucose linkages; humans can digest alpha linkages (starch) but not beta linkages (cellulose)
What structural feature distinguishes a DNA nucleotide's sugar from an RNA nucleotide's sugar?
DNA has deoxyribose (an H at the 2' position); RNA has ribose (an OH at the 2' position)
When enzymes build a single triglyceride, how many water molecules are produced, and why?
3; one water molecule is released for each of the 3 ester bonds formed
Given these electronegativity values, Boron = 1.8, Carbon = 2.5, Chlorine = 3.2, Selenium = 2.6, which bond is the most polar: C-Se, C-Cl, B-Cl, or Se-Cl?
B-Cl (largest difference, 3.2 - 1.8 = 1.4)
If the covalent bonds in a water molecule were nonpolar instead of polar, what state would water most likely be in at room temperature, and why?
A gas; no polarity means no hydrogen bonding between molecules, which is what normally keeps water liquid at room temperature
If two glucose molecules (C6H12O6) join via condensation synthesis, what is the molecular formula of the resulting disaccharide?
C12H22O11
A protein chain has 45 amino acids, another has 52. Are they classified the same way? Explain
No; 45 falls in the peptide range (2-49 aa), while 52 crosses into the polypeptide/protein range (50+ aa)
Phospholipids and triglycerides are held together by the same type of bond. What structural difference makes only phospholipids amphipathic?
Phospholipids replace one fatty acid with a phosphate group, giving them a hydrophilic head alongside hydrophobic tails; triglycerides have no polar head, so they're fully hydrophobic