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67 Terms
Hydrogen bond donor
A molecule/group with an H directly bonded to O, N, or F that can donate a hydrogen bond
Hydrogen bond acceptor
A molecule/group with a lone pair on O, N, or F that can accept a hydrogen bond
How do you know if two molecules can hydrogen bond?
One must have a donor and the other must have an acceptor
Can a carbonyl oxygen (C=O) hydrogen bond?
Yes, it can accept hydrogen bonds but not donate them
Why can HCN hydrogen bond with water?
The nitrogen can act as a hydrogen bond acceptor
Why is the H in HCN not usually a hydrogen bond donor?
Because it is bonded to carbon, not O, N, or F
Polar bond vs polar molecule
A polar bond is one unequal bond; a polar molecule depends on the overall shape and whether dipoles cancel
Why is CO2 nonpolar even though it has polar bonds?
It is linear, so the bond dipoles cancel
What makes something hydrophobic?
It is mostly nonpolar and does not interact well with water
What makes something hydrophilic?
It has polar or charged groups that interact well with water
In chemical shorthand, what do line ends and corners usually represent?
Carbon atoms
In chemical shorthand, are hydrogens on carbon usually drawn?
No, they are implied
In chemical shorthand, are atoms like O and N usually drawn?
Yes, they must be shown explicitly
What is an R-group?
The variable side chain of an amino acid
What is a peptide bond?
The C-N covalent bond linking two amino acids
How is a peptide bond formed?
By a dehydration/condensation reaction between the carboxyl group of one amino acid and the amino group of another
What is primary structure?
The amino acid sequence of a protein
What is secondary structure?
Local folding patterns like alpha helices and beta sheets
What stabilizes secondary structure?
Hydrogen bonds between backbone atoms
What is tertiary structure?
The overall 3D shape of one polypeptide, stabilized by R-group interactions
What is quaternary structure?
The interaction/arrangement of multiple polypeptide subunits
If lysine is replaced by aspartic acid, why can structure change?
The side chain changes from positive/basic to negative/acidic, which can alter ionic interactions
What is ATP hydrolysis?
ATP + H2O → ADP + Pi
What does a negative ΔG mean?
The reaction is exergonic and spontaneous
Does spontaneous mean fast?
No, it means energetically favorable, not necessarily rapid
What does a catalyst do?
It makes a reaction happen faster but does not change ΔG
What part of a phospholipid is hydrophilic?
The phosphate head
What part of a phospholipid is hydrophobic?
The fatty acid tails
Why do phospholipids form bilayers?
Heads face water and tails avoid water
Which crosses a membrane more easily: water or glucose?
Water, because it is much smaller
Which crosses a membrane more easily: water or an ion?
Water, because ions are charged
Which molecules have more chemical potential energy: reduced or oxidized molecules?
Reduced molecules
Why does a reduced molecule have more stored energy?
It has more C-H bonds and fewer bonds to oxygen
Why does CO2 have low chemical potential energy?
It is highly oxidized