Week 13 Flashcards
Polymer
Large molecules, composed of many subunits known as monomers
Condensation polymerisation
Usually involves ejection of a small stable molecule,
* E.g. HCl, CH3OH, H2O
Polymerisation is usually conducted…
above the boiling point of the ejected molecule, so it is lost as gas and doesn’t interfere with product
Polymers by addition
Addition of alkene monomers and react them with one another and form this growing chain
* Facilitated by a Ziegler-Natta catalyst
Ziegler-Natta catalysts
Ti, Zr, Hf or Al based
The most common plastics are derived from…
Petrochemicals
* Formed by this “addition” polymerisation reaction.
Nylon
Strong synthetic polymer
* The planar amide groups are very polar, so nylon forms multiple hydrogen bonds between adjacent nylon strands
*
Kevlar
Rigid/bullet-proof synthetic polymer
High strength from:
* Intermolecular hydrogen bonds formed between the carbonyl groups and in N-H groups.
* Also from aromatic pi-pi stacking interactions that occur between adjacent strands
Biopolymers
Polymers found in biological systems
* dd-peptidase: polyamide/peptide
* Cellulose: carbohydrate. The polymer is a polyacetyl.
* DNA: nucleic acid
Polymers can be biodegradable
Molecular structure closer to natural biopolymers makes it easier for microorganisms to break them down
Diverse functions of proteins
- structural shape and support
- mechanical work
- catalysts
- regulate body functions
- protection against disease
- active in storage and transport
Amino acids condense to form a
Peptide (amide) link
* Two amino acids condense to form a di-peptide and three amino acids form a tri-peptide etc.
Rotation around C–N bond
Restricted because the C–N bond has some C=N character
cis and tran isomers can exist
true
Primary protein structure
specific sequence of amino acids in a polypeptide chain
Secondary protein structure
Local folded structures that form with the polypeptide chain due to interactions between the atoms of the backbone.
* 𝛼 helix, 𝛽-pleated sheet
Tertiary protein structure
Interactions between the R groups of the different amino acids that make up the protein (hydrogen bonding, ionic bonding, dipole-dipole interactions and London or dispersion forces) - non-covalent bonds
Quaternary protein structure
Some proteins are made up of multiple polypeptide chains also known as subunits. When they subunits come together, they give the protein its quaternary structure
Acyclovir
Derivative of guanine.
Acylovir gets activated by phosphorylation both by viral and host enzymes. The resulting nucleotide becomes incorporated into the newly synthesised viral DNA genome.
* Premature termination of viral DNA synthesis
Penicillin
If cell walls are improperly made, water flow into the cell causing it to burst. The crosslinking reaction is catalyzed by an enzyme known as transpeptidase.
* Penicillin G, shown here, can mimic the peptide known as the D-alanyl- D-alanine very effectively and inhibit transpeptidase from performing its function.
Denaturing
Caused by heat, changing pH or chemical reaction
* Usually irreversible: alters biological and physical characteristics (e.g. less soluble)
* Irreversible destruction of both secondary and tertiary structures
* Primary stays the same
Random coil
What happens to a protein after being denatured
No useful or structural function
Covid virus contains many proteins
spike, membrane, envelope proteins
Polysaccharides
carbohydrate polymers that consist of several sugar molecules
Spike protein on Covid
Carbohydrate camouflage on the spike protein makes the virus much more difficult for the human immune system to recognise
Many drugs inhibit proteins by
mimicking their natural substrate
Polar covalents H-bond
H is bonded to a very electronegative element (F, O, N)
The H-bond is strongest when…
the bond angle is 180° as this gets the excess negative charges as far away from each other as possible
H-bond “dimer”
Molecules with many O, N or F atoms may have multiple H-bond sites.
Dimer present:
* In the gas phase, When formic acid (HCOOH) is in the gas phase (esp. at high pressures
* Long-chain carboxylic acids in sol.
H-bonds and DNA
The “double helical” structure of DNA is supported by H-bonds between complementary base pairs on the two intertwining strands
H-Bonded Networks
Some molecules that form multiple H-bonds do not “pair up” - form extended one- two- or three-dimensional networks.
A water molecule can form up to four H-bonds through its two electron lone pairs and two d+ hydrogens. This leads to a dense, 3-D network of H-bonded molecules in liquid and solid water
Unequal numbers of lone pairs and hydrogens in H-Bonded Networks
NH3 and HF
* Such H-bond networks affect physical properties like solubility and mixing behaviour, as well as boiling points
Concave meniscus
Water is more attracted to glass than to itself
Convex meniscus
Mercury is less attracted to glass than to itself
