Week 13

Question 1

Polymer

Answer 1

Large molecules, composed of many subunits known as monomers

Question 2

Condensation polymerisation

Answer 2

Usually involves ejection of a small stable molecule,
* E.g. HCl, CH3OH, H2O

Question 3

Polymerisation is usually conducted…

Answer 3

above the boiling point of the ejected molecule, so it is lost as gas and doesn’t interfere with product

Question 4

Polymers by addition

Answer 4

Addition of alkene monomers and react them with one another and form this growing chain
* Facilitated by a Ziegler-Natta catalyst

Question 5

Ziegler-Natta catalysts

Answer 5

Ti, Zr, Hf or Al based

Question 6

The most common plastics are derived from…

Answer 6

Petrochemicals
* Formed by this “addition” polymerisation reaction.

Question 7

Nylon

Answer 7

Strong synthetic polymer
* The planar amide groups are very polar, so nylon forms multiple hydrogen bonds between adjacent nylon strands
*

Question 8

Kevlar

Answer 8

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

Question 9

Biopolymers

Answer 9

Polymers found in biological systems
* dd-peptidase: polyamide/peptide
* Cellulose: carbohydrate. The polymer is a polyacetyl.
* DNA: nucleic acid

Question 10

Polymers can be biodegradable

Answer 10

Molecular structure closer to natural biopolymers makes it easier for microorganisms to break them down

Question 11

Diverse functions of proteins

Answer 11

• structural shape and support
• mechanical work
• catalysts
• regulate body functions
• protection against disease
• active in storage and transport

Question 12

Amino acids condense to form a

Answer 12

Peptide (amide) link
* Two amino acids condense to form a di-peptide and three amino acids form a tri-peptide etc.

Question 13

Rotation around C–N bond

Answer 13

Restricted because the C–N bond has some C=N character

Question 14

cis and tran isomers can exist

Answer 14

true

Question 15

Primary protein structure

Answer 15

specific sequence of amino acids in a polypeptide chain

Question 16

Secondary protein structure

Answer 16

Local folded structures that form with the polypeptide chain due to interactions between the atoms of the backbone.
* 𝛼 helix, 𝛽-pleated sheet

Question 17

Tertiary protein structure

Answer 17

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

Question 18

Quaternary protein structure

Answer 18

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

Question 19

Acyclovir

Answer 19

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

Question 20

Penicillin

Answer 20

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.

Question 21

Denaturing

Answer 21

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

Question 22

Random coil

Answer 22

What happens to a protein after being denatured

No useful or structural function

Question 23

Covid virus contains many proteins

Answer 23

spike, membrane, envelope proteins

Question 24

Polysaccharides

Answer 24

carbohydrate polymers that consist of several sugar molecules

Question 25

Spike protein on Covid

Answer 25

**Carbohydrate camouflage** on the spike protein makes the virus much more *difficult* for the human immune system to recognise

Question 26

Many drugs inhibit proteins by

Answer 26

*mimicking* their natural **substrate**

Question 27

Polar covalents H-bond

Answer 27

H is bonded to a very **electronegative** element (**F, O, N**)

Question 28

The H-bond is strongest when...

Answer 28

the bond angle is **180°** as this gets the *excess* **negative** charges as far *away* from each other as possible

Question 29

H-bond “dimer”

Answer 29

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.

Question 30

H-bonds and DNA

Answer 30

The “**double helical**” structure of DNA is supported by **H-bonds** between *complementary* **base pairs** on the two intertwining strands

Question 31

H-Bonded Networks

Answer 31

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

Question 32

Unequal numbers of lone pairs and hydrogens in H-Bonded Networks

Answer 32

NH3 and HF * Such H-bond networks affect **physical** properties like solubility and mixing behaviour, as well as boiling points

Question 33

Concave meniscus

Answer 33

Water is more attracted to glass than to itself

Question 34

Convex meniscus

Answer 34

Mercury is less attracted to glass than to itself