Polymers + hydrogen bonding

Question 1

What is polymerisation

Answer 1

process in which relatively small molecules, called monomers, combine chemically to produce a very large chainlike or network molecule, called a polymer.

Question 2

Describe the process of making polymers by condensation

Answer 2

condensation polymerisation involves ejection of a small stable molecule e.g. HCl, CH3OH, H2O

Question 3

What is a polymer

Answer 3

A polymer is a molecule which has a variable chain length

Question 4

Describe the process of making polymers by addition

Answer 4

Addition polymerisation involves the addition of alkene monomers to a growing chain.

It is facilitated by a catalyst (E.g. Ziegler-Natta catalysts) (Ti, Zr, Hf or Al- based)

Question 5

WHat are examples of condensation polymerisation

Answer 5

Polyamides and polyesters

Question 6

What are examples of addition polymerisation

Answer 6

Polyethylene (H), polypropylene (CH3), polyvinyl chloride (PVC) (Cl), polystyrene (Phenol ring)

Question 7

WHat sorts of polymer structures allow for polymers to be biodegradable?

Answer 7

Molecular structure closer to naturally occurring biopolymers make it easier for microorganisms to break them down.

Question 8

What are some various functions of proteins

Answer 8

Provide structural shape and support (collagen)

Do mechanical work (actin and myosin)

Acts as catalysts or enzymes (carbonic anhydrase)

regulate body functions (hormones) (insulin)

Provide protection against disease (immunoglobulins)

Active in storage and transport (hemoglobin)

Question 9

How are proteins formed

Answer 9

Proteins act as polyamides.

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. Proteins contain chains of >50 amino acids (up to >1000)

With 20 amino acids to choose from, there are a variety of proteins able to be formed

Basically proteins are polymers of amino acids

Question 10

Can cis and trans peptide isomers be formed?

Answer 10

Yes

Question 11

What are peptide bonds?

Answer 11

A peptide bond is a covalent bond that links amino acids together to form a protein.

Question 12

What are the types of protein structures?

Answer 12

Primary structure
Secondary structure
Tertiary structure
Quarternary structure

Question 13

What is the primary structure of a protein

Answer 13

It is the basic level and is the particular linear sequence of amino acids comprising one polypeptide chain

Question 14

What is the secondary structure of a protein

Answer 14

It is the regular folding of regions into specific structural patterns within one polypeptide chain. H bonds between carbonyl oxygen and peptide bond.

The two most common secondary structural elements are alpha helices and beta sheets

local folded structures that form within a polypeptide due to interactions between atoms of the backbone

Question 15

What is the tertiary structure of a protein

Answer 15

It is the 3D arrangement of all amino acids in a single polypeptide chain. This structure is usually conformational, native and actiev and is held together by multiple non covalent interactions

Overall 3D arrangement of its polypeptide chain in space. Stabilised by outside polar hydrophilic hydrogen and ionic bond interactions and internal hydrophobic interactins between nonpolar amino acid side chains

Question 16

What is the quarternary structure of a protein

Answer 16

Specific spatial arranagement and instructions of proteins

Association of several protein chains or subunits into a closely packed arrangement. Each of the subunits has its own primary, secondary and tertiary structure. Held together by hydrogen bonds and van der waals forces between non polar side chains

Question 17

How can knowledge of enzyme structure and mechanisms be used to benefit society?

Answer 17

Allows us to design inhibitors which can act as medicines.

Inhibitors have a similar chemical structure to the enzyme which will cause a negative effect and as a result they can block or distort the site of binding by the enzyme

E.g. penicillin inhibitting transpeptidase to kill bacteria

Question 18

What is denaturing a protein

Answer 18

Denaturation implies the destruction of the tertiary structure of a protein molecule and the formation of random polypeptide chains.

Question 19

How is denaturing a protein possible?

Answer 19

It is caused by the relatively weak intermolecular forces. Denaturing specifcally is caused by heat, changing pH or chemical reaction

Typically it is irreversible; alters biological and physical characteristicsG (e.g. less soluble)

Question 20

Go more in depth about polymers

Question 21

What are hydrogen bonds? How do they occur?

Answer 21

They occur when H is bonded to a very electronegative element such as (F,O,N), and as a result the bond is polar covalent.

This is one of the strongest intermolecular forces possible.

A hydrogen bond can be thought of as a bond between the hydrogen atom in one molecule and the lone pairs of the F,N or O atoms in another.

Question 22

What are the common properties of F,O, N

Answer 22

They are the most electronegative elements

They are small (2s and 2p electrons in valence shells)

They have lone pairs

Question 23

How do we draw H bonds

Answer 23

We indicate H bonds using a dotted or dashed line. The H bond is strongest when the bond angle is 180 degrees as this gets the excess negative charges as far away from each other as possible

Question 24

Can hydrogen bonds occur in an intramolecular fashion?

Answer 24

Yes they can, even though they are typically considered a kind of intermolecular force. H bonds can occur between different functional groups within the same molecule as long as it is between H and either; F, O, or N

Question 25

Are hydrogen bonds intermolecular. WHat is their nature?

Answer 25

Yes they are typically intermolecular bonds

Molecules with many O, N or F atoms may have multiple H bond sites. For example with formic acid (HCOOH), it can form a H bond “dimer”

Question 26

What is the necessity for H bonds?

Answer 26

H bonds assist in holding DNA together.

I.e. H bonds between A and T, and also H bonds between C and G

Question 27

What is the relevance of H bonds in DNA?

Answer 27

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

Question 28

How many H bonds can a water molecule form?

Answer 28

up to four

Question 29

Are molecules only limited to forming pairs of Hydrogen bonds?

Answer 29

No some molecules that form multiple H bonds don’t just only pair up, but they can actually form extended one- two- or three-dimensional networks

Question 30

How are boiling points determined? (Discuss dispersion forces and hydrogen bonds)

Answer 30

Boiling points are directly correlated/related with the strength of the intermolecular forces.

Thus, stronger IMF such as hydrogen bonds will result in a higher boiling point. Additionally, if there is a molecule with increased electrons, it will typically lead to increased dispersion forces which further increases the strength of intermolecular forces –> bigger molecules have greater intermolecular forces.

Question 31

Is a weaker or stronger IMF more likely to increase the surface tnesion

Answer 31

The stronger the IMF, the higher the surface tension

When the molecules of the liquid shrink into the minimum surface, then this tendency is known as surface tension. As the intermolecular forces increase, the area of space becomes less, and the surface tension increases.

Question 32

What is surface tension

Answer 32

Surface tension is the property of surface of liquids which allow it to resist external forces, due to the cohesive nature of molecules.

Tension of surface film of a liquid caused by attraction of particles in surface by bulk of liquid which tends to minimise surface area

Question 33

explain why concave meniscuses exist

Answer 33

Exist when the molecules in the liquid are attached to the glass more than to itself ii.e. water

Question 34

explain why convex meniscuses exist

Answer 34

Exist when the molecules in the liquid are attracted more to the glass than to itself. i.e. mercury

Question 35

What is capillary action/ capillarity?

Answer 35

Capillary action is the ability of a liquid to flow in narrow spaces without the assistance of, or even in opposition to, external forces like gravity.

Question 36

What does capillary action rely on

Answer 36

Relies on the strong interaction between water molecules and the walls of capillaries