General Biological Chemistry - Johnathan Cox

Question 1

What is a Lewis structure?

Answer 1

All atoms are shown, as well as all covalent bonds

Question 2

What are reduced structures?

Answer 2

All carbons omitted, hydrogens attached to Carbon omitted, hydrogens attached to heteroatoms left in

Question 3

What is a heteroatom?

Answer 3

A non carbon/hydrogen atom

Question 4

What do curly arrows indicate?

Answer 4

Movement of the least stable pair of electrons

Question 5

What is resonance shown by?

Answer 5

A double headed arrow, not in equilibrium

Question 6

How can a species’ stability be indicated by resonance?

Answer 6

The more resonance structures that a species has, the more stable it is

Question 7

What can resonance be described as?

Answer 7

The delocalisation or ‘spreading’ of charge

Question 8

What is a resonance hybrid?

Answer 8

Shows possible resonance structures with a dashed line

Question 9

What is tautomerism?

Answer 9

The movement of one or ore double bonds and a small atom, usually hydrogen but could also be fluorine

Question 10

What is an example of tautomerism?

Answer 10

The changing of adenine from amino form to imino form

Question 11

What is conjugation?

Answer 11

Alternation of single and double bonds, to form a ‘partial’ double bond

Question 12

What can conjugation be described as?

Answer 12

Net stabilisation of the system

Question 13

What is the relationship between the change in energy and wavelength in conjugation?

Answer 13

As the change in energy gets smaller, the wavelength gets larger

Question 14

When does the wavelength of light emitted by conjugated compounds reach the visible spectrum?

Answer 14

When there are 8 or more conjugated double bonds

Question 15

What is the change in energy in conjugation created by?

Answer 15

Movement of electrons from the ground state bonding orbital to the antibonding orbital

Question 16

As conjugation increases, what happens to energy change and wavelength?

Answer 16

Energy change decreases, wavelength increases

Question 17

What is the name of the molecule which gives lobsters their colour?

Answer 17

Astaxanthin

Question 18

How many conjugated double bonds does astaxanthin have?

Answer 18

13

Question 19

What does astaxanthin form a complex with?

Answer 19

Crustacyanin

Question 20

Why do lobsters change from slate blue to red?

Answer 20

Astaxanthin and crustacyanin form a twisted complex, and when denatured, the crustacyanin leaves the complex

Question 21

What are some of the importances of acids/bases?

Answer 21

Proteins, enzymes, DNA (gel electrophoresis), biological interactions

Question 22

What is a Bronsted acid?

Answer 22

Proton donor

Question 23

What is a Bronsted base?

Answer 23

Proton acceptor

Question 24

What kind of pKa do strong acids have?

Answer 24

Low

Question 25

What kind of Ka do strong acids have?

Answer 25

High

Question 26

Which side of an equilibrium is favoured, in terms of pKa?

Answer 26

The side with the weaker acid, so higher pKa

Question 27

What is the equation for Ka?

Answer 27

[A-][H3O+] / [HA]

Question 28

How can Keq be calculated?

Answer 28

log(Keq) = pKa(RHS) - pKa(LHS)

Question 29

What factors affect acid strength?

Answer 29

H-A bond strength, stability of A-, inductive effect

Question 30

How does H-A bond strength affect acid strength?

Answer 30

If the bond is weak, then the acid is strong as it will dissociate easily

Question 31

How does stability of A- affect acid strength?

Answer 31

If it is stable, then the acid is strong as it will stay dissociated

Question 32

How does inductive effect affect acid strength?

Answer 32

Non electron donating groups eg Methyl, can destabilise a negatively charged atom

Question 33

What is the Henderson Hasselbalch equation?

Answer 33

pH = pKa + log([A-]/[HA])

Question 34

What is the pH when [A-] and [HA] are equal?

Answer 34

The pKa value

Question 35

What is a Lewis base?

Answer 35

A lone pair donor

Question 36

What is a Lewis acid?

Answer 36

A lone pair acceptor

Question 37

HA + H2O -->

Answer 37

A- + H3O+

Question 38

HB+ + H2O -->

Answer 38

B: + H3O+

Question 39

The more available the lone pair...

Answer 39

...the stronger the base

Question 40

The more stable the B-H+...

Answer 40

...the stronger the base

Question 41

What changes between Oxygen to Nitrogen?

Answer 41

Increasing basicity | Decreasing electronegativity

Question 42

What is the availability of the lone pair governed by?

Answer 42

Electronegativity of the atom with the lone pair Delocalisation of the lone pair Inductive effects

Question 43

If +B-H has a high pKa, how strong is it?

Answer 43

Strong

Question 44

What is the barrier to rotation?

Answer 44

The difference in energy between two conformers

Question 45

Which conformer is more energetically favoured?

Answer 45

Staggered

Question 46

Which conformer is the highest energy conformation?

Answer 46

Eclipsed

Question 47

Why is staggered conformation more energetically favoured?

Answer 47

Due to electron repulsion

Question 48

Why are hydrocarbon chains drawn as zig zags?

Answer 48

Due to staggered confromations

Question 49

Why is a chair conformation more stable than boat?

Answer 49

Because it is staggered

Question 50

What can cyclopentane exist as?

Answer 50

An envelope conformation