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Question 1

What is Maltose’s linkage?

Answer 1

Two glucose units joined thorough C-1 of left hand sugar and at C-4 of the right hand sugar

• -> alpha 1,4-glycosidic linkage
• -> As bond from C-1 (anomeric carbon) is pointing down
• -> It is a reducing sugar

Question 2

What is Cellobiose linkage?

Answer 2

Two glucose units linked group B linkage (1,4)

Question 3

What is Surcrose’s linkage?

Answer 3

D-glucose and D-fructose linked
–> Glucose in pyranose form (A)
–> Fructose in furanose form (B)
Non reducing

Question 4

What is Amylose’s linkage?

Answer 4

Polysaccharide of glucose units

–> Alpha

Question 5

What is Cellulose’s linkage?

Answer 5

Polymer of glucose with b-1,4 glycosidic bonds
- Digestive enzymes have reactive sites which are the right shape for α-1,4’-glycosidic linkages
β-1,4’-glycosidic links do not fit

Question 6

What is the reactivity order of acid derivatives?

Answer 6

Amide < carboxylic acid = ester &laquo_space;acid anhydride = acid chloride

Question 7

Amino acid stereochemistry?

Answer 7

• -> All are chiral exept for glycine
• -> All are S except for cysteine
• -> Fisher is drawn with COOH at the top and R group at the bottom
• -> All natural chiral acids exist to L form (NH2 is on the left)

Question 8

What is the Isoelectric point?

Answer 8

Isoelectric point (pI) is the pH at which the maximum number of molecules have a
nett zero charge
--> Corresponds to first eq point

Question 9

Why do peptides adopt secondary structures?

Answer 9

In an aqueous environment, the chain will adopt a conformation so as to expose
the polar side chains (hydrophilic groups) and bury the non polar side chains
(hydrophobic groups) ie maximise favourable non-covalent interactions
–> Stabilises

Question 10

What are disulphide bridges?

Answer 10

Disulfide linkages can also strongly influence the conformation and
shape of peptides

Question 11

What are the steps to peptide synthesis?

Answer 11

1. Protect amino groups with BOC (removed later with acid)
2. Make Gly-OMe (deprotect later with base)
3. DCC reaction catalyst
4. Deprotect

Question 12

Why does peptide hydrolysis proceed with difficulty?

Answer 12

•H2O is a poor nucleophile
•the C=O of an amide is unreactive towards nucleophiles
–> Can be achieved by heating with a strong acid

Question 13

What are the properties of Chymotrypsin?

Answer 13

• -> Enzyme found in the digestive system
• -> Catalyses the hydrolysis of peptide bonds, specifically the peptide bonds on the carboxy side of a aromatic amino acid
• -> Recognises aromatic side chains (via a hydrophobic binding pocket)
• -> The binding site position the peptide bond for processing which contains a catalytic triad

Question 14

What are the properties of Carboxypeptidase A?

Answer 14

–> It recognises the carboxylate of the C-terminal amino acid and efficiently hydrolyses the adjacent peptide bond. Thus it effectively clips off the C-terminal residue and exposes the next one for processing

Factors:

1. Reactants held close together
2. Zn2+ makes C=O more suseptible to nucleophilic attack
3. H2O is deprotonated to make a better nucleophile

Question 15

Why is the OH group of tyrosine able to act as a proton donor?

Answer 15

Usually the proton of an alcohol group is not acidic.
However the OH group of tyrosine is attached to a
benzene ring and this influences its acidity and
reactivity.

Question 16

What are nucleosides?

Answer 16

Nucleosides are formed by the combination of a sugar unit with a purine or pyrimidine base
–> In each case the bases are attached to the sugar at C-1’ in the β-orientation
(same side of ring as C-5’)

Question 17

Basic/acidic centres of Nucleosides?

Answer 17

N functions are more nucleophilic
than O functions
• The NH2 group is amide-like and is not
appreciably nucleophilic
• N-9 is not appreciably nucleophilic
• Attack is likely at N-1, N-3 or N-7

Question 18

What are Nucleotides?

Answer 18

Nucleotides are phosphate derivatives of nucleosides

Phosphate is usually connected to the 5’ position of the sugar

Question 19

ATP hydrolysis factors?

Answer 19

The negative charges on the phosphates of ATP repel nucleophiles.
• Hydrolysis is normally very slow but is rapid in enzyme-catalysed reactions
• Mg2+ enzyme mediated hydrolysis of ATP in the active site (decreases negative charge - Nu can readily approach)

Question 20

What is the Nucleic acid stucture?

Answer 20

Polymers of nucleotides
linked by phosphate
ester bonds in the 5’
and 3’ positions of the
sugar
--> triphosphate at C'5 and Oh group at C'3

Question 21

What are the properties of Nucleic acid hydrolysis?

Answer 21

RNA is faster then DNA

–> 2’ OH group in RNA - internal nucleophile helps to break the linkage

Question 22

What is the rate unit?

Answer 22

Mol L-1 S-1

Question 23

What is a second order rate unit?

Answer 23

L mol-1 s-1

Question 24

What is a first order rate unit?

Answer 24

s-1

Question 25

What is a third order rate unit?

Answer 25

L2mol-2s-1