Section A—Carbohydrates

1. What do the various parts of the name aldohexose stand for?

2. A sugar is a member of the D series if, in a Fischer projection written with the highest oxidation state carbon at the top, the hydroxyl of the                   ____ chiral centre is on the                                   side of the main carbon chain.

3. Draw a Fischer projection for a D-aldopentose in which all the hydroxy groups have the same relative configuration.

4. Name the two functional groups which combine to form a hemi-acetal?        and                                      

5. Draw the structure of      (a) 1-propanol

(b) propanal

6. a) The following molecule is 5-hydroxypentanal. This molecule can form a cyclic hemi-acetal. Draw the cyclic structure. Detailed stereochemistry is not required for Q6. a) & b).

CH

OH    

O

b) Draw a 6-membered ring form of the following carbohydrate (ignore any detailed stereochemistry).

O

H-C 

OH

HO             

OH

OH

CH2OH

7.  a) Draw the lowest energy chair conformer of cis-1,3-dimethylcyclohexane.

b) In the cyclic form of D-mannose below OH

OH

HO                         OCH3

H

i) Circle the axial –OH group(s).

ii) Indicate the anomeric centre and state whether it is the α- or β- anomer (justify).

iii) Is this a reducing sugar?

iv) What is the stereochemical relationship between anomers of cyclic D-Mannose?

v) Which is the least sterically demanding position (axial or equatorial) in the chair conformer shown above?

c) Draw the Fischer projection of L-Allose.  Draw a diastereoisomer of L-allose, defining diastereoisomers.

CHO

H           OH

H           OH

H           OH

H           OH

CH2OH

D-Allose

8. Complete the following equation for the combination of two monosaccharides to form a disaccharide: C5H10O5   +   C6H12O6     à __________     +    _____

9. a) Draw the structure of the disaccharide formed by the combination of the two monomers shown.

b) What is the name of the link that is formed between the monomers, showing where it is on the diagram?

CH2OH

O    OH

     OH   H     HO                  H

H       OH

CH2OH

     OH   H     

H      OH

10.  Name  a  polysaccharide  and  state  the  monosaccharide(s)  that would  be formed from  its  total

hydrolysis

Section B—Amino acids and proteins

11. Write the general structure for: (a) a primary amine                             

(b) a carboxylic acid                            

12. Write the general structure for an α-amino acid                                   

13. Because an amino acid contains both a basic and an acidic function in the same molecule, the preferred structure at neutral pH is:

14. This is called a                                                   and it has a net charge of        .

15. Peptides are formed by making an                              bond between the                                 part of one amino acid and the                                                    part of another.

16.  (a) Draw the structure of a dipeptide made from two molecules of glycine.

(b) Between which two atoms is the bond formed (indicate on the diagram)?

17. Residual amino groups will be protonated in acid conditions and residual carboxylic acid groups will be deprotonated in base. What will be the overall charge on the peptide in Q16 at pH 12?

18. Peptides and proteins undergo                                                             (reaction with water) in which the peptide bonds are broken and the constituent                                   are liberated. This reaction can be catalysed by                                  or (in the body)                                         .

19. a) What products, and in what relative amounts, would be formed from complete hydrolysis of the following

H2NAla-Gly-Ser-Ser-Ala-Gly-GlyCO2H

peptide:

b) Write the three-letter abbreviations for the following tetrapeptide

OH

CH3   O                O       CH2  O      CH3   O

+ H3 N─CH─  ─  ─CNCH2─  ─  ─CNCH─  ─  ─CNCH─  ─CO–

H                H                H

20.                                                            Name  TWO  interactions  responsible  for  holding  a  protein chain in a defined three-dimensional structure.

Section C— Fats and oils

21. An ester is made from a carboxylic acid and an alcohol and has general structure:

R—______________ — R'

22. Fats and oils are a special type of ester (a triglyceride) in which the alcohol component is named

with structure

23. The acid component of fats and oils is a "fatty acid". Write a general structure for a fatty acid.

24. Therefore, the structure of a triglyceride is:

25. Oils have a lower m.p. than do fats (by definition, a fat is a solid at                            temperature). What structural feature in oils results in this lower m.p.? __________________

26. Why does this structure give a lower m.p.?

27.  Ethylene  (unsaturated) can  be converted to ethane  (saturated)  by  reaction with  hydrogen. Write a balanced equation for this reaction and name a suitable catalyst. What is this reaction called?

Now show the same chemistry for conversion of any oil to a fully saturated fat.

28. As fats and oils are esters they undergo ester reactions, in particular, hydrolysis. Write an equation for the hydrolysis of the fat:

CH2—O—CO—(CH2)14—CH3

|

CH—O—CO—(CH2)14—CH3

|

CH2—O—CO—(CH2)14—CH3

29. What is the key difference between the molecular structure of phospholipids and triglycerides (fats and oils)? Which part of the phospholipid is polar?

Section D – Nucleic acids

30. (a) The following structure consists of two units - a sugar unit linked to a base

unit. What type of structure is this compound?

(b) What is the third unit that is linked to this structure to form a nucleotide?

(c) Nucleotides are linked together by                           functional groups to

form polynucleotides (nucleic acids). These linkages can be broken by                                       .

31.  Match the process with the description

32. (a) A key feature of the structure of DNA is the strong hydrogen bonds between the complementary base pairs. Show the bonding between the following base pair of cytosine and guanine.

(b) What sequence of bases on one strand of  DNA  is complementary to the sequence  5’- GCGTATCAA-3’ on the other strand?