Carbohydrates - monosaccharides

Question 1

Compounds containing the elements C, H and O in the ratio:

e.g.

Answer 1

(CH2O)n

C6H12O6

Question 2

Can be defined as sugars and their derivatives

5 points

Answer 2

1. Deoxy-sugars
2. Sugar acids
3. Amino-sugars
4. Phospho-sugars
5. Acetyl-sugars, etc

Question 3

Functions
Structural:
3 points

Answer 3

1. cellulose, hemicelluloses in plants
2. chitin in insects
3. components of cell membranes + sub-cellular organelles

Question 4

Functions

Cell Recognition:

Answer 4

cell surface carbohydrates enabling cells to recognise each other

Question 5

Functions

Metabolism:

Answer 5

metabolic intermediates, energy substrates

Question 6

Functions

Energy store:

Answer 6

starch in plants and glycogen in animals

Question 7

Carbohydrate groups - Sugars

Monosaccharides:

Answer 7

1. Single sugars

2. Basic units of carbohydrates

Question 8

Carbohydrate groups - Sugars
Oligosaccharides:
2 points

Answer 8

1. 2-10 residues

2. Di-, tri-, tetra-, penta-, hexa-, octa-, nona-, deca-saccharides

Question 9

Carbohydrate groups - ‘Poly’-sugars
Polysaccharides:
2 points

Answer 9

1. > 20 residues

2. Macromolecules with long chains

Question 10

Aldehyde

Answer 10

R-CHO

Question 11

Ketone

Answer 11

R-COR

Question 12

carbonyl

Answer 12

C=O

Question 13

Sugars - polyhydroxy carbonyl compounds

Answer 13

1. polyhydroxy = 2 or more hydroxyl (-OH) groups

2. carbonyl = C=O

Question 14

Monosaccharides

3 points

Answer 14

1. simplest units of carbohydrates
2. Cannot easily be broken down to simpler compounds
3. Basic ‘building’ blocks -other classes of carbohydrates are derived from them

Question 15

Monosaccharides are classified according to:

2 points

Answer 15

1. number of C atoms in their structure: trioses (3), tetroses (4), pentoses (5), hexoses (6)
2. whether an aldehyde (aldose) R-CHO or ketone (ketose) R-COR

Question 16

drawing monosacharides

Answer 16

convention to draw the C atoms in monosaccharides in a vertical line (chain with the lowest numbered carbon atom at the top of the chain)

Question 17

e.g. of naming monosaccharide

H - C = O
H - C - OH 
H - C - OH 
H - C - OH 
|
H

Answer 17

Tetrose and aldose = aldotetrose

general name for aldose with 4 carbons… aldopentose, aldohexoses, aldotrioses

Question 18

Common aldoses
where groups found
2 points

Answer 18

1. All have the aldehyde (-CHO) group on the top C (C1) and

2. CH2OH on the lowest C (the highest numbered C, e.g. C6)

Question 19

Common aldoses

general formula and e.g.

Answer 19

Within a group, individual monosaccharides have the same general formula, but differ in the arrangement of their -OH groups

e.g. hexoses,
C6H12O6,

Question 20

common aldroses

triose

Answer 20

Glyceraldehyde

Question 21

common aldroses

tetrose

Answer 21

Erythrose

Question 22

common aldroses

pentose

Answer 22

Ribose

Question 23

common aldroses

hexose

Answer 23

Glucose

Question 24

Common ketoses
groups
2 points

Answer 24

1. All have the ketone (-C=O) group on the second top C (C2)
2. CH2OH on first and last C

Question 25

Common ketoses general formula and arrangement of OH groups 3 points

Answer 25

Within a group, individual mono-saccharides have the same general formula, but differ in the arrangement of their -OH groups eg. hexoses, C6H12O6

Question 26

'D' Ketose family general names 6 points

Answer 26

``` no of Cs 3 - Ketotriose 4 - Ketotetrose 5 - Ketopentoses 6 - Ketohexoses ```

Question 27

what structure is this ``` CH2OH C=O HO - C - H H - C - OH H - C - OH CH2OH ```

Answer 27

D - Fructose | a ketohexose

Question 28

What structure is this ``` CHO H C OH HO C H H C OH H C OH CH2OH ```

Answer 28

D - (+) - glucose Aldohexose

Question 29

What structure is this ``` CHO HO C H HO C H H C OH H C OH CH2OH ```

Answer 29

D- (+) - mannose aldohexose

Question 30

What structure is this ``` CHO H C OH HO C H HO C H H C OH CH2OH ```

Answer 30

D- (+) - galactose aldohexose

Question 31

Aldose and ketose names | 3 points

Answer 31

1. aldose names end in -ose 2. ketose names end -ulose 3. related aldose and ketose only have -OH arranged differently on C atoms 1 and 2

Question 32

Epimers | 3 points

Answer 32

1. Different compounds (structures) with the same molecular formula 2. differ by configuration at only one carbon 3. Important because biological systems can differentiate between them

Question 33

Epimer e.g. | 2 points

Answer 33

1. Glucose and galactose differ from each other only in respect to the arrangement of atoms in space 2. Have the same atoms joined to the same atoms but the opposite configuration at C4

Question 34

Memorising sugar epimers

Answer 34

see desktop | james bond, swear, bruce lee

Question 35

Reactions of –OH groups of monosaccharides (part 1) 3 points and e.g.

Answer 35

1. Intramolecular (taking place within the same molecule): 2. a hydroxyl (-OH) group will react with a carbonyl (C=O) group 3. form a hemiacetal e.g. R - OH + CORH = C OH R H RO

Question 36

Reactions of –OH groups of monosaccharides Monosaccharides with 5 or more C atoms form 4 points

Answer 36

1. internal hemiacetals 2. Results in a ring structure 3. Forms a new chiral (asymmetric) C (a C atom with four different groups bonded to it) 4. bonded to 2 O atoms – called anomeric C

Question 37

Reactions of –OH groups of monosaccharides In a ring form, the –OH attached to the anomeric C1 can point 4 points

Answer 37

1. below the ring (a) OR above the ring (b) (this applies only to D-sugars) 2. a and b structures called anomers 3 5-membered rings are furanoses 4. 6-membered rings are pyranoses

Question 38

Glucose (Glc) | 4 points

Answer 38

1. Most abundant monosaccharide; aldose 2. Central to cell metabolism 3. Building block for the most abundant polysaccharide - cellulose 4. Found in monosaccharide form in plants, fruits, honey, blood, lymph and cerebrospinal fluid

Question 39

Fructose (Fru) | 3 points

Answer 39

1. Most biologically important ketose 2. Found in the free form in leaves, fruit and honey 3. Major function is as component of sucrose (commercially extracted from sugarcane or beetroot) Building block of fructan (storage polysaccharide)

Question 40

Ribose (Rib) | 2 points

Answer 40

1. Aldopentose; component of ribonucleic acid (RNA) | 2. Its reduced form - deoxyribose – important in deoxyribonucleic acid (DNA)

Question 41

Galactose (Gal) | 4 points

Answer 41

1. Major function is as component of lactose (Glc+Gal) 2. Present in milk products 3. Building block of galactans (structural cell wall polysaccharides from plants) 4. Component of the antigens present on blood cells that determine blood group

Question 42

Mannose, Xylose and Arabinose are

Answer 42

not normally found in the free form but are important components of polysaccharides (e.g. plant hemicelluloses)

Question 43

Summary | Aldoses have an aldehyde group on

Answer 43

top C (C1)

Question 44

Summary | Ketoses have a keto group on the

Answer 44

second C (C2)

Question 45

Summary | aldoses and ketoses can both exist as

Answer 45

trioses, tetroses, pentoses and | hexoses

Question 46

Summary | Epimers e.g.

Answer 46

mannose, glucose and galactose

Question 47

Summary | Anomers e.g.

Answer 47

a glucose | b glucose

Question 48

Summary The most common monosacharides: 4 points

Answer 48

1. Glucose – the most abundant aldose central to the metabolism, building block of cellulose in plants 2. Fructose – a component of disaccharide sucrose 3. Ribose – a component of RNA and DNA 4. Galactose – component of lactose and many structural polysaccharides found in the plant cell walls