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Biochemistry > Carbohydrates - monosaccharides > Flashcards

Carbohydrates - monosaccharides Flashcards

1
Q

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

e.g.

A

(CH2O)n

C6H12O6

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2
Q

Can be defined as sugars and their derivatives

5 points

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

Functions
Structural:
3 points

A
  1. cellulose, hemicelluloses in plants
  2. chitin in insects
  3. components of cell membranes + sub-cellular organelles
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4
Q

Functions

Cell Recognition:

A

cell surface carbohydrates enabling cells to recognise each other

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5
Q

Functions

Metabolism:

A

metabolic intermediates, energy substrates

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6
Q

Functions

Energy store:

A

starch in plants and glycogen in animals

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7
Q

Carbohydrate groups - Sugars

Monosaccharides:

A
  1. Single sugars

2. Basic units of carbohydrates

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8
Q

Carbohydrate groups - Sugars
Oligosaccharides:
2 points

A
  1. 2-10 residues

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

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9
Q

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

A
  1. > 20 residues

2. Macromolecules with long chains

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10
Q

Aldehyde

A

R-CHO

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11
Q

Ketone

A

R-COR

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12
Q

carbonyl

A

C=O

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13
Q

Sugars - polyhydroxy carbonyl compounds

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

2. carbonyl = C=O

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14
Q

Monosaccharides

3 points

A
  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
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15
Q

Monosaccharides are classified according to:

2 points

A
  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
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16
Q

drawing monosacharides

A

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)

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17
Q

e.g. of naming monosaccharide

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

Tetrose and aldose = aldotetrose

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

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18
Q

Common aldoses
where groups found
2 points

A
  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)

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19
Q

Common aldoses

general formula and e.g.

A

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

e.g. hexoses,
C6H12O6,

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20
Q

common aldroses

triose

A

Glyceraldehyde

21
Q

common aldroses

tetrose

A

Erythrose

22
Q

common aldroses

pentose

A

Ribose

23
Q

common aldroses

hexose

A

Glucose

24
Q

Common ketoses
groups
2 points

A
  1. All have the ketone (-C=O) group on the second top C (C2)
  2. CH2OH on first and last C
25
Q

Common ketoses
general formula and arrangement of OH groups
3 points

A

Within a group, individual mono-saccharides have the same general formula,

but differ in the arrangement of their -OH groups

eg. hexoses,
C6H12O6

26
Q

‘D’ Ketose family
general names
6 points

A 
no of Cs 
3 - Ketotriose 
4 - Ketotetrose
5 - Ketopentoses 
6 - Ketohexoses
27
Q

what structure is this

CH2OH
C=O
HO - C - H
H - C - OH 
H - C - OH 
CH2OH
A

D - Fructose

a ketohexose

28
Q

What structure is this

CHO
H C OH 
HO C H 
H C OH 
H C OH 
CH2OH
A

D - (+) - glucose

Aldohexose

29
Q

What structure is this

CHO 
HO C H 
HO C H 
H C OH 
H C OH 
CH2OH
A

D- (+) - mannose

aldohexose

30
Q

What structure is this

CHO 
H C OH 
HO C H 
HO C H 
H C OH 
CH2OH
A

D- (+) - galactose

aldohexose

31
Q

Aldose and ketose names

3 points

A
  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
32
Q

Epimers

3 points

A
  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
33
Q

Epimer e.g.

2 points

A
  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
34
Q

Memorising sugar epimers

A

see desktop

james bond, swear, bruce lee

35
Q

Reactions of –OH groups of monosaccharides (part 1)

3 points and e.g.

A
  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

36
Q

Reactions of –OH groups of monosaccharides

Monosaccharides with 5 or more C atoms form

4 points

A
  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
37
Q

Reactions of –OH groups of monosaccharides

In a ring form, the –OH attached to the anomeric C1 can point

4 points

A
  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

  1. 6-membered rings are pyranoses
38
Q

Glucose (Glc)

4 points

A
  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
39
Q

Fructose (Fru)

3 points

A
  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)
40
Q

Ribose (Rib)

2 points

A
  1. Aldopentose; component of ribonucleic acid (RNA)

2. Its reduced form - deoxyribose – important in deoxyribonucleic acid (DNA)

41
Q

Galactose (Gal)

4 points

A
  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
42
Q

Mannose, Xylose and Arabinose are

A

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

43
Q

Summary

Aldoses have an aldehyde group on

A

top C (C1)

44
Q

Summary

Ketoses have a keto group on the

A

second C (C2)

45
Q

Summary

aldoses and ketoses can both exist as

A

trioses, tetroses, pentoses and

hexoses

46
Q

Summary

Epimers e.g.

A

mannose, glucose and galactose

47
Q

Summary

Anomers e.g.

A

a glucose

b glucose

48
Q

Summary
The most common monosacharides:
4 points

A
  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

Biochemistry (17 decks)

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