Describe the straight-chain formula of glucose and the structural difference between Alpha-glucose and Beta-glucose



Straight chain formula of glucose

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Figure1. D-glucose
Red part: Aldehyde functional group (C=O)
Pink part: Hydroxyl or Alcohol functional group (-OH)
Blue part: place which identifies 'D' and 'L' when the hydroxyl group is on the right hand side it is 'D', when it is on left then it is 'L'
YOU need to be able to draw the straight chain structure of glucose from memory. You don't need to be able to distinguish between the D and D forms.

Distinguishing between the alpha and beta structures of glucose

The position of -OH indicates the difference.
Starting from C 1 in alpha glucose the -OH alcohol groups go down, down, up down.
In beta glucose they go up, down, up down.

Unlike 2-amino acids alpha and beta are not entaniomers or mirror images of one another because on each carbon atom the -OH group is either above or below the plane. In the ring structure Carbon 6 is the only one that is not chiral, or in other words does not have four different group attached to it.

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Figure2. **Alpha and Beta Glucose in the Haworth Structures**
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Figure 3. Alpha and Beta Glucose in Ring from
Notice that the -OH group on C1 is are inverted in alpha and beta glucose.

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Figure 4: Apha and beta structures of glucose