Lecture 14. The Structures of Carbohydrates Flashcards
What is a simple carbohydrate in terms of structure ?
They are aldehydes or ketones with multiple hydroxyl groups
How can simple carbohydrates which are monosaccharides be described by ?
The number of carbon atoms in the structure and according to whether they are aldehyde sugars (aldoses) or ketones (ketoses)
What is glucose ?
Aldohexose, six carbon aldehyde sugar
What is fructose ?
A ketohexose, a six carbon ketone sugar
What is ribose ?
An aldopentose, a five carbon aldehyde sugar
What is D-glyceraldehyde ?
A natural enantiomer
How to draw a fischer projection ?
- Orient the carbonyl group towards the top of the page
2. Squash the structure down, with the carbon bakbone in a vertical line
What does each diastereomer theoretically exist as ?
A pair of enantiomers
How do many sugars exist predominantly as in water ?
Cyclic hemiacetals
What is a furanose ?
A five membered ring
What is a pyranose ?
A six membered ring
What does a wavy bond indicate ?
That both stereoisomers form
What are anomers ?
Cyclic monosaccharides or glycosides that are epimers
What is an anomeric centre ?
In the ring closed hemiacetal form it is the ex-carbonyl carbon
What does the D-glucose pyranose form exist as ?
A shape known as the chair conformation in which all bond angles are 109.5 degrees
