Biochem 153A: Week 4 Discussion Handout

Biochem 153A: Week 4 Discussion

I. Take Quiz
II. MONOSACCHARIDES
Objectives: Be able to draw Fischer and Haworth projection structures for glucose; Know the epimers mannose and galactose (fructose, too); Understand carbohydrate enantiomers, anomers, and glycosidic linkages.

1. The sugar family is a bunch of carbohydrates that exist as enantiomers.
All biological sugars are : D or L ?
What do you suppose would happen if you ingested L-glucose?

2. Drawing glucose:
straight chain, Fischer projection, then "lying down" (hypothetical), now a pyranose ring, Haworth projection

3. Epimers of Glucose
Mannose is a epimer of glucose.
Fischer projection, Haworth projection

Galactose is a epimer of glucose.
Fischer projection, Haworth projection

Fructose looks a lot like glucose. However, it is not an epimer of glucose.
Fischer projection, Haworth projection

4. Glycosidic linkages: Find the anomeric carbon--look for 2 oxygens. Decide if it is in acetal or hemiacetal form.
The "oside" ending means that the anomeric carbon is an ___.
The "ose" ending means that the anomeric carbon is a _.
ex. 4-Methyl-beta-D-mannopyranose ex. O-Methyl-beta-D-mannopyranoside

III. DISACCHARIDES
Objectives: Know the compositions and linkages for maltose, cellobiose, lactose, and sucrose; Be able to name any linkage; Understand directionality from NRE to RE; Recognize glycosidic linkages

1. Drawing a dissacharide:
ex. Maltose
Circle the glycosidic bond

2. Naming linkages: Directionality from NRE (non-reducing end) to RE (reducing end)
Why is the "reducing end" named as such? How can it be recognized?

3. Dissacharide:its monosaccharide composition, glycosidic linkage, cartoon structure

maltose

cellobiose

lactose

sucrose

IV. POLYSACCHARIDES
Objectives: Know the compositions and linkages for cellulose, amylose, glycogen, hyaluronic acid; Understand the implications of alpha vs beta linkages in the structure-function relationship.

1. alpha -linkages in polysaccharides usually result in an overall structure that is _.
Thus, alpha -linked polysaccharides are ideal for a function.
beta-linkages in polysaccharides usually result in an overall structure that is .
Thus, beta -linked polysaccharides are ideal for a _________ function.

2. polysaccharide: its monosaccharide composition, linkages, any branching?, overall structure, biol. function

cellulose

amylose

amylopectin

glycogen

hyaluronic acid

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