Download L01_2002

Bio 366: Biological Chemistry 2
Lecture 1: Course Introduction and
Review of Carbohydrate Structure
Instructor: Dr. Caro-Beth Stewart
Teaching Assistant: None
Course URLs:
http://www.albany.edu/faculty/cs812/bio366/bio366_2002.html
or
http://www.albany.edu/biology/courses/index.html
Look at the online syllabus regularly for reading list
updates and any changes to the course schedule!
These notes will be posted online after the class.
Last year’s notes are available through the link to the
2001 web site.
Examples of exams from previous years are also
available on the 2001 web site for ABio366. Please
note, however, that the format for the exams this year
will be quite different.
Required (or at least strongly recommended!)
readings will be posted on the 2002 web site, and
PDF of selected journal articles will also be made
available to you.
Notice that students will be required to give classroom
presentations to the class during the last three class
sessions. These presentations will cover recent,
important advances in a biochemical topic of the
student’s choice. More information about this will be
given throughout the term. Do not panic! Students
from previous years (nearly) unanimously claim that
the experience is both highly educational and fun.
Review of
Metabolism
(various places in text)
&
Carbohydrate structure
(mostly from Chapter 8)
METABOLISM--the biosynthesis (anabolism) and degradation
(catabolism) of complex metabolites.
We'll focus on metabolism of "food" in humans
over the next few weeks:
1. Carbohydrates (sugars)
2. Lipids (fats)
3. Amino acids (proteins)
4. Nucleic acids (DNA and RNA—not used for
major nutritional purposes in humans, but
are metabolized for energy purposes by
some animals such as ruminants)
Fig. 13.2
OVERVIEW OF
CATABOLISM:
Glycolysis,
TCA (citric acid) cycle,
Oxidative-phosphorylation
Sugars, proteins & fats all
feed into these cycles.
CARBOHYDRATE metabolism
• GLYCOGEN metabolism.
To understand this material, you must first learn (review)
some basic SUGAR structures (especially GLUCOSE).
Most of this material comes from Chapter 8 of Voet, Voet
and Pratt (VVP).
You're expected to know:
• Carbohydrate and sugar nomenclature, especially
pertaining to GLUCOSE monomers and
polysaccharides.
• The numbering system of glucose (and, later, ribose)
• The reducing end of sugars
• Storage polysaccharide structures (a-amylose and
amylopectin)
• The structural polysaccharides, cellulose and chitin.
• The peptidoglycan wall of bacteria
Carbohydrates or saccharides are the most abundant
biological molecules, and are composed of (see figures in
Chapter 8 for structures):
Simple sugars:
monosaccharides
have single unit
disaccharides
have two units
sucrose = "sugar" legally!
You must know the numbering system of glucose (see next
slide, Fig. 8-4), as it helps make sense of the bond names.
a-D-glucopyranose
D-glucose
(linear form)
ß-D-glucopyranose
(pyranose = sugar with a six-membered ring)
•GLUCOSE is a major metabolic fuel source in living
organisms which is degraded via glycolysis to
produce ATP.
•Higher organisms protect themselves from potential
fuel shortages by storing glucose by polymerizing it
into high molecular mass GLUCANS, or glucose
polysaccharides — complex carbohydrates with
monosaccharides held together by "glycosidic"
bonds (the bond connecting the anomeric carbon to
the acetyl oxygen) between neighboring units.
•Enzymes that hydrolyze glycosidic bonds are referred
to as glycosidases.
In PLANTS:
The major glucose storage substance is STARCH,
which is a mixture of...
a-amylose,
an a(14)-linked glucan, usually
several thousand glucose units
long
amylopectin,
&
like amylose, but has a(16)
branches every 24-30 residues on
average; up to 106 glucose
units/molecule
These are stored in the cytoplasm of plant cells.
Fig. 8-10:
a-Amylose
a-Amylose is a
regularly repeating
polymer that form a
left-handed helix.
Compare a-amylose:
To cellulose:
The major structural
component of plant cell
walls. Is a linear polymer
of up to 15,000 D-glucose
residues.
WHAT’S THE DIFFERENCE?
a-amylose:
Compare Figure 8-10 (aamylose structure)….
a(1 4) linkage
Cellulose:
to Figure 8-9 (cellulose
structure) to see the
structural consequences
of these different linkages
b(1 4) linkage
In ANIMALS:
The storage glycan of animals is GLYCOGEN, which differs
from amylopectin only in that the branches occur every 8-12
residues.
Glycogen occurs in granules of about 100-400 Å diameter
in cytoplasm of cells that use it most.
For example:
• Muscle has a maximum of 1-2% of its weight in glycogen.
• Liver has a maximum of 10% by weight. Combined, this is
about a 12 hour energy supply for the body (about 1 day).
["Carbohydrate loading" fills these glygogen stores.]
Fig. 8-11: a beautiful micrograph of a liver cell showing
stored glycogen:
Glycogen granules also
contain the enzymes that
catalyze glycogen synthesis
and degradation, as well as
some regulatory enzymes.
Chitin is the major structural component of the exoskeletons of
crustaceans, insects, and spiders. It is also present in the cell
walls of most fungi and many algae.
PEPTIDOGLYCAN is the major
structural component of the cell
walls of gram-positive bacteria.
It is digested by the enzyme
LYSOZYME, causing the cells to
‘lyse’ (break open).