Lec 3: Carbohydrates Flashcards
what are the fucntions of carbohydrates?
- provide a rapid and readily available supply og energyfor celular reactions e.g muscle l & liver glycogen
- Form part of important molecules in the cell e.g Sugar-phosphate backbones in DNA double helix
- Form markers on the cell surface which aid cell recognition e.g Blood group markers
what is monosacchride and disaccharide? what is the general formula
monosaccharides: any of the class of sugars (e.g. glucose) that cannot be hydrolysed to give a simpler sugar.
general formula: (CH2O)n
disaccharide: dimer= 2 monoscaccharides
what is a oligosaccharide
what is a polysaccharide
Oligosaccharide: is a saccharide polymer containing a small number (typically three to ten) of monosaccharides (simple sugars)
Polysaccharide: polymer of monosaccharide units linked together
which is the Fischer Projection and Haworth Projection of this glucose molecule
*Note*: Naming monosaccharides
*Monosaccharides contain an aldehyde or ketone functional group and hydroxyl groups
3 C- triose
4 C- tetrose
5 C- pentose
6 C- hexose
7 C- heptsoe
8 C- octose
9 C- nonose
10- decose
what is the name of the molecule?
*Note*: isomers of aldohexose
what is the chemical formula?
C6H12O6
what are n-deoxymonosaccharides?
these are monosaccharides where the hydroxyl group [OH] is replaced with [H]
what is a stereoisomers?
each of two or more compounds differing only in the spatial arrangement of their atoms
They have:
- they have the same chemical formula
- the same orders and types of bonds
but are non -overlapping mirror images of each other and thus have
- Different spatial arrangements
- Different biological functions
D-isomers and L-isomers
what is a chiral carbon centre
carbon with 4 different groups coming of it
what is meant by the oxidation/reduction of a carbon
oxidation is a process by which a carbon atom gains bonds to more electronegative elements, most commonly oxygen. Reduction is a process by which a carbon atom gains bonds to less electronegative elements, most commonly hydrogen.
*Note*: How to assign sugars as L or D
- If the OH on the bottom chiral centre points to the right = D
- If the OH on the bottom chiral centre points to the left = L
what is cyclization
in what conditions to monosaccharides cyclize?
this is where the hydroyl [OH] group on the second to last carbon reacts with carbonyl group [C=O]
Resulting product for an aldose = a hemiacetal
Resulting product for a ketose = a hemiketal
monosaccharides cyclize spontaneously under normal conditions
what is an anomeric carbon?
- an anomeric carbon is a stereocenter
- It depends on which direction the hydroxyl [OH] group attaches to the carbon
- so the anomeric carbon is either alpha or beta
(alpha= H above, beta= H below)
can happen for both hemiacetal and hemiketals
what 2 possible products arise from the cyclization of D-glucose?
the OH group can attack planar C=O gorup from either side
so you get:
α and β anomers of D-glucopyranose
how can you tell the difference between alpha and beta glucose?
in alpha glucose the OH is below the plane
in beta glucose the OH is above the plane
how is glucose generated?
from the production of starch
*Note* Generation of ATP from glucose
*Note* Fructose structure
what is maltose made up of? where does the glycosidic link form?
where is it usually present
made up of: a-1,4 alpha glucose and a-1,4 beta glucose
alpha - 1,4 glycosidic link
present in;
- germinating seeds/grains
- metabolism of maltose by yeast yields ethanol and CO2
what is lactose formed by?
made up of: beta glucose and galatose molecules
beta-1,4 glycosidic link
what is amylose?
long linear chains
of alpha-1,4-linked-D-glucose
residues that has a coiled structure
what is amylopectin
linear chains of α-1,4-linked D-glucose residues
joined through α-1,6-linked branch points
Has a brush-like structure
where is starch found vs glycogen?
starch: amyloplasts (non pigmented plant cell organelles) and chloroplasts (from roots, tubers, seeds and fruits)
glycogen: in animals, liver and muscle cells
