W3 - Polysaccharides (lecture) Flashcards
Which glycosidic bonds are present in maltose, sucrose and lactose?
M - 1-4-glycosidic bond, S - 1-2-glycosidic bond, L - 1-4-glycosidic bond
Is the glucose molecules in maltose, sucrose and lactose alpha or beta?
M- both alpha, S - alpha, L - beta
Where are maltase, sucrase and lactase located?
Surface of of small intestine
What bonds are present in glycogen, an energy storage homopolysaccharide and what does this tell about the structure?
alpha 1-4 and 1-6 glycosidic, it’s branched
Structural polysaccharides such as cellulose have beta glycosidic linkages (cellulose has beta 1-4), what does this tell about it’s structure?
Forms linear polymers that can stack
Why does the stacking of cellulose molecules render it water insoluble?
OH bonds are used in H-bonds in between chains so aren’t accessible to the water molecules
The exoskeleton of insects, crustaceans and fungi contain chitin, what monosaccharides are in chitin?
N-glucosamines
What bonds form between glucosamines in chitin?
beta 1-4 glycosidic
Chitosan is a deacetylated chitin, what is it used for in medicine?
Bandages, surgical thread and weight loss
What type of glycosidic linkages are present in storage polysaccharides such as starch (plants) and glycogen (animals)?
alpha-glycosidic
Out of starch and glucose solution, which has the lowest osmotic pressure?
Starch
Amylose comprises 20% of starch, it is unbranched and contains maltose disaccharides but what causes the helical/spiral shape?
The alpha-1-4-glycosidic bonds
Amylopectin comprises 80% of starch and is banched with alpha-1-4 and 1-6 bonds, at how many glucose residues is each branch point?
Every 6-8 glucose residues
Amylopectin is moderately soluble in water, how many reducing C-1 and non-reducing C-4 ends are there?
C-1 = 1, C-4 = many
In the liver theres what % of glycogen by weight and what % of glycogen in muscle?
8% weight of liver is glycogen, 1% in muscle
Glycogen is sparingly soluble and forms colloidal solutions, what makes it slightly different to amylopectin in terms of structure?
It’s even more highly branched and the branches in glycogen tend to be shorter
Glycosaminoglycans are heteropolysaccharides, most associate non-covalently with proteins (85% carb + 15% proteins), what are they composed of?
Repeating sequence of 2 monosaccharides where one is a an amino sugar
Glycoproteins are usually short, branched oligosaccharides covalently attached to a protein backbone, what percentage is carb and what is protein?
1-20% carb and 99-80% protein
There are heparin and hyaluronate units in GAGs, what 3 types of sulfate units can also make up glycosaminoglycans?
Dermatan, keratan and chondroitin 6-
What do all mucopolysaccharidoses result in medically?
SKeletal deformities and reduced life expectancies
What is a proteoglycan?
Protein associated with mucopolysaccharides
Proteoglycans have aggrecan brushes, what is caused when they lose these aggrecan brushes?
Osteoarthiritis
Heparin is secreted by mast cells lining blood vessels, the liver and lung, what does it inhibit?
Blood clotting by binding/inhibiting antithrombin
Enzymes can be specific to the type of glycosil linkages when assembling oligosaccharides, what are these enzymes called?
Glycosiltransferases
What can glycosil transferases define?
ABO blood groups
What form the core for a variety of glycoproteins?
3 mannoses and 2 acetylglucosamines
What does erythropoietin do?
Stimulates RBC production
Where does glycosylation take place? (where specifically is N and O linked)
Lumen of ER (N-linked) and GA (N and O linked)
During N-glycosylation the oligosaccharide needs to be activated, what does it bind to and where on the molecule to do this?
Dolichol phosphate, binds at phosphate end of molecule
To identify oligosaccharides and their binding sites what are used?
Oligos - MALDI-TOF spectrometry, binding sites - proteases
What is the universal carbohydrate recognition protein used to recognise for binding specificity?
Lectins
How does a virus recognise a host cell? (general example)
Hemagglutinin of influenza virus binds to sialic acid residues on host cell membrane
