W3 - Polysaccharides (lecture)

Question 1

Which glycosidic bonds are present in maltose, sucrose and lactose?

Answer 1

M - 1-4-glycosidic bond, S - 1-2-glycosidic bond, L - 1-4-glycosidic bond

Question 2

Is the glucose molecules in maltose, sucrose and lactose alpha or beta?

Answer 2

M- both alpha, S - alpha, L - beta

Question 3

Where are maltase, sucrase and lactase located?

Answer 3

Surface of of small intestine

Question 4

What bonds are present in glycogen, an energy storage homopolysaccharide and what does this tell about the structure?

Answer 4

alpha 1-4 and 1-6 glycosidic, it’s branched

Question 5

Structural polysaccharides such as cellulose have beta glycosidic linkages (cellulose has beta 1-4), what does this tell about it’s structure?

Answer 5

Forms linear polymers that can stack

Question 6

Why does the stacking of cellulose molecules render it water insoluble?

Answer 6

OH bonds are used in H-bonds in between chains so aren’t accessible to the water molecules

Question 7

The exoskeleton of insects, crustaceans and fungi contain chitin, what monosaccharides are in chitin?

Answer 7

N-glucosamines

Question 8

What bonds form between glucosamines in chitin?

Answer 8

beta 1-4 glycosidic

Question 9

Chitosan is a deacetylated chitin, what is it used for in medicine?

Answer 9

Bandages, surgical thread and weight loss

Question 10

What type of glycosidic linkages are present in storage polysaccharides such as starch (plants) and glycogen (animals)?

Answer 10

alpha-glycosidic

Question 11

Out of starch and glucose solution, which has the lowest osmotic pressure?

Answer 11

Starch

Question 12

Amylose comprises 20% of starch, it is unbranched and contains maltose disaccharides but what causes the helical/spiral shape?

Answer 12

The alpha-1-4-glycosidic bonds

Question 13

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?

Answer 13

Every 6-8 glucose residues

Question 14

Amylopectin is moderately soluble in water, how many reducing C-1 and non-reducing C-4 ends are there?

Answer 14

C-1 = 1, C-4 = many

Question 15

In the liver theres what % of glycogen by weight and what % of glycogen in muscle?

Answer 15

8% weight of liver is glycogen, 1% in muscle

Question 16

Glycogen is sparingly soluble and forms colloidal solutions, what makes it slightly different to amylopectin in terms of structure?

Answer 16

It’s even more highly branched and the branches in glycogen tend to be shorter

Question 17

Glycosaminoglycans are heteropolysaccharides, most associate non-covalently with proteins (85% carb + 15% proteins), what are they composed of?

Answer 17

Repeating sequence of 2 monosaccharides where one is a an amino sugar

Question 18

Glycoproteins are usually short, branched oligosaccharides covalently attached to a protein backbone, what percentage is carb and what is protein?

Answer 18

1-20% carb and 99-80% protein

Question 19

There are heparin and hyaluronate units in GAGs, what 3 types of sulfate units can also make up glycosaminoglycans?

Answer 19

Dermatan, keratan and chondroitin 6-

Question 20

What do all mucopolysaccharidoses result in medically?

Answer 20

SKeletal deformities and reduced life expectancies

Question 21

What is a proteoglycan?

Answer 21

Protein associated with mucopolysaccharides

Question 22

Proteoglycans have aggrecan brushes, what is caused when they lose these aggrecan brushes?

Answer 22

Osteoarthiritis

Question 23

Heparin is secreted by mast cells lining blood vessels, the liver and lung, what does it inhibit?

Answer 23

Blood clotting by binding/inhibiting antithrombin

Question 24

Enzymes can be specific to the type of glycosil linkages when assembling oligosaccharides, what are these enzymes called?

Answer 24

Glycosiltransferases

Question 25

What can glycosil transferases define?

Answer 25

ABO blood groups

Question 26

What form the core for a variety of glycoproteins?

Answer 26

3 mannoses and 2 acetylglucosamines

Question 27

What does erythropoietin do?

Answer 27

Stimulates RBC production

Question 28

Where does glycosylation take place? (where specifically is N and O linked)

Answer 28

Lumen of ER (N-linked) and GA (N and O linked)

Question 29

During N-glycosylation the oligosaccharide needs to be activated, what does it bind to and where on the molecule to do this?

Answer 29

Dolichol phosphate, binds at phosphate end of molecule

Question 30

To identify oligosaccharides and their binding sites what are used?

Answer 30

Oligos - MALDI-TOF spectrometry, binding sites - proteases

Question 31

What is the universal carbohydrate recognition protein used to recognise for binding specificity?

Answer 31

Lectins

Question 32

How does a virus recognise a host cell? (general example)

Answer 32

Hemagglutinin of influenza virus binds to sialic acid residues on host cell membrane