carbs

Question 1

How many asymmetrical centres does aldoses have?

Answer 1

four: Asymmetrical centres at C2, C3, C4, C5

Question 2

what blood group is referred to as the universal donor?

Answer 2

O as it has no antigens on it. AB is the universal rcipient as it has both types of antigen

Question 3

Glyceraldehyde has 1 chiral centre. From this information deduce how many isomers Glyceraldehyde has.

Answer 3

Glyceraldhdye has 2 isomers. To work out the number of isomers a carbohydrate has use the formula 2n where n is the number of chiral centres the carbohydrate has. Glyceraldehyde has 1 chiral centre, so 2^1 = 2. Hence glyceraldehyde has 2 isomers

Question 4

What is the empirical formula for carbohydrates?

Answer 4

(CH2O)n

Question 5

what constitutes l and d isomer configuration?

Answer 5

side of projection of hydroxyl group (OH) from the chiral centre furtherst away from carbonyl group (the COOH at the end )
> right hand side - D sugar
> left hand side - L sugar

Question 6

anomer.. waht mean?

Answer 6

Anomer is the term used in carbohydrate chemistry for the formation of the new chiral centre when the carbonyl carbon (end carbon) forms a new covalent bond when reacted with the hydroxyl group (OH)
> making a circle/ ring
The formation of this bond leads to the carbonyl carbon becoming chiral and can exist in two forms in three dimensional space where alpha is down and beta is up depeding on which way the OH is facing

Question 7

what formation can alpha and beta glucose be in to be stable ring structures

Answer 7

boAt and chair
> saturated carbons have 109 degree bond angles
> also true of pyranose and fumarose rings

Connective tisseus: Storage=alpha linked. Structure=beta linked

Question 8

What is the diffece between a O- and an N- glycosidic bond

Answer 8

Hydroxyl group Reacting with anomeric carbon

Or nitrogen reacting with anomeric carbon

This is a condensation reaction removing water. This is also a covalent reaction

Question 9

Which structures are non reducing ?
Cylcic
Non cyclic

Answer 9

Cyclic structures are non reducing as they can’t open up (the aldyhyde end can’t be reduced in aqueous solution )

Question 10

What bond does lactose have
Glu - glu
Glu-fru
Glu - gal
Glu-glu4

Answer 10

Beta gal - Glu4

Question 11

What is the difference between homopolymer and heteropolymer

Answer 11

Hetero polymer made up of many various subunits

Question 12

What is the gross strucutre of cellulose and chitin

Answer 12

B1-4 glucose

B1-4 linked with N acetyl glucosamine (NAG) - heteropolymer

Question 12

Chitin has one carbon that is ‘derivitised’

What does that mean

Answer 12

Hydroxyl group is replaced with acetylated amino group

Hydroxyl groups can also be replaced by phosphates, amines, alkyls, sulphates

Question 12

What are lectins
A polysaccharide found in prokaryotes 
B polysaccharide found in bread 
C proteins that can recognise and bind to carb specific structures 
D hormone responsible for feeling hungry

Answer 12

Option C
E. G in influenza the lectin Hemaggutin that recognises sialic acid on host surface of glycoprotein so can penetrate the membrane and break glycosidic bond to realease virus

Question 13

What is the minimum carbon number that can exist as a ring structure in aldoses and ketones?

Answer 13

In aqueous solutions, 4 plus aldehydes and 5 plus ketones as covalent bonds form between the carbonyl and hydroxyl group =anomer

Question 16

Waht is an epimer?

Answer 16

Where 2 carbohydrates differ in only one chiral carbon Centre (Flipping of the H-C-OH)
Spacial orientation

E. G B-D galactose is a C4 epimer of B-D glucose

Question 17

Which of the following carbohydrates does not have a role as an energy source?
Monosaccharides
Glycolipids
Disaccharides
Starch
Glycogen

Answer 17

glycolipids as they act as signalling/receptor moelcules as many of them can be made - very varied