Carbohydrates

Question 1

Formula of carbohydrates .

Answer 1

Cn(H2O)n

Question 2

What are the hydrates of carbon

Answer 2

Sacharides
Monosaccharides, disaccharide- 1unit ,2unis
Oligosaccharides- few units
Polysaccharide- 100-1000s units
Triose, Tetrose, pentose- 3C, 4C, 5C

Question 3

What are the functions of carbohydrates

Answer 3

Energy transport and storage
Structural function- bacterial cell wall
Informative activity- cell and protein signalling

Question 4

What are the two major carbohydrates families?

Answer 4

Aldoses and ketoses

Question 5

What are the derivatives of main carbohydrates ?

Answer 5

Aldoses - D-glyceraldehyde
Ketoses- Dihydroxyacetone

Question 6

Characteristics of carbohydrates

Answer 6

1- asymmetric (chiral) carbons
2- AA are usually L, however carbohydrates are D
3-carbohydrates are optically active- rotate the monochromatic plane polarized light in opposite directions
4-many exists in cyclic forms. They carbonyl groups have a tendency to react reversibly to alcohols forming a hemiketal, pr hemiacetal

Question 7

Conditions of cyclic carbohydrates ?

Answer 7

1-Must have a carbonyl group and one or more alcoholic hydroxyls
2-steric ? 4 or less carbon cant form rings because they are unstable, so the carbohydrates must have or more carbons

Question 8

Characteristics of cyclic compounds

Answer 8

1- reversible
2- more stable
3-create an additional chiral centre

Question 9

What are the two structure glucose can form?

Answer 9

a-D-Glucopyranose / A-anomers - OH on C1 is same side of C6
b-D-Glucopyranose/ B-anomer- OH on C1 is opp side of C6
These two structures are drawn in HAWARTH diagram
-And these two structures are called anomers , bcz these isomers only differ at hemiketal or hemiacetal C
-they are both planar but not entirely bcz they can both exist in chair and boat form

Question 10

Draw the two structures

Question 11

Why are there two cyclic structures of glucose?

Answer 11

As we said earlier, cyclic structures create an extra chiral centre, in glucose these chiral centre can be created in two different ways on C1

Question 12

What is pyranose and why is it favoured

Answer 12

Pyranose are 6 membered sugar-rings, they are more favoured due to more numbers of carbons makes it more stable over the 5 membered ring.
It also contains the ring pyran

Question 13

Can sugars exist as Fischer structures?

Answer 13

Yes they can
- these are chain structures that are correct / stable for C3 to C4however, compounds with higher number of Cs , cyclic structure is more stable
- in aqueous solution (water)- a,b and fisher exist in equilibrium
- a and b interconvert through little amount of chain structure

Question 14

Which structure of glucose is most stable in water?

Answer 14

B > a>chain(fischer)
64>36>0.01%

Question 15

What is mutarotation? And how is it measured?

Answer 15

It is the inter conversion between a anomer and b anomer through trace amounts of chain structure
It can be measured using plane-polarized light.

Question 16

How can mutarotations be measured using plane-polarized light

Answer 16

Pure A-anomer rotates light at +112
Pure b-anomer rotates light at +19
A mixture of these two rotates light at
0.36x(112)+0.64x(12)=+53

Question 17

Diving deeper into the glucose anomers partially planar ability ,recall why they are not completely planar?

Answer 17

Because each of them can exist in 2 conformation
Chair and boat confirmation

Question 18

Which of the conformation of glucose (chair or boat )is more stable or preferred?

Answer 18

Chair conformation is more preferred be cause it is less crowding/hindrance of bulkier groups around the ring

Question 19

What are the two positions of groups on these conformation?

Answer 19

E- equatorial- group-is in plane to the planar part of ring
A- axial - group is perpendicular to planar part of ring

Question 20

Which of the positions ( E or A) is more stabLe and why?

Answer 20

Equatorial because less steric is hindrance of the groups around the ring

Question 21

Recall that in aq solutions , the most abundant structure of glucose was in B anomers, why is this so?

Answer 21

Yes, it was 64%
This is because only the b anomer can put all of its bulkier group (oh) in equatorial positions.

Question 22

Draw the boat and chair conformation of a anomer

Question 23

Draw the two chair conformation of b anomer and state which is more abundant in aqueous solution

Question 24

Recall that glucose can exist in cyclic structures as 6 carbon ring or 5 carbon ring , however 6carbon ring ring was preferred. What do you call a 6 carbon ring of glucose and why is it preferred.

Answer 24

A 6 carbon ring is called pyranose
Due to the pyran ring
It is preferred because it is more stable as it contains more number of carbons.

Question 25

Similarly, what is a 5 C carbohydrate ring called?

Answer 25

Furanose

Question 26

State the characteristics of furanose

Answer 26

- less stable -puckered

Question 27

Draw the furanose as hemiacetals

Question 28

Draw the furanose as puckered

Question 29

What are the six sugar derivatives? 1- Sugars are reduced

Answer 29

1- SUGARS CAN BE REDUCED - glyceraldehyde - reduced to glycerol -glucose is reduced to D- glucitol (Sorbitol) by adding H - we can observe the pattern that REDUCTION OF SUGAR GIVES ALCOHOL

Question 30

2- sugars are oxidized

Answer 30

1- linear monosaccharides acts as reducing agent Sugars/monosaccharides are oxidized - they have aldehyde groups (aldoses ) oxidized to give aldonic acid (the aldehyde is oxidized to carboxyl groupg) - quantification of sugars can be done using 1-Fehlings test 2-Tolens test

Question 31

Explain tollens test and fehlings test

Question 32

3-Phosphate added to sugar

Answer 32

Sugar phosphate esters are important in 1- dna neuclic molecule 2-important for energetic processes 2-recognition of sugar molecules bcz uncharged become neg charged 4- also limits the.transport through membrane Sun charged sugar can pass, charge cant

Question 33

3-Amino groups added to sugar

Answer 33

One or more hydroxyl group replaced with NH2 a-D-glucosamine 1- naturally occuring 2- connective tissues 3- cartilage(lubricant for joint and backbone) 4-joint fluid/senomial a-D-galactosamine 1-Amino derivative of galactose 2-Part of glycoprotein/glycolipids They are both epimers

Question 34

5-addition of acetyl groups-Acetylation

Answer 34

N-acetyl+glucosamine 2- important in bacterial cell wall-peptidoglycan 3- help block cell wall of pathogens- acting as medicine 4- found in fungal/insects cell Eg- Deacytelase

Question 35

6-Deoxy-sugars

Answer 35

These are riboses-5c sugars nucleic acid molecules in DNA and RNA a-D-ribose a-D-2-deoxyribose- sugar component of DNA

Question 36

Difference between hemiacetals and acetals

Question 37

What are the two ways you can get acetal or ketal?

Answer 37

1- hemiacetal or hemiketal reacts with alcohol—-> water and acetal/ketal 2-cyclic sugar with aldehyde /ketone group+another sugar—-> water and acetal/ketal BUT this is enzyme catalysed

Question 38

Draw a diagram for all these sugar derivatives

Question 39

Name the disacharides

Answer 39

1-maltose -Isomaltose 2-Cellobiose 3-Lactose 4-Sucrose 5-Trehalose

Question 40

1- MALTOSE

Answer 40

2- (1-4)glycosidic bonds btw two glucose molecules forms maltose 3- glycosidic bonds in Starch is broken down by amylase 3- dimeric -1 glucose is a-glucose/ a-D-glucopyranose (acetal) 2nd glucose is b-D-glucopyranose/b-D-gkucose (hemiacetal) Acetal glucose- nom-reducing sugars and non mutarotation Hemiacetal- has reducing end and mutorotations

Question 41

Iso-maltose

Answer 41

-Formed the same way as maltose- however 1-6 glycosidic bonds formed - “MADE FROM HYDROLYSIS OF DEXTRANS”-dextrans hydrolysis, is just the bonding of a-glucopyranose and b-glucopyranose by 1-6 glycosidic bonds - the OH of a glucopyranose reacts with CH2OH of b-glucopyranose -IMPORTANT IN -surgical procedures -radiology -cosmetics contains this

Question 42

3-Cellobiose

Answer 42

- cellobiose is the formed by b1-4 glycosidic bonds between a and b D glucopyranose -for ed by the breakdown of cellulose, hydrolysis of cellulose, reduction of cellulose due to addition of h20

Question 43

Lactose

Answer 43

—formed by b 1-4 glycosidic bonds between galactose and glucose sugars - main sugar found in milk

Question 44

4-Sucrose

Answer 44

- made by a1,b2 glycosidic bond between D-glucopyranose (a1) and D-fructofuranose (b2) -only disacharide sugar that is mom-reducing sugar and therefore non mutarotations -called an invert sugar because sucrose rotates light at +66 before hydrolysis However form 1.1 mixture of glucose (52) and fructoses (-92) after hydrolysis and therefore a mixture of free glucose and fructuse roates light at -39

Question 45

5-Trehalose

Answer 45

-formed by a1-a1 glycosidic bonds btw two glucose molecules - non reducing -non mutarotations -energy storage in insevts

Question 46

Recall, how many sugar units are present in Oligosacharides?

Answer 46

More then 15 to 100

Question 47

Is it appropriate to say ovligosacharides are repeating unit of disaccharide?

Answer 47

Yes , the bond form between monosaccharides can be repeated in various length forming oligosacharides Because the hydroxyl groups (OH) can react with an ANIMERIC carbon (the carbon that formed the carbonyl carbon in the straight chain, and reacted with OH to form cyclic structures)

Question 48

What are the important ovligosacharides?

Answer 48

Those that are attched to lipiids or proteins outside of an animal cell These oligosaccharides helps in cell cell recognition/signalling

Question 49

Gave two main functions of ovligosacharides

Answer 49

1- cell cell interactions, cell cell recognition/signalling Especially in the brain in nervous sys 2- 2- act as antigens coating blood cells and determining ABO blood system.

Question 50

Recall some information regarding polysaccharides from previous understanding

Answer 50

1-chains of 100s to 1000s of units 2-functions— storage and structural roles 3-we are going to learn about 3 types of polysaccharides A-starch - amylose and amylopectin B-glycogen C-Dextrans

Question 51

Describe in detail, the two main roles of polysaccharides

Answer 51

1- Storage -like starch and glycogen acts as energy storage , they are compact, which helps the body to remove or add units when needed 2- structural role eg cellulose- fold up in organized structure, forming tough and becoming resistant to degradation

Question 52

Compare and contrast between amylose and amylopectin - they play the structural role

Answer 52

Amylose Brached: no Bonds: a1-4 glycosidic bond Heix formation: yes 4000 per chain Amylopectin Branched : yes Bond: a1-6 glycosidic bonds Helix formation : no Function: linked approx 200 amyloseChains

Question 53

Glycogen and dextran

Answer 53

Glycogen - more branched then starch -contain less units per chain (15-20) Dextrans -contain a(1-4),a(1-3),a(1-6) glycosidic bonds Incomplete hydrolysis of starch and. glucose — maltose- a(1-4) -isomaltose- a(1-6)

Question 54

Importance of alinked polymers in storage

Answer 54

Found in plants seeds , stores sugars for germinating seed Easy to digest therefore act as a energy source of food for animals The sugar used to ferementation for the production of whiskey is made of grain, that sugar is got from the prdocess of malting

Question 55

Cellulose

Answer 55

Made of b(1-4) glycosidic linkages Recall which disacharide has this Not digested by human But animals have a rumen that produces cellulase to break down cellulose to sugars Function- very fribrous so used in textiles(cotton, linen), ind fibre(hemp, sisal) and paper A high amout if wod is cellulose

Question 56

Peptidoglycan

Answer 56

Found in bacterias Made of alternating b1-4 Nacetylglucoseamine and N acetylmuramic acid These two are cross linked by short peptidase Makes up the 3D mesh like cell wall structure that provides rigidity to the bacteria and protects it from osmotic stress

Question 57

Lysosome

Answer 57

Lysosome hydrolizes the b linkages Part of non specific HOS DEFENCE SYSTEM tear saliva milk egg white