Carbohydrates Flashcards
Formula of carbohydrates .
Cn(H2O)n
What are the hydrates of carbon
Sacharides
Monosaccharides, disaccharide- 1unit ,2unis
Oligosaccharides- few units
Polysaccharide- 100-1000s units
Triose, Tetrose, pentose- 3C, 4C, 5C
What are the functions of carbohydrates
Energy transport and storage
Structural function- bacterial cell wall
Informative activity- cell and protein signalling
What are the two major carbohydrates families?
Aldoses and ketoses
What are the derivatives of main carbohydrates ?
Aldoses - D-glyceraldehyde
Ketoses- Dihydroxyacetone
Characteristics of carbohydrates
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
Conditions of cyclic carbohydrates ?
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
Characteristics of cyclic compounds
1- reversible
2- more stable
3-create an additional chiral centre
What are the two structure glucose can form?
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
Draw the two structures
Why are there two cyclic structures of glucose?
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
What is pyranose and why is it favoured
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
Can sugars exist as Fischer structures?
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
Which structure of glucose is most stable in water?
B > a>chain(fischer)
64>36>0.01%
What is mutarotation? And how is it measured?
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.
How can mutarotations be measured using plane-polarized light
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
Diving deeper into the glucose anomers partially planar ability ,recall why they are not completely planar?
Because each of them can exist in 2 conformation
Chair and boat confirmation
Which of the conformation of glucose (chair or boat )is more stable or preferred?
Chair conformation is more preferred be cause it is less crowding/hindrance of bulkier groups around the ring
What are the two positions of groups on these conformation?
E- equatorial- group-is in plane to the planar part of ring
A- axial - group is perpendicular to planar part of ring
Which of the positions ( E or A) is more stabLe and why?
Equatorial because less steric is hindrance of the groups around the ring
Recall that in aq solutions , the most abundant structure of glucose was in B anomers, why is this so?
Yes, it was 64%
This is because only the b anomer can put all of its bulkier group (oh) in equatorial positions.
Draw the boat and chair conformation of a anomer
Draw the two chair conformation of b anomer and state which is more abundant in aqueous solution
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.
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.
Similarly, what is a 5 C carbohydrate ring called?
Furanose
State the characteristics of furanose
- less stable
-puckered
Draw the furanose as hemiacetals
Draw the furanose as puckered
What are the six sugar derivatives?
1- Sugars are reduced
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
2- sugars are oxidized
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
Explain tollens test and fehlings test
3-Phosphate added to sugar
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
3-Amino groups added to sugar
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
5-addition of acetyl groups-Acetylation
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
6-Deoxy-sugars
These are riboses-5c sugars nucleic acid molecules in DNA and RNA
a-D-ribose
a-D-2-deoxyribose- sugar component of DNA
Difference between hemiacetals and acetals
What are the two ways you can get acetal or ketal?
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
Draw a diagram for all these sugar derivatives
Name the disacharides
1-maltose
-Isomaltose
2-Cellobiose
3-Lactose
4-Sucrose
5-Trehalose
1- MALTOSE
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
Iso-maltose
-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
3-Cellobiose
- 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
Lactose
—formed by b 1-4 glycosidic bonds between galactose and glucose sugars
- main sugar found in milk
4-Sucrose
- 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
5-Trehalose
-formed by a1-a1 glycosidic bonds btw two glucose molecules
- non reducing
-non mutarotations
-energy storage in insevts
Recall, how many sugar units are present in Oligosacharides?
More then 15 to 100
Is it appropriate to say ovligosacharides are repeating unit of disaccharide?
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)
What are the important ovligosacharides?
Those that are attched to lipiids or proteins outside of an animal cell
These oligosaccharides helps in cell cell recognition/signalling
Gave two main functions of ovligosacharides
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.
Recall some information regarding polysaccharides from previous understanding
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
Describe in detail, the two main roles of polysaccharides
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
Compare and contrast between amylose and amylopectin - they play the structural role
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
Glycogen and dextran
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)
Importance of alinked polymers in storage
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
Cellulose
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
Peptidoglycan
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
Lysosome
Lysosome hydrolizes the b linkages
Part of non specific HOS DEFENCE SYSTEM
tear saliva milk egg white
