4. Carbohydrates Flashcards
Brief importance of carbohydrates (4)
- Major means of storing energy in plants and animals.
- Structural components of nucleus acids.
- cell walls in bacteria
- main component of cellular recognition, such as antigens.
Definition of carbohydrate
A carbohydrate is a compound with 3 or more carbon atoms which has an aldehyde or keto functional group and two or more hydroxyl groups.
Monosacharides
Simplest sugar, >3 C but typically up to 7C. Some also have P,S atoms. Poly hodroxy aldhydes or ketones.
Tetroses have how many carbons?
4
Oligosacharides
Have 2 or more sugar units. Most common are disaccharides and trisacharides.
Polysacharides
Have many units of sugars in them, they are polymers and can be infinite units.
Monosacharides can be divided into 2 groups….
Aldehydes or ketones.
Trioses are aldotriose of ketotriose etc.
Simplest carbohydrate monosacharides
Glyceraldehyde and dihydroxyacetone
Term for Mirror image isomers?
Enantiomers
Stereoisomers (optical isomer)
D structural form (right) of carbohydrates is the
Naturally occurring form. Not the L form.
Epimers
Optical isomers or stereoisomers. The same except for the configuration around one carbon atom.
Diastereoisomer
Related to epimers although with Differences around multiple carbons rather than just one.
Most important carbohydrate molecule
D-glucose
Conjugated carbohydrate examples
DNA, Blood groups are dependent on the conjugation differences.
Peptidoglycan, keratin sulphates.
Chiral centre means that the compound can have…..
It is possible to have optical isomers of the carbohydrate.
Anomers
Two compounds are anomers if they differ in configuration only around the carbon atom that may yield a carbonyl group on hydrolysis (the potential carbonyl carbon).
Mutarotation
The process by which an anomer is inter-converted into the allowing anomer.
Haworth formulae used to tell which isomer you are looking at.
- If carbon 6 is above the ring, it is a d sugar, and if it is below the ring it is an L-sugar.
- if the hydroxyl group on the anomer if carbon (c1 for aldoses) is above the ring it is a beta. Below it is an alpha
If the hydroxyl group is lower than the plain of the cyclic compound, the compound is considered…
An Alpha form
Does glucose have reducing ability and why?
Yes, due to the functional group not inside the ring.
Does sucrose have reducing ability? And why?
Nope, sucrose functional group is encircled in the cyclic nature of sucrose.
Glycosidic bond
Two -OH groups react together to form a bond. For example methanol and glucose can form a glycosidic bond.
What is a disaccharide ?
Is a compound made from two sugar units joined by a glycosidic bond. Lactose, maltose, sucrose
Maltose has what sugar units?
Glucose with a glycosidic bond to glucose
Lactose is made of what sugar units?
Glucose with a glycosidic bond to galactose.
Sucrose
Glucose + fructose.
Very sweet. A glucose and b fructose unit.
Homopolysaccharides
Starch, glycogen and cellulose: all of which are composed of glucose units arranged differently/joined together.
Starch contains two types of glucose polymers…
Amylose and amylopectin.
Amylose consists of
Glucose units joined by a links
Amylopectin consists of
Glucose joined by alpha links with some branches alpha 1-6 links.
Where is glycogen stored in the body?
Liver and muscles.
Substances that contain repeating segments which consist of two or more different carbohydrate units.
Heteropolysaccharides
Polysaccharides that contain only one type of sub unit.
Homopolysaccharides
Botrytis produces large amounts of polyphenol oxidase and charecteristic….. ………
Carbohydrate polymer. The polymer rapidly blocks the small pore sized filters used in bulking bottle fermentation. Trichoderma viride van cleave this polymer allowing more efficient filtration.
a - amylase
Severs glycosidic bonds at any 1-4 bond position in the molecule chain.
(Endoamylase)
b - amylase
Breaks down starch during malting of barley for beer. It cleaves starch molecules at every second 1-4 glycosidic bond.
Role of glycogen in animals
Energy storage in animals, mainly in the liver.
How glycogen differs structurally to cellulose?
Both made up of repeating units of glucose. In cellulose the gluc units are joined by a beta 1-4 glycosidic bond, while in glycogen the bonds are alpha 1-4 with alpha 1-6 branch points.
Difference between beta and alpha glycosidic bonds?
Celluloses stereochemistry allows it to pack more uniformly giving it a stronger structure with beta glycosidic bonds/linkages. Connects at the 1-4 carbon. Alpha connects at the 1-6 carbon allowing it to branch.
