Carbohydrates Flashcards
What is a Carbohydrate?
A polyhydroxyaldehyde or polyhydroxyketone, or a substance which gives these compounds upon hydrolysis
What is a monosaccharide and it’s general formula?
Monosaccarides are a source of energy in metabolic processes that cannot be further simplified. Their basic formula:
Cn(H2O)n, where n = the number of carbon atoms and varies from 3-8
What are the two types of monosaccharides?
- Aldose = has an aldehyde group
- Ketose = has a ketone group
How are monosaccharides named?
They are classified by the number of carbon atoms present. tri -3 tetr-4 pent-5 hex-6 hept-7 oct-8
Are enantiomers and distereoisomers possible in carbohydrates?
Yes as carbohydrates have stereogenic centres
What is a fischer projection?
A 2 dimensional representation of a 3 dimensional organic molecule, it is commonly used to represent monosaccharides
How do we put molecules into the fischer projection?
rotate the molecule 90 degrees clockwise from the top and then 180 degrees backwards until the hydrogens are level with the plane of paper
What is a D monosaccharide versus an L monosaccharide?
D-monosaccharide= the -OH group on it’s penultimate (2nd to last) carbon is on it’s right
L-monosaccharide= the -OH group on it’s penultimate carbon is on it’s left
What form are all natural sugars found in?
the D form
What are cyclic sugars?
When one or more series of atoms in the sugar compound connect to form a ring shape
What are hemiacetals?
compounds which form as a result of aldehydes or ketones reacting with alcohols
Which groups/compounds can become cyclic?
Those hemiacatels which contain 5 or 6 carbon atoms
What is similar about monosaccharides in cyclic 5/6 membered hemiacetals?
They have hydroxyl and carbonyl groups in the same molecules
What are Haworth Projections?
a common way of writing a structural formula to represent the cyclic structure of monosaccharides
What is a beta and alpha anomer?
b- OH on the anomeric carbon is cis to the terminal -CH2OH (up)
a-OH on the anomeric carbon is trans to the terminal-CH2OH
What are anomers and anomeric carbons?
Anomeric Carbon - new stereocentre resulting from cyclic hemiacetal formation
Anomers - Carbohydrates that differ based on the configuration at the anomeric carbons
What are 5/6 membered ring structures called?
6 membered are called pyranose and 5 members are called furanose
For pyranoses, the 6 membered ring is more accurately represented as a strain free chair conformation
What is a multirotation?
The change in specific rotation that accompanies the interconversion of a and b anomers in an aqueous solution
What is a glycoside formation?
when the OH of an anomeric carbon is replaced by an OR (variable R)
Does a gylcosidic formation change the anomeric carbon?
Yes. After this occurs the carbon is called the glycosidic carbon as it can no longer do multirotation
Can all sugars bind to each other?
Yes as they are all alcohols
What is the difference between an alpha and a beta link?
an alpha link forms below the monosaccharide and a beta forms above
What are N-Glycosides?
These are compunds formed when the anomeric carbon of a cyclic hemiacetal undergoes a reaction with an NH group from an amine
What is cellulose?
A polysaccharide with several thousand D-glucose units joined by beta 1,4 links.
It provides structure in plants as the H bonds can contribute to rigidity and toughness
What is Starch?
A polysaccharide of inidividual glucose units joined by alpha 1,4 links
It is fully digestible and an essential part of the human diet which is only found in plant material
What is starch made up of?
Amylose (20%) and Amylopectin (80%)
Describe Amylose
A polysaccharide which is soluble in water and consists of several hundred to thousand D glucose units linked in long chains
it tends to curl into helices
Describe Amylopectin
A polysaccharide which has up to 100,000 glucose units per molecules and an alpha 1,6 branch approximately every 25 units along the chain
it is not soluble and has a hirachial structure
What is Glycogen?
Glycogen is how energy is stored in animals, it is stored in the liver and muscles
Structurally, glycogen is similar to amylopectin but much more branched
