Unit 2 - Carbohydrates

Bioch 310: Structures of carbohydrates, aldoses, ketoses, optical features and stereochemistry, hemiacetals and hemiketals.

Function of carbohydrates

Serve as nutrients and are a source and storage form of energy.

Where to find carbohydrates

In the cell membrane, extracellular matrix, biomolecules like nucleic acids, proteins and lipids

Isomerase

Enzyme responsible for the isomerization from an aldehyde (aldose) to a ketone (ketose)

Monosaccharides

Simple sugars with the general chemical formula (CH2O)n where 3 ≤ n ≤ 9

Note: sugars with less than 3 carbons are just referred to as aldoses and ketoses

Aldose

sugar molecule with an aldehyde group

Ketose

Sugar molecule with a ketone group

What are the only 2 trioses?

1. Glyceraldehyde

2. Dihydroxyacetone

*Both are present in glycolysis

Triose

3 carbon sugar

Hexose

6 carbon sugar

Isomers

Same formula but different structure with distinct chemical properties

What molecule is used as a reference to describe all other isomers

Glyceraldheyde

What does D- conformation mean

(Dextarotation) the -OH is to the right and the structure rotates plane polarized light to the right

What does L- conformation mean

(Levorotation) The -OH is to the left and the structure rotates plane polarized light to the left

All biological relevant sugars are what type of sugars?

D-sugars

All biologically relevant amino acids are what type of amino acids?

L-amino acids

Stereoisomers

Have the same chemical formula and carbon connectivity but differ in the spatial orientation of their atoms.

Spatial orientation of certain chemical groups can affect the optical properties of the molecule

Isomers

Always have the same chemical formula

Constitutional isomers

same molecular formula but a different bonding arrangement among the atoms

Stereoisomers

identical molecular formulas and arrangements of atoms but differ in the spatial orientation of groups in the molecule.

Two types: 1. enantiomers 2. diastereoisomers

What defines D- and L-

the carbon stereogenic centre furthest away from the carbonyl group