Molecules of Life Flashcards
1) Name the 4 main classes of biological molecules and their building blocks
- Carbohydrates: sugars
- Lipids : fatty acids
- Proteins : amino acids
- Nucleic acid : Nucleotides
2) Which functional groups are present in carbohydrates?
Carboxyl COOH and hydroxyl OH
3) What are monosaccharides with aldehyde or ketone groups called, and give an example of each?
Aldoses : glyceraldehyde - ribose, glucose
Ketoses : dihydroxyacetone - ribulose, fructose
4) When do monosaccharides form ring structures?
In aqueous solutions, 5 carbon and 6 carbon sugars spontaneously form ring structures
- the carbonyl group C=O (aldo/keto) reacts with a hydroxyl group
5) Define the terms isomer, enantiomer, anomer and epimer
- Isomer: compounds with the same molecular formula but a different arrangement of atoms
- Enantiomer: monosaccharides can be optical isomers or enantiomers, which are mirror images of each other (cannot be super imposed on each other)
- Anomer: where two isomers have a difference in configuration at one (anomeric) carbon
- Epimer: stereoisomers that differ in configuration at one chiral centre (anomers are epimers)
6) Give an example of 3 epimers
- D-glucose, D-mannose and D-galactose
7) How do beta glucose and alpha glucose ring structures vary?
- Beta: BUDUD
- Alpha : ADDUD
- the position of the hydroxyl groups differs
- C1 is the anomeric carbon so alpha and beta glucose are anomers
8) What happens to alpha and beta glucose in solution?
They rapidly interconvert, constantly changing between the two forms.
- this stops once a polymer is formed via bonding (glycosidic)
9) What is a polysaccharide and give 3 examples
- polymers of glucose which act as energy sources
- e.g. glycogen in animals and starch in plants (split into amylose and amylopectin)
10) How does beta 1,4 linkage differ from alpha 1,4 linkage in glucose molecules?
[hydrogens removed are always from the OH group]
- alpha: loses 2 hydrogens and forms glycosidic bond at bottom
- beta: loses 2 hydrogens and forms a diagonal glycosidic bond (OH group at top on one side and at bottom on other side)
11) Describe the chemical features and properties of lipids
- hydrophobic but soluble in organic solvents
- length and structure (saturation) of fatty acid chain determines physical properties like shape and melting point
- TAGs formed by ester linkages between FA and glycerol
12) In what form are lipids stored for energy?
Intercellular fat droplets
13) What does amphipathic mean and give an example
- molecule has a hydrophilic head and hydrophobic tail
- e.g. glycerophospholipids
- these aggregate in an aqueous environment, e.g. forming a bilayer as the cell membrane
14) What are steroids formed from?
Fused alkyl rings form the basis for steroid hormones and steroid lipid cholesterol
15) Give 2 features of cholesterol
- Rigid structure that inserts itself between phospholipids in the cell membrane and regulates fluidity
- Has an OH group so it can integrate into cell membranes (polar, so close to hydrophilic heads)
