BoC macromolecules L1 Flashcards
Average size of nucleotide
300Da
Average amino acid size
110 Da
Size of glucose `
180 Da
DNA and glycogen Mr…
over 10 MDa
Small RNA Mr ~
50 kDA
Proteins range of Mr
Insulin small, 5.5kDa, Titin large, 10MDa
Draw glyceraldehyde in both forms
see notes (central carbon chiral)
Chiral molecules…
Rotate plane polarised light left or right
How are carbon atoms numbered in sugars
so carbonyl group has the smallest number
Sugars are assigned D-configuration if…
chiral centre with the highest number is the same as chiral centre of D-glyceraldehyde ie OH group on right
Fancy word for mirror images
Enantiomers
In nature which configuration do sugars take
D config
If a molecule has n chiral centres how many possible isomers are there?
2^n
Sugars differing in only 1 chiral centre named…
epimers
What is the intramolecular cyclisation reaction in glucose?
rotation of the bond between C4 and C5 allows the hydroxyl group on C5 to react with aldehyde on C1 to form a 6-membered ring structure called the pyranose ring
What is the anomeric carbon?
The new chiral centre at C1 on glucose, previously the carbonyl carbon
Draw alpha and beta glucose
see notes (alpha -oh C1 down)
In solution sugars are in equilibrium between…
cyclic and open chain forms
at 30 degrees a solution of D glucose contains…
2/3 beta-D-glucopyranose, 1/3 alphaD-glucopyranose, only a very small amount of linear form
Draw chair and boat glucose configuration
see notes
Which is more stable, boat or chair?
Chair because fewer clashes between oxygens
In disaccharides where does the glycosidic bond occur?
Between the anomeric carbon one one sugar and a hydroxyl group on the other
Draw maltose
see notes
Why are disaccharides highly diverse?
There are 2 possible isomers of the anomeric carbon and these can react with a number of hydroxyl groups on the other sugar
Which disaccharide polymerises to make cellulose?
Cellobiose, made of D-beta-glucose
What gives cellulose strength?
Adjacent chains H bonding each other
Describe glycogen
Energy store in liver/muscles, has 1-6 branch point ~every 10 monomers, alpha 1-4 linkages make it curved not straight like cellulose (with beta 1-4 linkages), made of D-alpha-glucose
Describe starch
polymer of D-alpha-glucose, amylose=no branch points, amylopectin= branch points ~every 20 monomers (see notes)
Why does glycogen have a more open energy structure?
ready access to enzymes that mobilise sugar monomers when energy is needed and re synthesise polysaccharides when it is plentiful
specificity of starch/cellulose production in plant depends on…
ability of enzymes to discriminate between beta and alpha forms
