Stuff I need to remember

Question 1

Reducing sugars

Answer 1

*A reducing sugar is one that reduces another compound and is itself oxidized
*Sugars with an anomeric carbon(free carbonyl group in linear form) are reducing sugars.

Question 2

Explain Bennedict’s test

Answer 2

The reducing sugar (carbonyl group) reduces the cupric ions (Cu2+) to cuprous (Cu+) and is itself oxidised to a carboxylic acid.Cu+ then forms copper oxide (Cu2O) and precipitates out of solution as a brick-red-coloured compound. This change in colour of the blue Benedict’s reagent is indicative of this reaction taking place, identifying the sugar in the reaction as a reducing sugar.

Question 3

Describe a glycosidic bond

Answer 3

It is formed through a dehydration reaction (condensation reaction), where a molecule of water is removed as the bond is created. OH of anomeric carbon 1 is removed and H of Carbond 4 of the other molecule is removed.

Linkage: The bond typically forms between the anomeric carbon (carbon-1) of one sugar molecule and a hydroxyl group (–OH) on another molecule. The anomeric carbon is the carbon that becomes a new chiral center when the sugar cyclizes (forms a ring structure).

Question 4

Ribosomal RNA

Answer 4

Ribosomes are the site of protein synthesis *Ribosomes are about 2/3 RNA & 1/3 protein
*rRNA serves as a scaffold for ribosomal proteins
*All ribosomes contain 2 rRNA subunits: large (LSU-60S) and small (SSU-40S)
*Structural and catalytic functions in protein translation, LSU has “APE” sites (“P” catalyzes bond formation) and SSU binds and holds mRNA

Question 5

Secondary structure of rRNA

Answer 5

High sequence complementarity allows extensive intra-strand base-pairing leading to a highly folded pattern
*Creates multiple stem loop structures, 4 domains
*Very similar secondary structures are observed across species (see next slide

Question 6

Phylogenetic comparison of secondary structure of rRNA

Answer 6

*Folding pattern is conserved across species, while nucleotide sequence varies
*Evolutionarily conserved rRNA secondary structure ensures all ribosomes function similarly in protein synthesis
Phylogenetic comparison of secondary structure of rRNA

Question 7

Transfer RNA (tRNA)

Answer 7

*Small polynucleotide chains: 73 to 94 nucleotides each
Several bases usually methylatedEach amino acid has at least one unique tRNA which carries the amino acid to the ribosome
*Aminoacyl-tRNA molecules are the substrates of protein synthesis.Functions to transfer amino acids to growing polypeptide chains during translation at the ribosome