Question

Question 1 Describe the following terms in your own words 1.1 Methylation 1.2 Glycosidic bond 1.3 Homologous recombination 1.4 Peptidyl transferase 1.5 Shine-Dalgarno sequence Question 2 9 COMPAS

biochemistry

Answer 1

Methylation :- Basically methylation is the addition of methyl group on the subtrate, the substrate undergoes alkylation with only methyl group to replace hydrogen group. In biological methylation the process is catalysed by various ezymes such processes can involve regulation of gene expression, regulation of protein function, and RNA processing which is very important under epigenetics. It involves various types of methylation that is  

1 Methanogenesis

2 O-Methyltransferases (catalyzed by enzymes called caffeoyl-CoA O-methyltransferase, biosynthesis of lignols, percursors to lignin)

3 protein modification using methylation

4 Methionine synthase processing

5 Biomethylation to convert  heavy elements into more mobile or lethal derivatives

Glycosidic bond :-  Thses are also called as gycosidic lunkages which joins the carbohydrate and are colvanet type of bonds. The bond is mainly present between the hemiacetal or hemiketal group of a saccharide and the hydroxyl group of compounds. Examples of compounds containing glycosidic linkages are

1 Hesperidin

2 Naringin

3 Rutin

4 Quercitrin

Homologous recombination :- The type of recombination which occurs only between the two similar molecules of RNA or DNA which involves exchange of nucleotide sequence. It is very useful when there is a cut or a break in the DNA molecules. Homologous recombination is conserved across all three domains of life as well as DNA and RNA viruses therefore it is universal biological mechanism this process many differ from organisms to organisms but the basic steps remains constant. Homologous recombination which occurs during DNA repair results in non-crossover products, in effect restoring the damaged DNA molecule as it existed before the double-strand break.

Peptidyl transferase :- It is an enzyme which forms peptide bonds between adjacent amino acids using tRNAs during the translation process of protein biosynthesis.

In Prokaryotes, the 50S (23S component) ribosome subunit contains the peptidyl transferase component which acts as a ribozyme. it's center on the 50S subunit lies at the lower tips (acceptor ends) of the A- and O- site tRNAs.

In Eukaryotes, the 60S (28S component) ribosome subunit contains the peptidyl transferase component which acts as the ribozyme.

speeds up the reaction by lowering its energy of activation by providing proximity and proper substrate orientation.

Shine-Dalgarno (SD) Sequence :-   Australian scientists John Shine and Lynn Dalgarno. (SD) Sequence is a ribosomal binding site in bacterial and archaeal messenger RNA, which is located around 8 bases upstream of the start codon 'AUG'. The Shine-Dalgarno sequence exists both in bacteria and archaea, some chloroplast and mitochondrial transcripts. AGGAGG is SD sequence in Escherichia coli