Biological molecules


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Biological molecules

  1. 1. DNA & RNA as heredity Material
  2. 2. Nucleic Acids Nucleic acids store, transmit and express genetic information. Nucleic acids are composed of subunits called nucleotides. Nucleotides contain a phosphate group, a sugar and a ring of carbon and nitrogen atoms. The ring is also known as the base because it can accept hydrogen ions (protons). Nucleotides are linked together by bonds between the phosphate group of one nucleotide and the sugar of the next one. In this fashion, nucleotides form long chains.
  3. 3. TYPES OF RNA•Messenger RNA (mRNA) :carries information about a protein sequence to theribosomes, the protein synthesis factories in the cell.2. Transfer RNA(tRNA) :is a small RNA chain of about 80 nucleotides thattransfers a specific amino acid to a growing polypeptide chain at the ribosomalsite of protein synthesis during translation.3. Ribosomal RNA(rRNA): is the catalytic component of the ribosomes. In thecytoplasm, ribosomal RNA and protein combine to form a nucleoprotein called aribosome. The ribosome binds mRNA and carries out protein synthesis.
  4. 4. Transcription Transcription is the process of creating an equivalent RNA copy of a sequenceof DNA Both RNA and DNA are nucleic acids which use base pairsofnucleotides as a complementary language that can be converted back and forthfrom DNA to RNA in the presence of the correct enzymes. During transcription,a DNA sequence is read by RNA polymerase, which produces a complementary,antiparallel RNA strand. As opposed to DNA replication, transcription results inan RNA complement that includes uracil (U) in all instances where thymine (T)would have occurred in a DNA complement.Transcription is the first step leading to gene expression.
  5. 5. Translation is the third stage of protein biosynthesis (part of theoverall process of gene expression). In translation,messenger RNA (mRNA) produced by transcription is decoded by theribosome to produce a specific amino acid chain, or polypeptide, thatwill later fold into an active protein. Translation occurs in the cellscytoplasm, where the large and small subunits of the ribosome arelocated, and bind to the mRNA. The ribosome facilitates decoding byinducing the binding of tRNAs with complementary anticodonsequences to that of the mRNA. The tRNAs carry specific amino acidsthat are chained together into a polypeptide as the mRNA passesthrough and is "read" by the ribosome in a fashion reminiscent to thatof a stock ticker and ticker tape.