Unit Three“Cell Proliferation and Genetics”

“Protein Synthesis”

From Gene to Protein

• The way in which the “Control Center” of the cell, which is the DNA in the nucleus, enables the efficient operation of the remainder of the cell is via Protein Synthesis

• Recall that proteins maintain the proper function of the cell by acting as enzyme that regulate the vital chemical reactions of the cell

• In essence, DNA makes RNA makes Protein so that the protein can maintain homeostasis (equilibrium)

RNA Structure

• RNA has a very similar structure to DNA

• It also has a Sugar, Phosphate Group, and Nitrogenous Bases

• It is different in that it is single stranded i.e. it is one side of a ladder

RNA Structure

• RNA’s nitrogenous bases are the same as in DNA except Thymine (Pyrimidine) is replaced by Uracil

• There is no Thymine in RNA• Since it is single stranded it is less complex

compared to DNA• RNA serves as the genetic material in viruses,

and it is also found in other organisms but with a different role in the cells

Categories of RNA

• Ribosomal RNA (rRNA) – DNA serves as template for production of rRNA; formed in the nucleus of a cell; moves into the cytoplasm to bond with proteins; rRNA + proteins make up Ribosomes (site of protein synthesis)

• Messenger RNA (mRNA) – DNA serves as template for production of mRNA; mRNA contains code for protein synthesis; it takes code out of nucleus to ribosomes for subsequent protein synthesis

Categories of RNA

• Transfer RNA (tRNA) – DNA serves as template for production of tRNA; once produced in nucleus moves out into cytoplasm; locates ribosomes and delivers its amino acids for assembly by ribosomes using the already delivered code by mRNA

• rRNA = factory• mRNA = operational system• tRNA = building materials

Protein Synthesis

• There are two stages of Protein Synthesis:– 1. Transcription – the copying of the Nucleic Acid

instructional code (DNA to RNA)– 2. Translation – the translating of the Nucleic Acid

code into Amino Acid code that results in the building of proteins

Transcription

• Transcription is the synthesis of RNA from a DNA template – 1. DNA unwinds and separates – 2. RNA Polymerase makes mRNA from DNA– 3. Newly completed mRNA moves into the

cytoplasm for Translation

Translation

• Translation is the making of proteins using the three types of RNA that came from the nucleus– 1. rRNA joins to the Ribosome– 2. Protein Synthesis begins using the code of the

mRNA and the amino acid building materials the tRNA’s have brought to the Ribosome

Transcription

Translation

Transcription & Translation Overview

Controlling Protein Synthesis

• Controlling Transcription – A protein called a “Repressor” can attach to the DNA

making it impossible for the RNA Polymerase to attach to the DNA

– In order for RNA Polymerase to attach properly to one strand of the DNA double helix, the DNA must be unzipped with the assistance of a protein called an “Activator”

– RNA Polymerase is guided to its transcription start point, the “Promoter”, by proteins called “Enhancers”

Protein Synthesis Summary

• https://www.youtube.com/watch?v=itsb2SqR-R0

• https://www.youtube.com/watch?v=NJxobgkPEAo