Protein Synthesis

Subdecks (2)

Cards (73)

  • DNA Replication
    1. 1
    2. 2
    3. 3
  • DNA & Genes
    • DNA contains genes, sequences of nucleotide bases
    • Genes code for polypeptides (proteins)
    • Proteins are used to build cells and do much of the work inside cells
  • Flow of Information: The "Central Dogma" of Molecular Biology
    5
  • DNA
    • DNA is found inside the nucleus
    • Proteins are made in the cytoplasm of cells by organelles called ribosomes
    • Ribosomes may be free in the cytosol or attached to the surface of rough ER
  • Genes & Proteins
    • Proteins are made of amino acids linked together by peptide bonds
    • 20 different amino acids exist
  • Polypeptides
    Amino acid chains are called polypeptides
  • DNA Begins the Process
    1. DNA's code must be copied and taken to the cytosol
    2. In the cytoplasm, this code must be read so amino acids can be assembled to make polypeptides (proteins)
    3. This process is called PROTEIN SYNTHESIS
  • RNA
    • RNA has a sugar ribose, DNA has a sugar deoxyribose
    • RNA contains the base uracil (U), DNA has thymine (T)
    • RNA molecule is single-stranded, DNA is double-stranded
  • Three Types of RNA
    • Messenger RNA (mRNA) copies DNA's code & carries the genetic information to the ribosomes
    • Ribosomal RNA (rRNA), along with protein, makes up the ribosomes
    • Transfer RNA (tRNA) transfers amino acids to the ribosomes where proteins are synthesized
  • Messenger RNA

    • Long Straight chain of Nucleotides
    • Made in the Nucleus
    • Copies DNA & leaves through nuclear pores
    • Contains the Nitrogen Bases A, G, C, U ( no T )
  • Messenger RNA (mRNA)

    • Carries the information for a specific protein
    • Made up of 500 to 1000 nucleotides long
    • Sequence of 3 bases called codon
    • AUG – methionine or start codon
    • UAA, UAG, or UGA – stop codons
  • Ribosomal RNA (rRNA)

    • rRNA is a single strand 100 to 3000 nucleotides long
    • Globular in shape
    • Made inside the nucleus of a cell
    • Associates with proteins to form ribosomes
    • Site of protein Synthesis
  • The Genetic Code
    • A codon designates an amino acid
    • An amino acid may have more than one codon
    • There are 20 amino acids, but 64 possible codons
    • Some codons tell the ribosome to stop translating
  • Remember the Complementary Bases
    On DNA: A-T, C-G
    On RNA: A-U, C-G
  • Transfer RNA (tRNA)
    • Clover-leaf shape
    • Single stranded molecule with attachment site at one end for an amino acid
    • Opposite end has three nucleotide bases called the anticodon
  • Codons and Anticodons
    The 3 bases of an anticodon are complementary to the 3 bases of a codon
    Example: Codon ACU, Anticodon UGA
  • Pathway to Making a Protein
    1. DNA
    2. mRNA
    3. tRNA (ribosomes)
    4. Protein
  • Protein Synthesis
    The production or synthesis of polypeptide chains (proteins)
    Two phases: Transcription & Translation
    mRNA must be processed before it leaves the nucleus of eukaryotic cells
  • DNA → RNA → Protein
    1. Transcription
    2. RNA Processing
    3. Translation
  • Transcription
    The process of copying the sequence of one strand of DNA, the template strand
    mRNA copies the template strand
    Requires the enzyme RNA Polymerase
  • DNA
    • 5'-GCGTATG-3'
  • RNA
    • 3'-CGCAUAC-5'
  • Transcription
    • RNA Polymerase binds to DNA and separates the DNA strands
    RNA Polymerase then uses one strand of DNA as a template to assemble nucleotides into RNA
  • Transcription
    Promoters are regions on DNA that show where RNA Polymerase must bind to begin the Transcription of RNA
    Specific base sequences act as signals to stop, called the termination signal
  • mRNA Processing
    Introns, non-functional segments of DNA are snipped out of the chain
    Exons, segments of DNA that code for proteins, are then rejoined by the enzyme ligase
    A guanine triphosphate cap is added to the 5" end of the newly copied mRNA
    A poly A tail is added to the 3' end of the RNA
    The newly processed mRNA can then leave the nucleus
  • mRNA Transcript

    mRNA leaves the nucleus through its pores and goes to the ribosomes
  • Translation
    Translation is the process of decoding the mRNA into a polypeptide chain
    Ribosomes read mRNA three bases or 1 codon at a time and construct the proteins
  • Ribosomes
    • Made of a large and small subunit
    Composed of rRNA (40%) and proteins (60%)
    Have two sites for tRNA attachment --- P and A
  • Step 1- Initiation
    mRNA transcript start codon AUG attaches to the small ribosomal subunit
    Small subunit attaches to large ribosomal subunit
  • Step 2 - Elongation
    As ribosome moves, two tRNA with their amino acids move into site A and P of the ribosome
    Peptide bonds join the amino acids
  • Initiation
    • mRNA, 1-tRNA, 2-tRNA
  • Elongation
    • mRNA, 1-tRNA, 2-tRNA, 3-tRNA, 4-tRNA, 5-tRNA
  • Termination
    The end products of protein synthesis is a primary structure of a protein
    A sequence of amino acid bonded together by peptide bonds
  • Messenger RNA (mRNA)

    • A U G G G C U C C A U C G G C G C A U A A
  • Primary structure of a protein
    The sequence of amino acids bonded together by peptide bonds