Slide 1

Biomolecules - RNAs used for protein biosynthesis

• Ribonucleic acids (RNAs)
• Biological macromolecules
• Essential in the process of protein biosynthesis

Slide 2

Types of RNA molecules

• Messenger RNA (mRNA)
• Transfer RNA (tRNA)
• Ribosomal RNA (rRNA)

Slide 3

Messenger RNA (mRNA)

• Carries genetic information from DNA to ribosomes
• Contains codons that specify amino acids
• Transcribed from DNA during transcription

Slide 4

Transfer RNA (tRNA)

• Transfers amino acids to the ribosomes
• Contains anticodons that are complementary to the codons on mRNA
• Brings the correct amino acid to the growing polypeptide chain

Slide 5

Ribosomal RNA (rRNA)

• Forms the structure of the ribosomes
• Helps in protein synthesis by providing a site for mRNA and tRNA interaction
• Catalyzes the formation of peptide bonds between amino acids

Slide 6

Structure and Function of mRNA

• Single-stranded molecule
• Contains codons that code for specific amino acids
• Carries the genetic information from DNA to the ribosomes

Slide 7

Structure and Function of tRNA

• Cloverleaf-shaped structure
• Contains the anticodon that pairs with the codon on mRNA
• Binds to specific amino acids and carries them to the ribosomes

Slide 8

Structure and Function of rRNA

• Forms the two subunits of the ribosomes (large and small)
• Provides a site for mRNA and tRNA interaction
• Catalyzes the formation of peptide bonds between amino acids

Slide 9

Steps of Protein Biosynthesis

1. Transcription - mRNA is synthesized from the DNA template in the nucleus.
2. mRNA processing - Addition of a 5’ cap and a poly-A tail, as well as splicing out introns.
3. mRNA export - mRNA leaves the nucleus and enters the cytoplasm.
4. Translation - mRNA is decoded by ribosomes to synthesize proteins.

Slide 10

Summary

• RNAs involved in protein biosynthesis: mRNA, tRNA, and rRNA
• mRNA carries genetic information from DNA to ribosomes
• tRNA brings amino acids to the ribosomes
• rRNA forms the structure of ribosomes and catalyzes peptide bond formation

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Slide 11

The Central Dogma of Molecular Biology

• Describes the flow of genetic information in cells
• DNA –> Transcription –> RNA –> Translation –> Protein

Slide 12

Transcription

• Occurs in the nucleus
• DNA is used as a template to synthesize mRNA
• Enzyme involved: RNA polymerase
• The DNA double helix unwinds and RNA polymerase adds complementary RNA nucleotides to the growing mRNA strand

Slide 13

mRNA Processing

• Addition of a 5’ cap: Modified guanine nucleotide added to the 5’ end of mRNA
• Addition of a poly-A tail: String of adenine nucleotides added to the 3’ end of mRNA
• Splicing out introns: Non-coding regions of the mRNA are removed

Slide 14

mRNA Export

• Process by which mature mRNA leaves the nucleus and enters the cytoplasm
• Nuclear pore complexes allow the passage of mRNA molecules
• In the cytoplasm, mRNA is available for translation by ribosomes

Slide 15

Translation

• Occurs in the cytoplasm on ribosomes
• Ribosomes read the mRNA sequence and synthesize proteins
• Three nucleotides on mRNA (codon) code for a specific amino acid
• tRNA brings the corresponding amino acid to the ribosome based on the codon on mRNA

Slide 16

Steps of Translation

1. Initiation: Ribosome binds to the mRNA, tRNA carrying the first amino acid binds to the start codon
2. Elongation: tRNA molecules bring amino acids to the ribosomes, forming a polypeptide chain
3. Termination: Ribosome reaches a stop codon on mRNA, and the polypeptide chain is released

Slide 17

Genetic Code

• The set of rules that map the nucleotide sequence to amino acids
• Codons are three-nucleotide sequences on mRNA
• 64 different codons, out of which 61 code for amino acids and 3 are stop codons
• Example: AUG codes for the amino acid methionine, which is often the start codon

Slide 18

Examples of Genetic Code

• UCU: Serine
• GGG: Glycine
• UGA: Stop codon
• ACA: Threonine
• AUG: Methionine (start codon)

Slide 19

Equations involved in Protein Biosynthesis

• Transcription: DNA –> mRNA

  • DNA + RNA polymerase → mRNA

• Translation: mRNA –> Protein

  • mRNA + ribosomes + tRNA → Protein

Slide 20

Summary

• The Central Dogma: DNA –> Transcription –> mRNA –> Translation –> Protein
• Transcription: DNA is transcribed into mRNA, involving RNA polymerase
• mRNA Processing: Addition of 5’ cap, poly-A tail, and splicing out introns
• mRNA Export: Transport of mature mRNA from the nucleus to the cytoplasm
• Translation: mRNA is decoded by ribosomes, and tRNA brings specific amino acids to synthesize proteins

Slide 21

Structure of Proteins

• Proteins are large, complex macromolecules
• Made up of amino acids joined together by peptide bonds
• Have a primary, secondary, tertiary, and quaternary structure

Slide 22

Primary Structure

• Refers to the sequence of amino acids in a protein
• Determines the shape and function of the protein

Example:

• Primary structure of insulin: A chain: Gly-Gly-Ile-Glu-Cys-Cys-Thr-Ser-Ile-Cys-Ser-Leu-Tyr-Gln-Leu-Gly-Lys-Glu-Cys-Cys-Arg-Leu-Gln-Asn-Tyr-Cys-Cys

Slide 23

Secondary Structure

• Refers to the local folding of the protein chain
• Common secondary structures include alpha helices and beta sheets

Example:

• Alpha helix: Spiral arrangement with hydrogen bonds between amino acids
• Beta sheet: Folded arrangement with hydrogen bonds between adjacent strands

Slide 24

Tertiary Structure

• Refers to the overall three-dimensional structure of a protein
• Determined by interactions between the side chains (R groups) of amino acids

Example:

• Tertiary structure of myoglobin: Compact globular shape with hydrophobic and hydrophilic regions

Slide 25

Quaternary Structure

• Refers to the arrangement of multiple protein subunits
• Only present in proteins composed of more than one polypeptide chain

Example:

• Quaternary structure of hemoglobin: Made up of four subunits, each containing a heme group

Slide 26

Denaturation of Proteins

• Denaturation refers to the disruption of protein structure
• Can occur due to heat, pH changes, or exposure to chemicals

Example:

• Cooking an egg denatures the protein in the egg white, changing its texture and properties

Slide 27

Protein Functions

• Proteins have a wide range of functions in living organisms
• Examples include:
  • Enzymes: Speed up chemical reactions
  • Structural proteins: Provide support and strength to cells and tissues
  • Transport proteins: Carry molecules across cell membranes

Slide 28

Protein Synthesis

• DNA contains the instructions for protein synthesis
• Transcription and translation are the key steps in protein synthesis

Equations:

• Transcription: DNA → mRNA
• Translation: mRNA + ribosomes + tRNA → Protein

Slide 29

Transcription in Protein Synthesis

• Transcription occurs in the nucleus
• DNA serves as a template for the synthesis of mRNA
• RNA polymerase binds to the DNA and adds complementary RNA nucleotides

Example:

• Transcription of the gene for insulin involves the synthesis of preproinsulin mRNA

Slide 30

Translation in Protein Synthesis

• Translation occurs in the cytoplasm on ribosomes
• mRNA is decoded by ribosomes to synthesize proteins
• tRNA brings the corresponding amino acids based on the codon on mRNA

Example:

• Translation of the mRNA in the insulin-producing cells results in the synthesis of insulin