bio 101

Overview of Amino Acids and Proteins

  • There are 20 different amino acids in nature.
  • The variety in nature is created by the permutation and combination of these amino acids.
  • Amino acids can be positively charged (indicated by a plus sign) or negatively charged.
  • Polar amino acids are those that are water-loving, while Nonpolar amino acids do not love water.

Classification of Amino Acids

  • Amino acids are classified based on their properties and how they behave in relation to water:

    • Polar: Water-loving, includes charged amino acids.
    • Nonpolar: Hydrophobic, stay away from water.

  • Examples of specific amino acids include:

    • Glycine
    • Alanine
    • Valine
    • Leucine
    • Isoleucine
    • Methionine

Structure of Proteins

  • Amino acids are joined in chains to form protein molecules.

  • The folding of proteins is critical.

    • They fold into three dimensions, similar to a staircase structure.
    • Water-loving amino acids orient toward the outside, while water-hating amino acids are located inside the protein.

  • The sequence of amino acids is determined by genes, which instruct ribosomes on how to arrange these amino acids:

    • The gene sequence directly impacts protein structure and function.

Polar vs. Nonpolar Amino Acids

  • Memorization:
    • Polar: Water-loving (hydrophilic)
    • Nonpolar: Water-hating (hydrophobic)
    • Example discussion with Leucine (a nonpolar amino acid):
    • Expected location is inside the protein to avoid water exposure.
    • Example discussion with Serine or Proline (polar amino acids):
    • Expected location is outside the protein facing the water.

Peptide Bonds and Protein Folding

  • Amino acids are connected by peptide bonds.

  • There are four levels of protein folding:

    1. Primary Structure:
    • Long chain of amino acids (polypeptide)
    1. Secondary Structure:
    • Forms like a helix (staircase) or pleated sheet.
    1. Tertiary Structure:
    • 3D folding occurs, with links formed by disulfide bridges, hydrogen bonds, etc.
    1. Quaternary Structure:
    • Multiple tertiary structures combine to form the final protein complex.

  • Example: Insulin consists of two polypeptides (A and B chain) linked by disulfide bridges.

Sickle Cell Anemia Example

  • In sickle cell anemia, a mutation in one amino acid leads to improper folding of hemoglobin, resulting in a sickle shape that cannot efficiently carry oxygen.
  • This condition serves as an adaptation for some against malaria but primarily presents as a disease.

Denaturation and Protein Structure

  • Denaturation:
    • Proteins lose their normal shape due to changes in temperature or pH.
    • Example: Boiling an egg causes albumin protein to transition from liquid to solid state.

Overview of Nucleic Acids

  • Nucleic acids (DNA and RNA) are vital for genetic material.
  • Types of nucleic acids:
    • DNA (Deoxyribonucleic Acid): Holds genetic information.
    • RNA (Ribonucleic Acid): Involved in protein synthesis.

DNA Structure and Function

  • DNA Structure:
    • Comprised of a double helix formed by base pairs connected by hydrogen bonds.
    • Components of DNA:
    • Nucleotide: Contains base, sugar, and phosphate.
    • Types of Bases:
    • Purines: Adenine (A) and Guanine (G)
    • Pyrimidines: Cytosine (C) and Thymine (T)
    • Base pairing: A-T (double bond), C-G (triple bond).

RNA Structure and Function

  • RNA is single-stranded, with three types:
    1. Messenger RNA (mRNA): Carries genetic information from DNA to ribosomes for protein synthesis.
    2. Transfer RNA (tRNA): Delivers amino acids to ribosomes during protein synthesis.
    3. Ribosomal RNA (rRNA): Along with proteins, forms ribosomes.

Central Dogma of Molecular Biology

  • Refers to the process of Transcription followed by Translation:

    • Transcription: DNA is copied into mRNA.
    • Translation: mRNA is translated to synthesize proteins.

  • Mutations in DNA can lead to misfolding of proteins, causing diseases like cancer.

Summary of Differences Between DNA and RNA

  • DNA:

    • Structure: Double-stranded
    • Sugar: Deoxyribose
    • Location: Nucleus
    • Function: Carries genetic information

  • RNA:

    • Structure: Single-stranded
    • Sugar: Ribose
    • Function: Transports instructions from DNA for protein synthesis

  • Replication: DNA is duplicated during cell division, ensuring genetic continuity.

Conclusion

  • The understanding of proteins and nucleic acids is critical for comprehending biological processes, including mutation impacts, protein synthesis, and cellular functions.