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A3P Lecture 9/11 Review: Organic Molecules

Steroids

  • Definition: Structural molecules and hormones composed of lipids made up of 4 carbon rings bound together.
  • Examples:
    • Cholesterol
    • Estrogen
    • Progesterone
    • Testosterone
    • Cortisol
  • Functions: Act as structural molecules and hormones.

Proteins

  • Definition: The most functionally diverse organic molecules in the body.
  • Functions:
    • Fuel molecules
    • Structural molecules
    • Hormones (e.g., protein hormones)
    • Receptors
    • Channels (protein pores/tunnels that allow chemicals to pass through cell membranes)
    • Pumps (proteins that force chemicals across membranes)
    • Enzymes (proteins that trigger chemical reactions)
    • Antibodies (immunity proteins that combat infection)
  • Composition: Made up of amino acids linked end-to-end, forming chain-like molecules.
    • There are 20 different types of amino acids.
  • Classification by Size:
    • Peptides: Small proteins made up of less than 50 amino acids.
    • Polypeptides: Large proteins made up of more than 50 amino acids.

Levels of Protein Structural Organization

  • 3 Levels of Protein Structural Organization:
    1. Primary Structure: The specific sequence of amino acids along the length of the molecule (e.g., Alanine, Ethaline). This is the linear arrangement of amino acids.
    2. Secondary Structure: Describes how the amino acid chain forms localized coils, folds, or loops (e.g., alpha-helix, beta-pleated sheets) along its length.
    3. Tertiary Structure: The complex 3-dimensional structure of the entire molecule, reflecting how the coils, folds, and loops interact with each other. This is considered the "native" and functional structure of a protein.

Protein Denaturation

  • Definition: The loss of a protein's native, tertiary, or 3-dimensional functional structure.
  • Causes: Can be caused by:
    • Heat
    • Extreme pH
    • High salt concentrations
    • Excessive mixing
  • Effect: Denaturation causes the protein to "unravel" and lose its functional structure, making it non-functional. For example, a Native Protein, when exposed to (Heat, Acid, Salt, Mixing), undergoes Protein Denaturation and can no longer be functional.

Nucleic Acids

  • Definition: Genetic molecules (carrying information) and energy/fuel molecules.
  • Composition: Made up of nucleotides, which are the building blocks of nucleic acids.
    • The transcript notes 6 different nucleotides (A, G, B, C, T, and U).

3 Major Nucleic Acid Types

  1. DNA (Deoxyribonucleic Acid):
    • Huge, chain-like molecules, often the largest known molecules.
    • Made up of nucleotides (A, G, C, T) linked end-to-end.
    • Primarily information molecules.
    • Contain genes: Segments of nucleotide sequences within DNA molecules that are decoded into RNA molecules through the process known as transcription.
    • Found within the nuclei of cells, where they are organized with protein bonds into structures called chromosomes.
  2. RNA (Ribonucleic Acid):
    • Chain-like molecules made up of nucleotides (A, G, C, U) linked end-to-end.
    • Produced from gene sequences during the process of transcription in the nucleus of a cell.
    • RNA molecules leave the nucleus and move into the cytoplasm, where they bind to ribosomes.
    • Ribosomes decode the RNA nucleotide sequence into protein molecules during a process called translation.

Gene Expression

  • 2 Stages of Gene Expression:
    1. Transcription:
      • A gene sequence on a DNA molecule (e.g., A B C T G A T) is transcribed into an RNA molecule.
      • During this process, the nucleotide 'T' (Thymine) in DNA is replaced by 'U' (Uracil) in RNA (e.g., G A U B C G A B C U G A U B).
    2. Translation:
      • The nucleotide sequence of the RNA molecule is decoded by ribosomes in the cytoplasm into a specific protein sequence, forming a protein molecule.

ATP (Adenosine Triphosphate)

  • Definition: The main energy molecule of our body.
  • Function: All cellular machinery binds and breaks down ATP to power various cellular processes.
  • Composition: Made up of a single nucleotide (Adenosine, 'A') to which 3 phosphates are attached (A-P-P-P).
  • Energy Release: When ATP is broken down, it releases energy and heat:
    • \text{ATP} \rightarrow \text{ADP} + \text{P} + \text{Energy/Heat}
    • Here, ADP (adenosine diphosphate, A-P-P) is formed when one phosphate group is removed from ATP.
  • ATP Synthesis: Cells constantly make new ATP by breaking down carbohydrates, triglycerides, proteins, and utilizing oxygen.