Notes day 3

Proteins and Their Importance

  • Ammonia and Dry Weight

    • Humans can be analyzed in terms of biochemical composition, where approximately 50% of dry weight is made up of proteins.

  • Functions of Proteins

    • Structure

    • Proteins are critical components of various structures in the body such as hair and nails.

    • Tendons, which connect muscles to bones, are made up of proteins.

    • Rhinoceros horns and elephant tusks, often mistakenly thought to be ivory, are actually composed of keratin, a type of protein.

    • Storage

    • Proteins play a role in storage, particularly in eggs, where yolk portions are rich in contractile proteins.

    • Transportation

    • Proteins transport oxygen in the bloodstream from the lungs to cells.

    • Defense

    • Antibodies, which are proteins, defend the body against pathogens like bacteria.

    • Many venom types, such as those from snakes, are protein-based.

  • Quiz Preparation

    • The instructor emphasizes understanding protein functions for exams, including structure, transport, and defense.

Enzymes: The Catalysts of Metabolism

  • Critical Role of Enzymes

    • Enzymes are essential for metabolic processes.

  • Understanding Enzyme Naming

    • Enzymes often have names ending in "-ase" which indicates they are proteins (e.g., lactase).

    • Common Patterns

    • "ACE" usually signifies an enzyme related to a specific substrate (e.g., lactase breaks down lactose).

Amino Acids: The Building Blocks of Proteins

  • Types of Amino Acids

    • There are 20 different amino acids that combine in various sequences to form proteins.

    • Some amino acids are polar, ionic, or nonpolar, which affects how the protein folds and functions.

    • Amino acids contain:

    • Amino Group

    • Carboxyl Group

    • Hydrogen Atom

    • R Group (varies among different amino acids)

  • Sulfur in Amino Acids

    • Notably, the amino acids methionine and cysteine contain sulfur, which is a unique characteristic among proteins.

  • Peptide Bonds

    • When amino acids link together via dehydration synthesis, they form peptide bonds, creating a polypeptide chain.

    • The bond occurs between the carbon of the carboxyl group of one amino acid and the nitrogen of the amino group of the adjacent amino acid.

Protein Folding and Structure

  • Levels of Protein Organization

    • Primary Structure

    • Sequence of amino acids in a polypeptide chain.

    • The order is critical; even one wrong amino acid can result in a malfunctioning protein.

    • Secondary Structure

    • Involves the initial folding of the chain into structures like alpha helices or beta-pleated sheets.

    • Tertiary Structure

    • Further folding and interaction lead to a three-dimensional shape, essential for protein function.

    • Quaternary Structure

    • Formed when multiple polypeptide chains come together, important for complex protein functioning (e.g., hemoglobin).

Denaturation and Renaturation

  • Process of Denaturation

    • Factors such as high temperature, pH changes, or certain chemicals can cause proteins to denature, unfolding them and rendering them nonfunctional.

    • Example: High fever can lead to heart muscle proteins unfolding, rendering them ineffective.

  • Renaturing

    • In some cases, denatured proteins can refold into their functional shape when conditions return to normal (renaturation).

    • Example: This is often not reversible, as in the case of a cooked egg.

The Function of Enzymes

  • Enzyme Mechanics

    • Enzymes possess an active site where substrates bind to undergo reactions (either breaking down molecules or synthesizing new ones).

    • Enzymes are specific to their substrates and can function repetitively without being used up in the process.

  • Enzyme Activation

    • The substrate must fit into the enzyme’s active site precisely for the reaction to take place, showcasing enzymes' specificity.

  • Time Efficiency Without Enzymes

    • The breakdown of food would take a vastly longer time without enzymes, emphasizing their biological significance.

Summary of Key Concepts

  • Key Terms

    • Amino Group

    • Carboxyl Group

    • Peptide Bond

    • Native Protein (functional protein after proper folding)

    • Denaturation (unfolding that leads to loss of function)

    • Renaturation (refolding to regain function)

  • Relationship with DNA

    • Proteins are synthesized based on the genetic information encoded in DNA.

    • RNA serves as the intermediary, facilitating protein synthesis within ribosomes.

  • Overall Significance

    • Proteins play multifaceted roles, from structural integrity to catalyzing metabolic reactions, underscoring their importance in biological systems.