Biological Macromolecules

Organic Chemistry and Chemical Reactions

Overview of Organic Chemistry

  • Percent Abundance of Elements

    • Over 90% of all chemistry in biology is based on four different atoms: Carbon (C), Hydrogen (H), Nitrogen (N), and Oxygen (O).

Organic Molecules

  • Molecules that contain carbon.

  • Carbon atoms form four bonds

  • The characteristic of an organic molecule is affected by its functional groups. (combination of particular atoms)

Types of Organic Molecules

Hydrocarbons

  • Contain only carbon (C) and hydrogen (H).

  • C-H Bonds: These bonds are covalent

  • Examples:

    • Methane: CH4

    • Ethane: C2H6

    • Propane: C3H8
      They are all hydrophobic.

Alcohols

  • Contain a hydroxyl functional group (OH).

  • Examples:

    • Methanol: CH3OH

    • Ethanol: C2H5OH

    • Propanol: C3H7OH

  • Small carbon chain alcohols are hydrophilic

Organic Acids

  • Contains a carboxyl (-COOH).

Amines

  • Contain an amino group (NH2).

  • Structure: Amines can exist in protonated forms (NH3) or as neutral species (NH2).

Amino Acids

  • Structure: Amino acids contain both an amino group (-NH$_2$) and a carboxyl group (-COOH).

  • Components:

    • Central carbon

    • Amino group

    • Carboxyl group

    • Side chain (R group) that varies for different amino acids.

Polymers

  • Large molecules made up of repeating smaller units called monomers.

  • Dehydration Synthesis: The process by which monomers are bonded together

  • Hydrolysis: removal of monomers from a polymer

Three main groups of organic molecules:

Carbohydrates

  • Contain numerous hydroxyls (OH) and a carbonyl (=O)

  • Used for energy storage and structural compounds

  • Many variations in chemical structure are possible ex. c6h12o6 glucose, fructose, galactose

  • Small changes in structure can sometimes result major changes in function.

  • Types of Carbohydrates:

    1. Monosaccharides: Single sugar units (e.g., glucose, fructose, galactose) all with the molecular formula C6H12O6

    2. Disaccharides: Formed by the combination of two monosaccharides (e.g., maltose = glucose + glucose; lactose = galactose + glucose; sucrose = glucose + fructose).

    3. Polysaccharides: Polymers of carbohydrates. Long chains of monosaccharides, serving as energy storage (e.g., starch, glycogen) and structural materials (e.g., cellulose).

Chitin

  • Not a carbohydrate, it is the main structural component of animal exoskeletons and fungal cells.

Lipids

  • Hydrophobic organic compounds

  • Main Functions:

    1. Energy storage

    2. Membrane structure

    3. Vitamins

    4. Chemical signaling (hormones)

  • Types of Lipids:

    • Fats: Lipids made of one glycerol molecule and three fatty acids.

    • Fatty Acids: Long-chain organic acids classified as either saturated (single bonds between carbon atoms) or unsaturated (one or more double bonds between carbon atoms).

  • Formation of Fats: Fatty acids are joined to glycerol molecules through dehydration synthesis.

Functions of Fats

  • Main Function: Energy storage

  • Additional Functions:

    • Waterproofing

    • Temperature regulation

  • Types of Adipose Tissue:

    • White fat tissue

    • Brown fat tissue

  • Waxes: Long carbon chain hydrophobic molecules that are malleable (change shape under pressure) and used as a waterproof coatings.

Phospholipids

  • Glycerol molecule with: 2 fatty acids and a phosphate group (PO4)

  • Properties:

    • Hydrophilic head

    • Hydrophobic tails

  • Principal components of membranes, creating a lipid bilayer.

Diverse Functions of Lipids with Ring Structures

  • Pigments (molecules that absorb different wavelengths of light)

  • Structure of membranes

  • Vitamins

  • Hormones (steroids)

  • Health Implication: High cholesterol levels can lead to a hardening and narrowing of the arteries

Proteins

  • The most diverse molecules in living organisms, polymers of amino acids.

  • 20 different types of amino acids (21 naturally occuring), side chains that contain:

    • Polar covalent bonds

    • Covalent bonds

    • Ionic bonds

    • Hydrophobic regions

    • Hydrophilic regions

  • Protein Structure:

    1. Primary: Amino acid sequence

    2. Secondary: Coiling or folding patterns

    3. Tertiary: Overall three-dimensional shape

Protein Functionality

  • Driver of movement within a cell

  • A protein’s function depends on its shape, which in turn depends on:

    1. Amino acid sequence

    2. Environmental Conditions: pH, temperature, salt concentration, and water content

    3. Interactions with other molecules

  • The shape of a protein can change due to environmental factors, which can affect its functionality significantly.

Functions of Proteins

  1. Movement

  2. Defense (e.g., antibodies) attack by grabbing on and making immobile

  3. Signaling (hormones)

  4. Transport

  5. Enzymes

    • Enzymes: Catalysts that control the rates of chemical reactions

    • Chemical Reactions: rearrangement of bonds between molecules.

Enzyme Action

  • Role of Enzymes: Enzymes have active sites that bind to reactants (substrates), facilitating chemical reactions.

  • Process:

  1. Binding of reactants changes the enzyme shape.

  2. Once the product is formed, it can no longer bind to the enzyme, causing the enzyme to return to its original shape.

Catalysis and Regulation of Enzymatic Reactions

  • Catalyst Role: Enzymes increase the rate of chemical reactions but are not modified.

  • Binding Events:

    • If the enzyme cannot bind to the reactant, the chemical reaction does not take place. ex. lactose some people dont have the enzyme but for maltose everyone has the enzyme that matches the shapee

    • Products of enzymatic reactions can also bind to enzymes, causing structural changes.

Feedback Control Mechanism

  • Regulates rates of reactions. Under these conditions the concentration of the product tends to be constant

    • High product concentration → many enzyme copies inactive → lower reaction rate

    • Low product concentration → most enzyme copies active → higher reaction rate which leads to a homeostasis of reactants and products

Denaturing Proteins

  • Permanently changing shape of a protein. Caused by changes in:

    • Temperature

    • pH

    • Salt concentration

    • Water content

    • Chemical reactions

Summary of Organic Molecules

Types of Organic Molecules

  • Carbohydrates:

    • Type: Starch, Glycogen, Cellulose

    • Function: Energy storage

    • Breakdown: Hydrolysis reactions

  • Lipids:

    • Subtypes: Fats, Phospholipids

    • Composition: More H per C than carbohydrates

  • Proteins:

    • Composition: Contain N and can be broken down via enzymatic reactions.

  • Lactose: A carbohydrate that not all humans can digest due to a lack of the enzyme lactase.

Term List

  • Carbohydrates

  • Cellulose

  • Glycogen

  • Enzymes

  • Fats

  • Hydrolysis

  • Lipids

  • Lactose

  • Phospholipids

  • Polymer

  • Proteins

  • Saturated

  • Starch

  • Unsaturated

Organic Chemistry Review

  • Refer to the Review Material section in UMLearn for further reinforcement of topics discussed.