Biol 101 Study Guide - Chapter 3

Chapter 3: The Molecules of Life

1. Organic and Inorganic Molecules

  • Definitions:

    • Differentiation between organic and inorganic molecules.

    • Organic molecules typically contain carbon and hydrogen.

  • Characteristics:

    • Organic molecules can return to their native state, while inorganic molecules are often stable since they are not based on carbon chemistry.

  • Chemical Formula Examples:

    • A molecule with the chemical formula CH₄ (Methane) is classified as organic.

    • A molecule with the chemical formula NH₃ (Ammonia) is classified as inorganic.

2. Versatility of Carbon Molecules

  • Atomic Number and Electrons:

    • The atomic number of carbon is 6.

    • There are 4 electrons in the outer shell of carbon.

  • Bond Types:

    • Carbon primarily forms covalent bonds as opposed to ionic bonds.

  • Bond Representation:

    • A single stick connecting two chemical elements (C-C) denotes a single bond, meaning 2 electrons are being shared.

    • A double stick connecting two chemical elements (C=C) denotes a double bond, meaning 4 electrons are shared.

  • Hydrocarbons:

    • A molecule made of just carbon and hydrogen is called a hydrocarbon.

3. Importance of Functional Groups

  • Functional Group Definition:

    • A combination of atoms attached to the carbon backbone that reacts in a consistent manner is termed a functional group.

  • Identifying Functional Groups:

    • Hydroxyl group (OH):

    • Conveys polarity and hydrophilicity to the molecule.

    • Carboxyl group (COOH):

    • Confers acidity to the molecule due to the presence of the hydrogen ion (H+).

    • As a carboxylic acid, it donates H+ in solution.

    • Amino group (NH₂):

    • Imparts basicity to the molecule, can accept H+.

    • Phosphate group (PO₄):

    • Typically confers negativity and is important in energy transfer (e.g., ATP).

  • Amino Acids:

    • Amino acids contain both an amino group (NH₂) and a carboxyl group (COOH) functional group.

4. Isomers

  • Definition:

    • An isomer is a molecule that shares the same chemical formula as another molecule but has a different structural arrangement.

  • Examples:

    • The two chemicals presented are being considered as potential isomers.

5. Macromolecules and Their Building Blocks

  • Definitions:

    • Macromolecule: A large biological molecule comprised of smaller subunits.

    • Monomer: A single subunit that can join together to form larger molecules.

    • Dimer: A molecule made up of two monomers.

    • Polymer: A large molecule formed by repeating units of monomers.

  • Dimer Composition:

    • A dimer consists of 2 monomers.

6. Dehydration Synthesis and Hydrolysis Reactions

  • Reactions:

    • Dehydration Synthesis:

    • Function: Builds polymers by combining monomers and expelling water.

    • Removes: A water molecule (H₂O) during the reaction.

    • Energy: This process generally requires the input of energy.

    • Hydrolysis:

    • Function: Breaks down polymers into monomers by adding water.

    • Adds: A water molecule is added.

    • Energy: This reaction releases energy.

  • Enzymatic Role:

    • Enzymes act as catalysts to speed up both hydrolysis and dehydration synthesis reactions, reducing the activation energy required.

7. General Structure and Characteristics of Organic Molecules

  • Categories:

    • Carbohydrates, Lipids, Proteins, and Nucleic Acids.

  • General Information:

    • Carbohydrates: Contain carbon, hydrogen, and oxygen (CHO) in a 1:2:1 ratio.

    • Structure: Chemical formula has the general form of (CₙH₂ₙOₙ).

    • Lipids: Contain more carbon than oxygen.

    • Proteins: Contain carbon, hydrogen, oxygen, and nitrogen (CHON).

    • Nucleic Acids: Contain carbon, hydrogen, oxygen, nitrogen, and phosphorus (CHONP).

  • Chemical Formula Examples:

    • A molecule with the formula C₁₀H₂₀O₂ depicts a fatty acid.

    • A molecule with the formula C₆H₁₂O₆ is glucose.

Carbohydrates

  • Monomers: Know the five monomers of carbohydrates:

    • Glucose, Fructose, Galactose: Same formula C₆H₁₂O₆ but different structural arrangements known as isomers.

    • Ribose: Has the chemical formula C₅H₁₀O₅, found in RNA.

    • Deoxyribose: Has the chemical formula C₅H₁₀O₄, found in DNA.

  • Disaccharides Formation:

    • Sucrose is made of glucose and fructose.

    • Lactose is made of glucose and galactose.

    • Maltose is made of glucose and glucose.

  • Joining Process:

    • The process used to combine two monosaccharides into a disaccharide is called dehydration synthesis.

  • Functions of Polysaccharides:

    • Starch: Energy storage for plants.

    • Glycogen: Short-term energy storage for animals.

    • Cellulose: Structural molecule in plant cell walls.

    • Chitin: Structural molecule in exoskeletons of arthropods.

Lipids

  • Storage: The long-term energy storage molecule in animals is triglycerides.

  • Hydrophobic Nature: Lipids are primarily hydrophobic.

  • Triglyceride Composition:

    • Consists of glycerol and three fatty acids.

  • Types of Fatty Acids:

    • Saturated fatty acid: No double bonds; generally solid at room temperature.

    • Unsaturated fatty acid: Contains one or more double bonds; generally liquid at room temperature.

  • Phospholipid Structure:

    • Hydrophilic Phosphate Head: Attracted to water.

    • Hydrophobic Fatty Acid Tails: Repel water, creating a lipid bilayer in membranes.

Proteins

  • Functions of Proteins: Include structural support, enzymes, transport, signaling, and antibodies.

  • Monomers: Consist of amino acids, which form peptide bonds with each other.

  • Amino Acid Structure:

    • Contains an amino group (NH₂) and a carboxyl group (COOH).

  • Protein Structure Levels:

    • Primary Structure: Sequence of amino acids (straight chain).

    • Secondary Structure: Formation of alpha helix and beta sheets.

    • Tertiary Structure: Three-dimensional structure emerges.

    • Quaternary Structure: Combination of multiple polypeptides to form a functional protein.

  • Folding Monitors: Chaperonins are proteins that assist in the correct folding of other proteins.

  • Misfolded Proteins: Known as denatured proteins; they do not function properly as they lose their structure.

  • Protein Denaturation: Can occur due to extreme heat, pH changes, and chemical modifications. Denatured proteins lose biological activity.

Nucleic Acids

  • Monomers: The basic unit is the nucleotide.

    • Components of Nucleotide: Comprises a sugar, a phosphate group, and a nitrogenous base.

  • DNA vs. RNA:

    • DNA:

    • Sugar: Deoxyribose.

    • Bases: Adenine (A), Thymine (T), Cytosine (C), Guanine (G).

    • A pairs with T (2 hydrogen bonds).

    • G pairs with C (3 hydrogen bonds).

    • Double helix structure.

    • RNA:

    • Sugar: Ribose.

    • Bases: Adenine (A), Uracil (U), Cytosine (C), Guanine (G).

    • A pairs with U in RNA.

    • Typically single-stranded.

  • Base Classification:

    • Purines: Adenine, Guanine.

    • Pyrimidines: Cytosine, Thymine, Uracil.

  • Watson and Crick: Described the double helix structure of DNA, highlighting complementary base pairing and antiparallel strands.