The Chemical Level of Organization: Organic Compounds and Comprehensive Study Guide to Organic Compounds

Criteria for Organic Compounds: A compound is classified as "organic" if it contains carbon and hydrogen atoms that are covalently bonded into chains or rings.
Additional Elements: In addition to carbon and hydrogen, organic compounds may include:
- Oxygen ( $O$ )
- Nitrogen ( $N$ )
- Phosphorus ( $P$ )
- Sulfur ( $S$ )
- Metal ions

Monomers: Small organic molecules that serve as the basic building blocks of larger structures.
Polymers: Large organic molecules composed of multiple monomers joined together.
Chemical Processes of Synthesis and Breakdown:
- Dehydration Synthesis: The process by which monomers are joined to form polymers. During this reaction, a water molecule ( $H_2O$ ) is removed. For example, the monosaccharides glucose and fructose undergo dehydration synthesis to form the disaccharide sucrose.
- Hydrolysis: The process of breaking down a polymer into its constituent monomers by adding a water molecule ( $H_2O$ ).

General Classification: Carbohydrates are categorized based on the number of sugar units they contain.
Monosaccharides (Monomers): These are the simplest sugars.
- Hexoses (Six-carbon sugars):
  - Glucose
  - Fructose
  - Galactose
- Pentoses (Five-carbon sugars):
  - Deoxyribose (found in DNA)
  - Ribose (found in RNA)
Disaccharides: These are formed by the bonding of two monosaccharides through dehydration synthesis.
- Sucrose: Formed from the bonding of Glucose + Fructose.
- Lactose: Formed from the bonding of Galactose + Glucose.
- Maltose: Formed from the bonding of two Glucose molecules.
Polysaccharides: These consist of numerous monosaccharides joined together.
- Starch: Includes forms such as Amylose and Amylopectin.
- Glycogen: The storage form of glucose in animals.
- Cellulose (Fiber): A structural polysaccharide found in plants.

Monomers (Nucleotides): The building blocks of all nucleic acids. Each nucleotide consists of:
1. One or more phosphate groups ( $PO_4^{3-}$ ).
2. A pentose sugar (either Ribose or Deoxyribose).
3. A nitrogen-containing base.
Nitrogenous Bases:
- Adenine ( $A$ )
- Guanine ( $G$ )
- Thymine ( $T$ ) - unique to DNA
- Cytosine ( $C$ )
- Uracil ( $U$ ) - unique to RNA
DNA (Deoxyribonucleic Acid):
- Structure: A double-helical molecule consisting of two strands.
- Backbone: Composed of sugar-phosphate groups.
- Bonding: The two strands attach via hydrogen bonds between complementary bases.
- Complementary Base Pairing: Adenine ( $A$ ) pairs with Thymine ( $T$ ), and Guanine ( $G$ ) pairs with Cytosine ( $C$ ).
RNA (Ribonucleic Acid):
- Structure: Typically single-stranded.
- Components: Contains the sugar ribose and uses the base Uracil ( $U$ ) in place of Thymine.
Adenosine Triphosphate (ATP):
- Classification: ATP is a specific type of nucleotide used as a primary energy carrier.
- Structure: Composed of Adenosine (Adenine + Ribose sugar) and three phosphate groups attached by high-energy bonds.
- Function: Provides necessary energy for most cell, tissue, and organ functions. Stages of phosphate attachment include:
  - Adenosine monophosphate (AMP)
  - Adenosine diphosphate (ADP)
  - Adenosine triphosphate (ATP)

Triglycerides: Composed of one Glycerol molecule attached to three Fatty Acids.
- Synthesis: Formed via dehydration synthesis where glycerol loses a hydrogen atom ( $H$ ) and the carboxyl groups on the fatty acids lose a hydroxyl group ( $OH$ ), releasing water ( $H_2O$ ).
Fatty Acid Saturation and Shape:
- Saturated Fatty Acids: These chains are straight and typically solid at room temperature (e.g., palmitic acid).
- Monounsaturated Fatty Acids: Contain one double bond which causes a kink in the chain (e.g., oleic acid).
- Polyunsaturated Fatty Acids: Contain two or more double bonds (e.g., linoleic acid). Unsaturated fats are typically liquid at room temperature.
Phospholipids: Composed of two fatty acids, a glycerol molecule, and a phosphate group.
- Properties: They contain both polar (hydrophilic phosphate "head") and non-polar (hydrophobic fatty acid "tails") regions.
- Example: Phosphatidylcholine.
Steroids and Sterols: These are ring-shaped lipids that are hydrophobic and insoluble in water.
- Example: Cholesterol.
Prostaglandins: Lipids derived from unsaturated fatty acids. They are synthesized at sites of tissue damage or infection and are involved in the body's response to injury and illness.

Amino Acid Structure (Monomers): Proteins are made of 20 different types of amino acids. Each amino acid consists of:
1. A central alpha ( $\\alpha$ ) carbon.
2. An Amino group ( $NH_2$ ).
3. A Carboxyl group ( $COOH$ ).
4. A variable Side chain (R-group).
Examples of Amino Acids:
- Tryptophan: A nonpolar amino acid.
- Cysteine: A polar amino acid.
- Glycine: The simplest amino acid.
Peptide Bonds: Formed via dehydration synthesis to link amino acids into peptides, polypeptides, or functional proteins.
Four Levels of Protein Structure:
1. Primary Structure: The specific linear sequence of amino acids in the polypeptide chain.
2. Secondary Structure: Maintained by hydrogen bonds between amino acids, resulting in shapes like the alpha ( $\\alpha$ ) helix or beta ( $\\beta$ )-pleated sheet.
3. Tertiary Structure: The final 3D shape assumed after folding, determined by interactions between R-groups. Proteins can be globular or fibrous.
4. Quaternary Structure: The assembly of two or more polypeptide chains (subunits) into a single functional protein (e.g., Hemoglobin). Note: Some proteins do not have a quaternary level.

Definition: Specialized proteins that facilitate chemical reactions.
Steps in an Enzymatic Reaction:
1. Substrate Approach: Substrates (reactants) approach the active sites on the enzyme.
2. Binding: Substrates bind to the active sites, forming an enzyme-substrate complex.
3. Facilitation: Internal changes within the enzyme-substrate complex facilitate the chemical interaction of the substrates.
4. Release: The products are released, and the enzyme returns to its original form, ready to catalyze the next reaction.