Organic Molecules Powerpoint

Carbon, Valence, and the Basis of Organic Molecules

  • Life’s molecular diversity is based on the properties of carbon.
  • Carbon forms covalent bonds by sharing electrons; valence determines how many bonds can be formed.
  • Methane as a simple example of carbon’s valence and bonding pattern.
  • Lewis dot structures and electron distribution diagrams illustrate valence electrons and how many electrons are needed to fill the valence shell.
  • Key concept: Valence = the number of bonds an element can form; for carbon, valence is 4.
  • Implication: Carbon can form diverse structures (chains, branches, rings) that underlie the shapes and functions of biomolecules.
  • Shape is tied to function: Bonding patterns (and resulting geometry) influence molecular behavior and interactions.
  • Carbon forms 4 outer hybrid orbitals, each with 1 electron available for sharing; this enables diverse bonding patterns.

Life’s molecular diversity and carbon bonding overview

  • Carbon’s tetravalence allows:
    • Straight or branched carbon skeletons (e.g., ethane, propane, butane)
    • Double bonds and rings leading to varied shapes and isomerism
  • Isomerism: Different arrangements of the same molecular formula (e.g., C4H8) yield distinct compounds with different properties.

Carbon skeletons and isomerism

  • Ethane: C2H6
  • Propane: C3H8
  • Alkenes: 1-butene, 2-butene (examples of isomerism in hydrocarbons)
  • Butane vs isobutane: different skeletons and formulas (C4H10) illustrating structural isomers and branching
  • Rings: Cyclohexane as an example of ring-containing hydrocarbons
  • Unbranched vs branched structures influence molecular shape and properties

Functional groups and their significance (general)</n- A few key functional groups are essential for the functioning of biological molecules due to their shapes, polarity, and ability to participate in chemical reactions.

  • Functional groups affect hydrophilicity/hydrophobicity, acid-base behavior, and bonding opportunities with other molecules.

Hydroxyl group (—OH)

  • Example: Ethanol (often written HO–CH2–CH3 or HO–)
  • Properties:
    • Polar (oxygen contributes polarity)
    • Hydrophilic; hydrogen bonding with water
    • Common in carbohydrates and proteins

Carbonyl group (C═O)

  • Examples: Acetone, Propanal
  • Properties:
    • Polar and hydrophilic
    • Present in ketones and aldehydes
    • Important in carbohydrates and proteins

Carboxyl group (—COOH)

  • Example: Acetic acid
  • Forms:
    • Nonionized form is polar and hydrophilic
    • Ionized form is negatively charged at physiological pH
  • Relevance:
    • Found in organic acids (fatty acids, amino acids, proteins)
    • Contributes to acid-base chemistry in biology

Amino group (—NH2)

  • Example: Glycine
  • Forms:
    • Nonionized form is polar
    • Ionized form can be positively charged at physiological pH (acts as a base)
  • Relevance:
    • Central to amino acids and proteins; hydrophilic

Amide group (—C(=O)NH)

  • Polar and hydrophilic
  • Found in proteins as part of peptide bonds; key functional group for peptide/linkage chemistry
  • Composition: C, O, N, H present in the group

Phosphate group (—OPO3H2)

  • Example: Glycerol phosphate
  • Properties:
    • Nonionized form is polar; ionized form is negatively charged at physiological pH
    • Hydrophilic
  • Relevance:
    • Found in phospholipids, nucleic acids, and ATP

Sulfhydryl group (—SH)

  • Example: Cysteine (often written HS–)
  • Properties:
    • Weakly polar and noncharged, but reactive
    • Can form disulfide bonds (S–S) between cysteine residues, cross-linking proteins
  • Relevance:
    • Important in protein structure and stabilization

Methyl group (—CH3)

  • Example: 5-Methylcytosine
  • Properties:
    • Nonpolar
  • Relevance:
    • Found in amino acids, proteins, and nucleic acids; can influence hydrophobic interactions and gene regulation patterns

Structure and function at the molecular level: functional groups matter!

  • Functional groups influence molecule shape, polarity, acidity/basicity, and reactivity.
  • Biological examples: Testosterone and Estradiol show how methyl groups and hydroxyl groups alter function and signaling.
  • Visual cues: CH3 groups and OH groups present in steroid frameworks and hormone molecules, affecting receptor binding and activity.

The four important classes of biological molecules

  • Carbohydrates, Proteins, Nucleic acids, Lipids
  • Macromolecules are polymers; monomer → polymer is the general pattern for three classes:
    • Carbohydrates: Monosaccharide → Polysaccharide
    • Proteins: Amino acid → Polypeptide
    • Nucleic acids: Nucleotide → Nucleic acid (DNA/RNA)
  • Lipids: Not polymers or traditional macromolecules; include phospholipids, triglycerides, steroids
  • Examples of polymers:
    • Carbohydrates: starch, glycogen, cellulose
    • Proteins: enzymes, structural proteins, transport proteins
    • Nucleic acids: DNA, RNA
  • Phospholipids illustrate lipids’ role in membranes and signaling

Short polymer and dehydration synthesis concepts

  • Short polymer; unlinked monomer; dehydration reaction forms a new bond; energy stored in the new bond (condensation)
  • Depolymerization (hydrolysis): polymer is broken into shorter polymers or monomers with the addition of water; energy released or consumed depending on context

Carbohydrates: structure, roles, and forms

  • Carbohydrates are also called saccharides
  • Roles: primary energy storage, structural components in cells
  • Abundance: among the most widespread organic molecules in nature
  • General formula: C<em>nH</em>2nOnC<em>nH</em>{2n}O_n (1:2:1 ratio)
  • Types by subunits:
    • Monosaccharides: one subunit (e.g., glucose, C6H12O6)
    • Disaccharides: two monosaccharides linked together
    • Polysaccharides: many subunits; storage or structural roles
  • Monosaccharides (glucose as example):
    • In linear form, number of carbons is determined by aldehyde/ketone position
    • In aqueous solution, many form ring structures
    • Anomeric carbon is the carbonyl carbon that becomes acetal/hemiketal in the ring
    • OH from another carbon participates in ring closure; energy-yielding and building-block roles

Disaccharides: linked monosaccharides by glycosidic bonds

  • Not all disaccharides act as primary energy sources in the body; some serve transport roles
  • Examples:
    • Maltose = glucose + glucose
    • Lactose = glucose + galactose
    • Sucrose = glucose + fructose
  • Glycosidic linkages:
    • Maltose: 1–4 glycosidic linkage
    • Sucrose: 1–2 glycosidic linkage
  • Formation: synthesis of glycosidic bonds via dehydration reactions

Storage polysaccharides and structural polysaccharides

  • Amylose (unbranched) and amylopectin (branched) are starch components in plants
  • Glycogen is highly branched and stored in animal muscle tissues
  • Cellulose is unbranched and forms the plant cell wall
  • Hydrogen bonding between glucose units stabilizes polysaccharide structures
  • Polysaccharides are all-glucose polymers but differ by linkage patterns and branching, leading to diverse functions: energy storage vs structure
  • Key examples:
    • Starch: amylose + amylopectin
    • Glycogen: highly branched storage in animals
    • Cellulose: linear, structural in plants

Proteins: diversity of function and structure

  • Proteins perform: enzymes, defense, transport, support, movement, signaling, storage
  • Proteins are made of amino acids linked by peptide bonds to form polypeptides
  • General structure of an amino acid:
    • Amino group (-NH2)
    • Carboxyl group (-COOH)
    • Central (α) carbon with a side chain (R group)
  • Side chains (R groups) determine properties of amino acids and protein structure

Amino acid properties by side-chain categories

  • Nonpolar (hydrophobic) R groups include:
    • Glycine (Gly, G)
    • Alanine (Ala, A)
    • Valine (Val, V)
    • Leucine (Leu, L)
    • Isoleucine (Ile, I)
    • Methionine (Met, M)
    • Phenylalanine (Phe, F)
    • Tryptophan (Trp, W)
    • Proline (Pro, P)
  • Polar (hydrophilic) R groups include:
    • Serine (Ser, S)
    • Threonine (Thr, T)
    • Cysteine (Cys, C)
    • Tyrosine (Tyr, Y)
    • Asparagine (Asn, N)
    • Glutamine (Gln, Q)
  • Basic (positively charged) R groups include:
    • Lysine (Lys, K)
    • Arginine (Arg, R)
    • Histidine (His, H)
  • Acidic (negatively charged) R groups include:
    • Aspartic acid (Asp, D)
    • Glutamic acid (Glu, E)
  • Charged, hydrophilic side chains contribute to protein polarity and function

Peptide bonds and protein formation

  • Amino acids join via peptide bonds (amide bonds) to form polypeptides
  • Basic depiction:
    • Carboxyl group of one amino acid reacts with the amino group of the next
  • Peptide bond formation details:
    • Dehydration reaction removes a water molecule to form -CO-NH- linkage between amino acids
    • Orientation: N-terminus (amino end) and C-terminus (carboxyl end) define directionality of the chain
  • Overall, the specific order of amino acids determines the protein’s structure (secondary, tertiary, quaternary) and thus its function
  • Terms:
    • Dipeptide: two amino acids linked by one peptide bond
    • Polypeptide: a longer chain of amino acids

Nucleic acids: information storage and transfer

  • Nucleic acids are informational polymers made of nucleotides
  • Each nucleotide consists of:
    • Phosphate group
    • Five-carbon sugar (pentose)
    • Nitrogenous base (one of A, G, C, T in DNA; A, G, C, U in RNA)
  • Nitrogenous bases are categorized as:
    • Purines: Adenine (A) and Guanine (G)
    • Pyrimidines: Cytosine (C), Thymine (T), Uracil (U)
  • DNA vs RNA nucleosides:
    • DNA uses deoxyribose sugar (lacks 2′-hydroxyl)
    • RNA uses ribose sugar (has 2′-OH)
    • Structural differences influence stability and function
  • Nucleotide components form the polynucleotide backbone via phosphodiester bonds:
    • Backbone alternates phosphate groups and pentose sugars
    • 5′ and 3′ ends define directionality
  • Nucleic acids store information through sequence variation of purines/pyrimidines
  • ATP and other nucleotides also function as energy carriers (three phosphate groups attached to adenosine):
    • ATP = adenosine triphosphate; energy transfer in cells

DNA vs RNA: nucleosides and sugar structure (illustrative)

  • Deoxyribose (DNA) vs Ribose (RNA) differ by the presence/absence of a 2′-hydroxyl group on the sugar
  • Nucleotide structure in both includes a base attached to a sugar, which is attached to a phosphate backbone
  • Nucleosides and nucleotides are foundational units for genetic information and energy transfer

Lipids: non-polymers with diverse roles

  • Lipids are not polymers and do not form long chains like carbohydrates, proteins, or nucleic acids
  • Key properties:
    • Hydrophobic and rich in nonpolar C–H bonds
    • High energy content per carbon; often > carbohydrates
    • Functions include energy storage, insulation, membrane structure, and signaling
  • Major lipid types include triglycerides, phospholipids, steroids, and other lipids

Triglycerides: fats and oils

  • Structure:
    • Glycerol backbone linked to three fatty acids via ester linkages
    • Fatty acids can be saturated or unsaturated
  • Saturated fats: triglycerides with many single C–C bonds in fatty acids; typically solid at room temperature
  • Unsaturated fats: fatty acids containing one or more C=C double bonds; typically liquid at room temperature
  • Physical property consequence: Saturated fats have a higher melting point than unsaturated fats/oils

Fatty acids and glycerol (illustrative backbone)

  • Glycerol backbone: HO–CH2–CH(OH)–CH2OH
  • Fatty acid chain: long hydrocarbon chain ending in –COOH
  • Ester linkage forms between glycerol hydroxyls and fatty acid carboxyl groups

Steroids: lipids with four fused carbon rings

  • Core structure: four interlocked carbon rings (cyclopentanoperhydrophenanthrene)
  • Examples shown:
    • Testosterone (with CH3 groups and a specific ring arrangement)
    • Estradiol (with hydroxyl groups attached to the ring system)
  • Roles:
    • Signaling molecules (hormones)
    • Structural and regulatory functions in various tissues

Connections, implications, and real-world relevance

  • Structure–function relationships underlie biological processes: conformations determine enzyme activity, receptor binding, and metabolic pathways
  • Polar vs nonpolar groups influence solubility, transport, and interactions in aqueous cellular environments
  • The balance of saturated and unsaturated fats influences membrane fluidity and energy storage strategies in organisms
  • Polymers (carbohydrates, proteins, nucleic acids) enable information storage, catalysis, and structure, while lipids provide energy, membranes, and signaling platforms
  • Ionization states of functional groups at physiological pH affect molecular behavior, interactions with water, and the overall charge of molecules (e.g., carboxylates, amines, phosphate groups)
  • Practical implications include nutrition (carbohydrate types, fats), biochemistry of metabolism (glycolysis, ATP), and medical relevance (hormones, protein structure, nucleic acid integrity)

Key formulas and numerical references (summarized)

  • Carbohydrate formula and ratio:
    • C<em>nH</em>2nOnC<em>nH</em>{2n}O_n with a typical carbohydrate ratio of approx. 1:2:1
  • Monosaccharide example:
    • Glucose formula: C<em>6H</em>12O6C<em>6H</em>{12}O_6
  • Glycosidic linkages in disaccharides:
    • Maltose linkage: ext1–4glycosidiclinkageext{1–4 glycosidic linkage}
    • Sucrose linkage: ext1–2glycosidiclinkageext{1–2 glycosidic linkage}
  • Polysaccharide examples (storage/structure): starch (amylose/amylopectin), glycogen, cellulose
  • Protein formation and bonds:
    • Peptide bond formation between amino acids via dehydration synthesis: extAminoacid<em>1−extCOOH+extAminoacid</em>2−extNH<em>2ightarrowextAminoacid</em>1−extCO−NH−extAminoacid<em>2+H</em>2Oext{Amino acid}<em>{1}- ext{COOH} + ext{Amino acid}</em>{2}- ext{NH}<em>2 ightarrow ext{Amino acid}</em>{1}- ext{CO-NH-} ext{Amino acid}<em>{2} + H</em>2O
  • Nucleotides and nucleic acids:
    • Backbone: phosphodiester bonds between phosphate and sugar units
    • 5′ to 3′ directionality defines information encoding
  • Lipids and energy:
    • Triglyceride: glycerol + three fatty acids via ester linkages
    • Energy storage per carbon in lipids generally higher than carbohydrates
  • Four fused-ring steroids and examples: testosterone, estradiol

Summary of core concepts

  • Carbon’s tetravalence enables vast molecular diversity, providing the backbone for life’s macromolecules
  • Functional groups govern solubility, reactivity, and interactions; their ionization states at physiological pH influence function
  • Macromolecules (carbohydrates, proteins, nucleic acids) are polymers built from monomers via dehydration synthesis and are broken by hydrolysis
  • Lipids are not polymers but are essential for energy storage, membranes, insulation, and signaling; steroids add a signaling role
  • The specific order of monomers (amino acids, nucleotides) defines the structure and function of proteins and nucleic acids, respectively
  • Real-world relevance spans metabolism, genetics, nutrition, and health; understanding these molecules helps explain how biological systems store energy, transmit information, and regulate processes