Macromolecules and Cellular Building Blocks - Vocabulary
Macromolecules and Foundational Concepts
Objective of today’s lecture: identify the building blocks of cells and understand the four macromolecules that compose life (carbohydrates, lipids, proteins, nucleic acids).
Core idea: macromolecule = a larger molecule; macro- vs micro- prefixes: macro = big, micro = small.
Four macromolecules (building blocks of cells)
Carbohydrates (sugars)
Lipids (fats and related molecules)
Proteins
Nucleic acids (DNA and RNA)
Genetic information: DNA is a nucleic acid; RNA is also a nucleic acid and serves in transcription/translation.
Hierarchy: macromolecule → monomer/polymer → cell → tissue → organ → organ system → organism.
Carbohydrates (aka sugars)
Monomer and polymer sizes:
Monomer: monosaccharide (one sugar). Prefix mono = 1; saccharide = sugar. General formula for many carbohydrates is repeated; common shorthand is for glucose type units.
Disaccharide: two monosaccharides joined by dehydration synthesis (removal of water). Resulting bond is a glycosidic linkage. Example: glucose + glucose → maltose; glucose + fructose → sucrose; galactose + glucose → lactose.
Polysaccharide: many monosaccharides linked; examples include starch, glycogen, cellulose, and chitin.
Monosaccharides (two examples):
Glucose (C6H12O6) and fructose (C6H12O6) differ slightly; the key difference is the position of the carbonyl group and thus the ring form, which affects sweetness (fructose is sweeter).
Monosaccharides can be drawn as straight chains or rings (often hexagonal rings) with carbons numbered 1–6.
Important functional notes:
Most carbohydrates share the basic formula with a typical small unit representing the ratio of elements.
Glycosidic linkage (bond) forms during dehydration synthesis:
Different combinations yield different disaccharides (e.g., ; ; ).
Major storage and structural polysaccharides:
Storage polysaccharides: starch (plants) and glycogen (animals); glycogen stored especially in muscles and liver.
Structural polysaccharides: cellulose (plants; cell walls) and chitin (exoskeletons of insects and crustaceans; fungal cell walls).
All are composed largely of glucose, but differences arise from how the glucose units are linked, creating different properties.
Plant vs animal storage and structure visuals:
Starch and glycogen resemble glucose-based chains; glycogen is highly branched, starch is more linear; cellulose forms parallel chains; chitin contains acetylated amino sugars.
In pictures, starch tends to look like a straight chain; glycogen shows branching; cellulose appears as parallel chains.
Practical connections and health notes:
FDA guidance: added sugar should be limited to about of daily calories.
High sugar intake is correlated with adverse health effects, including diabetes.
Daily per-year sugar consumption varies by population; the lecture notes highlight that average intake is not ideal.
Quick recap relationships:
Same building block (glucose) can form different polysaccharides by changing linkage order, yielding different structural and functional outcomes (energy storage vs structural support).
Lipids
General properties:
Diverse, hydrophobic (water-fearing) compounds composed largely of carbon and hydrogen.
Examples: fats (triglycerides), fatty acids (saturated vs unsaturated).
Hydrophobic due to predominance of C–H bonds (hydrocarbons).
Fats (triglycerides): structure and formation
Composed of a glycerol head linked to three fatty acid tails (a triacylglycerol).
Bonds between glycerol and fatty acids are ester bonds; formed by dehydration synthesis (loss of water).
Overall formation involves removal of three water molecules for three ester bonds.
Saturated vs unsaturated consequences:
Saturated fats: no double bonds; typically animal fats (butter, steak fat); usually solid at room temperature.
Unsaturated fats: one or more double bonds; often plant fats (olive oil) and some fish fats; typically liquid at room temperature.
Trans fats: produced by hydrogenation (adding H₂) to unsaturated fats, creating trans fats which are harder for the body to metabolize and are linked to health risks.
Phospholipids: key component of cell membranes
Structure: two fatty acid tails and a glycerol head with a phosphate group (hence the name phospholipid).
Heads are hydrophilic (water-loving); tails are hydrophobic (water-fearing).
Form a bilayer in aqueous environments, with hydrophilic heads facing water and hydrophobic tails shielding water.
Compared to triglycerides, phospholipids have two tails instead of three.
Steroids and cholesterol
Steroids share a four-ring core carbon skeleton and can serve as hormones.
Cholesterol is a precursor to steroids and is essential for steroid hormone synthesis.
Sex steroids (e.g., testosterone) are examples of steroid hormones; synthetic variants (anabolic steroids) are sometimes abused and can have serious health consequences.
Visual and health implications:
A phospholipid bilayer forms the core structure of the cell membrane, regulating entry/exit and maintaining cellular integrity.
Lipid health implications: balancing saturated, unsaturated, and trans fats is important for cardiovascular health.
Proteins
Diversity and function
Proteins are the most diverse macromolecules in terms of function.
Functions include:
Enzymes: speed up chemical reactions.
Transport proteins: move substances within and between cells.
Defensive proteins: antibodies.
Signaling proteins: facilitate communication between cells.
Receptor proteins: receive signals.
Contractile proteins: drive muscle contraction.
Structural proteins: provide support (e.g., collagen in skin).
Storage proteins: store amino acids or nutrients for later use.
Building blocks: amino acids
Proteins are polymers built from amino acids (monomers).
There are 20 standard amino acids; each has:
An amino group (-NH₂)
A carboxyl group (-COOH)
A hydrogen atom
An R group (side chain) that determines identity and properties.
The unique properties of each amino acid come from the R group.
A dipeptide or longer polypeptide is formed by linking amino acids via peptide bonds (a dehydration synthesis reaction).
Three key concepts for amino acids and proteins
Peptide bond: joins amino acids together in a chain.
Primary structure: linear sequence of amino acids.
Four levels of protein structure:
Primary: sequence of amino acids (polymer of amino acids).
Secondary: local folding patterns stabilized by hydrogen bonds between adjacent amino acids; forms α-helix or β-pleated sheet.
Tertiary: three-dimensional folding driven by various bonds (hydrogen bonds, ionic interactions, hydrophobic interactions, disulfide bridges).
Quaternary: two or more tertiary structures come together to form a functional protein (e.g., hemoglobin).
Shape determines function: different shapes enable different functions and interactions.
Denaturation: extreme heat or conditions cause loss of protein structure and function.
Misfolding and disease: prions are infectious proteins that can cause misfolding and severe disease (e.g., prion diseases).
Example: spider silk is a protein with remarkable mechanical properties.
Amino acid examples (conceptual):
Examples provided (e.g., leucine, aspartic acid, serine) show identical backbones with different R groups.
Practical notes:
A single protein can have many possible conformations, which underpins diversity of function across organisms.
Nucleic Acids
Purpose and types
Nucleic acids store and transmit genetic information.
Two main nucleic acids: DNA and RNA.
DNA is the blueprint for proteins; RNA is involved in the transcription and translation processes.
Building blocks: nucleotides
Each nucleotide consists of three parts:
A sugar (deoxyribose in DNA; ribose in RNA)
A phosphate group
A nitrogenous base
Nucleotides link to form nucleic acids via phosphodiester bonds (linking the sugar of one nucleotide to the phosphate of the next).
DNA vs RNA
DNA: double-stranded helix; bases A, C, G, T; contains the genetic code; backbone consists of sugar-phosphate strands.
RNA: single-stranded; bases A, C, G, U (uracil replaces thymine); acts as the messenger and decodes DNA to produce proteins.
Base pairing: A pairs with T in DNA; C pairs with G; in RNA, A pairs with U when pairing with a complementary strand or during transcription/translation contexts.
Gene and transcription/translation
Gene: a segment of DNA that codes for a trait.
Transcription: DNA is transformed into RNA (the RNA transcript serves as a working manual).
Translation: RNA is used to synthesize proteins via cellular machinery.
Mutations and evolution
Mutations: changes in the DNA sequence that can alter genetic information.
Over time, mutations contribute to evolution and variation within populations.
Recap of nucleotide concept
One nucleotide is built from: a sugar, a phosphate, and a nitrogenous base.
DNA vs RNA differences include strand number, sugar type, and bases used (A, C, G, T for DNA; A, C, G, U for RNA).
Basic chemistry and bonds (foundational concepts)
Atoms and subatomic particles
Atoms consist of protons (positive), neutrons (neutral), and electrons (negative).
The nucleus contains protons and neutrons; electrons orbit in electron shells/orbitals.
Covalent vs ionic bonds
Covalent bonds: sharing of electrons between atoms.
Ionic bonds: transfer of electrons from one atom to another, forming charged ions attracted to each other.
Polar vs nonpolar covalent bonds
Polar covalent bonds: unequal sharing of electrons (one atom pulls more strongly).
Nonpolar covalent bonds: equal sharing of electrons.
Water as a model of polarity
Water (H₂O) is a polar molecule with a partial negative charge on the oxygen and partial positive charges on the hydrogens.
Hydrogen bonds form between polar molecules (attraction between positive H and negative O).
Solutions and pH basics
A neutral solution on the pH scale is pH = 7.
Organic compounds all contain carbon (they are carbon-based, hence organic).
Functional groups and monomers vs polymers
Functional groups (e.g., hydroxyl OH in alcohol) determine chemical properties and reactivity.
Monomer: building block of a polymer; polymer: chain of monomers.
Examples of bonds linking monomers to form polymers:
Carbohydrates: glycosidic bonds (e.g., two monosaccharides forming a disaccharide).
Proteins: peptide bonds (joining amino acids).
Nucleic acids: phosphodiester bonds (linking nucleotides).
Monomers versus polymers: monomers are the building blocks; polymers are long chains of monomers.
Life's organizational levels (from smallest to largest)
Smallest unit: Atom
Molecules: chemical combinations of atoms
Cells: basic unit of life; four major types of macromolecules build the cell
Tissues
Organs
Organ systems
Organism
Population (same species in an area)
Community (multiple species in an area)
Ecosystem (biotic and abiotic factors in an area)
Biosphere (all ecosystems on Earth)
Domains of life and cellular organization
Three domains: Bacteria, Archaea, Eukarya.
Nucleus presence:
Eukarya have a nucleus; Bacteria and Archaea do not (they are prokaryotes).
Cellular organization:
Archaea and Bacteria: typically single-celled organisms.
Eukarya: organisms can be unicellular or multicellular; contains kingdoms Plantae, Animalia, Fungi, etc.
Mushrooms are multicellular and belong to the domain Eukarya.
Scientific method and core facts about life (review highlights)
Scientific method: key steps include forming a testable and falsifiable hypothesis; experiments and observations test hypotheses.
Four primary elements of living organisms (basic elements often emphasized): Carbon (C), Hydrogen (H), Oxygen (O), Nitrogen (N). [Note: the lecture mentions these as essential elements; other elements are also common in biology (e.g., phosphorus, sulfur), but C, H, O, N are core.]
Properties of life (five core traits):
Respond to environment (e.g., Venus flytrap closing on a catching prey).
Process energy (metabolism, energy extraction from nutrients).
Grow and develop.
Reproduce (sexually or asexually).
Adapt/evolve over time.
Quick reference: terms and concepts at a glance
Carbohydrates: monomer = monosaccharide; polymers = disaccharides, polysaccharides; energy storage and structural roles.
Lipids: hydrophobic; glycerol head + fatty acid tails; ester bonds; triglycerides; phospholipids; cholesterol and steroids; saturated vs unsaturated vs trans fats.
Proteins: polymers of amino acids; 20 amino acids; peptide bonds; four structural levels (primary, secondary, tertiary, quaternary); function depends on shape; denaturation and prions.
Nucleic acids: nucleotides; DNA vs RNA; base pairing (A-T, C-G in DNA; A-U, C-G in RNA); transcription and translation; genes.
Bonds and polarity: covalent vs ionic; polar vs nonpolar covalent; hydrogen bonds between molecules; intra-molecular bonding in macromolecules.
Structural-functional relationships: cell membranes (phospholipids) and membrane dynamics; steroid hormones; protein folding and function; nucleotide roles in heredity.
If you want, I can convert these notes into a printable one-page summary or build a Q&A flashcard set based on these topics.