Biology Macromolecules and Cell Structure - Vocabulary Flashcards
Cells and basic biomolecule composition
- Cells are made of a variety of organic molecules based on carbon: proteins, carbohydrates, lipids, nucleic acids.
- Core idea: four major classes of biomolecules with distinct monomers and functions:
- Carbohydrates
- Lipids
- Proteins
- Nucleic acids
- Functional groups add complexity to the basic structures.
Macromolecules and subunits (overview)
- Macromolecule, Monomer (subunit), Importance
- Carbohydrates: Monomer = simple sugars; joined by covalent bonds; Importance = energy storage, cell walls
- Lipids: No consistent repeating structure, but all are hydrophobic; Importance = membranes, energy storage, signals
- Proteins: Monomer = amino acids; joined by covalent bonds; Importance = structural support, enzymes to catalyze reactions, signals
- Nucleic acids: Monomer = nucleotides; joined by covalent bonds; Importance = encode and store genetic information
- The order of building blocks matters (sequence information is critical in nucleic acids and in determining protein structure).
- Functional groups add complexity to basic structures.
Synthesis and breakdown of macromolecules
- Dehydration/Condensation (synthesis) reaction:
- Covalent bond formed with loss of water: H-OH (H2O) is removed during bond formation between monomers
- General depiction: M1 + M2 -> M1–M2 + H2O
- Hydrolysis (breakdown) reaction:
- Water molecule is consumed to break a covalent bond in a macromolecule, yielding smaller units: M1 + M2 + H2O -> M1 + M2
- Key concept: dehydration builds polymers; hydrolysis breaks them down for utilization or remodeling.
Carbohydrates
- Why we need carbohydrates
- Immediate energy (e.g., glucose)
- Energy storage (e.g., starch in plants, glycogen in animals)
- Structural support (e.g., cellulose in plants)
- General composition: carbohydrates are made mostly of C, H, O in a ratio that reflects the formula C(H2O)n (e.g., glucose C6H{12}O_6)
- Simple vs complex carbohydrates
- Simple carbohydrates: monomers and dimers (monosaccharides and disaccharides)
- Complex carbohydrates: polymers (polysaccharides) like starch, glycogen, cellulose, chitin, collagen (structural contexts vary)
- Monosaccharides (simple sugars)
- General formula often written as Cn(H2O)_n
- Examples provided: glucose, galactose, fructose
- Glucose: linear form and cyclic form; cyclic glucose formula often represented as C6(H2O)_6 in ring form
- Disaccharides
- Formed by covalent glycosidic bonds between two monosaccharides (a dehydration reaction)
- Examples: maltose, sucrose, lactose
- Complex carbohydrates (polymers)
- Starch: energy storage in plants
- Cellulose: structural support in plant cell walls
- Glycogen: energy storage in animals
- Chitin: structural support in insects and crustaceans
- Collagen: structural support in animals
- Key concepts about carbohydrate bonding
- Glycosidic bond = covalent linkage between sugar monomers; essential to polymerize carbohydrates
- In synthesis, a dehydration reaction forms the glycosidic bond and releases water
- In breakdown, hydrolysis cleaves glycosidic bonds with the addition of water
- Important exam-type notes (from slides)
- Complex carbohydrates are made from monomers via dehydration/condensation reactions
- The term ‘mono/di-saccharide’ indicates the number of sugar units in the molecule
- Are simple sugars polar or non-polar? They are polar due to hydroxyl groups; generally soluble in water.
- The molecule shown as the glycosidic linkage is the covalent bond that links sugar units in complex carbs.
- Glucose, galactose, fructose structural highlights
- Glucose and galactose are aldohexoses; fructose is a ketohexose
- Monosaccharides can exist in linear or cyclic forms; cyclic glucose is common in solution
Lipids
- Lipids overview
- Lipids include fats and oils (triacylglycerols), phospholipids, and steroids
- Functions: store energy, form membranes, signaling, bile salts, hormones
- They are mostly non-polar organic molecules and hydrophobic
- Triacylglycerol (fats and oils)
- Structure: glycerol backbone + three fatty acid chains
- Formation: three fatty acids attach to glycerol via ester linkages
- Reaction representation:
ext{Glycerol} + 3 ext{ Fatty acids}
ightarrow ext{Triacylglycerol} + 3 H_2O - Notation often shown as glycerol + fatty acids → triacylglycerol (TAG) with ester linkages
- Fatty acids: saturated vs unsaturated
- Saturated fatty acids: all carbon atoms saturated with hydrogen; no C=C double bonds
- Unsaturated fatty acids: contain one or more C=C double bonds; fewer hydrogens on the chain
- Consequences: saturated fats tend to be solid at room temperature; unsaturated fats tend to be liquid at room temperature
- Melting behavior: longer chain length generally increases melting point; more unsaturation lowers melting point
- Phospholipids
- Structure: glycerol + two fatty acids + phosphate-containing head group
- Phosphate head group is polar (hydrophilic); fatty acid tails are nonpolar (hydrophobic)
- Amphipathic nature: part hydrophilic, part hydrophobic
- Function: form lipid bilayers in aqueous environments; fundamental building blocks of cell membranes
- Membrane assembly: phospholipids form bilayers with hydrophilic heads facing aqueous environments and hydrophobic tails inward
- Phospholipid vs other lipids (visual cues from slides)
- A phospholipid molecule contains a phosphate group and two fatty acid chains attached to glycerol
- In contrast, triacylglycerols have three fatty acids attached to glycerol and no phosphate
- Examples and identifications (from slides)
- A molecule featuring a phosphate group, a glycerol backbone, and two fatty acid chains is a phospholipid
- Lipids do not form traditional polymers; they are modular in structure rather than repeating subunits
- Steroids
- Structure: four interconnected carbon rings (fused) and various functional groups
- Typically nonpolar, and often described as hydrophobic; some steroids can have amphipathic features depending on substitutions
- Biological roles: steroid hormones regulate various physiological processes; examples include sex hormones
Proteins and amino acids
- Proteins are polymers of amino acids connected by peptide bonds
- Amino acids (monomers) structure
- Central carbon (C) bearing:
- amino group (–NH2 or –NH3+ in physiological pH)
- carboxyl group (–COOH)
- hydrogen atom
- variable side chain (R group) that determines identity and properties of the amino acid
- Functions and examples by protein type
- Enzymatic proteins: catalyze chemical reactions (e.g., digestive enzymes; hydrolysis of food molecules)
- Storage proteins: store amino acids (e.g., casein in milk; ovalbumin in egg white)
- Defensive proteins: protect against disease (e.g., antibodies)
- Transport proteins: move substances (e.g., hemoglobin transports oxygen)
- Hormonal proteins: coordinate organism activities (e.g., insulin regulates blood sugar)
- Receptor proteins: respond to chemical stimuli (cell membrane receptors detect signaling molecules)
- Contractile and motor proteins: enable movement (actin, myosin)
- Structural proteins: provide support (keratin, collagen, elastin)
- Polypeptide and peptide bonds
- Amino acids link via peptide bonds (a covalent bond between the carboxyl carbon of one amino acid and the amino nitrogen of the next)
- Peptide bond formation occurs via dehydration reaction
- Resulting chain is a polypeptide; the sequence of amino acids is the primary structure
- Protein structure levels (from the slides)
- Primary structure: sequence of amino acids; held by peptide bonds; N-terminus (amino) and C-terminus (carboxyl)
- Secondary structure: local folding patterns stabilized by hydrogen bonds between the backbone atoms; major motifs are alpha-helix and beta-pleated sheet
- Tertiary structure: overall 3D shape of a single polypeptide; stabilized by interactions among R groups (H-bonds, ionic bonds, disulfide covalent bonds, hydrophobic interactions)
- Quaternary structure: assembly of two or more polypeptides into a functional unit; interactions include H-bonds, ionic bonds, disulfide (covalent) bonds, and hydrophobic interactions
- Disulfide bridges
- A covalent bond between two cysteine residues; strengthens the tertiary or quaternary structure
- Notation: R–S–S–R'
- Denaturation
- The process of unfolding a protein, disrupting its structure and often its function
- Destabilizing interactions (e.g., heating) break down the higher-order structures while primary structure may remain intact in some cases
Nucleic acids (brief reference)
- Nucleic acids encode and store genetic information; monomer = nucleotides; polymer via covalent bonds
- Order of building blocks (sequence) is crucial for function and information content
- Which statements describe monomers for macromolecules that are polymers?
- Correct pairing includes amino acids (proteins) and glucose (carbohydrates) as monomers in their respective polymers
- Lipids do not have a true repeating monomeric unit in the same sense as proteins and polysaccharides; triglycerides and phospholipids are built from glycerol and fatty acids, not a polymer backbone
- Sample multiple-choice reinforcement:
- Which of the following are monomers used to make macromolecules that are polymers?
- A) glucose, fatty acid
- B) amino acid, fatty acid
- C) amino acid, glycerol
- D) amino acid, glucose
- Answer: D (amino acid for proteins; glucose for carbohydrates)
- Carbohydrates general formula: Cn(H2O)n (e.g., C6H{12}O6 for glucose)
- Glycosidic bond: covalent linkage between sugar monomers in carbohydrates
- Dehydration/Condensation reaction (synthesis):
- general form: M1 + M2
ightarrow M1–M2 + H_2O
- Hydrolysis (degradation):
- general form: M1–M2 + H_2O
ightarrow M1 + M2
- Triacylglycerol formation (lipids):
- ext{Glycerol} + 3 ext{ Fatty acids}
ightarrow ext{Triacylglycerol} + 3 H_2O
- Ester linkage (lipids): bond between glycerol and fatty acids in TAGs and phospholipids
- Phospholipid backbone and bilayer
- Phospholipid structure: glycerol + two fatty acids + a phosphate-containing head group
- Membrane arrangement: in water, phospholipids form a lipid bilayer with hydrophilic heads outward and hydrophobic tails inward
- Disulfide bridge in proteins: R-S-S-R'
- Peptide bond: the linkage between amino acids in a protein backbone, typically represented as the covalent bond between the carboxyl carbon of one amino acid and the amino nitrogen of the next
- Protein structure levels recap
- Primary: amino acid sequence
- Secondary: local folding (alpha-helix, beta-sheet) via backbone hydrogen bonding
- Tertiary: 3D folding due to interactions among R groups
- Quaternary: assembly of multiple polypeptides
Real-world connections and implications
- Carbohydrates are central to energy management in organisms and are a major dietary component; balance between quick energy (glucose) and storage carbohydrates (starch, glycogen) is biologically essential.
- Lipids provide dense energy storage, form biological membranes, and participate in signaling (steroids, phospholipids).
- Proteins are versatile, enabling structure, catalysis, transport, signaling, immunity, and movement; their function depends on their precise 3D structure, which in turn depends on their amino acid sequence and chemical environment.
- Understanding polymerization and hydrolysis concepts helps explain digestion and nutrient processing, as well as the regulation of metabolism.
Summary of sample exam-style prompts from the transcript
- Identify the type of bond that links sugar monomers in complex carbohydrates: Glycosidic bond.
- Distinguish between saturated and unsaturated fatty acids and explain how each affects membrane properties and melting points.
- Describe the formation of a phospholipid and its role in forming a lipid bilayer.
- Name the four levels of protein structure and the forces stabilizing each level.
- Explain dehydration/condensation and hydrolysis, including the general forms and the role of water in the reaction.
- Explain why cellulose is a major structural component in plants, while starch is a storage polysaccharide, and why humans cannot digest cellulose in the same way.
Quick cross-links to foundational principles
- Carbon-based chemistry: all macromolecules are built from a carbon backbone with a variety of functional groups, enabling diverse structures and functions.
- Covalent bonding (peptide bonds, glycosidic bonds, ester bonds) drives polymer formation and macromolecule stability.
- Non-covalent interactions (hydrogen bonds, ionic interactions, hydrophobic interactions) drive secondary, tertiary, and quaternary protein structure and membrane organization.
- Structure informs function: the specific arrangement of monomers and bonds determines whether a molecule acts as an enzyme, a structural component, a storage molecule, or a membrane constituent.
