BSC2010 Exam #1 Study Notes: Chapters 2-5 (Chemical Context of Life, Water and Life, Carbon and Molecular Diversity, Biological Macromolecules)

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Chapter 2: The Chemical Context of Life

Elements and Atoms

The study of biology begins with understanding the chemical elements that make up living matter and the structure of atoms.

Major Elements of Life: Four elements—carbon (C), hydrogen (H), oxygen (O), and nitrogen (N)—make up about 96% of living matter. Phosphorus (P) and sulfur (S) are also important.
Trace Elements: Elements required in minute quantities, such as iron (Fe), iodine (I), and zinc (Zn). These are essential for proper biological function.
Atomic Structure: Atoms consist of protons (positive charge), neutrons (neutral), and electrons (negative charge). Protons and neutrons contribute to atomic mass; electrons determine bonding behavior.
Atomic Number: Number of protons in the nucleus; defines the element.
Atomic Mass: Total mass of protons and neutrons.
Isotopes: Atoms of the same element with different numbers of neutrons. Isotopes may have different physical properties but similar chemical behavior.

Chemical Bonds and Interactions

Atoms interact through chemical bonds, which determine molecular structure and function.

Ionic Bonds: Formed when electrons are transferred from one atom to another, resulting in charged ions (cations are positive, anions are negative).
Covalent Bonds: Atoms share electrons; can be single, double, or triple bonds depending on the number of shared electron pairs.
Polar Covalent Bonds: Unequal sharing of electrons leads to partial charges within the molecule.
Hydrogen Bonds: Weak attractions between a hydrogen atom and an electronegative atom (e.g., oxygen or nitrogen).
Van der Waals Interactions: Weak, transient interactions due to fluctuating electron distributions.
Valence: The bonding capacity of an atom, determined by the number of unpaired electrons in the valence shell.
Molecular Shape: The three-dimensional shape of a molecule affects its biological function (e.g., enzyme-substrate specificity).

Chemical Reactions and Equilibrium

Chemical Reaction: The making and breaking of chemical bonds, leading to changes in the composition of matter.
Equilibrium: The point at which the forward and reverse reactions occur at the same rate; concentrations of reactants and products remain constant.
Reversibility: Most chemical reactions are reversible; the direction can be influenced by concentrations of reactants and products.

Chapter 3: Water and Life

Properties of Water

Water's unique properties are essential for life and arise from its molecular structure and hydrogen bonding.

Cohesion: Water molecules stick together due to hydrogen bonding, aiding in transport in plants.
Adhesion: Water molecules stick to other substances, important for capillary action.
High Specific Heat: Water can absorb or release large amounts of heat with little temperature change, stabilizing temperatures in organisms and environments.
Expansion Upon Freezing: Water is less dense as a solid than as a liquid, allowing ice to float and insulate aquatic environments.
Versatility as a Solvent: Water dissolves many substances due to its polarity, forming hydration shells around ions and polar molecules.

Emergent Properties and Their Biological Importance

Cohesion and Adhesion: Enable transport of water and nutrients in plants.
Temperature Moderation: High specific heat buffers organisms against rapid temperature changes.
Ice Floats: Aquatic life survives under ice during winter.
Solvent of Life: Facilitates chemical reactions and transport of substances in cells.

Calculations and Concepts

Molar Mass: The mass of one mole of a substance (in grams).
Molarity: Concentration of a solution, defined as moles of solute per liter of solution. Equation:
Specific Heat: Amount of heat required to raise the temperature of 1 g of a substance by 1°C. Equation: where = heat energy, = mass, = specific heat, = temperature change.
Calorie/Joule Conversion:

Acids, Bases, and pH

Acid: Substance that increases H+ concentration in solution.
Base: Substance that decreases H+ concentration.
pH Scale: Measures H+ concentration; ranges from 0 (acidic) to 14 (basic). Equation:
Biological pH Range: Most biological fluids have pH between 6 and 8.
Buffers: Substances that minimize changes in pH by accepting or donating H+.

Hydration Shells and Solubility

Hydration Shell: Sphere of water molecules surrounding a dissolved ion or polar molecule, stabilizing it in solution.
Solubility: Determined by the polarity of the solute and solvent; polar and ionic substances dissolve well in water.

Chapter 4: Carbon and the Molecular Diversity of Life

Carbon's Versatility

Carbon forms the backbone of biological molecules due to its ability to form four covalent bonds and diverse structures.

Abiotic Synthesis: Miller's experiment demonstrated that organic molecules could form under prebiotic conditions.
Bonding: Carbon can form single, double, or triple bonds with other atoms, leading to a variety of molecular shapes.
Isomers: Molecules with the same molecular formula but different structures. Types include structural isomers, cis-trans isomers, and enantiomers.

Functional Groups

Functional groups are specific groups of atoms attached to carbon skeletons that confer particular properties.

Functional Group	Structure	Properties	Example
Hydroxyl	-OH	Polar, forms hydrogen bonds	Alcohols (e.g., ethanol)
Carbonyl	-C=O	Polar, found in sugars	Aldehydes, ketones
Carboxyl	-COOH	Acidic, donates H+	Amino acids, fatty acids
Amino	-NH2	Basic, accepts H+	Amino acids
Sulfhydryl	-SH	Forms disulfide bonds	Thiols
Phosphate	-PO4	Contributes negative charge	ATP, nucleic acids
Methyl	-CH3	Nonpolar, affects gene expression	Methylated DNA

Chapter 5: The Structure and Function of Large Biological Molecules

Macromolecules and Their Formation

Biological macromolecules are formed by joining smaller units through dehydration reactions.

Dehydration Reaction: Removes water to form a covalent bond between monomers.
Hydrolysis: Adds water to break covalent bonds between monomers.

Carbohydrates

Monosaccharides: Simple sugars (e.g., glucose, fructose).
Disaccharides: Two monosaccharides joined by glycosidic linkage (e.g., sucrose).
Polysaccharides: Long chains of monosaccharides (e.g., starch, glycogen, cellulose).
Glycosidic Bonds: Covalent bonds between sugar monomers.
Branching: Structure affects function (e.g., glycogen is highly branched for rapid energy release).

Lipids

Fats: Composed of glycerol and fatty acids; classified as saturated (no double bonds), unsaturated (one or more double bonds), and trans fats.
Phospholipids: Major component of cell membranes; amphipathic nature (hydrophilic head, hydrophobic tails).
Steroids: Four fused rings; cholesterol is a precursor for steroid hormones.
Insolubility in Water: Due to nonpolar hydrocarbon chains.

Proteins

Amino Acids: Building blocks of proteins; contain amino group, carboxyl group, and side chain (R group).
Peptide Bonds: Link amino acids via dehydration reaction.
Levels of Protein Structure:
- Primary: Sequence of amino acids.
- Secondary: Alpha helices and beta sheets formed by hydrogen bonding.
- Tertiary: Overall 3D shape due to interactions among R groups.
- Quaternary: Association of multiple polypeptide chains.
Protein Folding: Occurs spontaneously or with help from chaperone proteins.
Functions: Enzymes, structural support, transport, signaling, defense, movement.

Nucleic Acids

Types: DNA (deoxyribonucleic acid) and RNA (ribonucleic acid).
Nucleotides: Composed of a nitrogenous base, pentose sugar, and phosphate group.
Nucleosides: Nitrogenous base + sugar (no phosphate).
Base Pairing: In DNA, adenine (A) pairs with thymine (T), guanine (G) pairs with cytosine (C). In RNA, uracil (U) replaces thymine.
Purines: Adenine (A), Guanine (G); Pyrimidines: Cytosine (C), Thymine (T), Uracil (U).
Antiparallel Structure: DNA strands run in opposite directions (5' to 3' and 3' to 5').
Differences between DNA and RNA:
- DNA: Double-stranded, deoxyribose sugar, thymine.
- RNA: Single-stranded, ribose sugar, uracil.

Comparison Table: DNA vs RNA

Feature	DNA	RNA
Strands	Double	Single
Sugar	Deoxyribose	Ribose
Bases	A, T, G, C	A, U, G, C
Function	Genetic information storage	Protein synthesis, gene regulation

Example: The sequence 5'-ATGC-3' in DNA pairs with 3'-TACG-5'.

Additional info: For protein structure determination, techniques such as X-ray crystallography and NMR spectroscopy are used. Chaperone proteins (chaperonins) assist in proper folding in vivo.