BIOSC 0150 — Foundations of Biology 1

BIOSC 0150 Study Guide

Foundations of Biology 1

This guide emphasizes biological chemistry, cells, metabolism, and introductory genetics. Those are the four modules in Pitt's published Fall 2021 BIOSC 0150 syllabus. An older catalog also describes organismal physiology, so a short physiology extension appears below. Follow your section's actual learning objectives when deciding how much time to spend on that extension. Sources for scope: Pitt Fall 2021 syllabus and archived catalog description.

These original notes focus on explanations and predictions rather than memorizing lists. The practice scenarios are invented. Quantitative relationships are study tools; not every section requires every formula.

Core content and connections

Biological chemistry

Water's polarity helps explain hydrogen bonding, dissolving ions, and the hydrophobic effect. Connect molecular structure to behavior: a nonpolar hydrocarbon region interacts differently with water than a charged group. Compare carbohydrates, lipids, proteins, and nucleic acids by their building blocks, bonds, and functions. Protein function depends on folding and chemical environment, not just the presence of amino acids.

Cells and membranes

Connect each organelle to a process. The nucleus houses most eukaryotic DNA; ribosomes synthesize proteins; the endoplasmic reticulum and Golgi process and route many proteins; mitochondria support aerobic ATP production. Membranes are selective barriers. Small nonpolar molecules, ions, and large polar molecules face different transport constraints. For ions, both concentration and electrical gradients matter.

Energy and metabolism

Trace matter and energy separately. Carbon atoms can move from glucose to CO_{2} while electrons move through carriers and energy is captured in ATP. Enzymes lower activation barriers without making an unfavorable reaction favorable by themselves. Cellular respiration includes glycolysis, pyruvate processing, the citric acid cycle, and oxidative phosphorylation. Photosynthesis uses light reactions and carbon fixation; plants also perform cellular respiration.

Genetic information

Distinguish DNA replication, transcription, and translation by their templates, products, locations, and enzymes. Relate the DNA sequence to RNA and then to a protein, while recognizing that some genes produce functional RNA rather than protein. Connect mitosis to maintaining chromosome sets and meiosis to forming haploid cells and genetic variation. Use inheritance probabilities only after establishing the genetic model.

Important vocabulary

Polar molecule: Molecule with uneven charge distribution and a net dipole.
Hydrophobic: Describes nonpolar regions that associate poorly with water.
Monomer: Small building unit of a polymer.
Hydrolysis: Bond cleavage involving water.
Condensation reaction: Bond formation that often releases a small molecule such as water.
Denaturation: Loss of a protein's functional structure, often without breaking its peptide backbone.
Prokaryote: Organism whose cells lack a membrane-bound nucleus.
Eukaryote: Organism whose cells contain a nucleus and other membrane-bound compartments.
Selective permeability: Allowing some substances to cross a barrier more readily than others.
Diffusion: Net movement down a concentration gradient due to random motion.
Osmosis: Net water movement across a selectively permeable membrane driven by water-potential differences.
Tonicity: Effect of a solution's effectively nonpenetrating solutes on cell volume.
Active transport: Transport against an electrochemical gradient using energy directly or indirectly.
Enzyme: Biological catalyst, usually a protein but sometimes RNA.
Active site: Region where an enzyme binds and acts on a substrate.
Activation energy: Barrier that must be overcome for a reaction to proceed.
ATP: Molecule that couples many energy-releasing and energy-requiring processes.
Redox reaction: Reaction involving electron transfer.
Chemiosmosis: Coupling ion movement down an electrochemical gradient to work such as ATP synthesis.
Gene: DNA sequence contributing to a functional RNA or protein product.
Allele: Alternative version of a genetic locus.
Genotype: Genetic composition at one or more loci.
Phenotype: Observable characteristic arising from genotype and environment.
Homologous chromosomes: Chromosome pair carrying corresponding genes, potentially with different alleles.
Sister chromatids: Replicated copies of one chromosome, initially nearly identical.
Codon: Three RNA nucleotides specifying an amino acid or translation stop.
Mutation: Change in genetic sequence; its functional effects vary.
Homeostasis: Regulated maintenance of internal conditions within a workable range.

Important formulas and quantitative ideas

pH ≈ −log_{10}[H^{+}] for dilute solutions using molar concentration as the approximation to activity. A one-unit pH decrease means about tenfold higher hydrogen-ion concentration.
ΔG = ΔH − TΔS. G is Gibbs free energy, H enthalpy, S entropy, and T absolute temperature. At constant temperature and pressure, negative ΔG favors the forward direction; it says nothing by itself about speed.
Surface-area-to-volume ratio of a sphere = 3/r. Since area = 4πr^{2} and volume = (4/3)πr^{3}, smaller spheres have greater area per unit volume.
Concentration c = n/V. This describes amount per volume; it does not by itself determine membrane permeability or tonicity.
Rate = change in measured quantity/time. State whether you measure substrate loss, product formation, or a proxy such as absorbance.
Independent-event product rule: P(A and B) = P(A)P(B). Independence must be justified, not assumed from convenience.
Mutually exclusive-event sum rule: P(A or B) = P(A) + P(B). If the events overlap, subtract P(A and B).
Complement: P(not A) = 1 − P(A). Useful for “at least one” inheritance questions.
Aerobic glucose oxidation, simplified: C_{6}H_{12}O_{6} + 6O_{2} → 6CO_{2} + 6H_{2}O, with energy captured in ATP and released as heat. It represents many reactions, not one step.
Photosynthesis, simplified net equation: 6CO_{2} + 6H_{2}O + light → C_{6}H_{12}O_{6} + 6O_{2}. Actual carbon fixation initially produces smaller carbohydrate intermediates; released O_{2} originates from water.
Percent change = (final − initial)/initial × 100%. A negative result indicates a decrease relative to the initial value.

Worked examples

Example 1 Cell size

A spherical cell's radius increases from 1 to 2 arbitrary units. Its area grows fourfold, volume grows eightfold, and area-to-volume ratio falls from 3 to 1.5 per unit length. This does not prove that all large cells fail; it explains why transport geometry becomes more demanding as size increases.

Example 2 Predicting an enzyme experiment

Suppose equal amounts of enzyme are tested at several substrate concentrations while pH and temperature stay constant. Initial reaction rate rises and then approaches a plateau. A reasonable model is that active sites become increasingly occupied. To test the model, repeat at a higher enzyme concentration; the plateau should rise if another factor is not limiting. A plateau alone does not establish the exact molecular mechanism.

Example 3 Inheritance probability

Under a simple single-gene complete-dominance model, Aa × Aa gives AA, Aa, Aa, aa with genotype probabilities 1/4, 1/2, 1/4. For two independent offspring, the probability both are aa is (1/4)^{2} = 1/16. A dominant phenotype does not mean the allele is common, beneficial, or evolutionarily superior.

Practice questions and answers

A solution changes from pH 7 to pH 5. Change in [H^{+}]? It rises 100-fold.
Does an enzyme change the equilibrium constant? No; it accelerates approach to equilibrium.
What happens to an animal cell in a hypertonic solution of nonpenetrating solute? It loses water and shrinks.
What directly powers ATP synthase in oxidative phosphorylation? An electrochemical proton gradient.
How do transcription and translation differ? Transcription makes RNA from a DNA template; translation uses mRNA to build a polypeptide.
Are sister chromatids the same as homologous chromosomes? No; replication copies and maternal/paternal homologs are different relationships.

Optional physiology extension

If assigned, add negative feedback, gas exchange, circulatory transport, endocrine signaling, and neuronal signaling. For each, identify the regulated variable, sensor, communication pathway, effector, and response. Connect diffusion distance and exchange area to transport. Distinguish an electrical signal along a neuron from chemical signaling at many synapses.

Review routine

For every process, answer: Where does it occur? What enters? What leaves? What supplies energy? What changes if one component stops working? Build comparison sheets for mitosis/meiosis, respiration/photosynthesis, and passive/active transport. Finish with an unfamiliar graph or experiment, not only vocabulary recall.