General Biology Exam I Study Guide: Foundations, Chemistry of Life, and Biological Molecules

Biology: The Study of Life

Characteristics of Living Things

• Definition of Life: Living things exhibit organization, metabolism, homeostasis, growth, reproduction, response to stimuli, and adaptation through evolution.

• Scientific Process: Involves observation, hypothesis formation, experimentation, data collection, and conclusion.

• Hypothesis vs. Prediction: A hypothesis is a testable explanation; a prediction is a specific outcome expected if the hypothesis is true.

Water and Carbon: The Chemical Basis of Life

Atoms, Bonds, and Molecules

• Atomic Structure: Atoms consist of protons, neutrons, and electrons. Atomic number = number of protons; atomic mass = protons + neutrons.

• Isotopes: Atoms of the same element with different numbers of neutrons.

• Electron Configuration: Determines chemical reactivity and bonding.

• Ionic vs. Covalent Bonds: Ionic bonds involve electron transfer; covalent bonds involve electron sharing.

• Electronegativity: The tendency of an atom to attract electrons in a bond.

• Hydrogen Bonds: Weak attractions between a hydrogen atom and an electronegative atom (e.g., O or N).

Properties of Water

• Emergent Properties: Cohesion, adhesion, high specific heat, high heat of vaporization, and solvent abilities.

• Polarity: Water is a polar molecule, allowing it to dissolve many substances.

• Hydrophilic vs. Hydrophobic: Hydrophilic substances interact with water; hydrophobic substances do not.

Macromolecules: Structure and Function

Polymers and Monomers

• Polymer Formation: Formed by dehydration (condensation) reactions; broken down by hydrolysis.

• Types of Macromolecules: Proteins, nucleic acids, carbohydrates, and lipids.

Proteins

• Amino Acids: Building blocks of proteins; contain amino, carboxyl, and R (side chain) groups.

• Functional Groups: Amino (-NH2) and carboxyl (-COOH) groups are always present; side chains determine properties.

• Levels of Structure:

  • Primary: Sequence of amino acids (peptide bonds).

  • Secondary: Alpha helices and beta sheets (hydrogen bonds).

  • Tertiary: 3D folding (various bonds and interactions).

  • Quaternary: Multiple polypeptides (subunit interactions).

• Denaturation: Loss of structure and function due to environmental changes.

Nucleic Acids

• Nucleotides: Composed of a phosphate group, a five-carbon sugar (ribose or deoxyribose), and a nitrogenous base (A, T, C, G, U).

• DNA vs. RNA: DNA contains deoxyribose and bases A, T, C, G; RNA contains ribose and bases A, U, C, G.

• Phosphodiester Bonds: Link nucleotides in a chain.

• Base Pairing: Hydrogen bonds hold DNA strands together (A-T, C-G).

• RNA Reactivity: RNA is more reactive due to the presence of a hydroxyl group on the 2' carbon of ribose.

Carbohydrates

• Monosaccharides: Simple sugars (e.g., glucose).

• Polysaccharides: Long chains (e.g., starch, cellulose, glycogen).

• Glycosidic Linkages: Covalent bonds joining monosaccharides.

• Cellulose vs. Starch: Cellulose has β-1,4 linkages (structural); starch has α-1,4 linkages (energy storage).

Lipids

• Types: Fats (triglycerides), phospholipids, steroids.

• Properties: Hydrophobic, nonpolar, grouped by insolubility in water.

• Saturated vs. Unsaturated Fats: Saturated fats have no double bonds; unsaturated fats have one or more double bonds (kinks in structure).

• Phospholipids: Amphipathic molecules with hydrophilic heads and hydrophobic tails; form biological membranes.

• Cholesterol: Important for membrane fluidity and as a steroid precursor.

Biological Membranes and Transport

Membrane Structure

• Phospholipid Bilayer: Forms the basic structure of cell membranes; amphipathic nature allows for selective permeability.

• Fluid Mosaic Model: Membranes are dynamic, with proteins and lipids moving laterally.

Transport Across Membranes

• Passive Transport: Movement down a concentration gradient; includes simple diffusion and facilitated diffusion (via channels or carriers).

• Active Transport: Movement against a gradient; requires energy (usually ATP).

• Osmosis: Diffusion of water across a selectively permeable membrane.

• Isotonic, Hypotonic, Hypertonic: Terms describing solute concentration relative to the cell; affect water movement and cell volume.

• Co-transport: Coupled transport of two substances across a membrane (symport or antiport).

• Channel vs. Carrier vs. Pump: Channels allow passive movement; carriers undergo conformational change; pumps use energy for active transport.

Concentration Gradient

• Definition: Difference in concentration of a substance across a space or membrane; drives diffusion and osmosis.

Classification of Biological Molecules

Recognizing Structures

• Be able to identify and classify carbohydrates, lipids, proteins, and nucleic acids based on their structural formulas.

Summary Table: Key Biological Molecules

Macromolecule	Monomer	Bond Type	Example
Protein	Amino acid	Peptide bond	Enzyme, hemoglobin
Nucleic Acid	Nucleotide	Phosphodiester bond	DNA, RNA
Carbohydrate	Monosaccharide	Glycosidic linkage	Starch, cellulose
Lipid	Fatty acid, glycerol	Ester bond	Triglyceride, phospholipid

Key Equations

• Energy in Chemical Bonds:

$\Delta G = \Delta H - T\Delta S$

• Osmosis (Water Potential):

$\Psi = \Psi_s + \Psi_p$

• Concentration Gradient (Fick's Law):

$J = -D \frac{dC}{dx}$

Additional info: This guide covers material from Chapters 1-7, including the chemistry of life, macromolecules, and membrane structure and function, as outlined in a typical General Biology curriculum.