Comprehensive Biology Exam Study Guide: Key Concepts and Skills

Ch. 1 – Evolution, the Themes of Biology, and Scientific Inquiry

Characteristics of Living Things

• Order: Living organisms exhibit complex but ordered organization.

• Regulation (Homeostasis): Ability to maintain stable internal conditions.

• Growth and Development: Organisms increase in size and complexity, following specific instructions coded in their DNA.

• Energy Processing: Use of energy to power activities and chemical reactions.

• Response to Environment: Ability to sense and react to stimuli.

• Reproduction: Production of offspring, passing genetic material to the next generation.

• Evolutionary Adaptation: Populations change over generations through adaptations that enhance survival and reproduction.

Levels of Biological Organization

• Biosphere (all life on Earth) → Ecosystems → Communities → Populations → Organisms → Organs/Organ Systems → Tissues → Cells → Organelles → Molecules

• Example: A leaf (organ) contains tissues, which are made of cells, which contain organelles, composed of molecules.

Controlled Experiments

• Definition: An experiment in which only one variable is changed at a time, while all others are kept constant.

• Purpose: To determine the effect of the independent variable on the dependent variable.

Hypothesis vs. Theory

• Hypothesis: A testable, tentative explanation for an observation.

• Theory: A broad, well-supported explanation for a wide range of phenomena, supported by extensive evidence.

• Example: "All living things are made of cells" is a theory; "If plants are given fertilizer, they will grow taller" is a hypothesis.

Ch. 2 – The Chemical Context of Life

Chemical Bonds Important to Biology

• Covalent Bonds: Atoms share electrons; strong and stable (e.g., H2O).

• Ionic Bonds: Transfer of electrons from one atom to another, forming charged ions (e.g., NaCl).

• Hydrogen Bonds: Weak attractions between a hydrogen atom and an electronegative atom (e.g., between water molecules).

• Van der Waals Interactions: Weak, transient attractions between molecules or parts of molecules.

Ch. 3 – Water and Life

Characteristics of Water

• Cohesion: Water molecules stick together via hydrogen bonds.

• Adhesion: Water molecules stick to other substances.

• High Specific Heat: Water resists temperature changes.

• Universal Solvent: Many substances dissolve in water due to its polarity.

• Ice Floats: Solid water is less dense than liquid water.

Moles and Molarity

• Mole: Amount of substance containing Avogadro's number ($6.022 \times 10^{23}$) of particles.

• Molarity (M): Moles of solute per liter of solution.

Formula:

$M = \frac{\text{moles of solute}}{\text{liters of solution}}$

Hydrophobic vs. Hydrophilic Substances

• Hydrophobic: Repel water; nonpolar (e.g., oils).

• Hydrophilic: Attract water; polar or charged (e.g., salts, sugars).

Ch. 4 – Carbon and the Molecular Diversity of Life

Characteristics of Organic Molecules

• Contain carbon atoms bonded to hydrogen, oxygen, nitrogen, and other elements.

• Form the backbone of biological macromolecules.

Types of Isomers

• Structural Isomers: Differ in covalent arrangement of atoms.

• Cis-Trans (Geometric) Isomers: Differ in spatial arrangement around double bonds.

• Enantiomers: Mirror images of each other; differ in arrangement around an asymmetric carbon.

Ch. 5 – The Structure and Function of Large Biological Molecules

Functions of Biomolecules

• Carbohydrates: Energy storage and structural support.

• Lipids: Long-term energy storage, membrane structure, signaling.

• Proteins: Enzymes, structure, transport, signaling, defense.

• Nucleic Acids: Store and transmit genetic information (DNA, RNA).

Polymerization

• Process of linking monomers to form polymers via dehydration reactions (removal of water).

Classification of Sugars

• By carbon number (triose, pentose, hexose).

• By functional group (aldose or ketose).

Levels of Protein Structure

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

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

• Tertiary: 3D folding (hydrophobic interactions, disulfide bridges, ionic bonds).

• Quaternary: Association of multiple polypeptides.

Ch. 6 – A Tour of the Cell

Limits to Cell Size

• Surface area-to-volume ratio limits cell size; efficient exchange of materials requires a high ratio.

Function of Cellular Structures

• Nucleus: Stores genetic material.

• Mitochondria: Site of cellular respiration.

• Chloroplasts: Site of photosynthesis (plants/algae).

• Endoplasmic Reticulum: Protein and lipid synthesis.

• Golgi Apparatus: Modifies, sorts, and packages proteins/lipids.

• Lysosomes: Digestion of macromolecules.

Cytoskeleton Composition

• Microtubules: Hollow tubes; cell shape, chromosome movement.

• Microfilaments: Actin filaments; cell movement, muscle contraction.

• Intermediate Filaments: Structural support.

Ch. 7 – Membrane Structure and Function

Passive Transport

• Simple Diffusion: Movement of small, nonpolar molecules down their concentration gradient.

• Facilitated Diffusion: Movement via transport proteins (channels/carriers) for ions and polar molecules.

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

Active Transport

• Movement of substances against their concentration gradient, requiring energy (usually ATP).

• Example: Sodium-potassium pump.

Membrane Permeability

• Small, nonpolar molecules (O2, CO2) move easily.

• Ions and large polar molecules require transport proteins.

Ch. 8 – An Introduction to Metabolism

Exergonic vs. Endergonic Reactions

• Exergonic: Release energy; spontaneous (e.g., cellular respiration).

• Endergonic: Require energy input; non-spontaneous (e.g., photosynthesis).

Potential vs. Kinetic Energy

• Potential Energy: Stored energy (e.g., chemical bonds).

• Kinetic Energy: Energy of motion (e.g., movement of molecules).

Activation Energy and Enzymes

• Activation Energy (Ea): Energy required to start a reaction.

• Enzymes: Lower activation energy, speeding up reactions.

Ch. 9 – Cellular Respiration and Fermentation

Catabolism vs. Anabolism

• Catabolism: Breakdown of molecules to release energy.

• Anabolism: Synthesis of complex molecules from simpler ones; requires energy.

Fermentation

• Anaerobic process; regenerates NAD+ by converting pyruvate to lactic acid or ethanol.

Glycolysis

• First step of cellular respiration; breaks glucose into two pyruvate molecules, producing ATP and NADH.

Ch. 10 – Photosynthesis

PURPOSE OF PHOTOSYNTHESIS

• Convert light energy into chemical energy (glucose) in plants, algae, and some bacteria.

Light and Dark Reactions

• Light Reactions: Occur in thylakoid membranes; produce ATP and NADPH, release O2.

• Calvin Cycle (Dark Reactions): Occur in stroma; use ATP and NADPH to fix CO2 into glucose.

Ch. 11 – Cell Communication

Location of Receptor Proteins

• Receptors can be located in the plasma membrane (for hydrophilic ligands) or inside the cell (for hydrophobic ligands).

Ch. 12 – The Cell Cycle

Stages of Mitosis

• Prophase: Chromosomes condense, spindle forms.

• Metaphase: Chromosomes align at the metaphase plate.

• Anaphase: Sister chromatids separate to opposite poles.

• Telophase: Nuclear envelopes reform, chromosomes decondense.

Ch. 13 – Meiosis and Sexual Life Cycles

Purpose of Cellular Division

• Growth, repair, and reproduction.

Haploid vs. Diploid Cells

• Haploid (n): One set of chromosomes (e.g., gametes).

• Diploid (2n): Two sets of chromosomes (e.g., somatic cells).

Ch. 14 – Mendel and the Gene Idea

Punnett Squares

• Tool to predict the probability of offspring genotypes and phenotypes from parental crosses.

Phenotypic and Genotypic Ratios

• Phenotypic Ratio: Ratio of observable traits in offspring.

• Genotypic Ratio: Ratio of genetic combinations in offspring.

• Example: Monohybrid cross (Aa x Aa): Genotypic ratio 1:2:1 (AA:Aa:aa), Phenotypic ratio 3:1 (dominant:recessive).

Ch. 16 – The Molecular Basis of Inheritance

DNA Replication

• Semiconservative process; each new DNA molecule has one old and one new strand.

Structure of DNA

• Double helix; sugar-phosphate backbone; complementary base pairing (A-T, G-C).

Enzymes in DNA Replication

• Helicase: Unwinds DNA.

• Primase: Synthesizes RNA primer.

• DNA Polymerase: Adds nucleotides to new strand.

• Ligase: Joins Okazaki fragments.

Ch. 17 – Gene Expression: From Gene to Protein

Codons and Anticodons

• Codon: Three-nucleotide sequence on mRNA that codes for an amino acid.

• Anticodon: Three-nucleotide sequence on tRNA complementary to the mRNA codon.

Ch. 18 – Regulation of Gene Expression

Function of Operons

• Clusters of genes under control of a single promoter; allow coordinated regulation in prokaryotes.

Tryptophan Operon

• Repressible operon; turned off when tryptophan is present.

Ch. 19 – Viruses

Lytic vs. Lysogenic Cycles

Feature	Lytic Cycle	Lysogenic Cycle
Viral DNA Integration	No	Yes (prophage)
Host Cell Fate	Lysis (cell bursts)	Cell survives, divides with viral DNA
Viral Production	Immediate	Delayed (can enter lytic later)

• Lytic: Virus replicates rapidly, destroys host cell.

• Lysogenic: Viral DNA integrates into host genome, replicates with cell, can later enter lytic cycle.