Biology 160 Final Exam Study Guide: Core Concepts and Learning Objectives

Overview of Key Biological Concepts

This study guide summarizes the essential learning objectives for a college-level introductory biology course, focusing on molecular and cellular biology, biochemistry, genetics, and energy transformations. The guide is organized by major topics and chapters, providing definitions, comparisons, and explanations to support exam preparation.

Comparative Cell Biology

Prokaryotes vs. Eukaryotes

• Structure: Prokaryotes lack a nucleus and membrane-bound organelles; eukaryotes possess both.

• Transcription & Translation: In prokaryotes, both occur in the cytoplasm; in eukaryotes, transcription occurs in the nucleus and translation in the cytoplasm.

• Cellular Respiration & Photosynthesis: Prokaryotes may use the plasma membrane for these processes; eukaryotes use mitochondria (respiration) and chloroplasts (photosynthesis).

• Cell Division: Prokaryotes divide by binary fission; eukaryotes by mitosis and meiosis.

• Gene Expression Regulation: Prokaryotes often regulate at the transcriptional level; eukaryotes use multiple levels (epigenetic, transcriptional, post-transcriptional, translational, post-translational).

Biomolecules: Structure and Function

Proteins, Nucleic Acids, Carbohydrates, and Lipids

• Proteins: Polymers of amino acids; function as enzymes, structural components, and signaling molecules.

• Nucleic Acids: DNA and RNA; store and transmit genetic information.

• Carbohydrates: Sugars and polysaccharides; provide energy and structural support.

• Lipids: Hydrophobic molecules (fats, phospholipids, steroids); form membranes and store energy.

Polymerization: Proteins, nucleic acids, and polysaccharides are formed by dehydration synthesis; lipids are assembled by different mechanisms.

Physical Properties: Determined by monomer composition and structure (e.g., hydrophobicity, solubility).

Chapter 2 – Chemistry and Water

Significance of Carbon

• Carbon forms four covalent bonds, enabling complex molecules essential for life.

Bond Types and Electronegativity

• Ionic Bonds: Transfer of electrons between atoms with large electronegativity differences.

• Nonpolar Covalent Bonds: Equal sharing of electrons (e.g., O2).

• Polar Covalent Bonds: Unequal sharing (e.g., H2O).

• Hydrogen Bonds: Weak attractions between polar molecules (e.g., between water molecules).

Water Structure and Properties

• Water is polar, forms hydrogen bonds, and has high cohesion, adhesion, and specific heat.

• Structural formula: H–O–H, with partial negative charge on O and partial positive on H.

Functional Groups

• Amino (–NH2): Acts as a base.

• Carboxyl (–COOH): Acts as an acid.

• Carbonyl (–C=O): Found in aldehydes and ketones.

• Hydroxyl (–OH): Increases solubility.

• Phosphate (–PO42–): Energy transfer.

• Sulfhydryl (–SH): Forms disulfide bonds in proteins.

• Methyl (–CH3): Nonpolar, affects gene expression.

Acids, Bases, and pH

• Acids donate H+; bases accept H+.

• pH scale: $\text{pH} = -\log_{10}[\text{H}^+]$

Chapter 3 – Proteins

Levels of Protein Structure

• Primary: Amino acid sequence (peptide bonds).

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

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

• Quaternary: Multiple polypeptides (subunit interactions).

Structure-Function Relationship: Protein function depends on its shape, which is determined by its structure.

Chapter 4 – Nucleic Acids

DNA and RNA Structure

• Primary: Nucleotide sequence.

• Secondary: Double helix (DNA), stem-loop (RNA); stabilized by hydrogen bonds.

• Tertiary: Supercoiling (DNA), complex folding (RNA).

Chapter 5 – Carbohydrates

Polysaccharide Structure and Function

• Starch: Energy storage in plants; alpha-1,4 glycosidic bonds.

• Glycogen: Energy storage in animals; highly branched.

• Cellulose: Structural in plants; beta-1,4 bonds.

• Chitin: Structural in fungi and arthropods; contains N-acetylglucosamine.

• Peptidoglycan: Bacterial cell walls; peptide cross-links.

Energy Storage: C–H bonds in carbohydrates store potential energy.

Chapter 6 – Lipids and Membranes

Types of Lipids

• Triacylglycerols: Energy storage fats.

• Fatty Acids: Hydrocarbon chains; saturated or unsaturated.

• Steroids: Four-ring structure (e.g., cholesterol).

• Phospholipids: Form bilayers in membranes.

Membrane Structure and Function

• Phospholipids have hydrophilic heads and hydrophobic tails, forming bilayers.

• Cholesterol modulates membrane fluidity.

• Transmembrane proteins facilitate selective transport.

Transport Across Membranes

• Osmosis: Water moves from low to high solute concentration.

• Facilitated Diffusion: Via channel or carrier proteins.

• Active Transport: Requires energy (e.g., ATP).

Chapter 7 – Inside the Cell

Cell Types and Organelles

• Bacterial Cells: No nucleus, cell wall, circular DNA.

• Plant Cells: Cell wall, chloroplasts, large vacuole.

• Animal Cells: No cell wall, lysosomes, centrioles.

• Organelle Function: Mitochondria (energy), ER (protein/lipid synthesis), Golgi (modification/sorting), lysosomes (digestion).

Chapter 8 – Energy and Enzymes

Bioenergetics

• Potential Energy: Stored in chemical bonds; high in nonpolar bonds.

• Spontaneous Reactions: Occur without input; increase entropy or release energy.

• Redox Reactions: Transfer of electrons; oxidation (loss), reduction (gain).

• Energetic Coupling: Exergonic reactions drive endergonic ones.

• ATP Hydrolysis: $\text{ATP} + \text{H}_2\text{O} \rightarrow \text{ADP} + \text{P}_i + \text{energy}$

• Enzymes: Lower activation energy, increase reaction rates.

Chapter 9 – Cellular Respiration

Overview and Steps

• Equation: $\text{C}_6\text{H}_{12}\text{O}_6 + 6\text{O}_2 \rightarrow 6\text{CO}_2 + 6\text{H}_2\text{O} + \text{energy}$

• Steps: Glycolysis, Pyruvate Processing, Citric Acid Cycle, Electron Transport Chain.

• NADH/FADH2: Electron carriers; transfer electrons to ETC for ATP production.

• ATP Synthesis: Driven by proton gradient across mitochondrial membrane.

• Fermentation: Regenerates NAD+ when oxygen is absent.

Chapter 10 – Photosynthesis

Overview and Mechanisms

• Equation: $6\text{CO}_2 + 6\text{H}_2\text{O} + \text{light} \rightarrow \text{C}_6\text{H}_{12}\text{O}_6 + 6\text{O}_2$

• Primary Energy Source: Converts solar energy to chemical energy.

• Light Reactions: Capture light, produce ATP and NADPH.

• Calvin Cycle: Uses ATP/NADPH to fix CO2 into sugars.

• Oxygen: Byproduct of water splitting; links to respiration.

Chapter 12 – Cell Cycle

Cell Division and Chromosome Structure

• Roles: Growth, repair, reproduction.

• Chromosomes: DNA wrapped around histones; centromere is the constricted region.

• Mitosis: Chromosomes align and separate via mitotic spindle.

Chapter 13 – Meiosis

Meiotic Division

• Roles: Produces gametes, genetic diversity.

• Reduction: Chromosome number halved during meiosis I.

• Chromosome Arrangement: Metaphase/anaphase differ between mitosis, meiosis I, and meiosis II.

Chapter 15 – DNA Replication

Mechanisms and Enzymes

• Structure: Double helix enables semi-conservative replication.

• Replication Fork: DNA polymerase synthesizes new strands; helicase unwinds; topoisomerase relieves tension; primase lays RNA primers; ligase joins fragments.

• Replication Bubble: Contains leading/lagging strands, Okazaki fragments, 5'/3' ends, origin.

Chapter 16 – How Genes Work

Genotype to Phenotype

• Central Dogma: DNA → RNA → Protein.

• Mutations: Can alter genotype and phenotype (silent, missense, nonsense, frameshift).

Chapter 17 – Transcription and Translation

Information Flow

• Template Strand: DNA strand used for mRNA synthesis.

• mRNA: Carries code to ribosome for polypeptide synthesis.

Chapter 18 – Gene Expression

Regulation and Differentiation

• Purpose: Ensures correct genes are expressed at the right time/place.

• Differential Expression: Leads to cell specialization.

Study Tips

• Focus on understanding concepts and connections, not just memorization.

• Practice drawing and labeling structures and pathways.

• Use vocabulary in complete sentences to reinforce understanding.