General Biology Final Exam Study Guide

Scientific Inquiry and the Nature of Life

Independent and Dependent Variables

• Independent variable: The factor you change or manipulate in an experiment. Its value is not affected by other variables in the experiment.

• Dependent variable: The factor that you measure in response to changes in the independent variable.

Core Themes in Biology

• Life is organized: Living things consist of cells, use DNA, and obtain and use energy.

• Genetic information: DNA encodes instructions for life and is passed to offspring.

• Evolution: Populations change over time through natural selection.

• Structure and function: Biological structures are adapted to their functions.

Chemical Context of Life

Atoms and Elements

• Atomic number: Number of protons in an atom.

• Mass number: Sum of protons and neutrons in the nucleus.

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

Types of Bonds

• Ionic bonds: Formed when one atom gives up electrons to another, creating charged ions that attract each other.

• Covalent bonds: Formed when atoms share electrons to fill their outer shells; strong bonds in most molecules.

• Hydrogen bonds: Weak attractions between a slightly positive hydrogen of one molecule and a slightly negative atom of another; important in water properties and DNA structure.

Properties of Water

• Cohesion: Water molecules stick to each other.

• Adhesion: Water molecules stick to other substances.

• High specific heat: Water resists temperature change.

• High heat of vaporization: Water absorbs a lot of heat to evaporate.

• Solvent of life: Many substances dissolve in water, facilitating biological reactions.

Biological Molecules

Acids, Bases, and pH

• Acids: Substances that release hydrogen ions (H+) in water.

• Bases: Substances that reduce hydrogen ions in water.

• pH scale: Measures acidity or basicity; lower pH = more acidic, higher pH = more basic.

Macromolecules

• Carbohydrates: Monomers are monosaccharides; function as energy storage and structural support.

• Lipids: Not true polymers; include fats, oils, and steroids; function in energy storage, cell membranes, and hormones.

• Proteins: Monomers are amino acids; function in structure, enzymes, transport, and signaling.

• Nucleic acids: Monomers are nucleotides; store and transmit genetic information (DNA and RNA).

Dehydration and Hydrolysis Reactions

• Dehydration synthesis: Joins monomers by removing water.

• Hydrolysis: Breaks polymers into monomers by adding water.

Cell Structure and Function

Cell Types

• Prokaryotic cells: Lack a nucleus and membrane-bound organelles (e.g., bacteria).

• Eukaryotic cells: Have a nucleus and organelles (e.g., plants, animals, fungi, protists).

Organelles and Their Functions

• Nucleus: Contains genetic material.

• Ribosomes: Synthesize proteins.

• Endoplasmic reticulum (ER): Synthesizes proteins (rough ER) and lipids (smooth ER).

• Golgi apparatus: Modifies, sorts, and packages proteins and lipids.

• Mitochondria: Site of cellular respiration and ATP production.

• Chloroplasts: Site of photosynthesis in plants and algae.

• Cell membrane: Regulates entry and exit of substances; selectively permeable.

Membrane Structure and Transport

Membrane Structure

• Phospholipid bilayer: Hydrophilic heads face outward, hydrophobic tails face inward.

• Proteins: Embedded in the membrane; function in transport, signaling, and structure.

Transport Mechanisms

• Passive transport: Movement of molecules down their concentration gradient without energy input (includes diffusion, facilitated diffusion, and osmosis).

• Active transport: Movement of molecules against their concentration gradient using energy (ATP).

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

Tonicity

• Isotonic: Equal solute concentration inside and outside the cell.

• Hypertonic: Higher solute concentration outside the cell; cell loses water.

• Hypotonic: Lower solute concentration outside the cell; cell gains water.

Metabolism and Enzymes

Metabolic Pathways

• Anabolic pathways: Build large molecules from smaller ones; require energy.

• Catabolic pathways: Break down molecules; release energy.

Enzymes

• Enzymes: Biological catalysts that speed up chemical reactions by lowering activation energy.

• Active site: Region on the enzyme where the substrate binds.

• Activation energy: The energy required to start a reaction.

Cellular Respiration and Photosynthesis

Photosynthesis

• Occurs in chloroplasts of plants and algae.

• Reactants: Carbon dioxide, water, light energy.

• Products: Glucose, oxygen.

Cellular Respiration

• Occurs in mitochondria of eukaryotic cells.

• Reactants: Glucose, oxygen.

• Products: Carbon dioxide, water, ATP.

Energy Flow

• Photosynthesis stores energy in glucose; cellular respiration releases energy from glucose to make ATP.

• These processes are interconnected in the cycling of matter and energy in ecosystems.

DNA Structure and Function

DNA Structure

• Double helix: Two strands of nucleotides wound around each other.

• Nucleotides: Consist of a sugar, phosphate group, and nitrogenous base (adenine, thymine, cytosine, guanine).

• Base pairing: A pairs with T, C pairs with G via hydrogen bonds.

• Antiparallel strands: Strands run in opposite directions (5' to 3' and 3' to 5').

DNA Replication

• Process of copying DNA before cell division.

• Each new DNA molecule consists of one old and one new strand (semiconservative replication).

Transcription and Translation

• Transcription: Making an RNA copy of DNA; occurs in the nucleus.

• Translation: Using mRNA to build a protein at the ribosome; tRNA brings amino acids to the ribosome.

Types of RNA

• mRNA: Messenger RNA; carries genetic code from DNA to ribosome.

• tRNA: Transfer RNA; brings amino acids to ribosome.

• rRNA: Ribosomal RNA; part of the ribosome structure.

Cell Division: Mitosis and Meiosis

Mitosis

• Produces two identical daughter cells for growth and repair.

• Stages: Prophase, Metaphase, Anaphase, Telophase, Cytokinesis.

Meiosis

• Produces four genetically unique gametes (sperm or eggs).

• Reduces chromosome number by half; includes two divisions (Meiosis I and II).

Haploid vs. Diploid

• Diploid (2n): Two sets of chromosomes (one from each parent).

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

Genetics and Inheritance

Mendelian Genetics

• Gene: Unit of heredity; codes for a trait.

• Allele: Different forms of a gene.

• Genotype: Genetic makeup (e.g., AA, Aa, aa).

• Phenotype: Physical expression of the genotype.

Hardy-Weinberg Equilibrium

• Describes a non-evolving population; allele and genotype frequencies remain constant.

• Equations:

  • $p + q = 1$ (allele frequencies)

  • $p^2 + 2pq + q^2 = 1$ (genotype frequencies)

Mutations and Chromosomal Disorders

• Point mutations: Change a single base pair; may be silent, missense, or nonsense.

• Frameshift mutations: Insertions or deletions that shift the reading frame.

• Chromosomal disorders: Changes in chromosome number or structure (e.g., Down syndrome).

Evolution and Population Genetics

Mechanisms of Evolution

• Genetic drift: Random changes in allele frequencies, especially in small populations.

• Gene flow: Movement of alleles between populations.

• Natural selection: Differential survival and reproduction based on inherited traits.

Speciation

• Allopatric speciation: Populations separated by a physical barrier evolve into different species.

• Sympatric speciation: New species arise without physical separation.

Fungi, Plants, and Animal Diversity

Fungi

• Decomposers; recycle nutrients in ecosystems.

• Can be mutualists, parasites, or pathogens.

Plant Diversity

• Vascular tissue: Xylem and phloem transport water, nutrients, and food.

• Seed plants: Gymnosperms and angiosperms; seeds protect and nourish embryos.

• Alternation of generations: Life cycle alternates between haploid (gametophyte) and diploid (sporophyte) stages.

Animal Diversity

• Major phyla: Porifera, Cnidaria, Platyhelminthes, Mollusca, Nematoda, Arthropoda, Echinodermata, Chordata.

• Chordates: Have a notochord, dorsal hollow nerve cord, pharyngeal slits, and post-anal tail at some stage.

• Vertebrates: Animals with backbones (fish, amphibians, reptiles, birds, mammals).

Summary Table: Key Biological Molecules

Macromolecule	Monomer	Function	Example
Carbohydrate	Monosaccharide	Energy storage, structure	Glucose, starch, cellulose
Lipid	Glycerol + fatty acids	Energy storage, membranes, hormones	Fats, oils, steroids
Protein	Amino acid	Structure, enzymes, transport	Hemoglobin, enzymes
Nucleic acid	Nucleotide	Genetic information	DNA, RNA

Additional info:

• Some explanations and examples have been expanded for clarity and completeness.

• Table entries and some definitions are inferred from standard biology curricula.