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Biology Exam 1 Study Guide: Foundations, Cells, and Biomolecules

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Foundations of Biology

Genes and Heredity

Genes are the fundamental units of heredity, composed of DNA, that encode instructions for building proteins and determining traits.

  • Gene: A segment of DNA that codes for a specific protein or functional RNA.

  • Example: The gene for eye color determines pigment production in the iris.

Three Domains of Life

All living organisms are classified into three domains based on cellular organization and genetics.

  • Bacteria: Prokaryotic, unicellular organisms with peptidoglycan cell walls.

  • Archaea: Prokaryotic, often extremophiles, with unique membrane lipids and no peptidoglycan.

  • Eukarya: Eukaryotic organisms, including protists, fungi, plants, and animals.

Prokaryotes vs. Eukaryotes

  • Prokaryotes: Lack a nucleus and membrane-bound organelles; include Bacteria and Archaea.

  • Eukaryotes: Have a nucleus and membrane-bound organelles; include Protista, Fungi, Plantae, and Animalia.

Domain Eukarya and Its Four Kingdoms

  • Protista: Mostly unicellular, diverse group.

  • Fungi: Decomposers, cell walls of chitin.

  • Plantae: Multicellular, photosynthetic, cell walls of cellulose.

  • Animalia: Multicellular, heterotrophic, no cell walls.

Binomial Nomenclature

  • Definition: The two-part scientific naming system for species, using Genus species (e.g., Homo sapiens).

Scientific Method

  • Steps:

    1. Observation

    2. Question

    3. Hypothesis

    4. Experiment

    5. Data Collection

    6. Analysis

    7. Conclusion

  • Experimental Controls: Variables kept constant to ensure valid results.

  • Scientific Theory vs. Law: A theory explains phenomena (e.g., evolution), while a law describes consistent observations (e.g., Mendel's laws).

Homeostasis

  • Definition: The maintenance of stable internal conditions despite external changes.

  • Example: Regulation of body temperature in mammals.

Chemical Context of Life

Atomic Structure

  • Atoms: Consist of protons, neutrons (nucleus), and electrons (orbitals).

  • Atomic Number: Number of protons in the nucleus.

  • Atomic Mass: Sum of protons and neutrons.

  • Electron Orbitals: Maximum electrons per shell: 2 (first), 8 (second), 8 (third).

Acids vs. Bases

  • Acids: Donate H+ ions; pH < 7.

  • Bases: Accept H+ ions; pH > 7.

pH and Buffers

  • pH: Measure of hydrogen ion concentration;

  • Buffers: Substances that minimize changes in pH by accepting or donating H+.

Types of Chemical Bonds

  • Ionic Bonds: Transfer of electrons between atoms.

  • Covalent Bonds: Sharing of electrons; can be polar (unequal sharing) or nonpolar (equal sharing).

  • Hydrogen Bonds: Weak attractions between polar molecules, especially involving hydrogen and electronegative atoms (e.g., O, N).

Water and Hydrogen Bonding

  • Properties: Cohesion, adhesion, high specific heat, solvent abilities.

  • Hydrogen Bonds: Responsible for water's unique properties.

Biological Molecules

Monomers and Polymers

  • Monomer: Small building block molecule (e.g., glucose, amino acid, nucleotide).

  • Polymer: Large molecule made of monomers (e.g., starch, protein, DNA).

  • Polymer Formation: Dehydration synthesis (removal of water).

  • Polymer Degradation: Hydrolysis (addition of water).

Structural Differences: Sugars, Amino Acids, Fatty Acids

Molecule

Structure

Function

Sugar (e.g., Glucose)

Ring or chain of carbon with hydroxyl groups

Energy source

Amino Acid

Central carbon, amino group, carboxyl group, R group

Protein building block

Fatty Acid

Long hydrocarbon chain with carboxyl group

Component of lipids

Starch vs. Glycogen

Property

Starch

Glycogen

Organism

Plants

Animals

Structure

Unbranched/branched chains of glucose

Highly branched chains of glucose

Function

Energy storage

Energy storage

Fatty Acids and Phospholipids

  • Fatty Acids: Saturated (no double bonds) or unsaturated (one or more double bonds).

  • Phospholipids: Glycerol backbone, two fatty acids, phosphate group; form cell membranes.

Protein Structure

  • Primary: Sequence of amino acids.

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

  • Tertiary: 3D folding due to side chain interactions.

  • Quaternary: Multiple polypeptide chains.

Nucleic Acids

  • DNA: Double helix, stores genetic information.

  • RNA: Single-stranded, involved in protein synthesis.

Cell Structure and Function

Cell Theory

  • All living things are composed of cells.

  • Cells are the basic unit of life.

  • All cells arise from pre-existing cells.

Cell Anatomy

  • Plasma Membrane: Phospholipid bilayer with embedded proteins; controls entry/exit of substances.

  • Cytoplasm: Jelly-like fluid inside the cell.

  • Nucleus: Contains DNA (eukaryotes only).

  • Ribosomes: Sites of protein synthesis.

  • Cell Wall: Rigid structure outside the membrane (plants, fungi, bacteria).

  • Energy Organelles: Mitochondria (cellular respiration), chloroplasts (photosynthesis in plants).

  • Cytoskeleton: Network of protein fibers for support, movement, and transport.

Cell Walls: Eukaryotic vs. Prokaryotic

Cell Type

Cell Wall Composition

Plant (Eukaryote)

Cellulose

Fungi (Eukaryote)

Chitin

Bacteria (Prokaryote)

Peptidoglycan

Archaea (Prokaryote)

Varied, no peptidoglycan

Cell Wall vs. Membrane

  • Cell Wall: Provides structural support and protection; not present in animal cells.

  • Plasma Membrane: Regulates movement of substances in and out of the cell; present in all cells.

Heterotroph vs. Autotroph

  • Heterotroph: Obtains energy by consuming other organisms.

  • Autotroph: Produces its own food (e.g., via photosynthesis).

Energy-Related Organelles

  • Mitochondria: Site of cellular respiration; produces ATP.

  • Chloroplasts: Site of photosynthesis in plants and algae.

Endosymbiotic Theory

  • Proposes that mitochondria and chloroplasts originated as free-living prokaryotes engulfed by ancestral eukaryotic cells.

  • Evidence: Double membranes, own DNA, ribosomes similar to bacteria.

Cytoskeleton: Function and Roles

  • Maintains cell shape.

  • Facilitates cell movement (e.g., cilia, flagella).

  • Assists in intracellular transport.

Plasma Membranes

  • Composed of a phospholipid bilayer with embedded proteins.

  • Functions: Selective permeability, communication, transport, cell recognition.

Characteristics: Prokaryotes vs. Eukaryotes

Feature

Prokaryotes

Eukaryotes

Nucleus

Absent

Present

Organelles

Few, not membrane-bound

Many, membrane-bound

Size

Small (1-10 μm)

Larger (10-100 μm)

Examples

Bacteria, Archaea

Plants, Animals, Fungi, Protists

DNA → RNA → Protein (Central Dogma)

  • Transcription: DNA to RNA (in nucleus for eukaryotes, cytoplasm for prokaryotes).

  • Translation: RNA to protein (in cytoplasm at ribosomes).

Viruses

Basic Virus Life Cycle

  • Attachment to host cell.

  • Entry of viral genetic material.

  • Replication and synthesis of viral components.

  • Assembly of new viruses.

  • Release from host cell (lysis or budding).

Microscopy

Focusing a Microscope

  • Start with lowest power objective.

  • Use coarse focus, then fine focus.

  • Adjust light and diaphragm as needed.

Additional info: Some explanations and tables were expanded for clarity and completeness based on standard biology curriculum.

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