Exam 1 Study Guide: Foundations of Biology, Chemistry of Life, and Cell Structure

Characteristics of Living Things

Defining Life

• Order: Living things exhibit complex but ordered organization.

• Regulation (Homeostasis): Organisms regulate their internal environment to maintain stable conditions.

• Growth and Development: Information carried by genes controls the pattern of growth and development.

• Energy Processing: Organisms obtain and use energy to power activities.

• Response to Environment: Living things respond to environmental stimuli.

• Reproduction: Organisms reproduce their own kind.

• Evolutionary Adaptation: Populations evolve over generations through adaptations.

Hierarchical Organization of Life

Levels of Biological Organization

• Atom → Molecule → Organelle → Cell → Tissue → Organ → Organ System → Organism → Population → Community → Ecosystem → Biosphere

• Each level builds on the previous, increasing in complexity.

Levels of Organization of Biodiversity

Classification of Life

• Domain (e.g., Bacteria, Archaea, Eukarya)

• Kingdom (e.g., Animalia, Plantae, Fungi, Protista)

• Phylum, Class, Order, Family, Genus, Species

• Each level represents a more specific grouping.

Theory of Natural Selection and Its Principles

Darwin's Theory

• Variation: Individuals in a population vary in traits.

• Inheritance: Some traits are heritable.

• Overproduction: More offspring are produced than can survive.

• Differential Survival and Reproduction: Individuals with advantageous traits survive and reproduce more.

• Result: Over generations, favorable traits become more common.

Scientific Method Concepts

Hypothesis, Theory, Control, and Variables

• Hypothesis: A testable explanation for an observation or question.

• Theory: A broad, well-supported explanation for a wide range of phenomena (e.g., theory of evolution).

• Control Group: The group not exposed to the experimental variable; used for comparison.

• Experimental Group: The group exposed to the variable being tested.

• Confounding Variable: An outside factor that can affect the outcome of an experiment if not controlled.

Chemical Basis of Life

Elements, Atoms, and Bonds

• Element: A substance that cannot be broken down into other substances by chemical means (e.g., carbon, oxygen).

• Compound: A substance consisting of two or more elements in a fixed ratio (e.g., H2O).

• Four Most Common Elements in Living Organisms: Carbon (C), Hydrogen (H), Oxygen (O), Nitrogen (N).

• Trace Elements: Elements required in very small amounts (e.g., iron, iodine).

• Protons: Positively charged particles in the nucleus.

• Neutrons: Neutral particles in the nucleus.

• Electrons: Negatively charged particles orbiting the nucleus.

• Atomic Number: Number of protons in an atom.

• Atomic Mass (Mass Number): Number of protons plus neutrons.

Chemical Bonds

• Covalent Bond: Atoms share electrons (e.g., H2O).

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

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

• Bonding Capacity: The number of bonds an atom can form, determined by the number of unpaired electrons.

• Electronegativity: An atom's attraction for electrons in a bond.

• Polarity: Unequal sharing of electrons leads to partial charges (e.g., water is polar).

Bonding in Water

• Within Water Molecules: Polar covalent bonds between H and O.

• Between Water Molecules: Hydrogen bonds.

Properties of Water That Support Life

• Cohesion: Water molecules stick together (surface tension).

• Adhesion: Water molecules stick to other substances.

• High Specific Heat: Water resists temperature changes.

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

• Universal Solvent: Many substances dissolve in water.

• Cause: All these properties arise from hydrogen bonding.

pH

• pH: A measure of hydrogen ion concentration; scale from 0 (acidic) to 14 (basic).

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

Organic Compounds and Carbon

Properties of Carbon

• Carbon: Forms four covalent bonds, allowing for diverse molecules.

• Backbone of Life: Carbon chains and rings form the skeletons of organic molecules.

Functional Groups (Six Main)

• Hydroxyl (-OH): Alcohols; polar.

• Carbonyl (C=O): Aldehydes and ketones.

• Carboxyl (-COOH): Acids; donates H+.

• Amino (-NH2): Amines; acts as a base.

• Sulfhydryl (-SH): Thiols; forms disulfide bonds.

• Phosphate (-PO4): Organic phosphates; energy transfer.

Dehydration Reaction and Hydrolysis

• Dehydration Reaction: Joins monomers by removing water.

• Hydrolysis: Breaks polymers into monomers by adding water.

Macromolecules

Carbohydrates

• Monomer: Monosaccharide (e.g., glucose).

• Disaccharide: Two monosaccharides joined (e.g., sucrose).

• Polysaccharide: Many monosaccharides (e.g., starch, glycogen, cellulose).

• Cellulose: Structural polysaccharide in plants; indigestible fiber for humans.

• Starch: Storage polysaccharide in plants.

• Glycogen: Storage polysaccharide in animals.

Lipids

• Triglycerides: Glycerol + 3 fatty acids; main form of stored energy.

• Saturated Fats: No double bonds; solid at room temperature.

• Unsaturated Fats: One or more double bonds; liquid at room temperature.

• Lipids: Hydrophobic molecules including fats, oils, phospholipids, and steroids.

Proteins

• Amino Acids: Monomers of proteins; 20 types.

• Peptide Bond: Covalent bond between amino acids.

• Levels of Protein Structure:

  • Primary: Sequence of amino acids.

  • Secondary: Alpha helix or beta sheet (hydrogen bonds).

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

  • Quaternary: Multiple polypeptides join.

• Denaturation: Loss of protein structure (and function) due to heat, pH, etc.

Nucleic Acids

• Monomer: Nucleotide.

• Polymer: DNA or RNA.

Monomers and Polymers of the Four Biomolecules

Biomolecule	Monomer	Polymer	Bond Type	Function
Carbohydrate	Monosaccharide	Polysaccharide	Glycosidic	Energy, structure
Lipid	Fatty acid, glycerol	Triglyceride, phospholipid	Ester	Energy storage, membranes
Protein	Amino acid	Polypeptide	Peptide	Enzymes, structure
Nucleic Acid	Nucleotide	DNA/RNA	Phosphodiester	Genetic info

Cell Structure and Function

Plasma (Cell) Membrane

• Structure: Phospholipid bilayer with embedded proteins (fluid mosaic model).

• Function: Controls entry/exit of substances; communication; cell recognition.

• Selective Permeability: Some molecules (e.g., small, nonpolar) pass easily; others (e.g., ions, large molecules) do not.

Prokaryotic vs Eukaryotic Cells

Feature	Prokaryotic	Eukaryotic
Nucleus	No	Yes
Membrane-bound organelles	No	Yes
Size	Small	Larger
Examples	Bacteria, Archaea	Plants, Animals, Fungi, Protists

Plant, Animal, and Bacterial Cell Properties

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

• Animal Cells: Lysosomes, centrioles, no cell wall.

• Bacterial Cells: No nucleus, cell wall, no membrane-bound organelles.

Cell Organelles

• Nucleus: Contains DNA; control center.

• Ribosome: Site of protein synthesis.

• Smooth Endoplasmic Reticulum (ER): Lipid synthesis, detoxification.

• Rough ER: Studded with ribosomes; protein synthesis and processing.

• Golgi Apparatus: Modifies, sorts, and ships proteins and lipids.

• Lysosomes: Digestive enzymes; breakdown of waste.

• Vacuole: Storage; large central vacuole in plants for water and nutrients.

• Chloroplasts: Photosynthesis in plants and algae.

• Cytoskeleton: Protein fibers for cell shape, movement, and transport.

Membrane Transport

Fluid Mosaic Model

• Describes the plasma membrane as a dynamic structure with proteins floating in or on the fluid lipid bilayer.

Selective Permeability

• Passes Easily: Small, nonpolar molecules (e.g., O2, CO2).

• Passes Less Easily: Ions, large polar molecules (e.g., glucose).

Osmosis and Tonicity

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

• Isotonic: Equal solute concentration; no net water movement.

• Hypotonic: Lower solute concentration outside; water enters cell.

• Hypertonic: Higher solute concentration outside; water leaves cell.

Passive and Active Transport

• Passive Transport: Movement of substances down their concentration gradient; no energy required (e.g., diffusion, facilitated diffusion, osmosis).

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

Enzymes

Structure and Function

• Enzyme: Protein catalyst that speeds up chemical reactions.

• Catalyze: To increase the rate of a reaction without being consumed.

• Active Site: Region on the enzyme where substrate binds and reaction occurs.

Example:

• Amylase: Enzyme in saliva that catalyzes the breakdown of starch into sugars.

Additional info: Where only terms were listed, academic context and definitions were added for completeness. Functional groups are the six most common in introductory biology. Table entries for biomolecules and cell types are standard for college biology.