General Biology: Foundations, Chemistry of Life, and Cell Structure

Study Guide - Smart Notes

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Purpose of living things: All living things reproduce, responding to environmental stimuli.
Natural selection: The environment selects for traits that enhance survival and reproduction, leading to adaptation and evolution. Traits are passed on through offspring.
Interdependence of organisms and the sun: Photosynthetic organisms (like plants) depend on the sun for energy, while animals depend on plants and other animals for food.
Organization of life: Life is organized hierarchically: organisms form populations, populations form communities, communities form ecosystems, and ecosystems make up the biosphere.
Levels of biological organization: Organ systems → organs → tissues → cells → organelles → molecules → atoms.
Domains of life: Three domains: Archaea, Bacteria, and Eukarya.
Scientific method: Steps used to investigate natural phenomena.

Elements: Pure substances consisting of one type of atom, represented by unique chemical symbols.
Atomic structure:
- Protons (positive charge) and neutrons (neutral) in the nucleus; electrons (negative charge) orbit the nucleus.
- Atomic number = number of protons.
- Atomic mass = protons + neutrons.
- Isotopes: Atoms of the same element with different numbers of neutrons.

Ionic bonds: Formed when electrons are transferred from one atom to another, creating charged ions (cations and anions) that attract each other.
Covalent bonds: Strongest type; formed when atoms share electron pairs.
Hydrogen bonds: Weak attractions between a hydrogen atom in one molecule and an electronegative atom (like oxygen or nitrogen) in another.
Polar vs. nonpolar molecules: Polar molecules have unequal sharing of electrons, leading to partial charges; nonpolar molecules share electrons equally.

The arrangement of electrons, especially in the outermost shell (valence electrons), determines how atoms interact and bond with each other.

Cohesion: Water molecules stick to each other via hydrogen bonds, leading to surface tension.
Adhesion: Water molecules stick to other polar or charged surfaces.
Solvent properties: Water dissolves many ionic and polar compounds, making it the "universal solvent."
High specific heat: Water absorbs and retains heat, moderating temperature changes.
Density: Ice is less dense than liquid water, so it floats.
pH and buffers: Water can dissociate into H+ and OH-; buffers help maintain stable pH in biological systems.

Acids: Proton donors; increase H+ concentration.
Bases: Proton acceptors; decrease H+ concentration.
pH scale: Ranges from 0 (acidic) to 14 (basic), with 7 as neutral. Each step is a tenfold change in H+ concentration.

All organic compounds contain carbon, usually hydrogen, oxygen, and sometimes nitrogen, phosphorus, and sulfur.
Dehydration synthesis: Builds polymers by removing water to form bonds.
Hydrolysis: Breaks down polymers by adding water to break bonds.

Proteins: Polymers of amino acids; perform structural, enzymatic, and regulatory functions.
Carbohydrates: Polymers of monosaccharides; provide energy and structural support.
Lipids: Hydrophobic molecules including fats, oils, and phospholipids; important for energy storage and membrane structure.
Nucleic acids: DNA and RNA; store and transmit genetic information.

Primary structure: Sequence of amino acids.
Secondary structure: Local folding (alpha helices, beta sheets) due to hydrogen bonding.
Tertiary structure: Overall 3D shape from interactions among side chains.
Quaternary structure: Multiple polypeptide chains forming a functional protein.
Denaturation: Loss of protein shape (and function) due to heat, pH, or chemicals.

Prokaryotic cells: Small, lack membrane-bound organelles, DNA in nucleoid region, have cell wall and ribosomes.
Eukaryotic cells: Larger, have membrane-bound organelles (nucleus, mitochondria, etc.), DNA in nucleus.

Phospholipid bilayer: Hydrophilic heads face outward, hydrophobic tails face inward.
Proteins: Serve as channels, receptors, enzymes, and structural components.
Fluid mosaic model: Membrane is flexible, with proteins and lipids moving laterally.

Diffusion: Movement of molecules from high to low concentration; passive process.
Osmosis: Diffusion of water across a selectively permeable membrane.
Facilitated diffusion: Passive transport aided by membrane proteins.
Active transport: Movement of substances against concentration gradient; requires energy (ATP).
Endocytosis: Cell engulfs material by forming a vesicle.
Exocytosis: Vesicle fuses with membrane to release contents outside the cell.

Feature	Prokaryotic Cells	Eukaryotic Cells
Size	Small (1-10 μm)	Larger (10-100 μm)
Nucleus	No true nucleus (nucleoid region)	True nucleus with nuclear envelope
Organelles	Absent	Present (mitochondria, ER, etc.)
Cell wall	Present (peptidoglycan in bacteria)	Present in plants/fungi (cellulose/chitin), absent in animals
Ribosomes	Smaller (70S)	Larger (80S)

Some details (such as the full list of organelles or the exact steps of the scientific method) were inferred based on standard biology curricula.