General Biology: Foundational Concepts and Principles

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Levels of Biological Organization

Hierarchy from Smallest to Largest

Biological systems are organized in a hierarchical structure, from the simplest to the most complex levels.

Atoms: The basic units of matter.
Molecules: Groups of atoms bonded together.
Organelles: Specialized structures within cells.
Cells: The basic unit of life.
Tissues: Groups of similar cells performing a function.
Organs: Structures composed of multiple tissues.
Organ Systems: Groups of organs working together.
Organisms: Individual living beings.
Populations: Groups of organisms of the same species.
Communities: Different populations living together.
Ecosystems: Communities plus their physical environment.
Biosphere: All ecosystems on Earth.

Emergent Properties

Definition and Examples

Emergent properties are characteristics that arise at each level of organization that are not present at lower levels.

Molecules: Exhibit properties (e.g., water's polarity) not found in individual atoms.
Cells: Life emerges from the interaction of organelles and molecules.
Tissues: Specialized functions arise from groups of cells working together.

Example: Muscle tissue contracts, a property not found in individual muscle cells alone.

Photosynthesis and Cellular Respiration

Role in Life on Earth

Photosynthesis and cellular respiration are fundamental processes for energy transformation in living organisms.

Photosynthesis: Converts solar energy into chemical energy (glucose) in plants, algae, and some bacteria.
Producers: Organisms that create food and energy through photosynthesis (e.g., plants, cyanobacteria).
Cellular Respiration: Breaks down nutrients to release energy (ATP) in most organisms.
Consumers: Organisms that use cellular respiration to obtain energy from food.

Equation for Photosynthesis:

Equation for Cellular Respiration:

Form Fits Function

Structure and Function in Biology

The structure of biological features is closely related to their function.

Example: Dolphins and fish both have streamlined bodies for efficient swimming, despite being different organisms.

Prokaryotic vs. Eukaryotic Cells

Main Features and Classification

Cells are classified as prokaryotic or eukaryotic based on their structure.

Prokaryotic Cells: Lack a nucleus and membrane-bound organelles. Found in Bacteria and Archaea.
Eukaryotic Cells: Have a nucleus and membrane-bound organelles. Found in Animals, Plants, Fungi, and Protists.

DNA, Replication, and Protein Synthesis

Genetic Information Flow

DNA stores genetic information and directs the synthesis of proteins.

Replication: The process by which DNA makes a copy of itself.
Protein Synthesis: DNA is transcribed into RNA, which is translated into proteins.

Central Dogma of Molecular Biology:

Feedback Mechanisms

Negative vs. Positive Feedback

Feedback mechanisms regulate biological processes.

Negative Feedback: Reduces the output or activity to maintain homeostasis (e.g., ATP inhibits cellular respiration).
Positive Feedback: Enhances the output or activity (e.g., platelet plug formation in blood clotting).

Taxonomy and Classification

Organization of Life

Taxonomy is the science of classifying organisms.

Largest Taxon: Domain
Smallest Taxon: Species
Three Domains: Bacteria, Archaea, Eukarya
Shared Features of Bacteria and Archaea: Prokaryotic cell structure, lack of nucleus
Unique Feature of Eukarya: Eukaryotic cell structure

Domain	Cell Type	Examples
Bacteria	Prokaryotic	E. coli
Archaea	Prokaryotic	Halophiles
Eukarya	Eukaryotic	Plants, Animals

Binomial Nomenclature

Scientific Naming of Organisms

Organisms are named using a two-part system: genus and species.

Genus: Capitalized and italicized (typed) or underlined (handwritten).
Species: Lowercase and italicized (typed) or underlined (handwritten).
Example: Homo sapiens

Evolution and Natural Selection

Darwin's Theory

Charles Darwin proposed the theory of natural selection in his manuscript "On the Origin of Species."

Descent with Modification: Species change over time, passing traits to offspring.
Driving Force: Variation and competition lead to survival of the fittest.

Atoms, Elements, and Isotopes

Structure and Properties

Atoms are composed of subatomic particles and form elements.

Particles: Protons (positive, mass ~1 amu, nucleus), Neutrons (neutral, mass ~1 amu, nucleus), Electrons (negative, mass ~0, orbitals)
Atomic Mass: Sum of protons and neutrons.
Isotopes: Atoms of the same element with different numbers of neutrons.

Particle	Charge	Mass	Location
Proton	+1	1 amu	Nucleus
Neutron	0	1 amu	Nucleus
Electron	-1	~0 amu	Orbitals

Additional info: Some isotopes are used in medicine for imaging and treatment (e.g., radioactive tracers).

Chemical Bonds

Types and Properties

Chemical bonds hold atoms together in molecules.

Covalent Bonds: Atoms share electrons; can be single, double, or triple bonds.
Ionic Bonds: Atoms transfer electrons, forming cations (+) and anions (-).
Hydrogen Bonds: Weak attractions between polar molecules.

Bond Type	Strength (in water)	Example
Covalent	Strong	H2O
Ionic	Weak	NaCl
Hydrogen	Weak	Between water molecules

Number of Electron Pairs Shared:

Single Bond: 1 pair
Double Bond: 2 pairs
Triple Bond: 3 pairs

Water: Properties and Significance

Polarity, Hydrogen Bonding, and Effects

Water is a polar molecule, allowing it to form hydrogen bonds and exhibit unique properties.

Polarity: Oxygen is more electronegative than hydrogen, creating partial charges.
Hydrogen Bonds: Form between water molecules, leading to cohesion and adhesion.
Cohesion: Water molecules stick to each other.
Adhesion: Water molecules stick to other surfaces.
Surface Tension: Result of cohesion; allows small objects to rest on water.
Meniscus: Curved surface in a container due to both cohesion and adhesion.
High Specific Heat: Water resists temperature changes, stabilizing climates and organisms.
Density: Ice is less dense than liquid water due to hydrogen bond arrangement.

Additional info: Water's high specific heat helps coastal cities maintain moderate temperatures and allows organisms to regulate body temperature.

Solutions, Acids, and Bases

Definitions and pH Scale

Solutions are mixtures of solutes dissolved in solvents. Water is a universal solvent for polar and ionic substances.

Solute: Substance dissolved.
Solvent: Substance doing the dissolving (often water).
Acids: Release H+ ions; pH < 7.
Bases: Release OH- ions; pH > 7.
pH Scale: Measures acidity/basicity; logarithmic scale.

Substance	pH Value
Stomach Acid	~2
Pure Water	7
Bleach	~12

Buffer: Substance that stabilizes pH by absorbing or releasing H+ ions.

Organic Molecules and Functional Groups

Categories and Properties

Organic chemistry studies carbon-based molecules essential for life.

Four Major Categories: Carbohydrates, Lipids, Proteins, Nucleic Acids
Hydrocarbons: Nonpolar, do not dissolve in water.
Isomers: Molecules with the same formula but different structures (structural, geometric, enantiomers).
Functional Groups: Groups of atoms that confer specific properties (e.g., carboxyl, amino, phosphate, methyl).

Functional Group	Properties	Example
Carboxyl (-COOH)	Makes molecule acidic, polar	Amino acids
Amino (-NH2)	Makes molecule basic, polar	Amino acids
Phosphate (-PO4)	Energy transfer, polar	ATP
Methyl (-CH3)	Nonpolar, affects gene expression	DNA methylation

ATP (Adenosine Triphosphate): The primary energy carrier in cells.

Additional info: Functional groups determine molecular interactions and biological activity.