General Biology Study Guide: Foundations, Chemistry of Life, and Biological Organization

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Characteristics of Life

Defining Life

Biologists identify several key characteristics that all living things share. Understanding these helps distinguish living organisms from non-living entities.

Cellular Organization: All living things are composed of one or more cells, which are the basic units of life.
Metabolism: Living organisms carry out chemical reactions to obtain and use energy.
Homeostasis: The ability to maintain stable internal conditions despite changes in the external environment.
Growth and Development: Organisms increase in size and undergo changes during their life cycle.
Reproduction: Living things produce offspring, either sexually or asexually.
Response to Stimuli: Organisms can sense and react to environmental changes.

Example: Humans maintain a constant body temperature (homeostasis), grow from infants to adults, and reproduce.

Additional info: Viruses do not meet all these criteria and are generally not considered alive.

Cellular Organization

Types of Cells

Cells are the fundamental units of life. There are two main types:

Prokaryotes: Cells without a nucleus or membrane-bound organelles. Example: Escherichia coli (bacteria).
Eukaryotes: Cells with a nucleus and membrane-bound organelles. Example: Human cells, plant cells.

Key Differences:

Prokaryotes are generally smaller and simpler.
Eukaryotes can be multicellular and have complex internal structures.

Growth, Development, and Metabolism

Growth vs. Development

Growth refers to an increase in size, while development involves changes in form and function during an organism's life cycle.

Growth Example: A seedling growing taller.
Development Example: A caterpillar transforming into a butterfly.

Metabolism

Metabolism is the sum of all chemical reactions in an organism, including those that build up (anabolism) and break down (catabolism) molecules.

Homeostasis

Homeostasis is the maintenance of stable internal conditions. For example, the body regulates blood glucose levels using insulin and glucagon.

Reproduction and Evolution

Asexual vs. Sexual Reproduction

Asexual Reproduction: Offspring arise from a single parent and are genetically identical.
Sexual Reproduction: Involves two parents and produces genetically diverse offspring.

Evolution

Populations evolve over time through changes in genetic makeup, not individuals. Evolution is driven by natural selection, mutation, and genetic drift.

Biological Organization

Levels of Organization

Biological systems are organized hierarchically:

Atom → Molecule → Tissue → Organ → Organism

Ecological Organization

Population: Group of individuals of the same species in an area.
Community: All populations in a given area.
Ecosystem: Community plus non-living environment.
Biosphere: All ecosystems on Earth.
Ecology: Study of interactions among organisms and their environment.

Classification and Evolution

Binomial Nomenclature

Scientific names use genus and species (e.g., Homo sapiens for humans).

Three Domains of Life

Bacteria: Prokaryotic, unicellular organisms.
Archaea: Prokaryotic, often found in extreme environments.
Eukarya: Eukaryotic organisms, includes four kingdoms.

Four Kingdoms of Eukarya

Protista: Mostly unicellular, diverse group.
Fungi: Decomposers, cell walls of chitin.
Plantae: Multicellular, photosynthetic.
Animalia: Multicellular, heterotrophic.

The Process and Method of Science

Scientific Method

Science progresses through observation, forming questions, developing hypotheses, conducting experiments, and building theories.

Observation: Gathering data using senses or instruments.
Question: Identifying a problem or area of interest.
Hypothesis: Testable explanation for observations.
Experiment: Testing the hypothesis under controlled conditions.
Theory: Well-supported explanation based on evidence.

Experimental Design

Experimental Group: Receives the treatment or variable being tested.
Control Group: Does not receive the treatment; used for comparison.

Example: Testing a new drug, the experimental group receives the drug, the control group receives a placebo.

Additional info: Experiments without control groups cannot determine if observed effects are due to the variable being tested.

Atoms and Molecules: The Chemical Basis of Life

Elements and Atoms

Atoms are the smallest units of matter, composed of protons, neutrons, and electrons.

Proton: Positive charge, found in nucleus.
Neutron: No charge, found in nucleus.
Electron: Negative charge, orbits nucleus.

Atomic Number: Number of protons in the nucleus.

Atomic Mass: Sum of protons and neutrons.

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

Radioisotopes: Unstable isotopes that decay, emitting radiation.

Chemical Bonds

Covalent Bond: Atoms share electrons.
Ionic Bond: Atoms transfer electrons, forming charged ions.
Hydrogen Bond: Weak attraction between polar molecules.

Valence Electrons: Electrons in the outer shell, involved in bonding.

Chemical Reactions

Chemical reactions involve breaking and forming bonds between atoms.

Reactants: Substances that start a reaction.
Products: Substances formed by the reaction.

Dynamic Equilibrium: When the rate of forward and reverse reactions are equal.

Redox Reactions

Oxidation: Loss of electrons.
Reduction: Gain of electrons.
Redox Reaction: Transfer of electrons between substances.

Water, Acids, and Bases

Water: Polar molecule, forms hydrogen bonds, high specific heat.
Acid: Substance that increases hydrogen ion concentration.
Base: Substance that decreases hydrogen ion concentration.
pH Scale: Measures acidity or alkalinity (0-14).
Buffer: Substance that stabilizes pH.

Equation:

Organic Compounds

Carbon Chemistry

Carbon atoms can form four covalent bonds, allowing for complex molecules.

Major Groups: Carbohydrates, lipids, proteins, nucleic acids.

Functional Groups

Functional groups are specific groups of atoms that confer particular properties to organic molecules.

Examples: Hydroxyl (-OH), carboxyl (-COOH), amino (-NH2), phosphate (-PO4), methyl (-CH3), sulfhydryl (-SH), carbonyl (C=O).

Polymers and Macromolecules

Monomer: Small molecule that can join to form polymers.
Polymer: Large molecule made of repeating monomers.
Macromolecule: Very large molecule, often a polymer.

Condensation and Hydrolysis

Condensation Reaction: Joins monomers, releases water.
Hydrolysis: Splits polymers, adds water.

Carbohydrates

Structure and Function

Monosaccharide: Simple sugar (e.g., glucose).
Disaccharide: Two monosaccharides joined (e.g., sucrose).
Polysaccharide: Many monosaccharides (e.g., starch, cellulose).

General Formula:

Ratio of C:H:O in carbohydrates: Usually 1:2:1

Examples:

Sugar: Quick energy source.
Starch: Energy storage in plants.
Cellulose: Structural component in plant cell walls.

Lipids

Types and Functions

Triglycerides: Energy storage, made of glycerol and three fatty acids.
Phospholipids: Major component of cell membranes.
Steroids: Hormones and membrane components.

Saturated vs. Unsaturated Fatty Acids: Saturated have no double bonds; unsaturated have one or more double bonds.

Hydrophobic vs. Hydrophilic: Lipids are generally hydrophobic (water-repelling).

Proteins

Structure and Function

Amino Acids: Subunits of proteins.
Peptide Bond: Joins amino acids.
Primary Structure: Sequence of amino acids.
Secondary Structure: Folding into alpha helices or beta sheets.
Tertiary Structure: Overall 3D shape.

Functions: Enzymes, structural support, transport, signaling.

R Group: Variable side chain of amino acids.

Table: Comparison of Cell Types

Feature	Prokaryote	Eukaryote
Nucleus	No	Yes
Organelles	No	Yes
Size	Small	Larger
Examples	Bacteria	Plants, Animals

Table: Four Major Organic Molecule Groups

Group	Monomer	Function
Carbohydrates	Monosaccharide	Energy, structure
Lipids	Fatty acid, glycerol	Energy storage, membranes
Proteins	Amino acid	Enzymes, structure
Nucleic acids	Nucleotide	Genetic information

Table: Levels of Biological Organization

Level	Description
Atom	Smallest unit of matter
Molecule	Group of atoms bonded together
Tissue	Group of similar cells
Organ	Structure with specific function
Organism	Individual living thing

Table: Domains and Kingdoms

Domain	Kingdoms	Example Organisms
Bacteria	None	E. coli
Archaea	None	Halophiles
Eukarya	Protista, Fungi, Plantae, Animalia	Algae, mushrooms, trees, humans