General Biology: Core Concepts and Cell Biology Study Guide

Core Concepts in Biology

Key Biological Terms and Definitions

Understanding foundational biological terms is essential for studying life sciences. These terms describe levels of organization, ecological relationships, and cellular structures.

• Biosphere: The global sum of all ecosystems; the zone of life on Earth.

• Ecosystem: A community of living organisms interacting with their physical environment.

• Community: All populations of different species living and interacting in a particular area.

• Population: A group of individuals of the same species living in a specific area.

• Organism: An individual living entity.

• Organ System: A group of organs that work together to perform a specific function.

• Organ: A structure composed of different tissues working together for a particular function.

• Tissue: A group of similar cells performing a common function.

• Cell: The basic unit of life.

• Organelle: Specialized subunit within a cell with a specific function.

• Molecule: Two or more atoms bonded together.

Producers vs. Consumers

Organisms are classified based on how they obtain energy.

• Producer (Autotroph): Organisms that produce their own food, typically through photosynthesis (e.g., plants, algae).

• Consumer (Heterotroph): Organisms that obtain energy by consuming other organisms (e.g., animals, fungi).

• Example: Grass (producer) is eaten by a rabbit (consumer).

Prokaryotic vs. Eukaryotic Cells

Cells are classified into two major types 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 plants, animals, fungi, and protists.

• Key Differences: Eukaryotes are generally larger and more complex.

Properties of Living Things

All living organisms share certain properties:

• Order (organized structure)

• Regulation (homeostasis)

• Growth and development

• Energy processing

• Response to environment

• Reproduction

• Evolutionary adaptation

Three Domains of Life

Life is organized into three domains based on genetic and cellular differences:

• Bacteria: Prokaryotic, unicellular organisms.

• Archaea: Prokaryotic, often found in extreme environments.

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

• Example: Humans belong to the domain Eukarya.

Evolution and Scientific Inquiry

Charles Darwin and Evolution

Charles Darwin proposed the theory of evolution by natural selection, explaining how species change over time.

• Natural Selection: Process where organisms better adapted to their environment tend to survive and reproduce.

• Example: Finches on the Galápagos Islands evolved different beak shapes to exploit different food sources.

Discovery Science vs. Hypothesis-Based Science

Scientific inquiry can be divided into two approaches:

• Discovery Science: Describes natural structures and processes through observation and analysis.

• Hypothesis-Based Science: Uses the scientific method to test explanations and predictions.

Scientific Method

The scientific method is a systematic approach to investigation.

• Observation

• Question

• Hypothesis

• Experiment

• Analysis

• Conclusion

Cell Structure and Function

Microscopy and Cell Size

Microscopes are essential tools for studying cells, which vary greatly in size.

• Light Microscope: Used for viewing cells and large organelles.

• Electron Microscope: Used for detailed views of cell structures.

• Cell Size: Cells range from small bacteria (1-10 μm) to large eukaryotic cells (up to 100 μm).

Animal vs. Plant Cells

Animal and plant cells share many features but also have key differences.

• Plant Cells: Have cell walls, chloroplasts, and large central vacuoles.

• Animal Cells: Lack cell walls and chloroplasts, have smaller vacuoles.

• Example: Only plant cells can perform photosynthesis.

Cell Membrane Structure

The cell membrane is a selectively permeable barrier composed of a phospholipid bilayer and proteins.

• Fluid Mosaic Model: Describes the membrane as a dynamic structure with proteins floating in or on the fluid lipid bilayer.

• Glycoproteins: Proteins with carbohydrate chains; involved in cell recognition.

• Cholesterol: Stabilizes membrane fluidity.

Cell Transport Mechanisms

Cells transport substances across membranes using various mechanisms.

• Passive Transport: Movement of substances down their concentration gradient without energy input (e.g., diffusion, osmosis).

• Facilitated Diffusion: Passive transport aided by membrane proteins.

• Active Transport: Movement against the concentration gradient, requiring energy (ATP).

• Endocytosis/Exocytosis: Bulk transport of materials into/out of the cell.

Osmosis and Tonicity

Osmosis is the diffusion of water across a selectively permeable membrane. Tonicity describes the effect of a solution on cell volume.

• Isotonic: No net movement of water; cell volume remains constant.

• Hypotonic: Water enters the cell; cell may swell.

• Hypertonic: Water leaves the cell; cell may shrink.

Cellular Components and Functions

Organelles and Their Functions

Each organelle within a eukaryotic cell has a specific function.

Organelle	Function
Nucleus	Stores genetic material; controls cell activities
Mitochondria	Produces ATP via cellular respiration
Ribosomes	Protein synthesis
Endoplasmic Reticulum	Protein and lipid synthesis
Golgi Apparatus	Modifies, sorts, and packages proteins
Lysosomes	Digests cellular waste
Chloroplasts	Photosynthesis (plants only)
Vacuole	Storage and structural support

Extracellular Matrix

The extracellular matrix (ECM) is a network of proteins and carbohydrates outside animal cells, providing structural support and regulating cell behavior.

• Components: Collagen, proteoglycans, fibronectin.

• Function: Cell adhesion, communication, and tissue integrity.

Cell Division and Genetics

Chromosomes and Chromatin

Genetic material is organized into chromosomes, which are composed of chromatin (DNA and proteins).

• Chromosome: A single DNA molecule with associated proteins.

• Chromatin: The complex of DNA and proteins that forms chromosomes.

• Sister Chromatids: Identical copies of a chromosome connected by a centromere.

Cell Cycle and Mitosis

The cell cycle describes the sequence of events in cell growth and division.

• Phases: Interphase (G1, S, G2), M phase (mitosis and cytokinesis).

• Mitosis: Division of the nucleus into two genetically identical daughter cells.

• Cytokinesis: Division of the cytoplasm.

Stages of Mitosis

Stage	Description
Prophase	Chromosomes condense, spindle forms
Metaphase	Chromosomes align at cell equator
Anaphase	Sister chromatids separate
Telophase	Nuclear envelope reforms, chromosomes decondense

Meiosis and Sexual Reproduction

Meiosis is the process by which gametes (sex cells) are produced, reducing chromosome number by half.

• Diploid (2n): Two sets of chromosomes.

• Haploid (n): One set of chromosomes.

• Homologous Chromosomes: Chromosome pairs with the same genes but possibly different alleles.

• Crossing Over: Exchange of genetic material between homologous chromosomes during meiosis, increasing genetic diversity.

• Polyploid: Having more than two sets of chromosomes.

Cellular Energy and Enzymes

ATP and Cellular Work

ATP (adenosine triphosphate) is the primary energy carrier in cells.

• ATP: Provides energy for cellular processes.

• Equation:

$\text{ATP} \rightarrow \text{ADP} + \text{P}_i + \text{energy}$

Enzymes

Enzymes are biological catalysts that speed up chemical reactions.

• Function: Lower activation energy of reactions.

• Factors Affecting Enzyme Activity: Temperature, pH, substrate concentration.

• Inhibition: Enzymes can be inhibited by specific molecules.

Summary Table: Cell Transport Mechanisms

Type	Energy Required?	Direction	Example
Diffusion	No	High to low concentration	Oxygen entering a cell
Facilitated Diffusion	No	High to low concentration	Glucose transport
Active Transport	Yes (ATP)	Low to high concentration	Sodium-potassium pump
Endocytosis	Yes (ATP)	Into cell	Phagocytosis
Exocytosis	Yes (ATP)	Out of cell	Secretion of hormones

Additional info: These notes expand upon the original question list, providing definitions, explanations, and examples for key concepts in general biology, suitable for college-level study.