IB Biology HL - A2.2: Cell Structure

Cell Theory

All organisms consist of one or more cells.

Basic Unit of Life

Cell is fundamental structure and function unit.

Pre-existing Cells

All cells originate from existing cells.

Scientific Theory

Well-supported explanation of natural world phenomena.

Inductive Reasoning

General conclusions from specific observations or patterns.

Deductive Reasoning

Specific predictions based on general principles.

Plasma Membrane

Controls substance movement; maintains cellular homeostasis.

Cytoplasm

Site of biochemical reactions; contains organelles.

Ribosomes

Synthesize proteins using genetic instructions.

DNA

Stores genetic information for cell function.

Prokaryotes

Unicellular organisms without membrane-bound organelles.

Cell Wall

Provides structural support; made of peptidoglycan.

70S Ribosomes

Smaller ribosomes found in prokaryotic cells.

Nucleoid

Region containing circular DNA in prokaryotes.

Eukaryotes

Complex cells with membrane-bound organelles.

Compartmentalization

Organelles allow specialized cellular functions.

80S Ribosomes

Larger ribosomes found in eukaryotic cells.

Nucleus

Stores DNA; controls cell activities.

Cytoskeleton

Provides structural support and facilitates transport.

Mitochondria

Powerhouse of the cell; site of ATP production.

Rough ER

Synthesizes and modifies proteins for export.

Smooth ER

Synthesizes lipids; detoxifies harmful substances.

Golgi Apparatus

Modifies, sorts, and packages proteins and lipids.

Lysosomes

Digestive vesicles that break down waste.

Vesicles

Small sacs for transporting materials within cells.

Vacuoles

Storage organelles; large in plant cells.

Animal Cells

Lack cell walls; contain centrioles.

Plant Cells

Have cell walls made of cellulose.

Fungal Cells

Contain chitin in cell walls.

Endosymbiosis

Theory explaining origin of eukaryotic organelles.

Evidence for Endosymbiosis

Structural, genetic, and behavioral similarities to prokaryotes.

Multicellular Organisms

Organisms composed of multiple specialized cells.

Evolution of Multicellularity

Involves cell clusters and specialization.