AP Bio Unit 2 Review

Cell Theory and Cell Types

Cell Theory

• All living organisms are composed of one or more cells, emphasizing cells as the fundamental building blocks of life.

• The cell is the basic unit of life, capable of carrying out all life processes like metabolism and reproduction.

• Rudolf Virchow's concept states that all cells arise from pre-existing cells, highlighting the continuity of life.

Prokaryotic vs. Eukaryotic Cells

• Prokaryotic Cells: Lack a nucleus and membrane-bound organelles, seen in bacteria and archaea.

• Eukaryotic Cells: Contain a nucleus and various organelles, allowing for specialized cellular functions.

• Endosymbiotic Theory: The theory that eukaryotic organelles like mitochondria and chloroplasts were once free living prokaryotes that were ingested by a larger prokaryotic host cell.

Cellular Organelles and Functions

Nucleus

• Function: Stores genetic material (DNA) and regulates cellular activities through gene expression.

• Structure: Surrounded by a double membrane (nuclear envelope) with nuclear pores for selective transport.

Ribosomes

• Function: Sites of protein synthesis, translating mRNA into polypeptide chains.

• Location: Free-floating in the cytosol or attached to the rough endoplasmic reticulum (ER).

Endoplasmic Reticulum (ER)

• Rough ER: Synthesizes and transports proteins, studded with ribosomes.

• Smooth ER: Involved in lipid synthesis, detoxification, and calcium ion storage.

Golgi Apparatus

• Function: Modifies, sorts, and ships proteins and lipids received from the ER.

• Structure: Composed of flattened membrane-bound sacs (cisternae) for processing cellular products.

Mitochondria

• Function: Generates ATP through cellular respiration, known as the powerhouse of the cell.

• Structure: Double membrane with inner membrane folds (cristae) for increased ATP production.

Membrane Structure and Transport

Fluid Mosaic Model

• Describes the cell membrane as a dynamic phospholipid bilayer with embedded proteins, cholesterol, and carbohydrates.

• Phospholipids: Form a semi-permeable barrier with hydrophilic heads outward and hydrophobic tails inward.

Membrane Proteins

• Transport Proteins: Facilitate substance movement across the membrane for selective permeability.

• Receptors: Bind signaling molecules to initiate cellular responses.

Selective Permeability

• Definition: Allows certain substances to cross more easily, maintaining homeostasis.

• Examples: Diffusion, osmosis, and facilitated diffusion based on molecule characteristics.

Transport Across the Membrane

• Passive Transport: Includes diffusion, osmosis, and facilitated diffusion.

• Active Transport: Requires ATP to move molecules against their concentration gradient.

Energy Conversion and Communication

Mitochondria and Cellular Respiration

• Aerobic Respiration: Converts glucose and oxygen into ATP through Glycolysis, Krebs Cycle, and Electron Transport Chain.

• Function: Essential for converting stored glucose energy into usable ATP.

Chloroplasts and Photosynthesis

• Equation: CO₂ + H₂O + Light → Glucose + O₂.

• Process: Occurs in chloroplasts, with light reactions and Calvin cycle in different compartments.

Cell Communication

• Signaling Pathways: Cells communicate through chemical signals and signal transduction for specific responses.

• Types of Signaling: Autocrine, Paracrine, and Endocrine signaling pathways.