Cell Biology Study Notes

Cell Theory
- All living organisms are composed of cells.
- The cell is the basic unit of life.
- All cells arise from pre-existing cells.
Types of Cells
- Prokaryotic Cells
  - Lack a true nucleus and membrane-bound organelles.
  - Examples: Bacteria and Archaea.
- Eukaryotic Cells
  - Have a true nucleus and membrane-bound organelles.
  - Examples: Plant cells, animal cells, fungi, and protists.
Cell Structure
- Plasma Membrane
  - Semi-permeable membrane that surrounds the cell.
  - Functions in transport, communication, and protection.
- Nucleus
  - Contains genetic material (DNA).
  - Controls cell activities and gene expression.
- Cytoplasm
  - Jelly-like substance where organelles are suspended.
  - Site of metabolic reactions.
- Organelles
  - Mitochondria: Powerhouse of the cell, site of ATP production.
  - Ribosomes: Site of protein synthesis.
  - Endoplasmic Reticulum (ER):
    - Rough ER: Studded with ribosomes, synthesizes proteins.
    - Smooth ER: Synthesizes lipids and detoxifies.
  - Golgi Apparatus: Modifies, sorts, and packages proteins and lipids.
  - Lysosomes: Contain digestive enzymes for waste breakdown.
  - Chloroplasts: Site of photosynthesis in plant cells.
  - Vacuoles: Storage of materials; larger in plant cells.
Cell Division
- Mitosis: Process of cell division resulting in two identical daughter cells.
- Meiosis: Special type of cell division that produces gametes (sperm and eggs) with half the chromosome number.
Cell Communication
- Cells communicate through chemical signals (hormones, neurotransmitters).
- Signaling pathways involve receptors and second messengers.
Cell Metabolism
- Catabolism: Breakdown of molecules to release energy.
- Anabolism: Synthesis of complex molecules from simpler ones, requiring energy.
Cell Cycle
- Phases: G1 (growth), S (DNA synthesis), G2 (preparation for mitosis), M (mitosis).
- Regulation by cyclins and cyclin-dependent kinases (CDKs).
Stem Cells
- Undifferentiated cells with the potential to develop into various cell types.
- Types: Embryonic stem cells and adult stem cells.
Cellular Transport
- Passive Transport: Movement of substances across the membrane without energy (e.g., diffusion, osmosis).
- Active Transport: Movement against the concentration gradient, requiring energy (e.g., sodium-potassium pump).

These notes encapsulate fundamental aspects of cell biology, allowing for quick reference and review of key concepts.

Cell Theory and Cell Types

All living organisms are comprised of cells, establishing the foundation of cell theory.
The cell is recognized as the fundamental unit of life, essential for all biological functions.
Cells originate from existing cells through processes of division.

Prokaryotic and Eukaryotic Cells

Prokaryotic cells lack a true nucleus and membrane-bound organelles; examples include bacteria and archaea.
Eukaryotic cells contain a true nucleus and membrane-bound organelles; examples include plant, animal, fungal, and protist cells.

Key Cellular Structures

The plasma membrane is semi-permeable, facilitating transport, communication, and protection for the cell.
The nucleus houses genetic material (DNA) and governs cell activities and gene expression.
Cytoplasm is a jelly-like matrix where organelles reside, serving as the site for metabolic reactions.

Organelles and Their Functions

Mitochondria: Known as the powerhouse of the cell, responsible for ATP production.
Ribosomes: Essential for protein synthesis, either free-floating or attached to the rough endoplasmic reticulum.
Endoplasmic Reticulum (ER):
- Rough ER synthesizes proteins due to ribosome presence.
- Smooth ER synthesizes lipids and detoxifies harmful substances.
Golgi Apparatus: Modifies, sorts, and packages proteins and lipids for transport or secretion.
Lysosomes: Contain digestive enzymes to break down cellular waste and debris.
Chloroplasts: Organelles involved in photosynthesis, found in plant cells.
Vacuoles: Storage organelles; notably larger in plant cells, holding various substances like nutrients and waste.

Cell Division Processes

Mitosis results in two genetically identical daughter cells, crucial for growth and repair.
Meiosis is a specialized division that produces gametes (sperm and eggs) with half the chromosome count.

Cell Communication Mechanisms

Cells utilize chemical signals (hormones and neurotransmitters) to communicate.
Signaling pathways include receptors and second messengers to relay messages and elicit responses.

Metabolic Processes

Catabolism refers to the breakdown of molecules, providing energy for cellular activities.
Anabolism involves the synthesis of complex molecules from simpler ones, requiring energy input.

Cell Cycle Phases

The cell cycle comprises phases: G1 (growth), S (DNA synthesis), G2 (prep for mitosis), and M (mitosis).
Regulation is driven by cyclins and cyclin-dependent kinases (CDKs) which ensure orderly progression through the cycle.

Stem Cells Characteristics

Stem cells are undifferentiated, possessing the potential to develop into various cell types based on signals in their environment.
Two main types: embryonic stem cells (which can become any cell type) and adult stem cells (more limited in potential).

Transportation Mechanisms

Passive transport enables movement across the membrane without energy expenditure, includes processes like diffusion and osmosis.
Active transport moves substances against their concentration gradient, requiring energy, exemplified by the sodium-potassium pump.